Journal of Polymer Science Part B: Polymer Physics

Cover image for Vol. 51 Issue 3

1 February 2013

Volume 51, Issue 3

Pages i–ii, 159–230

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    3. Reviews
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      Cover Image, Volume 51, Issue 3 (pages i–ii)

      Version of Record online: 18 DEC 2012 | DOI: 10.1002/polb.23234

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      Improving the crystallization behavior of poly(L-lactide) (PLLA) is a major research focus that could enlarge the potential for applications. Addition of nanofiller, which acts as a nucleating agent, has been shown to improve the crystallization behavior of PLLA. The content of the nanofiller exhibits a great role in determining the crystallization behavior. This is because both the density of nucleation sites and the growth rate of crystallites of PLLA are influenced by the content of the nanofiller. On page 183, Yong Wang and colleagues comparatively study the different effects of carbon nanotubes and montmorillonite on crystallization behaviors and mechanical and thermal properties of PLLA. They show that the two nanofillers exhibit different network structures. Consequently, different crystallization behaviors of PLLA are observed.

  2. Reviews

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      Hydration studies in polymer hydrogels (pages 159–175)

      Polycarpos Pissis and Apostolos Kyritsis

      Version of Record online: 4 DEC 2012 | DOI: 10.1002/polb.23220

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      Hydrogels are polymer networks that swell rather than dissolve in water because of their crosslinking, ideal for applications in biotechnology and medicine. Hydration studies on hydrogels are reviewed, using poly(hydroxyethyl acrylate) (PHEA) as a model system. The focus is on the organization of water in the hydrogel and the impact on the properties of the polymer matrix—essential to engineer properties for applications. The figure shows plasticization of glass transition and the α-relaxation in PHEA with increasing water fraction, and for comparison in a protein (BSA) and an organogel (PEA + p-xylene). The general trend is similar in the three systems, however, distinct differences can be observed.

  3. Full Papers

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    1. Molecular orientation and composition at the surface of spin-coated polyfluorene:Fullerene blend films (pages 176–182)

      Ana Sofia Anselmo, Andrzej Dzwilewski, Krister Svensson and Ellen Moons

      Version of Record online: 30 OCT 2012 | DOI: 10.1002/polb.23198

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      Blended films of the polymer APFO-3 and the fullerene PCBM can be used in organic solar cells. NEXAFS spectroscopy was used to probe the outermost surface composition of films with different blend ratios, spin-coated from different solvents. All surfaces were found to be polymer enriched, with compositional variations occurring through the surface region of the films. Angle-resolved NEXAFS spectra revealed a predominantly plane-on orientation of the polymer's conjugated system in pure APFO-3 films, an effect that is attenuated in the blend films.

    2. Comparative study of poly(L-lactide) nanocomposites with organic montmorillonite and carbon nanotubes (pages 183–196)

      Hai-ming Chen, Jie Chen, Li-na Shao, Jing-hui Yang, Ting Huang, Nan Zhang and Yong Wang

      Version of Record online: 5 OCT 2012 | DOI: 10.1002/polb.23182

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      Functionalized multiwalled carbon nanotubes (FMWCNTs) and organic montmorillonite (OMMT) are known to enhance the crystallization ability of poly(L-lactide) (PLLA). In this study, PLLA/OMMT exhibits a looser percolated network structure of nanofiller compared with the PLLA/FMWCNTs, and the restriction effect of OMMT on the diffusion of PLLA chain segments is also relatively smaller compared with that of FMWCNTs. Consequently, while nucleation sites in PLLA/OMMT are fewer than in PLLA/FMWCNTs, the former nanocomposites exhibit larger growth rate of crystallites, which is favorable for more perfect crystallites.

    3. Synthesizing a new dielectric elastomer exhibiting large actuation strain and suppressed electromechanical instability without prestretching (pages 197–206)

      Xiaofan Niu, Hristiyan Stoyanov, Wei Hu, Ruby Leo, Paul Brochu and Qibing Pei

      Version of Record online: 19 OCT 2012 | DOI: 10.1002/polb.23197

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      A new acrylic-based dielectric elastomer has been synthesized from industrial monomers. The amount of crosslinkers was used to successfully tune the maximum strain and suppress electromechanical instability in prestrain-free films. Addition of plasticizers increased strain sensitivity. A new elastomer with high overall actuation performance has been obtained capable of producing high strain (>100%), high energy density (>1 J g−1), good temperature, and frequency responses without requiring prestretching.

    4. Rheological and electrical analysis in carbon nanofiber reinforced polypropylene composites (pages 207–213)

      Antonio J. Paleo, J. Silva, F. W. J. van Hattum, Senentxu Lanceros-Méndez and A. I. Ares

      Version of Record online: 30 OCT 2012 | DOI: 10.1002/polb.23200

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      To correlate conductivity with rheological properties of carbon nanofiber (CNF) based nanocomposites, two different types of CNFs were incorporated a polypropylene matrix. Electrically, the two composites exhibited different responses: nonconducting and conducting as a function of volume fraction concentration. A large difference in the rheological behavior of both composites has been measured. Furthermore, after comparing electrical conductivity and rheological properties, it is concluded that G′/G″ is the most appropriate rheological parameter for comparing with electrical behavior.

    5. Viscoelasticity of nanobubble-inflated ultrathin polymer films: Justification by the coupling model (pages 214–224)

      K. L. Ngai, Daniele Prevosto and Luigi Grassia

      Version of Record online: 30 OCT 2012 | DOI: 10.1002/polb.23201

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      The anomalous viscoelastic creep behavior of ultrathin polymer films fabricated by nanobubble inflation is explained by the Coupling Model. Present in the glass-rubber transition region are the segmental α-relaxation, the sub-Rouse modes, and the Rouse modes. On decreasing film thickness, the α-relaxation is shifted to shorter times, due to reduction of intermolecular coupling, and to a lesser degree for the sub-Rouse modes, whereas the Rouse modes remain unchanged or becomes even slower. These differences cause the viscoelastic anomalies found in the nanobubble thin-film creep experiments.

    6. Influence of thermal history on mesoscale ordering in polydomain smectic networks (pages 225–230)

      Huipeng Chen, Ziniu Yu and Ronald C. Hedden

      Version of Record online: 8 NOV 2012 | DOI: 10.1002/polb.23207

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      The effect of thermal history on the mechanical behavior of smectic liquid crystalline elastomers is vital to know for their numerous applications, such as shape memory materials and soft actuators. Here, it is shown that the formation of larger, more stable smectic domains stiffens the material, increases the yield stress, and lowers extensibility. From a practical standpoint, crosslinker concentration can be used to suppress both domain growth and crystallization and decrease the material's sensitivity to thermal history.

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