Poly(methacryloyl-L- alanine-methyl ester) ii! has an optically active side chain and consists of thermoshrinking hydrogels upon crosslinking. We synthesized an uncrosslinked polymer of 1 by the gamma-ray polymerization method. For the prepared polymer, variable-temperature circular dichroism (CD) and H-1 NMR spectra were studied, and we found conformational changes in the optically active side chains during the thermally induced phase transition. Intense CD spectra reveal ordered conformation in the side chain of 1 below the phase transition temperature (similar to 28 degrees C). A well resolved H-1 NMR spectrum of 1 at 0 degrees C shows that the conformational angles in the polymer side chain are fixed at low-energy minima. With increasing temperature, the frozen side chain starts rotating vigorously and takes an unordered orientation.