Calculation of the of the swelling behavior of poly (N-isopropylacrylamide) in an associating solvent

The swelling theory of Browarzik was improved. Now the association effects of the solvent are taken into account by CALM and there is no longer a restriction with respect to the size of the solvent molecules. Besides the numerical treatment was essentially simplified. The improved theory was applied to calculate the swelling degree of several samples of cross-linked poly(N-isopropylacrylamide) (PNIPAAm) in pure water as function of temperature. Here, the interaction parameters were fitted to experimental cloud-point data of aqueous solutions of linear PNIPAAm. The theory was also applied to the swelling of cross-linked PNIPAAm in pure ethanol. Here the interaction parameters were assumed to take the value 0 because solutions of linear PNIPAAm in ethanol do not demix. In all considered cases, the calculated swelling degrees agree with experimental data from literature reasonably well.