Engineering biobased interpenetrating polymer networks based on plant (soybean) oil and polysiloxanes

Interpenetrating Polymer Networks (IPNs) are materials containing two or more immiscible components that have been polymerized and crosslinked in the presence of each other to form entangled (interpenetrated) networks. The intimate mixing of such crosslinked entangled networks results in a single-phase morphology on the macro scale and leads to interesting physical properties that are different than those of the individual polymeric components. Currently, products derived from IPNs find a wide range of applications in the industry. Of particular interest here are IPNs derived from polysiloxanes with rigid polymers such as polyacrylates or polystyrene, where the silicone phase provides high flexibility, water vapor permeability and biocompatibility.;This thesis reports on studies of newly engineered biobased IPN systems based on soybean oil and polysiloxanes. The soybean oil was silylated with vinyltrimethoxy silane via the "ene reaction" chemistry to provide the necessary crosslink sites. Similarly, oligomerized soybean oil was silylated and was used to provide a more viscous, higher molecular weight oil for the IPN formation. The second component in these IPNs was either a silanol terminated polydimethylsiloxane (PDMS) or carbinol containing hydrophilic polysiloxanes. High molecular weight PDMS was prepared by emulsion polymerization of silanol terminated dimethylsiloxane oligomers. Carbinol containing hydrophilic polysiloxanes were prepared by polymerization of 3-aminopropylmethyldiethoxysilane followed by a reaction of the amines with cyclic carbonate. These hydrophilic polysiloxanes were water-soluble independent of the water pH or their molecular weight and were characterized by high degree of hydrogen bonding.;A series of IPNs were prepared containing different concentrations of silylated soybean oil and silicone polymers. Different processing methods (e.g. a latex method and a solution method) were studied and IPNs were formed by the evaporation of the water or the solvent led to stable siloxane crosslinks. Another process involved IPNs prepared by dissolving the water soluble polysiloxanes in the water phase that was used to emulsify the silylated soybean oil.;The siloxane crosslinks control the morphology and prevents gross phase separation of the soybean oil phase and the silicone phase. A model, based on Donatelli's equation was constructed to determine the crosslink density of these networks, which was then correlated with the physical properties of these IPNs. The morphology of cast films from each of these IPNs revealed an intimate mixing of the two immiscible components with no apparent gross phase separation. The crosslink density, mechanical properties, thermal properties and surface properties of all IPNs were investigated and correlated with their composition.;These IPNs can be utilized as high release liners, low friction materials or as general protective coatings. The combination of natural product with polysiloxanes makes these IPNs also suitable for various applications in cosmetics and personal care. The IPNs containing the hydrolytically susceptible siloxy crosslinks can be utilized to prepare environmentally degradable materials that can be utilized in various control release applications.