(5aj) Novel Fabrication Methods for the Production of Polymer Films: Initiated Chemical Vapor Deposition and Templated Formation of Ionotropic Gels Using Patterned Paper

This poster will describe two methods for the production of polymer films. My graduate work at MIT focused on the use of initiated chemical vapor deposition (iCVD) to make a wide variety of polymer coatings such as poly(2-(perfluoroalkyl)ethyl methacrylate) (hydrophobic) [1], poly(glycidyl methacrylate) (adhesive) [2], and poly(furfuryl methacrylate) (?click chemistry?) [3]. Vapor deposition has the environmental benefit of using no solvents and the process can be used to conformally coat substrates with complex geometries such as fabrics and wires since there are no surface tension problems. Deposition rates as high as 300 nm/min can be achieved. The proposed polymerization mechanism is the classical free radical polymerization mechanism of vinyl monomers. Monomer and initiator gases are fed into a vacuum chamber where resistively heated wires are used to thermally decompose the initiator molecules into free radicals. The free radicals then attack the vinyl bonds of the monomer molecules. Propagation occurs on the surface of a cooled substrate. We have demonstrated that the iCVD process can be used to modify the surfaces of high-aspect-ratio (~100) polymeric membranes [4] and electrospun fiber mats [5, 6].

My postdoctoral work in the Whitesides group at Harvard focuses on the use of paper templates to fabricate shaped films of ionotropic hydrogels [7,8]. Solutions of polymers such as alginic acid, carrageenan, and carboxymethyl cellulose form films with defined shapes when brought into contact with patterned templates of paper wetted with aqueous solutions of multivalent cations. This method allows the production of topographically and topologically complex 3D shapes, such as interlocking rings and Möbius strips. The shaped films can be made magnetically responsive by using paramagnetic ions like holmium as the cross-linking ions or by suspending ferrite microparticles in the hydrogels. Heterogeneous films of ionotropic hydrogels can be fabricated through the use of multiple templates. These heterogeneous structures include single films where a pattern of one hydrogel is surrounded by another hydrogel (?gel-in-gel? structures), multilayered hydrogels, and hydrogels that contain a gradient in the concentration of cross-linking agent.

Relevant Publications:

[1] Gupta, M.; Gleason, K. K. ?Mechanistic Study of the Initiated Chemical Vapor Deposition (iCVD) of Poly(1H,1H,2H,2H-Perfluorodecyl Acrylate) (PPFDA) Thin Films?, Langmuir, 22, 10047, 2006.

[2] Gupta, M.; Gleason, K. K. ?Large Scale Initiated Chemical Vapor Deposition of Poly(glycidyl methacrylate) Thin Films?, Thin Solid Films, 515, 1579, 2006.

[3] Chen, G.; Gupta, M.; Chan, K.; Gleason, K. K., ?Initiated Chemical Vapor Deposition of Poly(Furfuryl Methacrylate)?, Macromolecular Rapid Communications, 28, 2205, 2007.

[4] Gupta, M.; Kapur, V.; Pinkerton, N. M.; Gleason, K. K. ?Surface Modification of High Aspect Ratio Pores and Surface Features by initiated Chemical Vapor Deposition (iCVD)?, Chemistry of Materials, 20, 1646?1651, 2008.

[5] Ma, M.; Gupta, M.; Li, Z.; Zhai, L.; Gleason, K. K.; Cohen, R. E;. Rubner, M.F.; Rutledge. G. C. ?Superhydrophobic fabrics produced by electrospinning and chemical vapor deposition?, Advanced Materials, 19, 255, 2007.

[6] Ma, M.; Mao, Y.; Gupta, M.; Gleason, K. K.; Rutledge. G. C.?Superhydrophobic fabrics produced by electrospinning and chemical vapor deposition?, Macromolecules, 38, 9742, 2005.

[7] Bracher, P. J.; Gupta, M.; Whitesides, G. M. ?Shaped Films of Ionotropic Hydrogels Fabricated Using Templates of Patterned Paper?, Advanced Materials, submitted.

[8] Gupta, M.; Bracher, P. J.; Whitesides, G. M. ?Heterogeneous Films of Ionotropic Hydrogels Fabricated Using Paper Substrates?, in preparation.