Synergist Immobilization Method for Photo-Grafting: Factors Affecting Surface Selectivity

摘要

The surface-selectivity of photo-grafting has been used as a crucial parameter to evaluate the grafting-from efficiency of the synergist immobilization method developed in our recent work. The factors that affect surface-selectivity of photo-grafting have been further investigated. It was shown that the competition of solvent with the membrane surface towards the generation of starter radicals led to a decrease in the degree of grafting and surface-selectivity of photo-grafting. High UV intensity made the functionalization mechanism more complicated, due to the generation of a new type of starter radical at the membrane surface with immobilized synergist in the absence of BP and because it could lead to cross-linking in the grafted layer. An appropriately low photo-initiator concentration was also required in order to achieve the ideal surface-selectivity of photo-grafting. In addition, this method has been successfully applied to the track-etched PET membranes. Pore size distributions as well as ethanol and water permeability of the membranes were used to retrieve information about the effective thickness of the grafted polymer layers.