Macromolecules 2001, 34, in press
Influence of Structural and Topological Constraints on the Crystallization
and Melting Behavior of Polymers:
3. Bisphenol-A Polycarbonate
A. Alizadeh, S. Sohn, J. Quinn and H. Marand,*
Departments of Chemistry and Materials Science and Engineering,
Virginia Polytechnic Institute & State University,
Blacksburg, VA 24061-0212
L.C. Shank and H.D. Iler
Department of Chemistry,
Eastern Mennonite University,
Harrisonburg, VA 22802-2462
Received August 14, 2000; Revised Manuscript Received March 8, 2001
ABSTRACT: In this paper we report differential scanning calorimetry studies
of the temperature and molar mass dependences for the primary and secondary
crystallization behavior of bisphenol-A polycarbonate (BAPC). The
molar mass dependence of the crystallization rate is found to be much stronger
during primary than during secondary crystallization, confirming our earlier
claims that primary and secondary processes occur by significantly different
mechanisms. Investigations of the secondary crystallization process
suggest the existence of a crossover phenomenon from secondary crystal
formation at low temperatures to isothermal lamellar thickening at high
temperatures. While the results of our low temperature studies of
BAPC provide further support for the model developed in a previous publication
on poly(arylene ether ether ketone), evidences from atomic force microscopy
and calorimetry of isothermal lamellar thickening above the crossover temperature
lead us to anticipate a more unified view of polymer crystallization.