Low‐temperature specific heat of polystyrene and related polymers (1.6° to 4°K)

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Abstract
The specific heat of polystyrenes of different origin and molecular weight, of α‐substituted and ortho‐substituted polystyrenes, and of polystyrenes crosslinked with different amounts of divinylbenzene have been measured between 1.6 and 4°K. The specific heat of all samples shows a temperature dependence that can not be explained by assuming a Debye frequency spectrum for the vibrational modes in these polymers. Good agreement is obtained by fitting the data to a superposition of a Debye T3 term and an Einstein specific heat with a characteristic temperature of 15–18°K. This localized frequency mode may have its origin in the one‐dimensional nature of the polymer chain. A simple calculation of the length of a polystyrene chain necessary to obtain these characteristic temperatures shows reasonable agreement with the number of Einstein oscillators observed in the samples.