Experimental investigation of the kinetics of nitroxide - mediated by gjjur4356

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									                                 Experimental investigation of the kinetics of nitroxide - mediated free                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 IPR
                                 radical polymerization (NMRP); Styrene and styrene - divinylbenzene
                                                                                                                                                   Afsaneh Nabifar, Neil T.McManus, Eduardo Vivaldo-Lima , Alexander Penlidis
                                                                                                                                 Institute for Polymer Research (IPR), Department of Chemical Engineering, University of Waterloo

2. Effect of (TEMPO/ BPO) Ratio                                                                                                                                                                                                                         1. Introduction / Objectives                                                                                                                                                                4. STY/DVB Copolymerization
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  1

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             0.9
   The larger the ratio (the more TEMPO in                                                                          1                                                                                                                                   Controlled radical polymerization (CRP) has become a promising                                                                                                                                                         Level of DVB does not have a large                                                            0.8
                                                                                                                   0.9
the recipe), the slower the polymerization .                                                                                                                                                                                                            technique for producing polymers with highly controlled structures and                                                                                                                                                                                                                                               0.7
                                                                                                                   0.8                                                                                                                                                                                                                                                                                                                              effect on the overall rate of polymerization,
   Existence of an apparent induction time                                                                                                                                                                                                              polydispersity index close to 1.1. The basic principle consists of                                                                                                                                                                                                                                                   0.6




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     Conversion
                                                                                                                   0.7
                                                                                                                                                                                                                                                        introducing into the reacting system a species, a stable nitroxide radical,                                                                                                                 although the rates of reaction with added                                                                                0.5
                                                                                       Conversion, X




at (TEMPO/ BPO) = 1.5 .Related to the time                                                                         0.6
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             0.4
                                                                                                                   0.5                                                                                                                                  able to trap the propagating radical in a nonpropagating species, as                                                                                                                        DVB are slightly faster than the rates seen
needed to reach an equilibrium between                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       0.3
                                                                                                                   0.4                                                                                  TEMPO/BPO=0.9
                                                                                                                                                                                                                                                        represented below:                                                                                                                                                                                                                                                                                                                                                                                                                                    0% DVB

activation and deactivation of polymer                                                                             0.3
                                                                                                                                                                                                        TEMPO/BPO = 1.1
                                                                                                                                                                                                                                                                                                                                                                                                                                                    with no DVB.                                                                                                             0.2                                                                                                                              1% DVB
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              1.5% DVB
                                                                                                                                                                                                        TEMPO/BPO=1.1,Idependent                                                                                                                                                                                                                                                                                                                                             0.1
                                                                                                                                                                                                        replicate
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              3% DVB
                                                                                                                   0.2                                                                                  TEMPO/BPO = 1.2                                                                                                        K act
radicals, which lasts about 2.5 hrs at those                                                                       0.1                                                                                  TEMPO/BPO = 1.5                                                       P +X                                                                       P       X                                                                                                                                                                                                                0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       0                         5                  10              15              20      25         30           35          40       45
                                                                                                                                                                                                                                                                                                                             K deact                                                                                                                                                                                                                                                                                                                                 Time (h)
conditions.                                                                                                         0                                                                                                                                                      (Active)                                                                      (Dormant)
                                                                                                                         0            1000               2000                      3000                           4000                           5000                                                                                                                                                                                                                                                                                                                                       Figure 6. STY/DVB Copolymerization with
   A complete replicate has been carried                                                                                                                 Time, t (min)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            (TEMPO/BPO =1.1), T= 120 °C, and different
                                                                                                                                                                                                                                                        P● represents the propagating radical, P-X the dormant (trapped) radical,                                                                                                                                                                                                                                                           levels of DVB.
out at (TEMPO/BPO) = 1.1 to obtain an idea of                                                                                Figure 1. Effect of (TEMPO/ BPO ) ratio on rate of
                                                                                                                                                                                                                                                        and X is the controller .                                                                                                                                                                                             150000                                                                                             11
                                                                                                                             polymerization. STY homopolymerization at                                                                                                                                                                                                                                                                                                                       Mn, 1%DVB                                                                                           1%DVB
the reproducibility of our data.                                                                                             120 °C.                                                                                                                    Experiments were carried out in bulk using 2, 2, 6, 6–tetramethyl-1-                                                                                                                                                                 Mw,1% DVB
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 10
                                                                                                                                                                                                                                                                                                                                                                                                                                                                              125000         Mn,1.5% DVB                                                                          9              1.5% DVB




                                                                                                                                                                                                                                                                                                                                                                                                                                          Average Molecular Weight (gr/mol)
                                                                                      35,000                                                                                                                                                            piperidinyloxy (TEMPO) as controller and dibenzoyl peroxide (BPO) as                                                                                                                                                                 Mw, 1.5% DVB
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  8
                                           Number average Molecular Weight (gr/mol)




