Rotem Horowitz, MSc Candidate Department of Materials Science and Engineering, Technion – Israel Institute of Technology, Haifa, Israel
PolyHIPEs, porous polymers with open-cell, highly interconnected pore structures are synthesized through templating within high internal phase emulsions (HIPEs), emulsions in which the internal phase occupies more than 74% of the volume. The porous structure and properties can be tailored by adjusting the HIPE composition and by modifying various synthesis parameters. PolyHIPEs synthesized within Pickering HIPEs are stabilized using nanoparticles (NPs) that can also function as centers of crosslinking and initiation. Previously, shape memory polyHIPEs (SMPHs) were synthesized using acrylate or methacrylate monomers bearing long, crystallizable, aliphatic side-chains. A temporary shape, imparted above the crystalline melt transition (Tm), was “locked in” upon quenching below the Tm. Shape memory behavior was produced by the crosslinked network returning to the original shape upon “unlocking” above the Tm. The use of HIPE-stabilizing, polymer crosslinking, surface-modified silica NPs was critical to achieving SMPHs. The objectives of this research were to develop novel families of SMPHs and to enhance the shape memory effect by varying the crystallizable monomer, the emulsification strategy (NPs, surfactant) and the cross- linking strategy (NP type, NP location) upon the macromolecular structure, porous morphology, crosslinked network, mechanical and thermal properties, and shape memory behavior. PolyHIPEs were successfully synthesized from acrylates and methacrylates with aliphatic sidechain lengths of 18 and 22. The porous structures were, for the most part, similar to those of typical SMPHs and the densities ranged from 0.13 to 0.20 g/cc. Novel HIPE stabilization moieties and polymer crosslinking moieties achieved shape recovery ratios of 100%, higher than achieved previously.
Supervisor: Prof. Michael S. Silverstein