Polymer morphology: Pure and applied

Polymer morphology has a unique role in macromolecular science. Because it deals primarily with images of microstructure, revealing actual organization in its inherent complexity rather than as oversimplified models, it provides a special wealth of information from which to draw inferences on molecular and other mechanisms involved in its formation and on the consequences for properties. The essential first step is to image the microstructure to allow the eye-brain combination to use its outstanding ability to interpret complex textural patterns. Not only have continual gains in fundamental understanding stemmed from corresponding advances in our ability to reveal and study morphology but so have insights leading to improved properties. These themes are illustrated with recent results for both pure and applied topics. The origin of spherulitic growth, the principal determinant of texture and thus properties in polymers, is a long-standing, sometimes controversial, issue. Now study of an academic system, monodisperse paraffins, has clearly negated the long-standing hypothesis of the responsibility of “impurities” in the melt. It also strongly supports previous suggestions that the essential cause is divergence of adjacent dominant lamellae from their branch points, due to the pressure of uncrystallized molecular cilia. The value of morphological studies in the development of commercial materials is illustrated, firstly, for advanced polyethylene fibers, both compacted and individual, in which novel longitudinal defects have been discovered, and then by details of impact-related failure in polypropylene copolymers.