Poly(N-vinyl imidazole) hydrogels polymerized in molds of different materials

Abstract

Hydrogels of N-vinylimidazole are polymerized in molds of different materials (acidic glass, basic glass, silanized glass, nylon, Teflon, pvc) to study the influence of the material on the gel properties. Molds are cylinders of very narrow diameter (2-8 mm) to enhance the influence of the wall. Confocal microscopy, glass transition, and degree of swelling are used to characterize the gels. A border with more dense polymer is formed close to the wall in all the materials. The hydrogels obtained in Teflon and pvc have higher glass transition, higher degree of swelling, and higher density of cross-links than the gels obtained in glass. Also, the reaction yield is lower in Teflon and pvc than in glass. For the narrower molds, the gels swell more in the direction normal to the wall than in the direction parallel to the wall, and this departure from isotropy is more noticeable in Teflon and pvc than in glass.