Thermal, dynamic mechanical, and dielectric relaxation techniques were used to determine the relaxation behavior of isotactic and syndiotactic poly(2‐hydroxyethyl methacrylate) (pHEMA). Activation energies Ea were determined for the dielectric γ relaxation and compared with those of poly(2‐methoxyethyl methacrylate) (pMEMA) to determine the influence of hydrogen bonding on side‐chain relaxation processes. No difference in Ea was observed between syndiotactic pHEMA and atactic (predominantly syndiotactic) pMEMA. Isotactic pHEMA, however, had Ea + 1 kcal/mole higher than that of syndiotactic pHEMA. This was attributed to improved side‐chain packing in the isotactic polymer.
synopsisThe thermal bulk polymerization of cholesteryl acrylate was carried out in the solid phase, the mesomorphic phase, and the liquid phase to study the effect of monomer ordering on polymerization rate and polymer properties. The rate increased with decreasing ordering (or enhanced mobility) of the monomer. Formation of inhibitive by-products during the polymerization limited conversions to 35%. The sedimentation constant SO = 6.2 S was the same for the polymers obtained in the three phases. The weightaverage molecular weight ( am) was 480,000 aa determined by ultracentrifugation. Poly-(cholesteryl acrylate) formed in bulk is randomly coiled when dissolved in tetrahydrofuran. The thermal properties of the monomer are given.
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