Reversible melting in nanophase-separated poly(oligoamide-alt-oligoether)s and its dependence on sequence length,crystal perfection,and molecular mobility

摘要

The degree of reversibility of the melting of multiblock copolymers of alternating oligoamides and oligoethers was investigated with respect to the composition andmolecular mass of the blocks.The analysis was conducted with temperature modulated calorimetry,and it revealed different degrees of reversibility of the melting process that depended on the block length,crystal perfection,and molecualr mibility.For the oligoamide blocks,the abmount of crystal that melts and crystallizes eversibly during quasi-isothermal anlaysis increases with decreasing molar mass,and shorter amide sequences form poorwer crystals that have a higher tendency toward reorganization.Reorganization of the oligoamides is also favored by thepresence of the more mobile oligoether units.Reversible melting of the oligoether segments is influenced by the presence of glassy and crystalline oligoamide blocks in the adjacent nanophases.Because of the segmented nature of the copolymers,the oligoether segments are not free to flow as in an isotropic melt but are anchored to the oligoamide surfaces with different degrees of restriction that change the local equilibrium of melting and recrystallization.A comparison of the copolymers with the corresponding homopolymers provides information about the role of molecular nucleation and mobility in the reversibility of melting.