ABSTRACT:SEC-MALS, small-angle X-ray scattering (SAXS), and viscosity measurements were made on tetrahydrofuran (THF) and n-hexane of a series of 4-vinylbenzyl and methacrylate ended poly(n-hexyl isocyanate) (PHIC) macromonomers (VB-HIC-n and MA-HIC-n, where n is a degree of polymerization of HIC and in a range from 21 to 192), together with higher molecular weight PHIC chains than the macromonomers. The molecular weight dependence of z-average mean-square radius of gyration hRg 2 i z and intrinsic viscosity [] of the macromonomers and PHIC chains in THF at 25 C were quantitatively described by the wormlike chain model with the stiffness parameter ð À1 Þ ¼ 63 nm, the molecular weight per unit contour length ðM L Þ ¼ 725 nm À1 , and the hydrodynamic diameter ðd B Þ ¼ 1:6 nm. The SAXS scattering profile of VB-HIC-57 in n-hexane at 25 C was also perfectly described in terms of the straight cylinder model. The results imply that the macromonomers may be regarded as a rigid rod molecule in THF and n-hexane. Cylindrical brushes consisting of polystyrene as a main chain and PHIC chains as a side chain were prepared by homopolymerizations of VB-HIC-46 and their dimensional properties were investigated in THF at 25 C by SAXS and SEC-MALS measurements. The molecular weight dependence of hRg 2 i z of the brushes was quantitatively explained by the wormlike cylinder model with the parameters of À1 ¼ 48 nm, M L ¼ 2:40 Â 10 4 nm À1 , the cross-sectional radius of gyration of the cylinder hRc 2 i o 1=2 ¼ 4:66 nm, and the end effect ( ¼ 16:7 nm) arising from side chains near the mainchain ends. It was concluded, therefore, that the main chain stiffness of the brush remarkably increases by the presence of densely located rodlike side chains. Direct observation of single brush of the poly(VB-HIC-46) deposited on a mica was made by scanning force microscopy (SFM) to reveal the cylindrical brushes consisting of rodlike side chains with ca. 15 nm in a thickness.
Methacrylate-ended rodlike macromonomers consisting of poly(n-hexyl isocyanate) (MA-HIC-n(2), where n is a degree of polymerization of n-hexyl isocyanate (HIC)) with narrow molecular weight distribution have successfully been synthesized in CH2Cl2 at room temperature by living coordination polymerization of HIC using 2-methacrylate ethyloxydichloro(cyclopentadienyl)titanium (IV) (1) as an initiator. The rodlike macromonomers prepared have carefully been characterized by size exclusion chromatography fitted with a multiangle laser light scattering (SEC−MALS) and 1H NMR spectroscopy. The radical copolymerization behavior of the rodlike macromonomers (M2) with methyl methacrylate (MMA) (M1) or styrene (ST) (M1) in benzene at 60 °C has thoroughly been studied and rationalized with a function of degree of polymerization of HIC. In region of degree of polymerization (n) higher than 26, the macromonomer's apparent reactivity (1/r 1) relative to MMA was found to be almost independent of n and macromonomer concentration but lower than MMA (1/r 1 is ca. 0.6). On the other hand, in the macromonomers with n less than 26, the reactivity appeared to steeply increase with decreasing n, because of weak aggregation due to hydrogen bond formation between terminal amide groups in benzene. In the copolymerization with ST (M1), the apparent reactivities (1/r 1) were also lower the reference value reported in the copolymerization of MMA with ST. The copolymerization behavior of MA-HIC-n macromonomers was compared with that of styryl-ended (VB-HIC-n, 1/r 1 ≈ 1.0) and methacryloyl-ended (Bz-HIC-n-MA, 1/r 1 ≈ 0.1) macromonomers and discussed from the structural point of views. The methacrylate functional group was thought to be much more subject to steric hindrance effects than the styrenic group.
The π-type organic thermoelectric conversion modules composed of p-type and n-type materials that convert low-temperature waste heat into electric energy have the potential to significantly increase energy efficiency. However, p-type and n-type materials are difficult to prepare by similar methods since they have opposite carriers. In this study, we achieved γ-cyclodextrin polymer-carbon nanotube (PγCyD-CNT) composite thermoelectric film that can control the carrier by the solvent effect. When the preparation solvent switched from water to N-methylpyrrolidone (NMP), the carriers of the film were converted from holes to electrons, and their power factor values at 345 K were 221.0 and 246.6 μW m−1K−2. Moreover, PγCyD-CNTs film prepared in NMP retained n-type characteristics for half a year under the ambient atmosphere. Interestingly, the residual NMP contained in the film acts as a dopant agent for CNTs, and the chemical interaction of γCyD and NMP in the polymer results in sustained n-doping.
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