Kinetic simulation, network analysis, and biomedical applications of PEG-containing network polymers synthesized from free -radical polymerizations
Abstract
Design of novel biomaterials for applications in biological recognition, drug delivery, or diagnostics requires a judicious choice of preparation conditions and methods for the production of well characterized three-dimensional structures, preferably by benign processes. In this work, the polymerization of poly(ethylene glycol) (PEG) methacrylates was examined by kinetic gelation modeling and kinetic analysis in order to ascertain the factors affecting the resulting structure. The kinetics of the polymerization and the structure of the final polymer network are strongly affected by the initial monomer structure and by the presence of solute materials. The propagation of the polymer chains becomes increasingly diffusion-limited with the incorporation of longer PEG grafts. In addition, a more heterogeneous network consisting of numerous microgel regions is produced as the length of the PEG graft is increased. In an effort to afford more control of the free-radical polymerization, a “living” radical polymerization with an iniferter ( initiator-transfer agent-ter minator) was also examined. The presence of an iniferter introduces a reversible termination reaction due to the presence of a dithiocarbamate group. Kinetic gelation modeling demonstrates that the reversible termination does not alter the pendent double bond reactivity in the polymerization of multifunctional monomers. However, the kinetics of these polymerizations is affected as the rate of polymerization drastically decreases due to the reversible termination. Various parameters of the reaction may be changed to increase the rate of polymerization and the conversion. Generally, more radicals must be introduced or the diffusion of monomers increased. Finally, polymerization with an iniferter can be used to create micropatterned surfaces. Novel, photosensitive polymers are created by the incorporation of dithiocarbamate groups from iniferters. A second monomer layer is then irradiated on these photosensitive polymers to form a copolymer. Patterns are created on the films by application of modified photolithographic techniques. The technique can be used to create patterns with depths from 5 μm to 80 μm. In addition, various polymers can be incorporated, including PEG methacrylates, styrene, and methacrylic acid, to synthesize regions with different physicochemical properties. Applications include surfaces for the selective adhesion of cells and proteins.
Degree
Ph.D.
Advisors
Peppas, Purdue University.
Subject Area
Chemical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.