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Thesis (Ph. D.)--University of Rochester. Dept. of Chemical Engineering, 2015.
Macro-porous polymers are most commonly prepared by solution- or melt-phase
methods including polymerization induced phase separation (PIPS), thermal induced
phase separation (TIPS) and other phase inversion techniques. While these techniques
have achieved exquisite control of pore size and porosity and are advancing technologies
related to membranes for separations, drug delivery, and cellular scaffolding of tissues or
implants, it remains challenging to form porous polymer as highly conformal layers or to
deposit precise amounts of porous polymer onto targeted areas.
This thesis develops multi-component vapor deposition polymerization (VDP)
techniques that force phase separation of as-deposited species, while, at the same time,
reactive polymerization is occurring, leading to kinetically trapped macro-scale structure
and morphology. It shows that rapid film growth rates can be achieved by initiated
chemical vapor deposition (iCVD) of poly(glycidyl methacrylate) from supersaturated
monomer vapor. Further, template-free methods were applied to fabricate continuousphase,
porous polymer films by simultaneous phase separation during vapor deposition
polymerization. To further understand the process, the degree of interaction between
condensed species was systematically varied and experiments were conducted using three
different porogens with different cohesive energy densities. Experiments show that the
morphology and porosity of the as-deposited polymer thin films depend on deposition
rate, crosslinker density, the mass transfer mobilities of phase-separating species, and the
interaction energies between species.
Chemical crosslinking around condensed porogen during vapor deposition
polymerization offers morphological control of porous polymer within thin, conformal
layers. In principle, this strategy could be translated to line-of-sight vapor deposition
methods, enabling porous polymer to be grown through a pattern mask, or even directly
onto part’s surface. The ability to control solid/ porous membrane growth and feature size
is relevant to the future work including laser fusion targets fabrication, stimuli-responsive
porous hydrogel thin films, and multi-stimuli responsive polymers.
