Dipole Moments of Some Poly(Dimethylsiloxane) Linear Chains and Cyclics

摘要

Dielectric constant measurements were carried out on poly(dimethylsiloxane) (PDMS) linear chains CH3-(Si(CH3)2O)x-Si(CH3)3 and cyclis (Si(CH3)2O)x for x approx. 10, 15 and 70, in cyclohexane and in benzene at 30 C. Mean-square dipole moments (mu sq) were calculated from these data, using the method of Debye. The values thus obtained for the linear chains are consistent with results previously reported for short, linear PDMS chains in the undiluted state. Discernible differences among the values in the two solvents and undiluted state are manifestations of the specific solvent effect known to be important in longer linear chains the networks of PDMS. The cyclics were found to have dipole moments very similar to those of the corresponding linear chains. The cyclics also showed a specific solvent effect, in the same direction as shown by the linear molecules.