Dynamic Optical Gratings Accessed by Reversible Shape Memory.

Shape memory polymers (SMPs) have been shown to accurately replicate photonic structures that produce tunable optical responses, but in practice, these responses are limited by the irreversibility of conventional shape memory processes. Here, we report the intensity modulation of a diffraction grating utilizing two-way reversible shape changes. Reversible shifting of the grating height was accomplished through partial melting and recrystallization of semicrystalline poly(octylene adipate).

Grafting Poly(OEGMA) Brushes from a Shape Memory Elastomer and Subsequent Wrinkling Behavior.

An azide-functionalized shape memory elastomer, poly(octylene diazoadipate-co-octylene adipate), has been grafted with poly(oligoethylene glycol) methacrylate (poly(OEGMA)) brushes via aqueous ARGET (activators regenerated by electron transfer) ATRP. Sequential swelling of the substrate followed by a grafting-from reaction yielded an incompressible brush layer on the shape-memory substrate. Upon heating the substrate above the Tm to return to the primary shape, uniaxial wrinkles perpendicular to the direction of strain with sizes of 27-33 μm appear in addition to micrometer-sized features formed on the temporary shape after grafting.

Shape memory particles capable of controlled geometric and chemical asymmetry made from aliphatic polyesters.

A novel method for producing monodisperse micro- and nanosized shape memory particles from various shape memory polymers (SMPs) is reported. This method uses a polydimethylsiloxane mold to uniformly deform particles from complex shapes to other well-defined shapes, harvest them without aggressive solvents or heat, and then return them to their original shapes upon heating above a preselected trigger temperature. By manipulating the material properties of both the mold and SMP, monodisperse asymmetric particles are easily achieved.

Switchable micropatterned surface topographies mediated by reversible shape memory.

Reversibly switching topography on micrometer length scales greatly expands the functionality of stimuli-responsive substrates. Here we report the first usage of reversible shape memory for the actuation of two-way transitions between microscopically patterned substrates, resulting in corresponding modulations of the wetting properties. Reversible switching of the surface topography is achieved through partial melting and recrystallization of a semi-crystalline polyester embossed with microscopic features.

It is the outside that counts: chemical and physical control of dynamic surfaces.

Materials capable of dynamically controlling surface chemistry and topography are highly desirable. We have designed a system that is uniquely able to remotely control the presented functionality and geometry at a given time by using a functionalizable shape memory material. This was accomplished by incorporating controlled amounts of an azide-containing monomer into a shape memory polymeric material.

Synthesis, crystal structures, and electronic properties of nonlinear fused thienoacene semiconductors.

Two fused thienoacene compounds with two-dimensional ring connectivity were synthesized, and their semiconducting properties were characterized. Both compounds have a crystal structure comprised of herringbone arrays of tight π-π stacks. Strong π-π interactions lead to self-assembly into well-defined crystalline thin films from the vapor phase for both compounds.