Epitaxial crystallization of polyesters on inorganic and organic substrates

A series of low-molecular-weight linear polyesters were epitaxially crystallized from dilute solution and the melt on a variety of organic and inorganic substrates. The rod-like polyester crystals which were formed assumed general orientations in alignment with substrate geometry. This yielded monodirectional orientation of these crystals on one of the organic substrates, and bidirectional orientation on the other surfaces. Heterogeneous nucleation on the organic substrates, trioxane and naphthalene, induced the growth of much larger epitaxial crystals than have previously been observed on inorganic substrates. Those polyesters, with a high percentage of methylene units per chain repeat, crystallized in an unusual polymorphic form when in contact with the organic substrates. Polymorphic transformation to the normal form was not possible under thermal treatment or with increased crystal thickness. The expected relationship between dipolar alignment in the polymer crystal and this polymorphism was established.