Dipole moments of poly(trimethylene oxide) chains

Abstract

Dipole moments of poly(trimethylene oxide) chains [CH2–CH2–CH2–O–]x were determined as a function of degree of polymerization and temperature by means of dielectric constant measurements in the thermodynamically good solvent carbon tetrachloride. The mean-square dipole moment was found to be directly proportional to the degree of polymerization x, or the number of skeletal bonds, thus demonstrating the absence of excluded volume effects on the dipole moment. According to previous studies, the unperturbed dimensions of this chain molecule are unusually small and essentially independent of temperature; this is apparently due to the high degree of conformational randomness in the trimethylene oxide repeat unit in that the two C–C skeletal bonds prefer gauche states whereas the two C–O bonds prefer trans states. The present results indicate that this randomness has a much smaller effect on the dipole moment and its temperature coefficient.