Membranes prepared from keratin–polyacrylonitrile graft copolymers

Abstract

SynopsisGraft copolymerization of acrylonitrile onto a soluble wool keratin derivative was studied with the reduced and carboxymethylated low-sulfur protein fraction from wool. Copolymerization was carried out under a variety of conditions with a redox system of ( N H~)~S~O B -N~~S O~ in 60% (w/w) aqueous ZnCl2 solution at 10°C. Monomer conversions higher than 90% were obtained by the stepwise addition of initiator. The graft products were successfully separated into grafted copolymer and homopolyacrylonitrile (PAN) by fractional precipitation or solvent extraction with DMF. Grafted PAN were isolated by acid hydrolysis of the keratin backbone. Characterization of grafted and homo-PAN was carried out by IR spectroscopy, amino acid endgroup analysis, and viscometry. On the basis of the results, effects of polymerization conditions on grafting parameters were discussed. Membranes were prepared from 60% aqueous ZnCl2 solution by using ice-cold water as the regenerating medium. All the membranes formed from the graft products were transparent. Observation by scanning electron microscopy showed that the surface consisted of rather spherical keratin domains regularly distributed in the PAN matrix. Selective hydrolysis of the keratin domains allowed a new type of porous PAN membrane to be obtained, with the inner walls of the pores being charged with amino acid residues attached to PAN chains as the endgroup.

Keratin Associations with Synthetic, Biosynthetic and Natural Polymers: An Extensive Review

“…Concerning the association between keratin and PAM or PAN, Schaller et al [147] described the preparation of composite membranes composed of Merino wool keratin and PAN, by graft polymerization of acrylonitrile (AN) onto a soluble keratin derivative. The authors, unfortunately, did not present any water adsorption data or thermomechanical characterization of the obtained composites [147].…”

“…Concerning the association between keratin and PAM or PAN, Schaller et al [147] described the preparation of composite membranes composed of Merino wool keratin and PAN, by graft polymerization of acrylonitrile (AN) onto a soluble keratin derivative. The authors, unfortunately, did not present any water adsorption data or thermomechanical characterization of the obtained composites [147]. On the other hand, Samal et al performed the graft polymerization of acrylamide (AM) onto wool fibres and observed water adsorption, and the mechanical properties (both max load and strain) increased proportionally the grafting, whilst thermal properties had the opposite behaviour (proportional decrease with increasing grafting) [148].…”

Alkali resistance of a casein‐acrylonitrile graft copolymer fiber

“…A lot of studies have been focused on the combination of acrylonitrile‐based polymers and natural polymers. The strategies reported are mainly classfied into two ways: (a) graft‐polymerization of acrylonitrile onto casein,1–7 silk fibroin,8–10 wool keratin,11, 12 soybean protein,13, 14 gelatin15 etc., and (b) blending of ployacrylonitrile and silk fibroin,16–18 chitosan and its derivative 19–22…”

Overview of Protein‐Based Biopolymers for Biomedical Application

“…Functional molecules can be loaded on the keratin using thiol–ene click chemistry reactions . Schaller et al demonstrated the grafting of polyacrylonitrile on keratin surface which also shows that the keratin functional groups are readily available (after the reduction of disulfide bond) for further modifications …”