Kimihiro Matsukawa

Discrimination of ethylene/vinyl acetate copolymers with different composition and prediction of the vinyl acetate content in the copolymers using Fourier-transform Raman spectroscopy and multivariate data analysis

Abstract Fourier-transform (FT) Raman spectra have been measured for twelve kinds of ethylene/vinyl acetate (EVA) copolymers with vinyl acetate (VA, the comonomer) varying in the 7 to 44 wt% range. Principal component analysis (PCA) has been carried out for the Raman spectra pretreated by multiplicative scatter correction (MSC) or normalization to discriminate the twelve samples. They are clearly discriminated from one another by a score plot of the PCA factor 1 and factor 2 based upon 36 Raman spectra in the series. Principal component (PC) weight loadings for factor 1 show that the discrimination relies largely upon the bands due to CO stretching and OCO bending modes of VA and those assigned to CC stretching modes of the ethylene unit. A peak corresponding to the CH 2 wagging mode, whose intensity is known to be sensitive to the crystallinity of polyolefines, appears strongly in PC weight loadings for factor 2, indicating that the score on factor 2 reflects the crystallinity of EVA. Partial least squares regression (PLSR) has allowed us to propose a calibration model which predicts the VA content in EVA with the correlation coefficient and standard error of prediction of 0.997 and 0.95 wt%, respectively.

Thermochromism and Structural Change in Polydiacetylenes Including Carboxy and 4-Carboxyphenyl Groups as the Intermolecular Hydrogen Bond Linkages in the Side Chain

We investigated the thermochromic behavior of polydiacetylenes including the carboxy and 4-carboxyphenyl groups as the side-chain substituents adjacent to the conjugated main chain, and then, the thermal stability and the thermochromism reversibility of the polymers were related to changes in the polymer conformations monitored by IR and Raman spectroscopies and powder X-ray diffractions. The polydiacetylenes with no or a phenylene spacer between the main chain and the carboxylic acid moiety were revealed to exhibit a thermal resistance for maintaining reversible thermochromism in a high temperature range, rather than polydiacetylenes with a conventional structure with a flexible alkylene spacer. The molecular stacking structures of the diacetylenes and the corresponding polymers in the crystals were discussed based on the results of an X-ray single-crystal structure analysis as well as the powder X-ray diffraction measurements.

Two-dimensional Fourier-transform Raman and near-infrared correlation spectroscopy studies of poly(methyl methacrylate) blends: 1. Immiscible blends of poly(methyl methacrylate) and atactic polystyrene

Abstract Fourier-transform (FT) Raman and near infrared (NIR) spectra have been measured for poly(methyl methacrylate) (PMMA) and its immiscible blends with atactic polystyrene (PS) of small PS contents from 1 to 10 wt.%. Generalized two-dimensional (2D) correlation spectroscopy has been applied to analyze the composition-dependent FT-Raman and NIR spectral variations of the immiscible blends. The synchronous 2D FT-Raman correlation analysis separates the Raman bans of the minority PS from those due to the majority PMMA. It detects the bands due to PS at 2900, 2856, 1562, 1494, 1201, 1184, 1156, 1130, 1097, 1069, 964, 904, 796, and 759 cm −1 , which are too weak to be observable from the one-dimensional blend spectra. The synchronous 2D Raman-NIR hetero-correlation analysis further separates NIR bands of PS from those of PMMA. It detects the bands at 6082, 5972, 5937, 5920, 4834, and 4663 cm −1 due to PS, which are virtually unidentifiable from the one-dimensional blend spectra. These results are further proved by the synchronous 2D NIR correlation analysis.

Photoinduced Bending of Self-Assembled Azobenzene-Siloxane Hybrid.

