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 (Tg), refractive index, transmissivity, Izod impact strength, Youngʹs modulus, hardness, tensile strength, tensile elongation at break, gas permeability coefficient and density were measured. All the polycrotonates have 65–90 °C higher Tg than the corresponding polymethacrylates.