宮前 孝行

Abstract We examined the electrostatic charging states of insulating polymer surfaces using sum-frequency generation (SFG) spectroscopy. For the negatively charged polypropylene, the SFG peak amplitudes increased significantly with increasing surface potential, indicating that the electric-field formed by the electrostatic charges directly affects the SFG signal intensities. In the organic thin films stacked on top of PMMA, an increase in the SFG signal of buried PMMA is observed, indicating that the electrostatic field formed by the electrical charges is extended into the bulk direction. In addition, visualization of the location and distribution of the charges is demonstrated using the SFG intensity variations.

Alkylsilane-derived hybrid films exhibiting excellent dynamic dewetting behaviors toward various liquids are promising, since they are smooth, highly transparent, and a low environmental burden. However, the detailed mechanism of their unique dynamic dewetting behaviors and its relation to the surface segregation of alkylsilanes during the film formation have not yet been clearly identified. In this study, we prepared various hybrid films by varying the mixing ratios of tetraethoxysilane (TEOS) and n-dodecyltriethoxysilane (C12TES) and investigated the changes in the s-CH2/s-CH3 peak strength ratios of the resulting hybrid films under dry and wet conditions by sum-frequency generation (SFG) spectroscopy. When the static/dynamic water contact angles significantly changed, it was clearly observed that the s-CH2/s-CH3 ratio of each hybrid film under dry and wet condition also changed markedly. With increasing TEOS concentration, the static contact angles became smaller, while the contact angle hysteresis tended to increase because of the increase in gauche defects at the air interface and hydrogen bonds. This finding suggests that the concentration and conformation of the alkyl chains derived from surface-segregated C12TES molecules play an important role in determining the final dewetting behaviors of the hybrid films to water.

In the direct melt bonding of isotactic polypropylene (iPP) to aluminum (Al), the blending of a small amount of maleic anhydride-grafted PP (PPgMA) with iPP was found to induce a dramatic improvement of the strength of adhesion. The effect of blending PPgMA was, however, limited, maximizing at similar to 20 wt % PPgMA. Incorporation of larger amounts of PPgMA reduced the strength of adhesion. We studied the mechanism of adhesion between Al and iPP by incorporating chemical functionality to the polymer side. The fracture surfaces produced by peeling off the interfaces were investigated by replicating the surface topographic features on a platinum thin film and analyzing them by scanning transmission electron microscopy (STEM) as well as by reconstructing three-dimensional (3D) surface structures with STEM tomography. The replica-STEM technique enabled us to visualize PP surface crystalline lamellar structures and their deformation upon the failure in 3D. We found that polymer/metal interfaces produced surface features in the failure that were similar to those associated with failure of entanglement-based polymer/polymer adhesion via chain pullout. A fractography study by replica-STEM suggested that the formation of a low-molecular-weight layer with low crystallinity at the interfacial region was responsible for the improvement of adhesion. The adhesion strength depended on the toughness of the "soft layer" and did not depend on the chemical bonding between PPgMA and Al. The interfacial chemical reaction between MA and the Al surface yielded PP with a grafted carboxylic acid (-COOH) group, which may have been excluded from the PP crystalline lamellae. We concluded that chemical bonding was not the primary reason for the improvement of adhesion, but it was necessary to induce the segregation of PPgMA in the interfacial region and the formation of the soft layer.

<p>Sum frequency generation imaging microscopy was applied to visualize the internal electric-field behavior in operating organic field effect transistors.</p>

Studies on hydrophilic surfaces showing excellent water sliding properties are very rare, despite the numerous practical advantages they offer. One of the authors has recently developed a smooth, transparent and sufficiently-thick hydrophilic film with low contact angle hysteresis (5 degrees) and small water tilt angles (6 +/- 2 degrees) through a simple sol-gel reaction of 2-[methoxy (ethyleneoxy)10propyl]trimethoxysilane (PEG-M) and tetraethoxysilane (TEOS). However, the origins of these unusual water sliding properties have not been clearly identified. As such, the impact of the addition of TEOS acting as a "nanospacer" or the identity of PEG terminal functional groups on the final static/dynamic wetting properties needs to be explored. In this study, we investigated the orientational/conformational states of PEG chains in PEG-M/TEOS and [hydroxy(ethyleneoxy)8-12propyl]triethoxysilane (PEG-OH)/TEOS hybrid films under wet and dry conditions using sum-frequency generation (SFG) spectroscopy. We found that PEG-M/TEOS hybrid film surfaces had no marked differences in the conformational states of PEG chains under wet or dry conditions, resulting in excellent water sliding properties as there was no energy barrier for water droplet motion. In contrast, PEG chains were completely disordered after contact with water in the PEG-OH/TEOS hybrid films due to hydration effects. This large conformational change between the liquid/solid and gas/solid interface at the three-phase contact line resulted in an unfavorable energetic barrier for water droplet motion, leading to the poor water sliding properties. TEOS did not physically work as a "nanospacer," but chemically worked as a binder to endow practically useful properties, such as good adhesion and versatility in substrates used, to our hybrid films.

