2D-COS-FTIR analysis of high molecular weight poly (N-vinyl carbazole) undergoing phase separation on purification and thermal annealing

Abstract

The effect of purification and annealing on the molecular structure of commercial poly (N-vinyl carbazole), PVK, has been probed by two-dimensional Fourier Transformation Infrared correlation spectroscopy, 2D-COS-FTIR. Subtle changes in the spectra of PVK were determined and correlated with changes observed to the multiple glass transition temperatures and the phase separation behaviors. Bands at 1626, 1600, 1575, 1482, 1454, 1332 and 1224 cm−1 were assigned to syndiotactic rich chain segments and decreased on annealing. While bands at 1616, 1590, 1550, 1478, 1444, 1322, and 1218 cm−1 were assigned to isotactic rich segments, and increased on annealing. The commercial PVK consisted of some sections of the polymer chains, which were predominantly syndiotactic and others isotactic. The predominantly isotactic sequences were insoluble and separate on thermal annealing into two phases with different compositions. 2D-COS-FTIR enabled the assignment of the FTIR bands that were related to change in tacticity.