Polymer Journal

doi: 10.1038/pj.2006.146pmid: N/A

Maeda, Mizuo

doi: 10.1295/polymj.PJ2006107pmid: N/A

Graft copolymers consisting of poly(N-isopropylacrylamide) and single-stranded DNA were found to form DNA-carrying nanoparticles above physiological temperature. Aggregation of the nanoparticles was induced at relatively high salt concentration by the hybridization of surface-anchored DNA with full-match complementary DNA. In contrast, single-base mismatches at the distal end stabilized the colloidal dispersion so that the dispersion remained transparent. The phenomenon is applicable to SNP typing.

Tian, Ming; Lu, Yonglai; Liang, Wenli; Cheng, Lijun; Zhang, Liqun

doi: 10.1295/polymj.PJ2005231pmid: N/A

Palygorskite (AT) mineral was selected as a nano-fiber precursor due to its unique structure characteristics and surface chemical property, to construct a novel nano-fiber/rubber nanocomposites by using a simple and cost-efficient preparation method. Upon shear force during traditional mechanical mixing, the numerous nano-fibers contained in palygorskite micro-powder were released into rubber matrix resulted from weak stacking force between nano-fibers and high shear stress associated with high viscosity of rubber matrix. Meanwhile these nano-fibers were orientated along the shear direction the same as micro-short fiber. In situ modification using silane coupling agent can improve the dispersion of AT and strengthen the interfacial bonding between AT and rubber. The result from dynamic mechanical thermal analysis shows that the incorporation of palygorskite into rubber matrix markedly lowers the loss factor of rubber in glassy transition region and increases storage modulus of rubber. These nanocomposites exhibit stress-strain characteristics that are similar to that of micro-short fiber reinforced rubber, evident anisotropy in mechanical properties, good processing properties, as well as low cost and easily practiced by industry.

Hameed, Tayyab; Hussein, Ibnelwaleed A

doi: 10.1295/polymj.PJ2005254pmid: N/A

The influence of M w of LLDPE on the rheological, thermal and mechanical properties of m-LLDPE/HDPE blends of low and high branch content (BC) was studied. Melt rheology of m-LLDPE blended with linear HDPE revealed strong influence of M w on melt miscibility at both branching levels. Low M w m-LLDPE/HDPE blends are suggested to be miscible at all compositions, while viscosity of high M w m-LLDPE/HDPE blends showed negative deviation from log additivity suggesting layered morphology of these blends. The DSC results suggest that compatibility in the solid state is independent of M w and BC. For all blends studied, the HDPE-rich blends were found to contain single crystal populations suggesting high degree of cocrystallization, whereas, m-LLDPE rich phase showed separate crystallization. The melt miscibility and the crystallization of high BC m-LLDPE blends with HDPE are suggested to be controlled by different factors. Small strain mechanical properties of these blends were found to be a strong function of blend compatibility and the specific properties of the blend components.

Furukawa, Tsuyoshi; Sato, Harumi; Kita, Yasuo; Matsukawa, Kimihiro; Yamaguchi, Hiroshi; Ochiai, Shukichi; Siesler, Heinz W; Ozaki, Yukihiro

doi: 10.1295/polymj.PJ2006056pmid: N/A

The present study is aimed at investigating the molecular structure, crystallinity, and morphology of polyethylene (PE) and polypropylene (PP) blends by using Raman mapping, scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). In this study, three kinds of PEs, high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and metallocene polyethylene (MEPE) were used. MEPE is one of the LLDPEs but its density is very low and its melt flow index (MFI) is very high. Blends of each PE and PP with a PP content ranging from 20 to 80 wt % with an increment of 20 wt % were prepared. Raman mapping images and SEM images show that the 80/20 blends of HDPE/PP and LLDPE/PP have similar dispersibility behavior and that only the 80/20 blend of MEPE/PP shows a different behavior in this respect. For the 20/80 blends, the differences are not so large. For the Raman mapping, the intensity ratio of the two bands at 1128 and 974 cm−1 was used. The former is due to a symmetric C–C stretching mode of all-trans –(CH2) n – groups of PE while the latter is assigned to a CH3 rocking mode of PP. MEPE/PP blends yield quite different X-ray diffraction patterns compared to HDPE/PP and LLDPE/PP blends; the MEPE/PP blends show that with increasing MEPE content the crystalline size of PP become smaller. DSC curves of MEPE/PP show that the peak area changes linearly with the blending ratio and that the crystallization temperature does not change for any blend. These results mean that the density and MFI of PE influences the blend properties.

