Lecture 6 Hybrid POSS by Ba8muCB3

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									   Lecture 6 Hybrid POSS

Class 1B: inorganic phase is made in-
  situ in organic continuous phase.

           in situ means “in place”
Making Hybrid Materials: Class 1B
    (in situ particle growth)




Ideally, no Solvent except for monomer(s)
No solvent with low tg organic polymers or in polymer melts
(< 100 °C) or if monomer will is soluble in polymer.

Otherwise solvent may be used to mix before casting.
Preparation by dissolving inorganic monomer in solid
organic polymer then polymerizing to form particles
Preparation by mixing inorganic monomer with liquid
    organic polymer & hydrolysis & condensation
Preparation by mixing inorganic monomer with solid
   organic polymer and allowing particles to form




                                Monomer polymerizes &
                                forms particles
                                    Silica-Nafion materials
                                    made this way are looked
                                    at later in lecture
 Polymers used in class 1B systems
• Elastomers: silicone, polybutadiene,
  polyisoprene
• Thermoplastics: polyurethanes,
  polycarbonates, polyvinylalcohol,
  polyacrylates, polysulfones, polyethylene
  oxide (PEO), polypropylene oxide (PPO)
• Thermosets: epoxies
• Polyionomers: Nafion
     Review of polymerizations
1) hydrolysis & condensation of M(OR)nor
  RSi(OR’)3
2) Reduction of metal compound
3) sulfidation of cations
4) photochemical or thermal decomposition
Hydrolysis & condensation of
  M(OR)n: the monomers

Silicon: Si(OR)4 or R’Si(OR)3

Aluminum: Al(OR)3 or AlCl3 6H2O


Transition metals: Mz(OR)n or MzCln hH2O

      z = oxidation number for metal
      n = number of alkoxide or halide in monomer
      h = number of coordinating waters
         Hydrolysis & condensation of Si(OR)4
      Hydrolysis
                         OR                          OH
                     RO Si OR       H2O          RO Si OR     ROH
                         OR                          OR


      Condensation
                OR             RO                OR RO
            RO Si OH          HO Si OR       RO Si O Si OR         HOH
                OR             RO                    OR RO


Water from
Condensation           OR                        OH
Hydrolyzes         RO Si OR       H2O        RO Si OR        ROH
Additional SiOR        OR                        OR


 Net Reaction
                       OR                 O O
                   RO Si OR       2 H2O    Si
                                              O
                       OR                 O
                                                 n
                                          SiO2

Catalyzed by acids (HCl,HNO3) or bases (NH3 aq, NaOH) or fluoride.
  Particles from hydrolysis & condensation of
                    Si(OR)4
• Typically leads to amorphous spherical particles (not quartz)
• Can template particles with ordered mesopores with surfactants
• Stober synthesis from TEOS with NH3 and water gives
 monodisperse particles
• Emulsion polymerization (water in oil) gives monodisperse particles
• Other preps give polydisperse particles
Hydrolysis & condensation of RSi(OR)3
  Particles from hydrolysis & condensation of
                    RSi(OR)3
• Typically leads to amorphous spherical particles
• Not as easy to prepare particles as with silica
• Can template particles with ordered mesopores with surfactants
• Stober synthesis from TEOS with NH3 and water affords
polydisperse particles
• Emulsion polymerization (two step) gives monodisperse particles
 Hydrolysis & Condensation of Mz(OR)n to
               form MOn/2
 M = Al, B, Ti, Zr, Cr, Fe…..
Hydrolysis: formation of monomeric MOH species




 Condensation: formation of “oxo” (neutral) M-O-M



                                 higher charge & higher pH
                                 More reactive, but too high shuts
                                 down condensation
     Hydrolysis & Condensation of
        Mz(OR)n to form MOn/2
Olation: formation of “oxo” (neutral) M-O-M




                         olation >> oxolation
  Particles from hydrolysis & condensation of
                    M(OR)n
• Particles may be amorphous or crystalline
• Some amorphous particles will crystallize with time.
• Stober synthesis from TEOS with NH3 and water does not work
• Emulsion polymerization (water in oil) gives monodisperse particles
• Many more molecular clusters are available through olation chemistry
Reduction of metals
Metal and Semiconducting Sulfides
Class 1B: in situ Silica-Nafion Nanocomposite
   Class 1B: in situ Silica-Nafion Nanocomposite




5 weight percent ex situ silica in Nafion




                                            In situ Silica particles
In situ filled Silica in polydimethylsiloxanes




 Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16
In situ filled Silica in polydimethylsiloxanes




 •Highly transparent

 •Does not require mechanical blending



 Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16
In situ filled Silica in polydimethylsiloxanes




 Journal of Polymer Science Part B: Polymer Physics, 2003, 41, 16
Silver particles made in situ
   polydimethylsiloxanes
Templating with
triblock copolymer
is formally a
Class 1B material

Polymer is template. After removal, silica remains
    Class 1B: In situ formation of
    inorganic phases in polymers
• Method for mixing at nanoscale without
  mechanical blending required-less chance for
  aggregation and segregation to occur (steric
  stabilization)
• Raises modulus and strength of materials
• In situ polymerization of inorganics selectively
  in blocks of block copolymers-first step to
  biomimetic mineralization.

								
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