Review spherulites: A personal perspective

Chain-folding is a central feature of the self-organizational aspect of polymer in the solid state, yet the ability of a polymer chain to organize into a folded morphology depends upon its length. The shorter chains seem to fold with relative ease in dilute solution crystallization, but in the melt where topological constraints are encountered, spherulitic crystallization is less facile especially in the higher molecular weight fractions. Polymer morphology and properties demonstrate this point clearly according to the experimental evidence, obtained from several sources and presented in this article. For topological and statistical reasons, longer chains are responsible for more interfacial disorder if the degree of crystallinity, density, mechanical behavior, "fold" surface free energy, "transition" from brittleness to toughness, and so on, may be used as guidelines. Spherulites of homopolymers or copolymers are undoubtedly less ordered than crystals of comparable MW fractions, if measured properties are a manifestation of morphology. The imperfections in spherulites are mainly associated with the quasi-amorphous interlamellar regions within them. Polymer crystallinity decreases as the molecular weight of polymer fractions increase at comparable crystallization temperatures or undercooling conditions. This trend is true for all polymers that have been studied extensively. (C) 2001 Kluwer Academic Publishers.