Polydimethylsiloxane Macromonomers

The co-styryl- and oo-methacryloylpolydimethylsiloxane macromonomers synthesized by Yamashita 291 were copolymerized with styrene and methyl methacrylate, respectively, using AIBN as the initiator. The yields were about 80 %, and the unreacted 

No indication is given of potential applications of these graft copolymers. Such materials could obviously be of interest for biomedical applications owing to the good biocompatibility of PDMS polymers. 

---

The first attempts to synthesize short macromolecules bearing at their chain end an active double bond were made by Greber et al.7) in 1962. They reacted the Grignard derivative of p-chlorostyrene with co-chlorodimethylsiloxane oligomers and obtained polydimethylsiloxane macromonomers bearing at their chain end a p.-vinyl phenyl group ... 

Difunctional polydimethylsiloxane macromonomers were prepared by Katz et al. 30) in a completely different way using a cationic process. The polymerization of the cyclic tetramer of poly(dimethylsiloxane) (D4) was carried out in the presence of a disiloxane containing carboxy groups. Since this compound acts as a transfer agent carboxylic groups are introduced as end groups into the polymer molecules. These groups are subsequently reacted with 2-hydroxyethyl acrylate. The obtained diunsaturated PDMS macromonomers... 

Figure 9.12 Cel permeation chromatogram of polydimethylsiloxane macromonomer prepared by anionic ring opening polymerization of D3 (Hell-stern, 1989).

Most dispersion polymerizations in C02, including the monomers methyl methacrylate, styrene, and vinyl acetate, have been summarized elsewhere (Canelas and DeSimone, 1997b Kendall et al., 1999) and will not be covered in this chapter. In a dispersion polymerization, the insoluble polymer is sterically stabilized as colloidal polymer particles by the surfactant that is adsorbed or chemically grafted to the particles. Effective surfactants in the dispersion polymerizations include C02-soluble homopolymers, block and random copolymers, and reactive macromonomers. Polymeric surfactants for C02 have been designed by combining C02-soluble (C02-philic) polymers, such as polydimethylsiloxane (PDMS) or PFOA, with C02-insoluble (C02-phobic) polymers, such as hydrophilic or lipophilic polymers (Betts et al., 1996, 1998 Guan and DeSimone, 1994). Several advances in C02-based dispersion polymerizations will be reviewed in the following section. 

The same authors attempted copolymerization of these silicone — type macromonomers with different monomers (e.g. styrene) with the aim of synthesizing graft copolymers. a,ra-Diunsaturated polydimethylsiloxanes were also synthesized by the same method starting from i,m-dichlorodimethylsiloxane oligomers. 

Living polymerization created the idea of Macromer (proposed by R. Milkovich, generic term is macromonomer) for synthesizing a graft copolymer of well-controlled structure. We reported the synthesis of polydimethylsiloxane (PDMS)... 

---