Radiation‐induced GMA/DMAA graft copolymerization onto porous PE hollow‐fiber membrane

Abstract

Radiation-induced graft copolymerization is a powerful technique to prepare a grafted chain with the desired properties pending onto the trunk material. In this work, a polyethylene hollow-fiber membrane was modified by this technique. The monomers glycidyl methacrylate (GMA) and N,N-dimethylacrylamide (DMAA) were cografted onto macroporous polyethylene hollow fiber with a grafting degree in the order of 200%. DMAA/GMA cografted membranes were compared to GMA grafted ones for the introduction of an amino acid as a specific ligand. Grafted membranes with a copolymer composition between 0 and 2 DMAA/GMA were prepared by soaking them in solutions of different mixtures of monomers. Copolymers were characterized by FTIR and their composition was estimated by the analysis of the ratio of carbonyl signals. Copolymers with a higher proportion of DMAA showed improved hydrophilic properties and higher conversion rates of epoxy groups on phenyalanine ligands than those of the GMA grafted ones. However, copolymers with a DMAA/GMA ratio higher than 1 showed a detrimental effect on the pure water flux.

Improved hollow-fibre membranes for dye-affinity chromatography

“…The polymerisation step brings about an increase of 27 to 35% in the unmodified membrane weight. The results in Table 1 indicate that the degree of grafting becomes higher as the proportion of DMAA in the monomer mixture increases; however, it was reported that such a difference in the degree of grafting does not play an important role in the subsequent coupling steps [10]. Those mass add-in quantities spread on a high internal surface area (15 m 2 /g, dry weight), thus effecting only a minimum change in the internal pore diameter.…”

“…Well-resolved carbonyl IR signal areas at 1600 -1665 cm -1 and 1700 -1765 cm -1 corresponding to DMAA and GMA respectively were used to estimate the copolymer composition. A calibration curve correlating the ratio of carbonyl IR signal areas and known monomer mixtures was previously performed as described in reference [10]. We assumed the carbonyl IR signal ratio of the monomer mixture samples and the carbonyl IR signal ratio of the grafted copolymer samples to be similar.…”

“…The monomer composition of the polymer layer in polyethylene membranes could be determined from its infrared spectrum [10]. However, in this case the complex adsorption bands of polysulfone interfere with the monomer carbonyl signals used previously to evaluate the polymer composition grafted onto polyethylene membranes.…”

“…GMA and different GMA : DMAA mixtures were used to obtain cografted copolymers with different hydrophilicity degrees. Grafted polymers have increasing degrees of hydrophilicity as the proportion of DMAA increases, thus meaning a deeper layer in an aqueous environment [10]. In order to further increase the hydrophilic character of the grafted polymer, a number of membranes were grafted with the most hydrophilic monomer mixture (GMA : DMAA = 1 : 3) and the epoxy groups were made to react with glucamine instead of ammonia.…”

“…However, in this case the complex adsorption bands of polysulfone interfere with the monomer carbonyl signals used previously to evaluate the polymer composition grafted onto polyethylene membranes. Thus, the monomer composition of the copolymer layer was estimated from its infrared spectrum as previously described [10]. The strong absorption and well resolved IR signals of carbonyl groups of both monomers allow straightforward estimation of the monomer ratio on the grafted copolymer.…”