Surface-selective photo-grafting on porous polymer membranes via a synergist immobilization method.
A novel synergist immobilization photo-graft polymn. method was developed to functionalize polymer materials in polar org. solns. This two-step method, based on the immobilization of tertiary amine groups as synergists for the photoinitiator benzophenone (BP), was evaluated for com. hydrophilized polypropylene (PP) microfiltration membranes. The hydrophilization of the PP membrane was due to a thin layer of a polyacrylate, and reaction conditions for the introduction of tertiary amino groups via an aminolysis reaction with N,N-diethylethylenediamine was optimized. Compared with the original membrane, aminolyzed membranes demonstrated high surface-selectivity for photo-grafting of polyacrylamide from methanol soln. The grafting d. and polymer chain length can be well controlled by adjusting the main functionalization parameters (synergist surface concn., BP concn., UV irradn. time and monomer concn.). The mechanism was analyzed based on the effects of the main functionalization parameters mentioned above. The membrane pore structure was verified to be well maintained based on SEM analyses, the pore size distribution and water permeability of the membranes. The primary functionalization via aminolysis should be applicable to all polymers with ester groups on their surfaces. Via the synergist immobilization method numerous monomers which are sol. in org. solvents can be effectively grafted onto polymer surfaces for various tailored functionalizations.
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