| Abstract: | Previously reported oligomeric PPSs prepared via the melt reaction of sulfur with excess p-diiodobenzene have been examined by optical microscopy and small-angle x-ray scattering (SAXS) techniques. A transition was seen from lamellar crystals for longer chains in the PPS samples of this work to a different type, which probably are extended chain crystals, occurring at about 20 DP. Spherulitic growth was observed optically for 38.8 DP and above. SAXS data established 31.8 DP as the point where a long period peak was first observed. The lamellar thickness of these bulk crystallized samples was established as about 50 Å which corresponds to a DP of 10. Maximum intensity of the SAXS peak increased with oligomer DP indicating increasing crystal perfection. Because of the random nature of the crystallization process, in PPS the average oligomer chain must be longer than three times this lamellar thickness to allow for folding and a spherulitic growth habit. © 1994 John Wiley & Sons, Inc. |
