Network formation and swelling behavior of photosensitive poly(vinyl alcohol) gels prepared by photogenerated crosslinking

Abstract

Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained.The proportion of the free water to the bound water in PVA-SbQ gels was 3.3-2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27-0.58. The water uptake after swelling of the gels in water increased 6-27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D , were (2.2-5.8)xlO-~cm2s-~ for a 88% saponified PVA with 1.3 mol% SbQ groups. The volume of the gel increased discontinuously about 10-fold for the 99% saponified PVA with 0.096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.-Poster presented at the "

Photo-Cross-Linkable PNIPAAm Copolymers. 1. Synthesis and Characterization of Constrained Temperature-Responsive Hydrogel Layers

“…Photo-cross-linking of thin films of hydrophilic polymers is a convenient pathway to the preparation of network layers with micrometer dimensions. This technique has been utilized in various applications like paint, printing, adhesives, dental materials, and photoresists. − Recent interest has been expanded to the fields of surface chemistry modifications and biotechnology. , Most of the photo-cross-linkable polymer systems have been based on poly(vinyl alcohol) − or polyacrylamide and its derivatives. , Despite significant development in the photo-cross-linking of hydrophilic polymers, there have been few reports on the preparation of smart hydrogels. − …”

“…The cross-linking reaction has been performed by photodimerization of chromophores like cinnamoyl, , coumaroyl, and stilbene derivatives ,,, or by decomposition of phenylazido groups. − However, these substituents are all hydrophobic, and when incorporated in a temperature-sensitive polymer, they produce a strong decrease in the phase transition temperature ( T c ). , With a stilbazolium salt as the chromophore and a chromophore content of 3 wt %, a T c below room temperature was obtained . It has been known for several years that N -substituted dimethylmaleimides undergo [2 + 2] cycloadditions with exposure to light, and polymers with pendant dimethylmaleimide (DMI) groups have been used in a variety of photopolymer applications .…”

“…[7][8][9] Recent interest has been expanded to the fields of surface chemistry modifications 10 and biotechnology. 11,12 Most of the photo-cross-linkable polymer systems have been based on poly(vinyl alcohol) [13][14][15][16] or polyacrylamide and its derivatives. 11,17 Despite significant development in the photo-cross-linking of hydrophilic polymers, there have been few reports on the preparation of smart hydrogels.…”

Preparation and properties of thin films of photocrosslinkable hydrophilic polymers

“…Most of the photochemical crosslinking reactions occur via cycloaddition reactions of photofunctional groups under UV irradiation. Cinnamoyl [19], coumarin [20,21], and styrylpyridinium (stilbazolium) [22][23][24][25][26] chromophores have been successfully employed as photochemically reactive pendant groups.…”

Mikrophasenseparation von photo-vernetzbaren Blockcopolymeren in dünnen Filmen

“…Styrylpyridinium-Salze,133,134 die Dimethylmaleinimid-Gruppe135,136 und die Coumarin-Derivate. 127 Für die Vernetzung verwendet man im Allgemeinen Licht im UV-und sichtbaren Spektralbereich von 250 bis 450 nm.…”