Liming Yang

An interesting grafting reactivity of EB preirradiated polypropylene film

Abstract An interesting grafting reactivity of electron beam preirradiated polypropylene (PP) film was found by grafting of acrylic acid (AAc) and acrylamide (AAm) repeatedly or intermittently. The preirradiated PP film could be grafted several times intermittently and the free radicals or peroxides on the samples could be determined after several times grafting reaction. The effects of storage time, reaction time and repeated reaction times on the degree of grafting were investigated. The trapped radicals, peroxy-radicals and peroxides on the preirradiated and reacted PP films were determined by using electron spin resonance (ESR) and 1,1-diphenyl-2-picryl hydrazyl (DPPH), respectively. An interpenetrating polymer networks (IPN) with both temperature and pH sensitive properties was obtained by two times grafting of AAm and AAc onto preirradiated PP film.

Preparation of interpenetrating polymer networks by two times grafting of monomers onto preirradiated polypropylene film

Abstract An interpenetrating polymer network (IPN) hydrogel was made by the grafting of acrylamide (AAm) and acrylic acid (AAc) onto preirradiated polypropylene (PP) film. AAm and AAc were grafted onto preirradiated PP film by two times grafting reaction. Thermo-sensitive behaviors were determined. The effect of first and second reactions on the degree of grafting was studied. Trapped radicals on samples with different storage conditions and reaction conditions were determined by electron spin resonance (ESR).

Synthesis and characterization of a pH-sensitive hydrogel made of pyruvic-acid-modified chitosan

Pyruvic-acid-type chitosan (PA-CS) was prepared by the reaction of an amine group on chitosan with a carbonyl group on pyruvic acid. Then, a novel hydrogel film was obtained via cross-linking of poly(ethylene glycol) diglycidyl ether (PEGDE) with PA-CS. 1H-NMR and FT-IR spectrometry were applied for the verification of the CS and PA-CS structure. The degree of swelling was studied by changing the molar ratio of PEGDE and PA-CS. Moreover, the swelling ratio of cross-linked membrane in different pH buffer solutions was measured. The result showed that the swelling of hydrogel exhibited obvious pH-sensitivity. The swelling ratio was higher at pH 1–4 and pH 7–12, but lower at pH 5–6.