Conformational transitions in polymethacrylates. Effect of the side chain

Abstract

The temperature dependences of viscometric, refractometric and densitometric data have been studied for several polymethacrylates: poly(methyl methacrylate), poly(isobutyl methacrylate), poly(phenyl methacrylate) and poly(cyclohexyl methacrylate) in methyl isobutyl ketone solution. It has been found that these polymers change their conformation over specific temperature ranges, as evidenced by sharp changes of the unperturbed dimensions (K_θ), refractive-index increment (dn/dc) and partial specific volume (v₂). The influence of the side group, particularly its nature and size, on the phenomenon has also been studied.

The results for poly(cyclohexyl methacrylate) are particularly interesting. The nature of the side group in this polymer allows a contribution from the side chain to the main-chain conformational transition.

Finally, several semi-empirical relations have been proposed which correlate different thermodynamic parameters.