EFFECTS OF TOPOLOGICAL CONSTRAINTS ON THE THERMAL BEHAVIOR OF POLYMERS
Clarence William Murray, III, Srivatsan Srinivas, and Herve Marand
National Science Foundation Science and Technology Center:
High Performance Polymeric Adhesives and Composites, and
Department of Chemistry
Virginia Polytechnic Institute and State University
Blacksburg, Virginia
ABSTRACT
In this study, differential scanning calorimetry was used to follow the effect of crosslinking on the thermal behavior of atactic poly(styrene). Samples were crosslinked either using an electron beam or through copolymerization with divinylbenzene. Where s the thermal behavior of samples crosslinked in the e-beam was independent of radiation dosage, that of samples crosslinked with various amounts of divinylbenzene was very much affected. In the latter series of samples, the glass transition temperature s elevated as crosslinking increased. While the glass transition temperature increased, the change in heat capacity decreased due to the decrease in mobility in the chain between the constraints. As expected, the molecular weight between constraints pl ys a very important role because the longer the chain, the larger the number of degrees of freedom and the lesser the effects of the constraints on the chain mobility.