A novel azobenzene-siloxane hybrid material displaying photoinduced macroscopic motions has been prepared by one-step organosilane self-assembly. Two types of alkoxysilane precursors with either pendant or bridging azobenzene groups were synthesized via thiol-ene click reactions. Hybrid films with well-ordered lamellar structures were obtained by hydrolysis and polycondensation of these precursors. The film with solely pendant azobenzene groups showed reversible and rapid d-spacing variation upon UV-vis irradiation, which was induced by the trans-cis isomerization of azobenzene moieties. The flexible, free-standing film obtained by co-condensation of two types of precursors showed reversible bending-unbending motions upon UV-vis irradiation. The partial cross-linking between the siloxane layers by bridging azobenzene groups was crucial for photoinduced distortion of the film. This film possesses high elastic modulus, good thermal stability, and shows large amplitude of photoinduced bending-unbending over a wide temperature range. This is the first report on photoinduced macroscopic motions of azobenzene-containing siloxane-based materials. These materials possess great potential for applications in smart devices and energy conversion systems.

Formation of Metal Nanoparticles on the Surface of Polymer Particles Incorporating Polysilane by UV Irradiation

Polystyrene particles incorporating poly(methylphenylsilane) (PMPS) were synthesized by miniemulsion polymerization. UV irradiation of the emulsion under air in the presence of metal salts such as HAuCl4.4H2O, AgNO3, and Na2PdCl4 led to the formation of metal nanoparticles on the surface of polymer particles; thus, metal nanoparticle/polymer hybrid particles were obtained. The structures of the hybrid particles were confirmed by the surface plasmon resonance band and transmission electron microscopy images. The formation of metal nanoparticles depended on the functional groups and charge on the surface of the polymer particle. The metal nanoparticles were formed due to the reduction of metal ions, accompanied by the oxidation of PMPS. The interaction between the surface of the polymer particle and the metal ions plays an important role in the formation of the metal nanoparticle.

Two-Dimensional Near-Infrared Correlation Spectroscopy Studies on Composition-Dependent Spectral Variations in Ethylene/Vinyl Acetate Copolymers: Assignments of Bands Due to Ethylene Units in Amorphous, Disordered, and Orthorhombic Crystalline Phases

Generalized two-dimensional (2D) correlation spectroscopy has been applied to the study of the composition-dependent near-infrared (NIR) spectral changes in 11 different ethylene/vinyl acetate (EVA) copolymers with vinyl acetate (VA) content from 6 to 42 wt %. The 2D synchronous correlation analysis of the 11 NIR spectra has separated the bands due to ethylene units from those due to the VA units. The obtained results are consistent with those reached by the calculation of the second derivative and by chemometrics analysis reported in our previous paper. However, the 2D correlation analysis has given clearer evidence for the band separation. Two-dimensional asynchronous correlation analysis has revealed out-of-phase variations between some bands due to ethylene and some bands due to VA and has determined the order of intensity change between them. On the basis of the order of intensity change, the bands of ethylene in the orthorhombic crystalline phase have been discriminated from those in the amorphous and disordered phases. This paper discusses the potentials of three powerful techniques, 2D correlation analysis, the calculation of the second derivatives, and that of regression coefficients in chemometrics, in unraveling rather complicated NIR spectra.

Synthesis of polysilane–acrylamide copolymers by photopolymerization and their application to polysilane–silica hybrid thin films

Abstract Various polysilane–acrylamide block copolymers have been prepared from photopolymerization of acrylamide-type monomers using poly(methylphenylsilane) (PMPS) as a macro-photo-radical initiator. The acrylamide block in the copolymers improved the hydrophilic property of PMPS. These PMPS–acrylamide block copolymers have been applied to formation of PMPS–silica hybrid thin films via sol–gel reaction. Homogeneous and transparent PMPS–silica hybrid thin films were obtained from a few PMPS–acrylamide block copolymers. It was found for these hybrid thin films based on hydrogen bonding formation between amide group and silanol group. The surface properties of hybrid thin films were evaluated by water contact angle measurement, scanning electron microscope (SEM), and atomic force microscope (AFM) images.

