Dynamic studies of polymerization in liquid crystal-polymer mixtures

This work studied the dynamic behavior of polymerization in films of liquid crystal (LC)-polymer mixtures by using the pump-probe technique. Chopped A r+ laser pulses were used as pump beams, and probed by a cw He-Ne laser. Th e experimental results indicated that the transmission of the probe beam wa s modulated in response to the chopping frequency of the pump beam. The mod ulation was such that transmission during the on-time of the pump beam was initially smaller than, then equal to, and finally larger than that in the off-time. Analyzing the transparency difference between the films with and without the Ar+ laser pulse allows us to recognize the three stages of poly merization process, initiation, propagation, and termination. Moreover, bot h the LC content in the sample and the chopping on/off ratio of the pump be am significantly affected the turning point occurred and the modulation amp litude of the probe beam. A model is proposed to explain these observed res ults. (C) 1999 American Institute of Physics. [S0021-8979(99)07424-1].