@article{oezcam_roskov_spontak_genzer_2012, title={Generation of functional PET microfibers through surface-initiated polymerization}, volume={22}, ISSN={["1364-5501"]}, DOI={10.1039/c2jm16017j}, abstractNote={In this study, we report on a facile and robust method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified with functional polymer brushes while avoiding chemical degradation. The surface of electrospun PET microfibers has been functionalized by growing poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) brushes through a multi-step chemical sequence that ensures retention of mechanically robust microfibers. Polymer brushes are grown via “grafting from” atom-transfer radical polymerization after activation of the PET surface with 3-aminopropyltriethoxysilane. Spectroscopic analyses confirm the expected reactions at each reaction step, as well as the ultimate growth of brushes on the PET microfibers. Post-polymerization modification reactions have likewise been conducted to further functionalize the brushes and impart surface properties of biomedical interest on the PET microfibers. Antibacterial activity and protein resistance of PET microfibers functionalized with PDMAEMA and PHEMA brushes, respectively, are demonstrated, thereby making these surface-modified PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring mechanically robust support media.}, number={12}, journal={JOURNAL OF MATERIALS CHEMISTRY}, author={Oezcam, A. Evren and Roskov, Kristen E. and Spontak, Richard J. and Genzer, Jan}, year={2012}, pages={5855–5864} }
 @article{roskov_atkinson_bronstein_spontak_2012, title={Magnetic field-induced alignment of nanoparticles in electrospun microfibers}, volume={2}, ISSN={["2046-2069"]}, DOI={10.1039/c2ra20489d}, abstractNote={We report on the facile and switchable alignment of superparamagnetic iron oxide nanoparticles measuring ∼18 nm in diameter in electrospun microfibers. Application of a magnetic field perpendicular to the electric field employed during electrospinning yields polymeric microfibers with nanoparticles aligned in one-dimensional arrays, thereby providing control over when and where the nanoparticles align. According to electron microscopy, the length over which alignment is desired can be judiciously selected, thereby making these nanomaterials excellent candidates for nanotechnologies requiring nanoscale alignment on-demand. Concurrent alignment of the electrospun fibers using established procedures provides a viable route to organic/inorganic materials possessing anisotropic properties that reflect multiscale alignment.}, number={11}, journal={RSC ADVANCES}, author={Roskov, Kristen E. and Atkinson, Jessie E. and Bronstein, Lyudmila M. and Spontak, Richard J.}, year={2012}, pages={4603–4607} }
 @article{arvidson_roskov_pate_spontak_khan_gorga_2012, title={Modification of Melt-Spun Isotactic Polypropylene and Poly(lactic acid) Bicomponent Filaments with a Premade Block Copolymer}, volume={45}, ISSN={["1520-5835"]}, DOI={10.1021/ma202246h}, abstractNote={While numerous studies have investigated the effect of adding a block copolymer as a macromolecular surfactant to immiscible polymer blends, no such efforts have sought to alter the properties of melt-spun bicomponent core–sheath filaments with a nonreactive compatibilizing agent. In this study, we examine the effect of adding poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) triblock copolymer to core–sheath filaments consisting of isotactic polypropylene (iPP) and poly(lactic acid) (PLA). Incorporation of the copolymer into blends of iPP/PLA is observed to reduce the size scale of phase separation. Interfacial slip between molten iPP and PLA layers is evaluated by rheology under steady-shear conditions. Addition of SEBS to the PLA sheath during filament formation reduces the tendency of PLA sheaths to crack prior to iPP core failure during tensile testing. In reversed filament configurations, the copolymer does not hinder the development of molecular orientation, related to fiber strength, during ...}, number={2}, journal={MACROMOLECULES}, author={Arvidson, Sara A. and Roskov, Kristen E. and Pate, Jaimin J. and Spontak, Richard J. and Khan, Saad A. and Gorga, Russell E.}, year={2012}, month={Jan}, pages={913–925} }
