Journal of Polymer Science Part B: Polymer Physics

Cover image for Vol. 50 Issue 7

1 April 2012

Volume 50, Issue 7

Pages i–ii, 455–522

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      Cover Image, Volume 50, Issue 7 (pages i–ii)

      Version of Record online: 23 FEB 2012 | DOI: 10.1002/polb.23055

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      Micro-mechanical strain sensors are demonstrated by subjecting carbon nanocones to an alternating electric field aligning them into single strings in a polymer matrix, as presented on page 477 by Henrik Høyer, Matti Knaapila, Jakob Kjelstrup-Hansen, Xuhai Liu, and Geir Helgesen. The strings have a length of 10 to 100 μm and a thickness of about 5 μm, corresponding to the thickness of a few particles. Since the particle fraction is an order of magnitude lower than the percolation threshold and makes the material transparent it can be UV-cured, thus locking the particles into place. The composites can subsequently be deflected resulting in a reversible piezoresistive effect. The obtained gauge factor of 50 is comparable to that of piezoresistive silicon cantilevers.

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    1. Correlation between processing conditions, microstructure and mechanical behavior in regenerated silkworm silk fibers (pages 455–465)

      Gustavo R. Plaza, Paola Corsini, Enrico Marsano, José Pérez-Rigueiro, Manuel Elices, Christian Riekel, Charlotte Vendrely and Gustavo V. Guinea

      Version of Record online: 29 DEC 2011 | DOI: 10.1002/polb.23025

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      Using a wet-spinning process and then drawing regenerated silkwork fibers during a post-spinning immersion in water gives a work to fracture comparable to that of natural silkworm silk fibers. This work shows that this process produces significant differences in the amorphous region of the fibers as compared with conventional spinning conditions, resulting in a microstructure more similar to spider silk than natural silkworm silk. Tuning of the fibers' tensile behavior is also possible.

    2. Nanomechanical properties in ultrathin polymer films: Measurement on rectangular versus circular bubbles (pages 466–476)

      Shanhong Xu, Paul A. O'Connell, Gregory B. McKenna and Sylvie Castagnet

      Version of Record online: 29 DEC 2011 | DOI: 10.1002/polb.23032

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      Much research effort has been invested in studying the effects of size and confinement on the glass transition temperature (Tg) in small molecules and ultrathin polymer films, often resulting in conflicting results. This study investigates the effects of geometry in membrane inflation experiments used to study Tg by using rectangular bubbles instead of circular ones. The change in geometry is shown not to change the polymer behavior significantly, despite the change from equibiaxial to plane strain.

    3. Individual strings of conducting carbon cones and discs in a polymer matrix: Electric field-induced alignment and their use as a strain sensor (pages 477–483)

      Henrik Høyer, Matti Knaapila, Jakob Kjelstrup-Hansen, Xuhai Liu and Geir Helgesen

      Version of Record online: 29 DEC 2011 | DOI: 10.1002/polb.23031

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      By using piezoresistive effects, composites containing conductive particles can be manipulated via an external electric field for use in sensing applications. Exotic carbon particles—carbon nanocones and discs—are aligned by electric field into wire-like strings in an ultraviolet light curable polymer matrix. The aligned wires act as promising electromechanical sensors with significantly higher sensitivity as compared to the nonaligned films.

    4. Modulation of cell responses by creating surface submicron topography and amine functionalities (pages 484–491)

      Jian-Je Chen, Quoc-Phong Ho and Meng-Jiy Wang

      Version of Record online: 27 DEC 2011 | DOI: 10.1002/polb.23024

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      A facile method to fabricate polystyrene-co-maleic anhydride (PSMAA) exhibiting well-ordered submicron pores by phase-separation and spin coating method is reported. The nanostructured PSMAA is further functionalized by dopamine blending or by nitrogen/hydrogen plasma treatments. The results show that the creation of a microenvironment and the integration of chemical functionalities provide promising effects for promoting the growth of mammalian cells.

    5. Development of new high transparent hybrid organic–inorganic monoliths with surface engraved diffraction pattern (pages 492–499)

      Sandra D. F. C. Moreira, Carlos J. R. Silva, Luis A. S. A. Prado, Manuel F. M. Costa, Victor I. Boev, J. Martín-Sánchez and M. J. M. Gomes

      Version of Record online: 29 DEC 2011 | DOI: 10.1002/polb.23028

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      Organic-silicate hybrids exhibit properties favorable for optics applications including moulds for diffraction gratings. Flexible hybrid xerogels with imprinted diffraction grating are obtained by sol-gel method using replica molding technique. Two types of hybrid materials (urea-silicate and amino-alcohol-silicate gels) are synthesized. The developed method allows a dramatic improvement of sample properties: high optical transparency (up to 96%), minimal shrinkage (down to 5.5%), a very smooth surface (average roughness of about 0.3 nm) and the material is thermally stable up to 200 °C.

    6. Temperature-based fluorescence measurements of pyrene in block copolymer micelles: Probing micelle core glass transition breadths (pages 500–515)

      Michelle M. Mok and Timothy P. Lodge

      Version of Record online: 29 DEC 2011 | DOI: 10.1002/polb.23029

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      Measurements of block copolymer micelle core glass transition temperatures (Tgs) are challenging, given the nanoscale volumes and small volume fractions being probed. Introduced here is a method for quantifying Tg breadths in micelle cores by inducing an increased level of pyrene molecules in the micelle cores and then monitoring their release upon heating using fluorescence. These release temperature ranges correlate closely to Tg results measured by DSC in semidilute solutions of the same materials.

    7. Electrical switching of microgel swelling and collapse for display applications (pages 516–522)

      Joseph P. Cook and D. Jason Riley

      Version of Record online: 24 JAN 2012 | DOI: 10.1002/polb.23039

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      Microgels—colloidally sized crosslinked polymer particles—can be made to swell and shrink in response to external stimuli. Here, it is shown that a change in pH sufficient to bring about a significant change in the turbidity of a microgel solution (as shown in the image) can be achieved by oxidizing/reducing a polyaniline electrode. Electrochemical switching of the dispersion from highly scattering to transparent for all visible wavelengths is achieved, demonstrating the potential for high-contrast electronic paper.