<p>Sum frequency generation spectroscopy was applied to confirm the presence of a chemical bond at the joining interfaces, suggesting that MDI primers can serve as a chemical bridge for urethane adhesives.</p>

Although plasma treatment of polymer surfaces has been extensively used to improve the adhesive properties, the mechanism has been still debated. In this study, we investigate the effects of NZ plasma treatment on a polypropylene surface using sum-frequency generation (SFG) vibrational spectroscopy, attenuated total reflectance infrared spectroscopy (ATR-IR), and Raman scattering. The ATR-IR measurements depict that C = O and O-H groups were introduced into the surface region after N-2 plasma irradiation; however, the SFG measurements confirm that these groups are not exposed toward the air side on the outermost surface of polypropylene. Furthermore, a variation in the crystallinity of the polypropylene surface is observed by the Raman scattering, which indicates that the treatment resulted in the formation of an amorphous phase. The variation in crystallinity approximately corresponds to the improvement in adhesion of the polypropylene. Therefore, the results indicate that, after performing the plasma treatment, the formation of the amorphous region is likely to depict a strong influence on the improvement of the adhesive properties than that depicted by other factors such as chemical bonding, surface roughness, and mechanical interlocking.

We investigated the molecular composition of the surface of beer and the orientations of these molecules on the beer surface using sum-frequency generation spectroscopy. By measuring the representative substances contained in beer, it was shown that hop-derived iso-alpha-acids and isoxanthohumol exist on the beer surface. Furthermore, these hop-derived molecules significantly contribute to the stability of beer foam by forming surface-active species with hydrophobic proteins on the beer surface.

Charges accumulated at the semiconductor/insulator interface of a top-contact bottom-gate organic field-effect transistors (OFET) with a channel length/width of 1000 mu m/1000 pm while applying a negative gate voltage are visualized in a probe region of 4 mm x 4 mm by electric-field induced sum-frequency generation spectroscopy. It is found the charges are accumulated not only inside but also outside the channel of the OFET. The accumulated charges are also found to be uniformly distributed on the semiconductor/insulator interface. The resolution of this mapping technique is explored to be 0.34 mm in the horizontal direction and 0.32 mm in the vertical.

Poly(ethylene-co-vinyl-n-octadecyl carbamate) (PEVODC) belongs to the general class of long alkyl side chain polymers, which are widely used as release coatings for pressure-sensitive adhesive (PSA) tapes. The physical and structural properties of PEVODC films and the mechanisms of the adhesion/abhesion processes were investigated using surface sensitive techniques. The surface free energies and the surface roughnesses of two films with different peel forces did not differ significantly. This suggests that surface free energy and surface roughness has little effect on the peel force. In contrast, sum frequency generation spectroscopy and X-ray diffraction analysis results showed that the orientation and crystallinity of the polymer that had the lower peel force were superior to those of the polymer with the higher peel force. This indicates that polymer orientation and crystallinity has a major effect on the peel force developed at the PEVODC/adhesive interface. The formation of highly ordered crystalline domains on the PEVODC surface effectively decreases the peel force. Finally, the intercalation of the polymer chains of both adhesives and release agents as well as the entanglement of polymers play critical roles in determining the adhesion/abhesion characteristics of the PEVODC coating.

Plasma gas-modified cyclo-olefin polymer (COP) surfaces and the interfaces between borosilicate glass and COP films were investigated by sum-frequency generation (SFG) vibrational spectroscopy. Upon exposure to oxygen gas plasma, the SFG signal intensities increased, indicating an improvement in the orientational order at the surface functional groups. In addition, thermal annealing following lamination improved the COP interphase molecular ordering and increased the number density of functional molecules at the interfaces.

Time-resolved electric-field-induced sum-frequency generation (EFI-SFG) spectroscopy was employed to study the charge behavior of multilayer organic light-emitting diodes (OLEDs). Through application of the square wave pulse bias to the OLEDs, compensation for the polarization charges in the electron transport layer and the generation of 4,4'-bis[N-(1-naphthyl-N-phenylamino)-biphenyl](alpha-NPD) cations were observed. When the pulse voltage was turned off, the a-NPD cations immediately disappeared, confirming that charge recombination occurs at the interfaces. We therefore concluded that time-resolved EFI-SFG is useful for directly probing the carrier behavior in OLEDs in addition to identifying the origin of the charge carriers present in OLEDs. (C) 2017 The Japan Society of Applied Physics

Non-destructive analyses are conducted on the intrinsic degradation of organic light-emitting diodes (OLEDs). After long- Term operation, sum-frequency spectroscopy reveals changes in the molecular orientation. Furthermore, change in the mobility of the OLEDs can be evaluated from impedance spectroscopy. Carrier trap behavior is also investigated via thermally stimulated current spectroscopy.

