Benlian Wang

On the intermolecular crosslinking of PVA chains in an aqueous solution by γ-ray irradiation

Abstract We studied how the polymer chains of poly(vinyl alcohol)(PVA) are crosslinked in its O 2 -free aqueous solution by γ -rays. The static–dynamic laser light scattering method was employed for determining the molecular weight ( M w ), hydrodynamic radius ( R h ) and radius of gyration ( R g ) for the original PVA ( M w =1.0×10 5 ) and its radiation products. The γ -ray irradiation from Co 60 to the PVA solutions with different concentrations was performed at different dose levels. It was found that both molar mass and size (i.e., R g and R h ) of the radiation products increased with a dose increase. The magnitude of these increases was enhanced by decreasing the polymer concentration ( C p ). In particular, at C p C p using the dose curves of M w . It became apparent that, regardless of C p , the intermolecular crosslinking reactions were dominant in the initial stage of irradiation. The radiation yield of intermolecular crosslinking was found to increase linearly when increasing C p , and at C p > the overlap concentration it asymptotically approached a limiting value estimated from the dimerization of pentane-2,4-diol as a model compound of PVA.

The influence of polymer concentration on the radiation-chemical yield of intermolecular crosslinking of poly(vinyl alcohol) by γ-rays in deoxygenated aqueous solution

Abstract The effect of polymer concentration on G value of intermolecular crosslinking of poly(vinyl alcohol) (PVA) during γ-ray irradiation is reported here. The G value, determined by the measurement of weight average molecular weight (Mw) from static light scattering, increased initially due to the polymer concentration and approached a maximum value of 0.5 × 10−7 mol J−1. It then markedly decreased for the more concentrated water-swollen PVA film (polymer concentration Cp>300 g dm−3). Our results suggest that polymer concentration plays an important role in the crosslinking and degradation reactions of PVA during γ-ray irradiation.

Viscometric, light scattering, and size‐exclusion chromatography studies on the structural changes of aqueous poly(vinyl alcohol) induced by γ‐ray irradiation

The crosslinking processes of aqueous poly(vinyl alcohol) (PVA) by γ-ray irradiation were studied by viscometry, dynamic and static light scattering (DLS and SLS), as well as size exclusion chromatography (SEC). Increases in the intrinsic viscosity ([η]), molecular weight (Mw), hydrodynamic radius (Rh), and radius of gyration (Rg), and a decrease in second virial coefficient (A2) were observed after γ-ray irradiation. However, both the values of [η] and A2 for irradiated PVA fell below the data of unirradiated PVA solutions, suggesting a conformational change of PVA chains after γ-ray irradiation. This structural change of PVA as a result of γ-ray irradiation was also indicated by the decreases in Rg/Rh from 1.5 to 1.39 by SLS and DLS, and in Mark–Houwink exponent αη from 0.54 to 0.26 by SEC-Viscometry. The broadening of the Mw distribution (MWD) as indicated by the polydispersity index increased from 2.2 to 6.5 because of γ-ray irradiation.

PVA Hydrogel as an Artificial Vitreous Body

This research goal is to explore biocompatible and extremely transparent artificial vitreous body, using poly (vinyl alcohol) (PVA) hydrogel. PVA of degree of polymerization (DP) 2,000 and DP 8,000 in aqueous solution were irradiated by gamma-ray to form hydrogels. These hydrogels were characterized by viscosity and dynamic light scattering to check about degradation and polymerization process. In vitro, the activity of Chemotaxis of PVA hydrogel is almost same as that of silicone. PVA hydrogels were implanted into vitreous bodies of rabbits. No abnormality was histologically observed in cornea, lens and vitreous body, except some damage to injection areas in a few cases. No inflammatory reaction was observed between PVA hydrogels and native vitreous body. The postoperative intraocular pressure (IOP) was maintained within 8 mmHg higher than before operation. PVA hydrogel seems to have good biocompatibility for clinical usage.