Non-monotonic molecular weight dependence of crystallization rates of linear and cyclic poly(epsilon-caprolactone)s in a wide temperature range

By using a commercial fast-scan chip-calorimeter, the effect of molecular weight on the isothermal crystallization rates of linear and cyclic poly(epsilon-caprolactone) samples (L-PCLs and C-PCLs) is investigated. The results confirm the non-monotonic molecular weight dependence of the crystallization rates of both L-PCLs and C-PCLs over a wide temperature range, previously observed only in the high temperature range, in which the medium molecular weight PCLs exhibit the highest crystallization rate. Chain-end effects of L-PCL with medium molecular weights induce faster crystallization rates in specific low temperature regions, in comparison to that for counterpart C-PCL. This phenomenon no longer exists in high molecular weight samples because of ‘diluted’ chain-end effects in long chain samples. © 2016 Society of Chemical Industry