Photochemical Attachment of Reactive Cross-Linked Polymer Films to Si/SiO₂ Surfaces and Subsequent Polymer Brush Growth

Abstract

Thin films consisting of a mixture of acrylate/methacrylate monomers were photochemically attached to modified silicon wafer surfaces. Reactive functionality was embedded into the photopolymer film by adding alkoxyamine monomers (inimers) that facilitate polymer brush growth in subsequent polymerization reactions. We present a careful examination of each of the steps, from substrate preparation to silane coupling agent coating, photopolymer attachment, and polymer brush growth. Several 3-methacryloxypropyl silanes were evaluated as silane coupling reagents. The surface roughness of wafers increased from 0.2 to 0.6 nm after treatment with silane. Curing of a thin photopolymer film did not increase the surface roughness. Interestingly, brushes of d8 polystyrene grown from the photopolymer surface displayed half the roughness of the underlying polymer layer, displaying a smoothing effect. All photopolymer films attached to the wafers utilizing a silane layer had excellent adhesion. We studied the film surfaces by water contact angle measurements, atomic force microscopy, and IR and X-ray photoelectron spectroscopies.

Study of surface modification of nano-SiO2 with macromolecular coupling agent (LMPB-g-MAH)

“…This indicates that the surface group of nano-SiO 2 has changed from Si-OH to Si-O-C. This proves that the macromolecular coupling agents are tightly absorbed at the surface of nano-SiO 2 by chemisorption, which are still existed on the surface of the modified particles even after being extracted by Soxhlets extractor among dimethylbenzene [30,1].…”

Poly(N‐isopropylacrylamide) Brush Fabricated by Surface‐Initiated Photopolymerization and its Response to Temperature

“…But their use is limited in exhibiting complex spatial distributions on surfaces such as gradients, and surface‐initiated living polymerization involves deposition of thiol‐ or silane‐terminated initiators 15. So a more effective and convenient technique based on surface‐initiated photopolymerization has attracted more interest16–19 which provides distinct advantages, such as a tolerance for moisture and a wide application to a variety of organic functional groups 20. Photochemical initiation also has advantages of low cost of operation and of potentially reducing or even avoiding negative effects on the bulk polymer 21.…”

One‐Step Growth of ca. 2–15 nm Polymer Thin Films on Hydrogen‐Terminated Silicon

“…The incorporation of some crosslinking in adsorbed polymer films through crosslinkers should increase their chemical stability. A similar idea was recently employed by Carter and coworkers, who immobilized a methacrylate‐terminated silane onto silicon oxide substrates and then showed surface polymer attachment during UV initiated solution polymerization 31. The one‐step method for growing polymers on hydrogen‐terminated silicon surfaces shown here appears to provide a simple, inexpensive way to covalently modify silicon wafers with tailored polymers produced from a variety of known monomers.…”