A long-term goal is to fabricate polymer materials that degrade after a selected lifetime and that degrade at a selected rate.To achieve this goal,it is necessary to understand the mechanisms of degradation and the factors that control the rate of degradation.This talk will describe our research on the various molecular and environmental parameters that affect the rate and onset of polymer photodegradation.None of the models currently used to interpret polymer degradation can adequately describe these data so a new model was developed based on the concept of multiple environments.Using this new model,the photochemical degradation rates of polymers can be fit very accurately.