 @article{ozcam_roskov_genzer_spontak_2012, title={Responsive PET Nano/Microfibers via Surface-Initiated Polymerization}, volume={4}, ISSN={["1944-8252"]}, DOI={10.1021/am201559f}, abstractNote={Poly(ethylene terephthalate) (PET) is one of the most important thermoplastics in ubiquitous use today because of its mechanical properties, clarity, solvent resistance, and recyclability. In this work, we functionalize the surface of electrospun PET microfibers by growing poly(N-isopropylacrylamide) (PNIPAAm) brushes through a chemical sequence that avoids PET degradation to generate thermoresponsive microfibers that remain mechanically robust. Amidation of deposited 3-aminopropyltriethoxysilane, followed by hydrolysis, yields silanol groups that permit surface attachment of initiator molecules, which can be used to grow PNIPAAm via "grafting from" atom-transfer radical polymerization. Spectroscopic analyses performed after each step confirm the expected reaction and the ultimate growth of PNIPAAm brushes. Water contact-angle measurements conducted at temperatures below and above the lower critical solution temperature of PNIPAAm, coupled with adsorption of Au nanoparticles from aqueous suspension, demonstrate that the brushes retain their reversible thermoresponsive nature, thereby making PNIPAAm-functionalized PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring robust microfibers.}, number={1}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ozcam, A. Evren and Roskov, Kristen E. and Genzer, Jan and Spontak, Richard J.}, year={2012}, month={Jan}, pages={59–64} }
 @article{gozen_zhou_roskov_shi_genzer_spontak_2011, title={Block copolymer self-organization vs. interfacial modification in bilayered thin-film laminates}, volume={7}, ISSN={["1744-6848"]}, DOI={10.1039/c0sm01169j}, abstractNote={Block copolymers remain one of the most extensively studied and utilized classes of macromolecules due to their extraordinary abilities to (i) self-assemble spontaneously into a wide variety of soft nanostructures and (ii) reduce the interfacial tension between, and thus compatibilize, immiscible polymer pairs. In bilayered thin-film laminates of immiscible homopolymers, block copolymers are similarly envisaged to stabilize such laminates. Contrary to intuition, we demonstrate that highly asymmetric block copolymers can conversely destabilize a laminate, as discerned from macroscopic dewetting behavior, due to dynamic competition between copolymer self-organization away from and enrichment at the bilayer interface. The mechanism of this counterintuitive destabilization is interrogated through complementary analysis of laminates containing mixtures of stabilizing/destabilizing diblock copolymers and time-dependent Ginzburg–Landau computer simulations. This combination of experiments and simulations reveals a systematic progression of supramolecular-level events that establish the relative importance of molecular aggregation and lateral interfacial structuring in a highly nonequilibrium environment.}, number={7}, journal={SOFT MATTER}, author={Gozen, Arif O. and Zhou, Jiajia and Roskov, Kristen E. and Shi, An-Chang and Genzer, Jan and Spontak, Richard J.}, year={2011}, pages={3268–3272} }
 @article{vargantwar_roskov_ghosh_spontak_2012, title={Enhanced Biomimetic Performance of Ionic Polymer-Metal Composite Actuators Prepared with Nanostructured Block Ionomers}, volume={33}, ISSN={["1022-1336"]}, DOI={10.1002/marc.201100535}, abstractNote={AbstractIonic polymer–metal composites (IPMCs) represent an important class of stimuli‐responsive polymers that are capable of bending upon application of an electric potential. Conventional IPMCs, prepared with Nafion and related polyelectrolytes, often suffer from processing challenges, relatively low actuation levels and back relaxation during actuation. In this study, we examine and compare the effects of fabrication and solvent on the actuation behavior of a block ionomer with a sulfonated midblock and glassy endblocks that are capable of self‐organizing and thus stabilizing a molecular network in the presence of a polar solvent. Unlike Nafion, this material can be readily dissolved and cast from solution to yield films that vary in thickness and exhibit enormous solvent uptake. Cycling the initial chemical deposition of Pt on the surfaces of swollen films (the compositing process) increases the extent to which the electrodes penetrate the films, thereby improving contact along the polymer/electrode interface. The maximum bending actuation measured from IPMCs prepared with different solvents is at least comparable, but is often superior, to that reported for conventional IPMCs, without evidence of back relaxation. An unexpected characteristic observed here is that the actuation direction can be solvent regulated. Our results confirm that this block ionomer constitutes an attractive alternative for use in IPMCs and their associated applications.}, number={1}, journal={MACROMOLECULAR RAPID COMMUNICATIONS}, author={Vargantwar, Pruthesh H. and Roskov, Kristen E. and Ghosh, Tushar K. and Spontak, Richard J.}, year={2012}, month={Jan}, pages={61–68} }