Influence of Entanglements on the Glass Transition and Structural Relaxation Behaviors of Macromolecules. 1. Polycarbonate

• Published in: Macromolecules Vol. 32; no. 20; pp. 6675 - 6678
• Main Authors: Huang, Dinghai, Yang, Yuming, Zhuang, Guoqing, Li, Binyao
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 05.10.1999
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Thermal and thermodynamic properties; Bisphenol A; Manufacturing process; Concentration effect; Amorphous polymer; Experimental study; Property processing relationship; Polycarbonate; Structure relaxation; Glass transition temperature; Growth from solution
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma990581g

We obtained the single-chain polycarbonate sample by a new fast evaporation method and found that the polycarbonate sample obtained by this method is completely amorphous, while the polycarbonate sample obtained by other methods all have a certain degree of crystallinity. The glass transition temperature (T g) of the sample decreases with the decreasing of concentration when the concentration of the prepared solution is below the critical value. The critical concentration we obtained from the T g dependence of concentration is 0.9% g/mL and is in accord with that obtained by viscometry and light scattering methods directly from the solution. The structural relaxation behavior is found also different from that of a normal bulk sample of polycarbonate. The enthalpic peak of the single-chain sample is lower than that of the bulk one, which corresponds to the lower glass transition temperature. The peak of the single-chain sample is lower and broader, and the relaxed enthalpy is much lower compared with that of the bulk sample. These results have been explained in terms of the effect of entanglement on the mobility of the segments in polymer and the compact conformation in the single-chain sample.