Polymethacrylic acid derivatives, 2. Spectroscopic study of the compact conformation to coil transition

The compact → coil conformational transition of hydrophilic-hydrophobic copolymers derived from poly(methacrylic acid) was studied by UV Spectroscopy. Two copolymers were used in this study: a Poly(N-methacryloylalanine-co-N-phenylmethacrylamide) (P50) and a poly(methacrylic acid-co-benzyl methacrylate) (S25). Both samples exhibit hypochromism in the absorption band of the aromatic chromophore when they are under the compact conformation: 7% and 30% hypochromism for P50 and S25, respectively. This difference is explained by differences in the hydrophobic side chain-side chain interactions between the aromatic residues. Increasing the temperature was found to increase strongly the hypochromism of S25 and to have little effect on P50.