Effect of gamma irradiation on latex film dissolution

Latex films have been prepared by annealing pyrene (Py)-labeled poly(methyl methacrylate)-polyisobutylene particles at the glass transition temperatur e (100 degreesC). These films were then irradiated by gamma rays from Co-60 in a gamma cell at room temperature at various dose rates (rad/h). Before dissolution the films were annealed at 200 degreesC for a 30 min time inter val to complete the film formation process. Steady-state fluorescence techn iques were used to monitor the dissolution of irradiated latex films. Disso lution of films in a chloroform-heptane (80%-20%) mixture was monitored in real time by the Py fluorescence intensity change. Relaxation constants, k( 0), and dissolution coefficients, D-d, Of polymer chains were measured. Two different regimes of D-d values were observed during dissolution, which ar e related to two different molecular weight distributions caused by scissio n and branching of polymer chains when they were irradiated and annealed. a zool Academic Press.