Development of a Directly Patterned Low-Surface-Energy Polymer Brush in Supercritical Carbon Dioxide

作者：Rastogi Abhinav; Paik Marvin Y; Ober Christopher K^*

来源：ACS Applied Materials & Interfaces, 2009, 1(9): 2013-2020.

DOI：10.1021/am9003733

• direct patterning
• polymer brush
• low surface energy
• supercritical carbon dioxide
• environmentally benign
• e-beam lithography
• poly(2,2,2-trifluoroethyl methacrylate)

Carbon dioxide (CO(2)) is a sustainable solvent because it is nonflammable, exhibits a relatively low toxicity, and is naturally abundant. As a selective, nonpolar solvent, supercritical CO(2) (scCO(2)) is an ideal fit for the development of low-surface-energy polymers. The development of directly patterned poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) brushes in scCO(2) was investigated. PTFEMA, in particular, was selected over other fluorinated polymers because of its very high electron-beam (e-beam) sensitivity. PTFEMA brushes were grown on silicon substrates via controlled surface-initiated atom-transfer radical polymerization of TFEMA. Surface analysis techniques including ellipsometry, contact-angle goniometry, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy were used to characterize the thickness, hydrophilicity, roughness, and chemical composition of the polymer brushes. PTFEMA brushes were directly patterned in a single step using e-beam lithography and were processed in an environmentally benign scCO(2) solvent. Tapping-mode AFM imaging confirmed the successful e-beam patterning and development of these brushes. The sensitivity of PTFEMA brushes toward direct patterning with the e-beam, followed by scCO(2) development, was studied and compared to development in tetrahydrofuran solvent. Using this direct-patterning method, Followed by dry development in scCO(2), highly resolved nanostructured polymer brush lines down to 78 nm could be prepared. This method can be generalized to prepare fluorinated low-surface-energy polymer brush surfaces in a single step for various applications.

• 出版日期2009-9