The dynamic dewettability of a smooth alkyl-terminated sol-gel hybrid film surface against 17 probe liquids (polar and nonpolar, with high and low surface tensions) was systematically investigated using contact angle (CA) hysteresis and substrate tilt angle (TA) measurements, in terms of their physicochemical properties such as surface tension, molecular weight/volume, dielectric constant, density, and viscosity. We found that the dynamic dewettability of the hybrid film markedly depended not on the surface tensions but on the dielectric constants of the probe liquids, displaying lower resistance to liquid drop movement with decreasing dielectric constant (epsilon < 30). Interfacial analysis using the sum-frequency generation (SFG) technique confirmed that the conformation of surface-tethered alkyl chains was markedly altered before and after contact with the different types of probe liquids. When probe liquids with low dielectric constants were in contact with our surface, CH3 groups were preferentially exposed at the solid/liquid interface, leading to a reduction in surface energy. Because of such local changes in surface energy at the three-phase contact line of the probe liquid, the contact line can move continuously from low-surface-energy (solid/liquid) areas to surrounding high-surface-energy (solid/air) areas without pinning. Consequently, the organic probe liquids with low dielectric constants can move easily and roll off when tilted only slightly, independent of the magnitude of CAs, without relying on conventional surface roughening and perfluorination.

The surface structures and the electronic states of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) blend films are studied by using doubly resonant infrared-visible sum frequency generation (DR-SFG) spectroscopy. The SFG spectra of P3HT indicate the co-existence of the ordered and disordered P3HT at the interface. In the P3HT:PCBM blend film, the peak located at 1460cm(-1), which is originated from the charge transfer state of PCBM, is observed.

Sum frequency generation (SFG) spectroscopy has been used to study the operational degradation of 4, 4 '-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (alpha-NPD)/tris(alpha-hydroxylquinoline) aluminum (Alq(3)) organic light-emitting diodes (OLEDs). A reduction in the SFG peak strengths of Alq(3) was found in aged OLEDs, indicating that the permanent dipole orientation in the Alq(3) layer was randomized as a result of long-term continuous operation. In contrast, the SFG signals derived from the alpha-NPD in aged samples were enhanced as compared to those of pristine OLEDs, and it can be attributed to an increase of the internal electric field near the interface by the long-term operation. (C) 2014 Elsevier B.V. All rights reserved.

ナノメートルサイズの微細孔を表面につくり込んだA5052アルミ合金を射出成形金型にインサートし，ポリフェニレンスルフィド(PPS)系樹脂を射出すると金属と樹脂が強度に接合した一体化物が得られる。本手法により得られる強固な接合をエネルギーフィルター透過型電子顕微鏡(EFTEM)により解析し，樹脂／金属接合界面の高分解能解析を可能にするための試料作製方法，およびEFTEMによる元素マッピング，電子エネルギー損失分光法(EELS)を用いた接合界面の解析手法の最適化を検討した。約20nmのアルミ表面の超微細孔に樹脂が侵入していることが明らかになり，高い接合強度の由来を明らかにすることが可能となった。

In this study, we investigated the hydrogels used for soft contact lens material (SCL) -air/water interface using the sum frequency generation (SFG) spectroscopy. We also investigated the orientation behavior of the water at the SCL material/water interfaces. The chemical conformations of the side chain of the SCL material changed more drastically than those of the main chain due to the change of the interfacial environment (air or water). The net-orientation behavior of the water at the SCL material/water interfaces were strongly influenced by the chemical conformation of the side chains of the SCL materials in water.

Surface structure of aqueous sulfuric acid solution at a typical atmospheric concentration (0.2x, x: mole fraction) is investigated by close collaboration of molecular dynamics (MD) simulation and sum frequency generation (SFG) measurement. The SFG spectra of both O-H and S-O stretching vibrations are provided with different sets of polarization combination. These sets of experimental spectra are consistently elucidated by the MD calculations. In modeling the surface structure, there exists a major uncertainty about local ion composition at the surface region. To address this uncertainty, we performed MD simulations with various assumptions on the local dissociation constants of sulfuric acid, and searched for the condition to be consistent with the experimental spectra. We have thereby concluded that the first acid dissociation of sulfuric acid is almost complete at the surface, while the second dissociation is more strongly suppressed than in the bulk liquid. The present MD simulation elucidates the ion distribution and molecular orientation at the sulfuric acid solution surface, and also the concentration dependence of the SFG spectrum.

