Lactone polymers. VIII. Dynamic mechanical properties of ϵ‐caprolactone and γ‐(tert‐butyl)‐ϵ‐caprolactone copolymers

The temperature dependencies of dynamic mechanical properties have been determined with a torsional pendulum for copolymers of ϵ‐caprolactone and γ‐( tert ‐butyl)‐ϵ‐caprolactone over the entire composition range. Copolymers containing at least 25 mol % (33 wt %) of γ‐( tert ‐butyl)‐ϵ‐caprolactone units are amorphous in nature. The experimentally obtained glass transition temperatures of the copolymers and poly(γ‐( tert ‐butyl)‐ϵ‐caprolactone) were used to calculate the glass transition temperature of amorphous of poly(ϵ‐caprolactone) according to the Fox relation. This value of −70°C is in excellent agreement with values obtained from similar calculations based on compatible blends of poly(ϵ‐caprolactone) with other homopolymers.