Myers Dawes Andras & Sherman LLP
Synthesis of functional polymers and block copolymers on silicon oxide surfaces by nitroxide-mediated living free radical polymerization in vapor phase
Nitroxide mediated free radical polymerization of vaporized vinyl monomers, including acrylic acid (AAc), styrene (St), N-2-(hydroxypropyl)methacrylamide (HPMA) and N-isopropyl acrylamide (NIPAAm), on silicon wafers is demonstrated. FTIR, ellipsometry and contact angle goniometry were used to characterize the chemical structures, thickness and hydrophilicity of the films. The growth of film is linearly proportional to its reaction time, leading to the easy and exact control of polymer film thickness from nanometers to submicrons. The capability of polymerizing various monomers allows us to fabricate various functional polymer brushes. The reversible thermo-responsiveness of a 200 nm thick grafted poly(NIPAAm) film in aqueous solution is demonstrated with over 50% change in thickness at its lower critical solution temperature. A tri-block copolymer of poly(AAc)-b-polySt-b-poly(HPMA) is successfully synthesized, proving the renewability of TEMPO-mediated polymerization at vapor phase. Surface polymer composition and morphology is thus controlled at nanoscale by utilizing vapor phase surface-initiated controlled polymerization.
The Regents of the University of California
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Ying Chih Jun Xiaoru
Chang Li Chen