Poly(dimethylsiloxane)urethane-co-poly (methyl methacrylate) with 2,4-toluene diisocyanate and m-xylene diisocyanate. I. Compatibility and impact strength of copolymers

In this study, slightly crosslinked poly(dimethylsiloxane)urethane-co-poly(methyl methacrylate) (PDMS urethane-co-PMMA) graft copolymers based on two diisocyanates, 2,4-toluene diisocyanate (2,4-TDI) and m-xylene diisocyanate (m-XDI), were successfully synthesized. Glass-transition behaviors of the copolymers were investigated. Results confirm that PDMS–urethane and PMMA are miscible in the 2,4-TDI system, but are only partially miscible in the m-XDI system. The methylene groups adjoining the isocyanate in the m-XDI system show increased phase-separation behavior over the 2,4-TDI system, in which the benzene ring adjoins the isocyanate. The functional group of PDMS–urethane improves the impact strength of the copolymers. The toughness depends on the compatibility of PDMS–urethane and PMMA segments in the copolymers. In the m-XDI system, the impact strength of the copolymer containing 3.75 phr macromonomer achieves a maximum value (from 13.02 to 22.21 J/m). The fracture behavior and impact strength of the copolymers in the 2,4-TDI system are similar to that of PMMA homopolymer, although they are independent of the macromonomer content in the copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1875–1885, 2002