Relaxation behavior of the ester groups (β dispersion) in some swollen polymethacrylates

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Abstract
By using a torsion pendulum at a frequency of 1 Hz, the relaxation behavior of poly(β-hydroxyethyl methacrvlate), polymethyl methacrylate, and polypropyl methacrylate in the temperature range of T = −30° to +130°C was studied. It was found that the substitution of the end methyl group of polypropyl methacrylate with a hydroxyl group resulted in an increase of 15°C in the temperature corresponding to the relaxation of the ester group in the side chains. The effect of the presence of low molecular weight compounds on the relaxation behavior of poly(β-hydroxyethyl methacrylate) in the β dispersion region (Tβ = 30°C/1 Hz) was qualitatively similar to the effect on the low-temperature dispersion γ. At a low content of diluent (up to the weight fraction W1 = 0.02), a new loss maximum was observed at a temperature T > Tβ. This maximum shifted toward lower temperatures with increasing w1. Changes in the intensity of the β dispersion and its shifting toward lower temperatures were also found with polymethyl methacrylate and polypropyl methacrylate. It follows from the results that the mechanisms of the effects of low molecular weight compounds on the γ and β secondary relaxations of polymeth-acrylates are of a similar nature.

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