INFRARED STUDY OF MOLECULAR AGGREGATION IN THE POLY(ALPHA-BENZYL L-GLUTAMATE) BENZYL ALCOHOL SYSTEM

Aggregation in poly(alpha-benzyl L-glutamate)/benzyl alcohol (PBLG/BA) systems has been studied by infrared spectroscopy. The amide and este r bands are found to be sensitive indicators of the state of aggregati on. PBLG/BA gels are shown to consist of side by side aggregates of PB LG which melt in three stages. Side-chain motions commence near 40-deg rees-C (I) followed by fragmentation of polymer bundles into elementar y fibrils (II) and dissociation of these elementary fibrils into indiv idual polymer chains (III). Transition temperatures for stages II and III are dependent upon molecular weight. Transition III may be accompa nied by subtle conformational changes in the alpha-helical molecular s tructure. Models of these conformational changes are proposed.