Interpretation of carbonyl band splitting phenomenon of a novel thermotropic liquid crystalline polymer without conventional mesogens: combination method of spectral analysis and molecular simulation.

A combination method of spectral analysis and molecular simulation was employed to interpret the carbonyl band splitting phenomenon of poly[di(butyl)vinylterephthalate] (PDBVT), a novel thermotropic liquid crystalline polymer, which can self-assembly into a two-dimensional hexagonal, columnar (2D Phi(H)) phase without conventional mesogens. Two-dimensional correlation infrared spectroscopy results of PDBVT during heating showed four splitting bands at 1707, 1712, 1731, and 1741 cm(-1). Accordingly, four PDBVT conformers were classified on the basis of carbonyls rotating in a pi-electron resonance system. Detailed spectral comparison and molecular dynamics (MD) simulation for the columnar phase of PDBVT were carried out to make a clear assignment of splitting bands to different conformers. The internal self-assembly nature of PDBVT can be concluded that the rotation of carbonyls at the 2-position (close to backbone) of the phenylenes would take place, along with the formation of the 2D Phi(H) phase. Meanwhile, the consecutive motions of PDBVT backbones with a distortion and extension in the mesophase formation and preparation processes have also been examined and reproduced by MD simulation. Finally, a good simulated conformity of the side chain size dependence of the liquid crystallinity of PDAVTs with experimental observations was achieved. This work combining spectral analysis and molecular simulation may bring some new insight into a better understanding of various physical chemical phenomena unintelligible before.