Seminar: Fabrication Methods for the Production of Polymer Films

Mork Family Department of Chemical Engineering and Material Science Presents:"Fabrication Methods for the Production of Polymer Films: Initiated Chemical Vapor Deposition and
Templated Formation of Ionotropic Gels Using Patterned Paper"Malancha Gupta
Harvard University
Cambridge, MAAbstractThis talk will describe two methods for the production of polymer films. The first method focuses on the use of initiated chemical vapor deposition to make a wide variety of polymer coatings such as poly(2-(perfluoroalkyl)ethyl methacrylate), poly(glycidyl methacrylate), and poly(furfuryl methacrylate). 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 process can be used to modify the surfaces of high-aspect-ratio (~100) polymeric membranes and electrospun fiber mats.The second method focuses on the use of paper templates to fabricate shaped films of ionotropic hydrogels. 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) and hydrogels that contain a gradient in the concentration of cross-linking agent.

Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116

Audiences: Everyone Is Invited

Contact: Petra Pearce Sapir