A route to produce novel three-dimensional structures in thin films is demonstrated. Such structures are most difficult to produce in a simple manner without the use of multiple fabrication steps. Here, we show the generation of 3-D cage-type structures using a combination of electrohydrodynamic instabilities and dewetting in a polymer/polymer/air trilayer. Removal of one of the components by use of a selective solvent or by degradation of one of the components reveals the formation of a three-dimensional structure, where one polymer is encased in the other. Thus, by coupling an external field with a surface field inherent to the polymers, a novel fabrication strategy is shown that has clear applications in microfluidics and microelectromechanical systems with extensions to patterned surfaces and structured fluids, like block copolymers.

Low viscosity, photocurable liquids are demonstrated as ideal materials for the formation of pillar arrays generated spontaneously by field-assisted assembly. Pillars form spontaneously via electrohydrodynamic instabilities that arise from the force imbalance at a film−air interface generated by an applied electric field. Conventional polymer films form pillars slowly as a result of their relatively large viscosities and are often process-limited by a requirement of heat to modulate rheological properties. In contrast, low viscosity liquids require no heat and form pillars orders of magnitude faster, as predicted by theory. The resulting structures are preserved by photopolymerization, eliminating the lengthy heating−cooling cycle necessary to process most polymers. The combination of nearly instantaneous formation and rapid photocuring at room temperature is ideal for patterning. Epoxy, vinyl ether, acrylate, and thiol-ene systems were evaluated for pillar formation. Relevant material properties were characterized (viscosity, dielectric constant, interfacial energy, kinetics) to explain the phenomenological behavior of each system during electrohydrodynamic patterning. The thiol-ene system formed pillar arrays nearly instantaneously and cured rapidly under ambient conditions. These are nearly ideal characteristics for pillar formation.

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The mechanical performance of thermoplastic elastomeric polyurethanes (PUs) before and after hydrolysis is investigated. These new PUs were prepared with a new asymmetric polyisobutylene-diol (PIB-diol), without the use of solvents, and with short reaction times. The PUs were made with dicyclohexylmethane 4,4′-diisocyanate and 1,4-butanediol in the hard segments and poly(hexamethylene carbonate) (PC)-diol and polyisobutylene (PIB)-diol in the soft segments. The functionality of PIB-diol was verified by mass spectrometry. Optimum solventless synthesis conditions and performance were found with a mixture of 50/50 PIB-diol/PC-diol (28.9 wt% PIB in the PU). This PU had 26.03 ± 1.19 MPa tensile strength with 286.92 ± 12.17% elongation before and 16.22 ± 0.65 with 301.17 ± 15.08% elongation after American Society for Testing and Materials (ASTM) hydrolytic stability testing. Importantly, after the hydrolytic stability testing, the stress–strain plot of this PIB–PU was similar to that of the control PC–PU. The PU with 70/30 PIB-diol/PC-diol (41.2 wt% PIB in the PU) performed slightly better but needed solvent during synthesis because of the high viscosity of the mixtures.