Memory effect on the crystallization behavior of poly(lactic acid) probed by infrared spectroscopy

Abstract

The influence of crystalline memory effect on poly(lactic acid) (PLA) crystallization was probed by time-resolved Fourier transform infrared spectroscopy (FTIR). The melt with different degrees of order was prepared by melting at various temperatures. The vibrational changes associated with inter- and intra-chain interactions during crystallization were monitored. In the initial period of crystallization, the order of intensity changes is as follows: 1458cm−1>1210cm−1≫921cm−1, 1458cm−1>1210cm−1>921cm−1, and 1458cm−1>1210cm−1∼921cm−1 for PLA melted at 190, 170, and 168°C, respectively. With increasing the degree of order, both the formation of skeletal conformational-ordered structure and, especially, the 103 helix structure are accelerated. The influence of memory effect on the crystallization kinetics was also discussed based on the Avrami model.