Melting temperature depression for low ether content polyether-polyester block copolymers with amide linkages

Melting behavior of a series of polyether-polyester block copolymers with low ether contents was studied. Significant melting-reorganization-remelting was suggested by means of differential scanning calorimetry. The equilibrium melting temperature of the copolymers was obtained by using the Hoffman-Weeks extrapolation. It has been found that the use of the on-set melting temperature for the Hoffman-Weeks plots is less reliable than the use of the corrected peak melting temperature. Copolymerization of polyetheramides with polyesters leads to a significant melting temperature suppression for the polyester crystal. We hypothesize that the locations of the junction points between blocks can be treated as chain ends for the crystallizable polyester blocks: the polyether-polyesters grow to form extended chain-like crystals with lamellar thickness limited by the polyester block length. For comparison, the nonlinear Hoffman-Weeks treatment, recently proposed by Marand, has also been applied to examine the behavior of melting temperature depression. Although the Tmo obtained from nonlinear extrapolation is much higher than the Tmo obtained from the Hoffman-Weeks extrapolation, similar trend regarding the composition dependence of Tmo have been found.