THERMAL CHARACTERIZATION OF POLY(PHENYLENE SULFIDE) OLIGOMERS

Oligomeric poly(phenylene sulfide)s (PPS's) prepared via the melt reaction of sulfur with excess p-diiodobenzene have been prepared and examined. We speculate that a transition from chain-folded crystals for longer chains in the PPS samples of this work to a different type such as extended-chain crystals for shorter chains occurs at 20 dp. This appeared to be substantiated by not only the T(m) but also the T(cc) and crystal reorganization peak data vs dp. The rate of crystallization seemed only to depend on oligomer length with the rate being faster at the shorter lengths, implying that addition of a chain to the growing crystal was limited mostly if not solely by viscosity effects and not the crystal habit. The crystallization from the glass (T(ch)) increased as a function of the logarithm of dp. Evidence was also seen for the inability to adequately quench samples to a completely glassy state; the shorter the chain the more difficult the quench. A relationship for T(g) vs oligomer length was also obtained which showed that a plateau level was reached at approximately 80 dp and was a linear function of log (dp) below that point, with a possible further increase in slope in the region of 10 dp and below. This relationship will provide a useful calibration against which other samples can be measured to estimate their dp. T(g)infinity, which we suggest is 98-degrees-C, is determined at significantly shorter chain lengths for this crystalline system than is seen for many reported amorphous systems.