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Polydispersity, PDI
                                                                                                                                                                                                                                                                                                                                                                                                                                                                              100000
                                                                                      30,000                                                                                                                                                            initiator. The objectives were:                                                                                                                                                                                                                                                                                           7
   As expected for typical CRP, the                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               6
                                                                                      25,000                                                                                                                                                                To observe the effect of TEMPO/ BPO ratio and polymerization                                                                                                                                                       75000
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  5
molecular weight trends are linear.                                                                                                                                                                                                                     temperature on conversion, molecular weights and polydispersity.                                                                                                                                                                                                                                                          4
                                                                                      20,000                                                                                                                                                                                                                                                                                                                                                                                   50000
   Higher values of the number average                                                                                                                                                                                                                      To generate a source of reliable experimental data for parameter                                                                                                                                                                                                                                                      3
                                                                                      15,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      2
molecular weights, Mn, are obtained when                                                                                                                                                                                                                estimation and model validation purposes.                                                                                                                                                                              25000
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  1

the (TEMPO / BPO) ratio is decreased.
                                                                                      10,000
                                                                                                                                                                                                                  TEMPO/BPO=0.9
                                                                                                                                                                                                                                                            To examine the NMRP of styrene in the presence of cross linking                                                                                                                                                        0                                                                                              0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      0.0                        0.1                    0.2              0.3           0.4       0.5              0.6          0.7       0.8
                                                                                       5,000
                                                                                                                                                                                                                  TEMPO/BPO=1.1
                                                                                                                                                                                                                  TEMPO/BPO=1.2
                                                                                                                                                                                                                                                        agent , divinylbenzene (DVB).                                                                                                                                                                                                  0.0     0.1    0.2   0.3    0.4
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             Conversion, X
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             0.5   0.6   0.7   0.8
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   Conversion, X
                                                                                                                                                                                                                  TEMPO/BPO=1.5
                                                                                                                    0                                                                                                                                   3. Effect of Temperature                                                                                                                                                                                                         Figure 7. Molecular weight development (Mn and                                                     Figure 8. PDI with respect to conversion for
                                                                                                                         0.0    0.1    0.2       0.3         0.4  0.5     0.6                      0.7               0.8              0.9        1.0
                                                                                                                                                                                                                                                                                                                                              1
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         Mw vs. conversion) for nitroxide-mediated radical                                                  nitroxide-mediated radical copolymerization of
                                                                                                                                                             Conversion, X
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         copolymerization of STY/DVB (DVB = 1 and 1.5                                                       STY/DVB (DVB = 1 and 1.5 wt %).
                                                                                                                             Figure 2. Effect of (TEMPO/BPO) ratio on the number                                                                                                                                                                                                                                                                                                         wt%).
                                                                                                                             average molecular weight. STY homopolymerization                                                                              As expected, the                                                                  0.8

                                                                                                                             at 120º C.                                                                                                                                                                                                                                                                                                                                         At the start of the polymerization the molecular weights are low, as seen with NMRP
                                                                                                                                                                                                                                                        polymerization proceeds
                                                                                                                                                                                                                                                                                                                             Conversion, X


                                                                                                                                                                                                                                                                                                                                             0.6
                                                                                                                    9
                                                                                                                                 TEMPO/BPO=0.9                3
                                                                                                                                                                                                                                                        faster at a higher                                                                                                                                                                          homopolymerization of styrene.
   The experimental data do not show                                                                                8            TEMPO/BPO=1.1
                                                                                                                                                             2.8
                                                                                                                                                                                                                  Ampoules, Run 7, GPC 2




                                                                                                                    7
                                                                                                                                 TEMPO/BPO=1.2
                                                                                                                                                             2.6

                                                                                                                                                             2.4
                                                                                                                                                                                                                  Predicted Profile

                                                                                                                                                                                                                                                        temperature.                                                                         0.4
                                                                                                                                                                                                                                                                                                                                                                                                                                                       The number average molecular weight shows a steady increase with conversion. In
much difference for various ratios. Very                                                                                         TEMPO/BPO=1.5               2.2


                                                                                                                                                                                                                                                                                                                                                                                                                                                    contrast, the weight average molecular weight of the samples increases abruptly with
                                                                                             Polydispersity, PDI




                                                                                                                                                       PDI




                                                                                                                    6                                         2
                                                                                                                                                                                                                                                                                                                                             0.2                                                                         T = 120

low values, between 1.07 and 1.2, are                                                                               5
                                                                                                                                                             1.8

                                                                                                                                                             1.6                                                                                                                                                                                                                                                         T = 130
                                                                                                                                                                                                                                                                                                                                                                                                                                                    conversion, prior to the gelation point. Subsequently, there is a drop in the weight average
                                                                                                                                                             1.4

