Nonisothermal Crystallization and Melting Behavior of Poly(ε-caprolactone)-b-Poly(ethylene glycol)-b-Poly(ε-caprolactone) by DSC Analysis

Nonisothermal crystallization kinetics and melting behavior of poly(epsilon-caprolactone)-b-poly(ethylene glycol)-b-poly(epsilon-caprolactone) triblock copolymer (PCL-PEG-PCL), in which the weight fraction of the PCL block is 0.87, has been studied by differential scanning calorimetry (DSC). The nonisothermal crystallization data at various cooling rates are analyzed with the Ozawa, modified Avrami, and Mo models. The modified Avrami and Mo models were found to describe the nonisothermal crystallization processes fairly well. The values of the Avrami exponent n were near three, suggesting the crystallization process with a three-dimensional crystallite growth by heterogeneous nucleation mechanism. The crystallization activation energy estimated from the cooling scans using Kissinger's method was 168.9 KJ/mol. The phenomenon of the double melting behavior was observed for the PCL block during melting process after nonisothermal crystallization, being the reflection of a complicated crystallization process and the existence of the amorphous middle PEG block. (C) 2009 Wiley Periodicals, Inc. J Appl. Polym Sci 114: 1133-1140, 2009