Conformational composition and molecular mobility in comb-shaped polymers with fluoroalkyl side groups:: Study by IR spectroscopy and quantum chemistry

IR spectra of comb-shaped polymers with fluoroalkyl side groups were studied in the 293-373 K range. It was shown that a number of absorption bands sharply change their intensity in the region of the phase transitions of poly(fluoroalkyl acrylate) and poly(fluoroalkyl methacrylate) in contrast to the amorphous poly(fluoroalkyl fumarate). The methods of vibrational spectroscopy and quantum chemistry were employed to study the structure and conformational composition of a comb-shaped poly(fluoroalkyl acrylate) exhibiting LC properties; it was established that four stable conformations of the polymer can exist. Using experimental and theoretical methods of vibrational spectroscopy, it was demonstrated that, in the phase transition of poly(fluoroalkyl acrylate) at 350 K, conformational changes are observed in the side chain of the polymer and these changes involve a rotation about a C-O bond of an ester group which leads to the breakdown of the layered structures formed by the side fluoroalkyl groups.