Synthesis and Characterization of Star Polymers and Cross-Linked Star Polymer Model Networks with Cores Based on an Asymmetric, Hydrolyzable Dimethacrylate Cross-Linker

A hydrolyzable dimethacrylate cross-linker, 2-methyl-2,4-pentanediol dimethacrylate (MPDMA), was synhesized by the reaction of 2-methyl-2,4-pentanediol and methacryloyl chloride in the presence of triethylamine. This cross-linker was used to prepare a neat cross-linker network and three cross-linked star polymer model networks (CSPMNs) of methyl methacrylate (MMA), as well as star-shaped polymers of MMA, by group transfer polymerization (GTP). Gel permeation chromatography (GPC) in tetrahydrofuran (THF) confirmed the narrow molecular weight distributions (MWDs) of the linear polymer precursors, and demonstrated the increase in molecular weight (MW) on each successive addition of cross-linker or monomer. Characterization of the star polymers by static light scattering (SLS) in THF showed that star polymers with MPDMA cores bear a relatively small number of arms, between 7 and 35. All star polymers and polymer networks containing the MPDMA cross-linker were hydrolyzed at room temperature in neat trifluoroacetic acid to yield lower-MW products.