The Development of Spherulites from Structural Units in Poly(bisphenol‑A‑carbonate)

Electron microscopic investigations have revealed that the surface of poly(bisphenol-A-carbonate) contains nodular units ca. 125 Å in size. It is shown that annealing thin films at temperatures near the glass transition, Tg, causes these nodules to enlarge. Tensile deformation results in the nodules breaking apart as the film elongates; however, if the sample has been annealed prior to stretching, the nodules appear to rearrange as shear occurs between them. It is suggested that each nodule represents a region containing a near-crystalline degree of molecular order. Featherlike structures, many microns in extent, are also observed to form in thin films annealed near the glass transition. They are thought to be precursors of spherulites. By annealing slightly above the glass transition, the spherulite development sequence has been observed to involve the creation of lamellae from initially broad, radiating arms.