Multiple melting behavior of poly(epichlorohydrin) enantiomorphs

Abstract

Differential scanning calorimetry (DSC) studies demonstrate that the multiple melting behavior observed in both R and S enantiomorphs of poly(epichlorohydrin), their equimolar blend and the stereoblock copolymer form follows two distinctly different patterns, depending on the crystallization conditions. Isothermal crystallization at large undercoolings results in primary crystallites which during the heating scan undergo a process of melting/recrystallization and final melting, evidenced by a triple melting peak endotherm with the shape and position of the highest melting peak strongly dependent on scanning rate. By comparison, isothermal crystallization at small undercoolings yields primary and secondary crystallized material which melts with a double peak endotherm, the shape of which depends strongly on the crystallization time, with no indication of reorganization during the scan. These melting behavior observations support previous suggestions about the role of enantiomorphism in the crystallization of the stereoblock copolymer. Characteristic slow overall rates of crystallization of poly(epichlorohydrin) make this polymer an ideal subject for the study and refinement of multiple melting in polymers.