MOLECULAR-WEIGHT DEPENDENCE OF INTRAMACROMOLECULAR END-TO-END PHOTODIMERIZATION RATE OF ALPHA,OMEGA-DIANTHRYL-POLYSTYRENE IN DILUTE-SOLUTION

The intramacromolecular photodimerization rate of a pair of terminal groups of alpha , omega -dianthrylpolystyrene (A-PS-A) was measured for the polymers with various degrees of polymerization, N, at high dilution. The extent of intramacromolecular photodimerization of A-PS-A during continuous irradiation by a high-pressure mercury lamp was determined from the change in fluorescence intensity of the anthryl groups attached to the polymer chain ends. The apparent rate constant K//F for the polymer end-to-end cyclization of A-PS-A in benzene at 30 plus or minus 1 degree C was found to be proportional to N** minus **n with n equals 1. 4 plus or minus 0. 2 for the range of N equals 280-3000.