Controlled Swelling of Poly(hydroxyethyl methacrylate) Hydrogels by Photochemical Grafting of Hydrophobic Acrylates

✍ Scribed by Rozenn Campan; Frédéric Cazaux; Xavier Coqueret

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 123 KB
• Volume: 287
• Category: Article
• ISSN: 1438-7492
• DOI: 10.1002/mame.200290026

✦ Synopsis

Abstract

The photochemically induced grafting polymerization of various alkyl acrylates onto cross‐linked poly(hydroxyethyl methacrylate) (PHEMA) was performed to reduce the hydrophilicity of the swellable network. Butyl, 2‐ethylhexyl and lauryl acrylate were used as monofunctional monomers for increasing the hydrophobic character, whereas hexanediol diacrylate was used as a multifunctional monomer with the additional feature of forming networks. The various steps of the grafting procedure were examined sequentially so as to optimize the overall hydrophobing effect. The grafting yield was shown to depend primarily of PHEMA swelling in the considered ethanol/monomer mixture. In spite of their high specific hydrophobic character, alkyl monoacrylates were shown to be less efficient because of lower grafting yield. Grafting initiation by hydrogen abstraction with benzophenone or by homolytic cleavage of a hydroxyalkyl‐phenone resulted in comparable grafting yields even with monofunctional monomers. The hardness measured for the water swollen rubbery materials correlated well to the equilibrium water content.

Shore A hardness as a function of the swelling ratio in water at T = 22 °C for grafted and ungrafted PHEMA hydrogels (same samples as those described in Table 5).

magnified imageShore A hardness as a function of the swelling ratio in water at T = 22 °C for grafted and ungrafted PHEMA hydrogels (same samples as those described in Table 5).