Structural differences exhibited by networks prepared by chemical or photochemical reactions II — Thermoelastic properties

Thermoelastic properties and swelling measurements were used to characterise networks obtained either by peroxide curing or by photocrosslinking. In agreement with previous studies, it was shown, on the one hand that the measured value of the average molecular weight of a network strand (M _c) depends on its method of determination and that the ratio M _cT/M _cv2m is a characteristic of each crosslinking process, on the other hand photo-crosslinked materials exhibit a more homogeneous distribution of the crosslink points than do peroxide cured samples. Important parameters such as f_e/f, the energetic contribution to the equilibrium retractive force, and d In < r²> ₀/dT, the temperature coefficient of the unperturbed dimension of the macromolecular chain, were determined.