                                                                                                                                                                                                                                                                                                                                              0
obtained.                                                                                                           4                                        1.2

                                                                                                                                                              1
                                                                                                                                                                   0   0.1   0.2   0.3   0.4      0.5       0.6      0.7      0.8      0.9   1
                                                                                                                                                                                                                                                                                                                                                   0             500     1000           1500     2000          2500           3000                  molecular weight (observed also as a decrease on PDI in Figure 9). This is because only the
                                                                                                                    3                                                                          Conversion                                                                                                                                                                             Time (min)
   Frequent sampling in the beginning of                                                                                                                                                                                                                                                                                                                                                                                                            soluble fraction of the produced material is being analyzed and typically this will be lower
                                                                                                                    2                                                                                                                                                                                                                                  Figure 4. Effect of temperature on the kinetics of
the experiment was done for (TEMPO/BPO)                                                                             1                                                                                                                                                                                                                                  the reaction.                                                                                molecular weight material.                          100
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                100

=1.5 to capture and verify the trends                                                                               0                                                                                                                                                                                                                                                                                                                                  The expected behavior of the gel content          90
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 90
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 80

                                                                                                                         0.0    0.1     0.2      0.3          0.4  0.5    0.6                      0.7               0.8              0.9         1.0                                                                        30,000
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 70




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              gel content (%)
predicted by a mathematical model.                                                                                                                             Conversion,X
                                                                                                                                                                                                                                                                                                                                                                                                                                                    increasing very rapidly after the gelation point at 80                                                                                                       60
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 50
                                                                                                                                                                                                                                                                                      Average moleculare weights (gr/mole)




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 40


                                                                                                                             Figure 3. Effect of TEMPO/BPO ratio on PDI. STY                                                                                                                                                                                                                                                                                                                             70
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 30
                                                                                                                                                                                                                                                                                                                             25,000
                                                                                                                                                                                                                                                           A slight reduction in                                                                                                                                                                    high conversions was obtained.                                                                                                                               20




                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      Gel content (%)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 10
                                                                                                                             homopolymerization at 120ºC.                                                                                                                                                                                                                                                                                                                                                                                                                        60                               0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      0.0   0.1   0.2   0.3   0.4 0.5 0.6    0.7   0.8   0.9   1.0
                                                                                                                                                                                                                                                                                                                             20,000
                                                                                                                                                                                                                                                        the values of Mn and                                                                                                                                                                            Compared to the copolymerization of                                                                                      50
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                conversion




                                                                                                                                                                                                                                                        Mw is observed at 130                                                15,000                                                                                                                 STY/DVB using conventional free radical                                                                                      40
5. Immediate Future Steps                                                                                                                                                                                                                               °C.                                                                  10,000                                                                                                                 polymerization (insert), the NMRP reaction leads                                                                             30
                                                                                                                                                                                                                                                                                                                                                                                                                      Mn,T = 120                                                                                                                                                 20
                                                                                                                                                                                                                                                                                                                              5,000                                                                                   Mw ,T = 120                   to a gelation point significantly shifted from
   Complete experiments for (TEMPO/ BPO) ratio                                                                                                                                                                                                                                                                                                                                                                        Mn,T = 130                                                                                                                                                 10                                                                                                                           1% DVB

verifications at 130 ° C.                                                                                                                                                                                                                                                                                                                     0
                                                                                                                                                                                                                                                                                                                                                                                                                      Mw, T = 130                   about 7 to 50% monomer conversion .This                                                                                       0
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              1.5% DVB


   Further experiments for Sty / DVB with frequent                                                                                                                                                                                                                                                                                                 0.0     0.1     0.2   0.3    0.4      0.5       0.6   0.7   0.8      0.9         1.0             relates to the manner of molecular weight                                                                                         0.0       0.1                               0.2          0.3           0.4   0.5    0.6               0.7         0.8     0.9      1.0
                                                                                                                                                                                                                                                                                                                                                                                      Conversion                                                                                                                                                                                                                                                               Conversion
sampling.                                                                                                                                                                                                                                                                                                                                                                                                                                           buildup in NMRP where the initial chain lengths                                                                                         Figure 9. Gel content values vs. conversion for
                                                                                                                                                                                                                                                                                                                                                       Figure 5. Effect of temperature on molecular
   Continue the experimental investigations of NMRP at                                                                                                                                                                                                                                                                                                 weights.                                                                                     are small, giving a reduced probability of                                                                                              STY/DVB copolymerization initiated with
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            (TEMPO/BPO = 1.1) at 120 °C
higher temperatures (150- 220 ° C)                                                                                                                                                                                                                                                                                                                                                                                                                  crosslinks

								
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