Dielectric absorption of various symmetrically substituted compounds of the type [CH3(CH2)3]2X in a polystyrene matrix

Abstract

Dielectric absorption studies have been made on symmetrically substituted compounds of the type [CH₃(CH₂)₃]₂X where X is: CO, SO, O, SO₂, [graphic omitted], NH, S, and SnCl₂, in a polystyrene matrix in the frequency range 10–15⁵ Hz over a temperature range 80–250 K. A plot of loss factor vs. temperature at a fixed frequency reveals two absorption peaks for each compound. The enthalpy of activation for both the low- and high-temperature absorptions is reasonably independent of the variation of the type of polar group X. The enthalpy of activation for the low-temperature absorption seems to be characterized largely by segmental rotation about the C—C bonds, and the high-temperature absorption may be attributed to molecular rotation. The movement of the polar group from the end to the centre of the hydrocarbon chain does not affect appreciably the enthalpy of activation of the molecular process. For the various polar groups, X, studied here, the nature and size of the polar group seem unimportant in determining the enthalpy of activation value for the intramolecular process.