Polymerization kinetics of pseudocrown ether network formation for facilitated transport membranes

Pseudocrown ethers were synthesized from the photopolymerization of metal c omplexes of poly(ethylene glycol 200) diacrylates (PEGB200DA) to yield poly meric networks that can be used in facilitated transport membranes. Metal i ons that potentially could be used as molecular templates were screened by first characterizing the polymerization of hydroxyethyl methacrylate (HEMA) in the presence of the metal salts. Thermal polymerizations and phot,polym erizations were used to elucidate which metals adversely effect the polymer ization reaction via radical scavenging, chain transfer, light absorption, and other side reactions. HEMA polymerizations were used to investigate the se effects because only linear polymers can form, and there will be no rate effects from cyclization. Photopolymerizations of templated PEG200DA exhib ited a decrease in autoacceleration as an indication of pseudocrown ether f ormation due to the reduction in the degree of cross-linking with cyclizati on. Four metal salts, Co(NO3)(2). 6H(2)O, Ni(NO3)(2).6H2O, Zn(NO3)(2). 6H(2 )O, and Cd(NO3)(2). 4H(2)O, were found to make suitable templating ions. Al though Cu(NO3)(2).(2.5)H2O and CrCl3. 6H(2)O formed appropriate complexes w ith PEG200DA, these metals act as radical scavengers and did not permit the desired polymerization. The peak rate was decreased up to 69% for the part ially dried Co(II)/PEG200DA complex at a metal concentration of 1.27 M. Fac ilitated transport membranes exhibited a selectivity of 1.3 for potassium o ver sodium and 27.5 for potassium over neodymium, and a benchmark compariso n was made to an analogous polymer inclusion membrane that contained dibenz o-18-crown-6 as the carrier which had similar selectivities.