Photolithographically Patterned Covalently Bonded Polythiophene Films using in Tandem Sol-gel, Surface Initiated Free Radical and Redox Polymerization Methods

Anand Ghanashyam Sedekar
Naveen Chandrasekaran
Sudhir Mulik
Lia Sotiriou-Leventis, Missouri University of Science and Technology
Nicholas Leventis, Missouri University of Science and Technology

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A bifunctional monomer, 3,4-bis(vinyloxy)thiophene (BVOT), that can be polymerized both by radical as well as by redox chemistry was utilized in the fabrication of lithographic patterns of conducting polymer films via a sol-gel method. The judicious use of several chemistries yields polythiophene patterns covalently bonded to substrate showing superior adhesion relative to physically bonded counterparts. The films were characterized electrically and mechanically. Surface confinement starts with a bidentate free radical initiator (Si-AIBN) synthesized via condensation reaction between 3-aminopropyltriethoxysilane (APTES) and azobiscyano-valeric acid. Si-AIBN is attached to the surface of glass by hydrolysis of the ethoxy groups and reaction with the hydroxyl groups on the class surface. Subsequently, BVOT was free-radically polymerized via the vinyl groups by surface of glass. In turn, dangling thiophene groups can in principle be polymerized oxidatively. But, as the distance and spatial orientation of the thiophene groups is such that they cannot be polymerized by their own, they were bridged by oxidative copolymerization with EDOT. This unique film-making method offers the obvious advantage of excellent adhesion are compared to the physically bonded films. In addition, crosslinking offers excellent hardness and chemical stability. In a slight twist, films were successfully patterned photolithographically showing that patterns of any desired electrical circuit can be made easily.