Optical properties of organic–inorganic hybrid thin films containing polysilane segments prepared from polysilane–methacrylate copolymers

Abstract Optical properties of polysilane–silica hybrid thin films have been studied to examine confinement effects of polysilane segments in silica matrices. Polysilane–methacryloxypropyltrimethoxysilane copolymers are synthesized from photo-radical copolymerization of 3-methacryloxypropyltrimethoxysilane and using polymethylphenylsilane. Organic–inorganic hybrid thin films with homogeneously dispersed polysilane segments are successfully prepared from the copolymers by a sol–gel method. It is found that UV light-induced degradation of photoluminescence of the polysilane–silica hybrid thin films is suppressed in comparison with that of polymethylphenylsilane at 10 K, and that UV light exposure decreases the refractive index of the polysilane–silica hybrid thin film from 1.60 to 1.40 at room temperature. It is also found that the degree of the anisotropy of the linearly polarized photoluminescence approaches to the theoretical upper limit with decreasing polysilane content in the polysilane–silica hybrid thin films. These results indicate that the fabrication of polysilane–silica hybrid thin film is a new approach for future polysilane based opto-electronic devices.

Low‐Temperature Processable Organic‐Inorganic Hybrid Gate Dielectrics for Solution‐Based Organic Field‐Effect Transistors

Organic fi eld-effect transistors (OFETs) have received considerable attention as promising candidates for realizing fl exible, large-area, and low-cost electronics such as active-matrix displays, electronic papers, and radio-frequency identifi cation tags. In recent years, solution-processable OFETs, based on soluble organic materials, have attracted increasing interest. This is because layers of OFETs can be deposited at low temperatures, using low-cost solution processes such as spin-coating, ink-jet printing, and screen printing, which are all ideally suited for the realization of fl exible and low-end OFETs. [ 1 ] The charge mobility of soluble organic semiconductors has signifi cantly improved in the last few years and a fi eld-effect mobility exceeding 1 cm 2 V − 1 s − 1 , which is comparable to that of amorphous silicon, has recently been achieved in OFETs based on polymer semiconductors [ 2 , 3 ] and soluble small molecules. [ 4 , 5 ] Recent interest has also been directed towards the development of reliable solutionprocessable gate dielectrics, since the electrical performances of OFETs are known to largely depend on the material properties of gate dielectrics and organic semiconductors. [ 1 , 6 ] For example, the surface properties of gate dielectrics, including free energy [ 6 , 7 ] and roughness, [ 8 ] signifi cantly infl uence the ordering of deposited organic semiconductors. Indeed the charge mobility of poly(3-hexyl thiophene) (P3HT) semiconductors has been reported to increase by orders of magnitude upon surface modifi cation of gate dielectrics with hydrophobic selfassembled monolayers (SAMs). [ 6 , 7 ] Furthermore, the chemical

Two-dimensional Fourier-transform-Raman and near-infrared correlation spectroscopy studies of poly(methyl methacrylate) blends: 2. Partially miscible blends of poly(methyl methacrylate) and poly(4-vinylphenol)

Abstract Fourier-transform (FT)-Raman and near-infrared (NIR) spectra have been measured for poly(methyl methacrylate) (PMMA) and its partially miscible blends with poly(4-vinylphenol) (PVPh) of small content from 1 to 10 wt.%. Generalized two-dimensional (2D) correlation spectroscopy has been applied to analyze the composition-dependent FT-Raman and NIR spectral variations of the blends. The 2D FT-Raman correlation analysis is effective in analyzing the hydrogen-bonding interaction between PMMA and PVPh, which is responsible for the partial miscibility of the blends. It detects a band at 1706 cm −1 for the hydrogen-bonded CO of PMMA, and two bands at 599 and 549 cm −1 for the ester group whose Raman intensities are very sensitive to the intermolecular hydrogen bonding effect. The Raman-NIR hetero-correlation analysis detects two bands at 6764 and 4637 cm −1 for the hydrogen-bonded hydroxyl group of PVPh, and one band at 5052 cm −1 for the hydrogen-bonded carbonyl group of PMMA. All these bands are not readily identifiable from the one-dimensional (1D) spectra.