Morphological implications of the interphase bridging crystalline and amorphousregions in semi-crystalline polymers

Abstract

In semi-crystalline polymers a range of morphologies can be obtained in which a chainmay traverse the amorphous region between the crystals or fold back into the crystals leading to adjacentor nonadjacent reentry, depending on the molecular architecture and crystallization conditions. Thiscauses topological variations on the crystal surface and the occurrence of an interphase between thecrystalline and amorphous domains, thus affecting the mechanical properties. In this chapter, wewill discuss how the morphology within the interphase plays a prominent role in drawability,lamellar thickening and melting of thus crystallized samples. Normally, for linear polymers it isanticipated that extended chain crystals are thermodynamically most favorable, and ultimately, takingthe example of linear polyethylene, it has been shown that such chains would form extended chain crystals.However, this condition will not be realized in a range of polymers upon crystallization fromthe melt, such as those which do not show lamellar thickening or in branched polymers where the sidebranches cannot be incorporated within the crystal and hence fully extended chains are not possible.From a series of experiments, it is shown that with sufficient time and chain mobility, althoughextended chain crystals are not achievable, the chains still disentangle and a thermodynamicallystable morphology is formed with a disentangled crystallizable interphase.