Preparation and properties of disyndiotactic poly(alkyl crotonate)s

Ethyl, n-propyl, iso-propyl and n-butyl crotonates were polymerized by group transfer polymerization (GTP) using ketene trialkylsilyl acetals as initiators in the presence of mercury (II) iodide as catalyst and iodotriethylsilane as co-catalyst. Predominantly disyndiotactic polymers with number-average molecular weights ranging from 56,000 to 90,000 were obtained almost quantitatively. Thermal and mechanical properties of poly(alkyl crotonate)s, such as glass transition temperature (T_g), refractive index, transmissivity, Izod impact strength, Young's modulus, hardness, tensile strength, tensile elongation at break, gas permeability coefficient and density were measured. All the polycrotonates have 65–90 °C higher T_g than the corresponding polymethacrylates.