History of Crystalline Polymers

The history of crystalline polymers closely parallels the development of polymer science itself. This paper discusses, in historical perspective, the work that led to the recognition that crystalline polymers exist and to the understanding of the structure, morphology, and properties that evolved. A chronological approach is taken and the cornerstones of major discoveries delineated. Initially there was a period where significant physical observations were made but could not be explained because the concept of polymers, no less crystallinity, was unheard of. Early x-ray diffraction work was extremely difficult to interpret for similar reasons. When it was established that polymers existed as bona fide molecular entities, structural analysis using classical diffraction methods soon followed. The principles of crystallization kinetics and the thermodynamics of fusion were firmly established by theory and experiment and found to have the same scientific basis as similar phenomena in low molecular weight substances. Modern emphasis has been directed to the influence of crystalline morphology on properties. The internal, interfacial, and external structures of the elementary lamella crystallite have been subject to divisive discussion for about two decades. Facts and fantasies associated with this problem are separated by considering recent experimental and theoretical results. Finally, emerging areas of research and unifying concepts are presented.