Ramdhanie, Lisa I; Aubuchon, Steven R; Boland, Eugene D; Knapp, Danielle C; Barnes, Catherine P; Simpson, David G; Wnek, Gary E; Bowlin, Gary L

doi: 10.1295/polymj.PJ2006062pmid: N/A

Poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) have long been popular polymers in the development of tissue engineering scaffolds due to their biocompatibility, bioabsorbability, and good tensile strength. Electrospinning is an attractive approach for the production of non-woven, nano- to micron-scale fibrous tissue engineering scaffolds of complex geometries. In this study, we characterize electrospun blends of PLA and PGA via scanning electron microscopy, tensile testing, differential scanning calorimetry, and phase contrast microscopy to gain a better understanding of these blended structures for potential use in biomedical applications.

Inagi, Shinsuke; Naka, Kensuke; Iida, Daisuke; Chujo, Yoshiki

doi: 10.1295/polymj.PJ2006068pmid: N/A

The electron-donating polymer containing vinylogous TTF unit in the main chain was successfully obtained by oxidative polymerization of bisdithiafulvene (bisDTF) (1). The polymer was soluble in common organic solvents such as chloroform and toluene. Structural characterization of the polymer was provided by 1H and 13C NMR spectroscopies. The number-average molecular weight of the polymer was estimated as 5,400 by gel permeation chromatographic analysis (chloroform, polystyrene standards). Optical and electrochemical properties of the polymer were studied by UV-vis analysis and cyclic voltammetry. Charge transfer complex of the polymer with tetracyanoquinodimethane (TCNQ) was obtained in a DMSO solution.

Hashidzume, Akihito; Ueno, Yusuke; Sato, Takahiro

doi: 10.1295/polymj.PJ2006066pmid: N/A

The conformation of a photoresponsive polymer bearing azo units in the main chain, poly(propionaldehyde azine) (PrAz), in tetrahydrofuran was investigated by viscosity measurements before and after trans-to-cis photoisomerization and also by the rotational isomeric state (RIS) model. Before photoisomerization (i.e., in the case of trans-pPrAz), viscosity data indicated that pPrAz took a more extended conformation than did a diene polymer analog poly(butadiene). The RIS model analysis revealed that the extended conformation of pPrAz arose mainly from the difficulty of gauche conformation around the carbon-carbon bond in the main chain. After trans-to-cis photoisomerization (i.e., in the case of pPrAz consisting of trans and cis units), viscosity data indicated that the photoisomerization led to a slight extension of the pPrAz chain. The RIS model analysis explained that the photoisomerization formed preferentially the anti-cis isomer, resulting in a larger characteristic ratio to avoid severe steric hindrance between the ethyl groups on neighboring main-chain carbon atoms.

Endo, Kiyoshi; Kondo, Yoshiyuki

doi: 10.1295/polymj.PJ2006058pmid: N/A

Polymerization of trans-2-butene with (α-diimine)Ni(II) complex in combination with R3Al (R=CH3, C2H5, i-C4H9), Et2AlCl, EtAlCl2 and methylaluminoxane (MAO) was investigated. Et2AlCl and EtAlCl2 as well as MAO were found to be an effective cocatalyst for the polymerization of trans-2-butene to give a high molecular weight of the polymer in good yields, but R3Al did not give any polymers. In contrast to MMAO catalyst system, a less amount of Et2AlCl to (α-diimine)Ni(II) is enough to reach a high active for the polymerization, and (α-diimine)Ni(II)/Et2AlCl catalyst gave an optimum rate at the Al/Ni mole ratio of about 20 for the polymerization of trans-2-butene. The results obtained from a kinetic study demonstrate that the control of molecular weight is possible in the polymerization of trans-2-butene with (α-diimine)Ni(II)/Et2AlCl catalyst. The polymer obtained with (α-diimine)Ni(II)/Et2AlCl catalyst at 20 °C consists of –CH2–CH2–CH(CH3)– units and minor units derived from 1-butene produced by isomerization from trans-2-butene. Such minor structures can be negligible by decreasing the polymerization temperature.

Kim, Hwang Yong; Kim, Hye Jeong; Kim, Jin Kon

doi: 10.1295/polymj.PJ2006086pmid: N/A

We investigated the effect of interfacial reaction and morphology on the rheological properties of a reactive bilayer polymer system consisting of end-functionalized polystyrene with carboxylic acid (PS-mCOOH) and poly(methyl methacrylate-ran-glycidylmethacrylate) (PMMA-GMA). We found that the complex viscosity (|η*|) of the reactive bilayer was unusually higher than the predicted value from the inverse relationship which holds for non-reactive bilayer, even though the interfacial roughness generated from PMMA-graft-PS copolymers formed in situ from the reaction near the interface was much smaller than the thicknesses of two plates of PS-mCOOH and PMMA-GMA. This indicates that in addition to the effect of the improved mechanical strength or interfacial mixing between chains by the presence of graft copolymers located near the interface, the roughness of the interface greatly influences |η*| of the reactive bilayer.