Synthesis of heterotactic poly(methyl methacrylate) by

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					               Synthesis of heterotactic poly(methyl methacrylate)
            by free radical polymerization of catechol dimethacrylate
                                     Yoichi SAITO and Reiko SAITO*

        Department of Organic & Polymeric Materials; Tokyo Institute of Technology,
              2-12-1-E4-7, Ookayama, Meguro-ku, Tokyo, 152-8552, JAPAN
                               rsaito@polymer.titech.ac.jp

Introduction.
        Tacticity is one of the important factors for the physical properties of polymers. For
example, glass transfer temperature (Tg) of poly(methyl methacrylate) (PMMA) depends on
the syndiotacticity. Syntheses of syndiotactic and isotactic PMMAs by radical polymerization
have been well reported. However, heterotactic PMMA is rarely synthesized. The physical
properties of heterotactic PMMA are not investigated. Thus, the establishment of a simple
method to synthesize the heterotactic PMMA is requested.
        To synthesize heterotactic polymer, polymerization must proceed with r-addition and
m-addition alternatively (Scheme 1). Some divinyl monomers can be cyclopolymerized with
intra-molecular and inter-molecular proceeding alternatively (Scheme 2). Thus, the divinyl
monomer, which can control intra- and inter-molecular proceeding, will be useful to
synthesize heterotactic polymer.
        Catechol dimethacrylate (catechol-DVM) has two vinyl groups on ortho-substitution.
Intra-molecular proceeding of vinyl groups in catechol-DVM will be controlled. Because of
the steric hindrance of the catechol groups, inter-molecular proceeding will be controlled.
Thus, heterotactic polymer will be obtained from cyclopolymerization of catechol-DVM
(scheme 3). The purposes of this work are the synthesis of heterotactic PMMA by free radical
polymerization of catechol-DVM, and the investigation of the physical properties of
heterotactic PMMA, such as Tg and second virial coefficient.
                                  r addition                                               m addition
        H   R H   R R    H R         H      R           H   R H    R R        H R   HH         R       R
                                 ∗                                                         ∗
    H   HH    H H   H H     H                       H   HH     H H     H H      H H    H

                                Scheme 1: Synthesis of heterotactic polymer


                         inter molecular addition                                     intra molecular
                                                                                      addition
                            ∗
                                                                                                   ∗




                        Scheme 2: Cyclopolymerization of divinyl monomer



Experimental, results, and discussion.
        Catechol-DVM was synthesized by esterification of catechol with methacrylic
chloride in pyridine at 0 °C. The number of vinyl groups of catechol-DVM per molecule (=
2.0) was determined by 1H-NMR analysis. And then, catechol-DVM was polymerized by free
radical polymerization with azobisisobutyronitrile (AIBN) or Cu-mediated atom transfer
         O                                                                                                    O       O
                                                                        O         O                               O       O
                 O           free radical                                   O         O
             O              polymerization
                     O                               O        O                       O       O
                                                         O        O                       O       O


     catechol-DVM
                                                                      poly(catechol-DVM)


                                                                  O       O
                                                                                                      O       O
                                                                      O       O                           O       O
             hydrolysis

                     methylation
                                             O        O                       O       O
                                                 O        O                       O       O

                                                     heterotactic poly(methyl methacrylate)

             Scheme 3: Synthesis of heterotactic poly(methyl methacrylate) from catechol-DVM

radical polymerization (ATRP) in dimethylacetamide (DMA), dimethyl sulfoxide (DMSO),
and dimethylformamide (DMF). Polymerized products were converted to PMMA by
hydrolysis with sodium hydroxide and methylation with trimethylsilyldiazomethane.
Molecular weight and molecular weight distribution of poly(catechol-DVM) and resulting
PMMAs were determined by GPC. The degree of cyclization of poly(catechol-DVM) and the
tacticity of resulting PMMAs were determined by 1H and 13C NMR analysis. The resulting
PMMAs were heterotactic-rich with more than 95 mol % of the ratio of mr triad.
         The physical properties of the heterotactic-rich PMMAs derived from catechol
dimethacrylate were measured. Glass transition temperature and the second virial coefficient
of the heterotactic-rich PMMAs in solvents were measured by DSC and SLS analysis,
respectively. On the session, we will discuss the effects of the arrangement of vinyl groups,
the method of radical polymerization, and the solvents for polymerization on tacticity. The
physical properties of heterotactic-rich PMMAs, such as glass transition temperature and
second virial coefficient will also be discussed.