Chemical modification of the surface of poly(dimethylsiloxane) by atom-transfer radical polymerization of acrylamide

The chemical modification of the surface of poly(dimethylsiloxane) (PDMS), which was made using Sylgard 184 with polyacrylamide by atom-transfer radical polymerization (ATRP), was investigated by using Fourier transform infrared (FTIR) spectroscopy to characterize the functional groups on the surface. A UV-ozone plasma generator was used to oxidize the surface of the PDMS for time periods ranging from 2 to 30 min. The resulting silanol groups were reacted with a gaseous trichlorosilane bearing an initiator for atom-transfer radical polymerization, (1-trichlorosilyl-2-m-p-cMoromethylphenyl)ethane, and subsequent atom-transfer radical polymerization with acrylamide was carried out in water. Damage to the material became evident after 30 min. Attenuated total internal reflectance FTIR showed that the amount of polyacrylamide bound to the surface reached a maximum after 15 min of oxidation, suggesting that the surface silanols reached a maximum concentration at this time. The surface exhibited a 20-fold improvement in resisting irreversible adsorption of lysozyme, compared to bare PDMS, and a 10-fold improvement compared to bare glass. Unlike oxidized PDMS, which reverts fully to being hydrophobic after 2 days, the contact angle of the surface treated by ATRP of acrylamide was shown to remain hydrophilic for at least, 1 month.