CHAIN TOPOLOGY (LINEAL VERSUS CYCLIC) INFLUENCE OVER POLYCAPROLACTONES CRYSTALLIZATION

Abstract

In this work, the morphology and crystallization of cyclic polycaprolactones (C-PCL) obtained by click chemistry techniques are studied and the results compared with those obtained with linear polycaprolactones (L-PCL) of the same molecular weight Moreover, cyclic and linear blends were prepared in solution in 95/5, 90/10, 80/20 compositions. C-PCLs exhibit a higher nucleation density, crystallization and melting temperatures in comparison with L-PCL. Additonally, C-PCLs display faster nucleation, spherulitic growth and overall crystallization rates than L-PCL. These results are explained by the higher supercooling (the melting equilibrium temperature of the C-PCLs are higher than L-PCLs) and diffusion of C-PCLs. These effects are present in thermal fractionation, in which C-PCLs show a remarkable annealing capacity. The C/L blends show a drastic decrease, which are described as a synergistic negative effect, on the thermal properties and crystallization kinetics at low L-PCL contents, due to the threading effect of the linear on the cyclic chains.