Co-reporter:Anne-Martine S. Jackson, Sergei S. Sheiko, and Valerie Sheares Ashby
Langmuir 2015 Volume 31(Issue 19) pp:5489-5494
Publication Date(Web):April 29, 2015
DOI:10.1021/la504826w
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. Swelling equilibration time (t1) and grafting reaction time (t2) were varied to control wrinkle formation and size. In this manner, we were able to create unique, anisotropic hierarchical surface structures with different length scales and patterns.
Co-reporter:Sara A. Turner, Jing Zhou, Sergei S. Sheiko, and Valerie Sheares Ashby
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 11) pp:8017
Publication Date(Web):May 13, 2014
DOI:10.1021/am501970d
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. This behavior is monitored with atomic force microscopy (AFM) and contact angle measurements. We demonstrate that the magnitude of the contact angle variations depends on the embossment pattern.Keywords: microstructured surfaces; responsive surfaces; reversible shape memory; surface topography; topological structure change;
Co-reporter:Sarah M. Brosnan;Anne-Martine S. Jackson;Yapei Wang
Macromolecular Rapid Communications 2014 Volume 35( Issue 19) pp:1653-1660
Publication Date(Web):
DOI:10.1002/marc.201400199
Co-reporter:Sarah M. Brosnan ; Andrew H. Brown
Journal of the American Chemical Society 2013 Volume 135(Issue 8) pp:3067-3072
Publication Date(Web):January 15, 2013
DOI:10.1021/ja308080g
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. These materials are capable of physically changing surface geometry over a broad range of length scales from >1 mm to 100 nm. Using copper-assisted click chemistry, they can be functionalized with a variety of molecules to yield different surfaces. Combining these features gave materials that can change both the presented geometry and functionality at tunable transition temperatures.
Co-reporter:Hayden T. Black, Afshin Dadvand, Shubin Liu, Valerie S. Ashby and Dmitrii F. Perepichka
Journal of Materials Chemistry A 2013 vol. 1(Issue 2) pp:260-267
Publication Date(Web):26 Sep 2012
DOI:10.1039/C2TC00032F
A series of oligothiophenes containing either electron withdrawing perfluorohexyl substituents or an electron deficient benzothiadiazole core, or both, were synthesized and their properties were evaluated by optical spectroscopy, cyclic voltammetry and DFT calculations. The charge transport properties of these compounds were studied in field effect transistors, revealing how the majority charge carrier is affected by the chemical substitution. Incorporation of benzothiadiazole significantly lowers the LUMO energy of the oligomers, but does not affect the HOMO. On the other hand, perfluoroalkyl groups lowered both the HOMO and LUMO, and were essential for achieving electron conductivity in this series of compounds.
Co-reporter:Duy M. Le;Michael A. Tycon;Christopher J. Fecko ;Valerie S. Ashby
Journal of Applied Polymer Science 2013 Volume 130( Issue 6) pp:4551-4557
Publication Date(Web):
DOI:10.1002/app.39604
ABSTRACT
Recently, indirect activation of the shape memory effect has become an increasingly popular triggering modality for shape memory polymer biomaterials. Amongst the known methods for remote activation, near-infrared radiation (NIR) remains relatively unexplored, specifically for semicrystalline materials, which possess sharp thermal transitions. Herein, poly(ε-caprolactone) (PCL) networks were photo-polymerized from branched precursors doped with 150 nm surface modified gold nanoshells with a surface plasmon resonance of approximately 800 nm. The effect of nanoparticle loading on the thermal, mechanical, and shape memory properties of the PCL matrix were examined. The PCL nanocomposites exhibited excellent shape fixation and nearly quantitative shape memory recovery in response to low intensity NIR irradiation. Further, the heat dissipated by the irradiated nanocomposites to the surrounding medium was found to reach a maximum at biologically relevant temperatures. As such, this nanocomposite system represents a highly attractive candidate for many biomedical shape memory applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4551–4557, 2013
Co-reporter:Duy M. Le;Karina Kulangara;Andrew F. Adler;Kam W. Leong
Advanced Materials 2011 Volume 23( Issue 29) pp:3278-3283
Publication Date(Web):
DOI:10.1002/adma.201100821
Co-reporter:Hayden T. Black, Shubin Liu, and Valerie Sheares Ashby
Organic Letters 2011 Volume 13(Issue 24) pp:6492-6495
Publication Date(Web):November 22, 2011
DOI:10.1021/ol202662s
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. Field effect transistors were fabricated, affording identical hole mobilities of 3.0 × 10–3 cm2/(V s) and Ion/off > 105.
Co-reporter:Hayden T. Black, Afshin Dadvand, Shubin Liu, Valerie S. Ashby and Dmitrii F. Perepichka
Journal of Materials Chemistry A 2013 - vol. 1(Issue 2) pp:NaN267-267
Publication Date(Web):2012/09/26
DOI:10.1039/C2TC00032F
A series of oligothiophenes containing either electron withdrawing perfluorohexyl substituents or an electron deficient benzothiadiazole core, or both, were synthesized and their properties were evaluated by optical spectroscopy, cyclic voltammetry and DFT calculations. The charge transport properties of these compounds were studied in field effect transistors, revealing how the majority charge carrier is affected by the chemical substitution. Incorporation of benzothiadiazole significantly lowers the LUMO energy of the oligomers, but does not affect the HOMO. On the other hand, perfluoroalkyl groups lowered both the HOMO and LUMO, and were essential for achieving electron conductivity in this series of compounds.
Co-reporter:Jason M. Rochette
Macromolecules () pp:
Publication Date(Web):March 8, 2013
DOI:10.1021/ma302354a
The synthesis of a library of poly(ester urethane)s (PEUs) containing pendant photoresponsive moieties afforded through the incorporation of one of two novel bifunctional monomers resulted in degradable materials with a range of tunable thermal and mechanical properties. Utilizing light irradiation, macroscopic temporary shapes were fixed by increasing the cross-link density of a thermoset network via photoinduced reversible [2 + 2] cycloaddition of cinnamamide or cinnamate pendant groups under UV light (λ = 302 nm). Further irradiation with UV light (λ = 254 nm) led to the cleaving of the temporary cross-links and recovery of the original shape. Examination of these materials under physiological conditions displayed tunable degradation with rates faster than PCL-based materials, and initial biocompatibility studies exhibited negligible cytotoxicity for HeLa cells based on results of ATP assay. The ability to tune thermal properties also allowed specific polymer compositions to boast transition temperatures within a range of applicable temperature for thermal shape memory.
![Poly[oxy(1,6-dioxo-1,6-hexanediyl)oxy-1,8-octanediyl]](http://img.cochemist.com/ccimg/32200/32146-48-8.png)
![Poly[oxy(1,6-dioxo-1,6-hexanediyl)oxy-1,8-octanediyl]](http://img.cochemist.com/ccimg/32200/32146-48-8_b.png)