We present the investigation of the vibrational and electronic states of tris(8-hydroxyquinoline) aluminum (Alq(3))/Al (Alq(3) on Al) interfaces by using two-color infrared-visible sum frequency generation (SFG) spectroscopy. The visible wavelength dependence of the SEG spectra of the 2 rim thick Alq(3)/Al consists of the vibrational bands derived from the Alq(3) at the Al interfaces. The intensities of the peaks derived from the ring stretching modes of the quinolate ligands were significantly enhanced due to the double resonance effect. In contrast, the SFG electronic spectrum obtained from the output photon energy dependence of the SFG peak amplitudes derived from the C=C bands of the Al on Alq(3) interfaces does not show the wavelength dependences, indicating that the electronic-resonance associated with the pi-pi* transitions in the quinolate rings are almost vanished at the Al deposited on the Alq(3). The disappearance of the electronic-resonance of the C=C stretching modes must be caused by the perturbation of the HOMO and LUMO of pristine Alq(3)by the interaction with the Al. The spectral features of the two-color SFG spectra of the Al/LiF/Alq(3) system show quite different behavior from those of Alq3/A1 and Al/Alq(3). The shift of the C=C stretching modes toward lower frequencies is indicative of the formation of the Alq(3) anionic states upon reaction with Li at the interface. Additional broad bands around 1335 and 1450 cm(-1), which show the weak excitation wavelength dependence, might be due to the existence of the Li-reacted graphitic carbon-like Alq(3).

The air/PFO and the buried electrode/PFO interfaces have been investigated by two-color SFG spectroscopy. Due to the interface confinement effects, the planes of PFO rings are nearly parallel to the surface plane, and the optical band gaps become smaller at the interfaces than those of the bulk.

The electrochemical interface between a polycrystalline Pt electrode and the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]) has been studied by in-situ IR-visible sum-frequency generation (SFG) spectroscopy. Potential dependent adsorption/desorption processes of OTf anions has been monitored within the electrochemical window. SFG results indicate that the ions form a double layer structure at the interface. Significant adsorption/desorption hysteresis has been observed for the anions on the Pt surface. (c) 2010 Elsevier B.V. All rights reserved.

We present the first measurement of the interfacial vibrational and electronic states of single-walled carbon nanotubes (SWCNTs) on a silver substrate by using two-color IR-visible sum frequency generation (SFG). With an input visible light of 532 nm, the G-bands of the SWCNTs deposited on silver were clearly observed, while they were absent on glass or silicone substrates. The observation of the G-band SFG signal shows the existence of coupling between the vibrational and electronic states at the SWCNTs/silver interface, The shape of the two-color SFG spectra of the SWCNTs showed remarkable dependence on the visible excitation wavelength of 470 to 640 nm. The dependence is ascribed to the resonance of the SFG photon energy with the electronic transition energy of the semiconducting SWCNTs.

The surface structures of ionic liquids 1-CnH2n+1-3-methylimidazolium tetrafluoroborate (BF4-), trifluoromethanesulfonate (OTf) and bis(trifluoromethylsulfonyl)amide (TFSA) with n = 4, 8, and 10 were investigated by ultraviolet photoemission spectroscopy (UPS) and metastable atom electron spectroscopy (MAES). The MAES spectra reveal that the anions and cations share the surface of the room-temperature ionic liquids (RTILs) with a shorter alkyl chain at n = 4 although the alkyl chain layer tends to cover the outermost surface in the case of RTILs with longer alkyl chains of n = 8 and 10. Comparison of UPS and MAES spectra demonstrates that the nonpolar groups such as the alkyl chain and the CF3 group Point toward the vacuum side, while the polar groups such as the SO3 and SO2 groups face toward the bulk side. A double-layered structure at the Surface, which consists of an alkyl chain layer and a polar layer containing anions and imidazolium rings, is proposed from these observations.

IR-visible sum frequency generation (SFG) vibrational spectroscopy was employed to investigate the microscopic structures at interfaces between room temperature ionic liquids and various molecular liquids. The alkyl chain of the [C(n)mim](+) polar cation orients toward the hydrophobic (CCl(4)) phase at the CCl(4)/ionic liquid interface, while it orients randomly or points towards the ionic liquid phase at a D(2)O/ionic liquid interface. An anomalous enhancement in the amplitude of the CD(3) asymmetric stretching mode is observed at a butanol/ionic liquid interface, suggesting the formation of a hydrophobic layer which consists of the alkyl chains of the butanol and the [C(n)mim](+) cation.

The electrochemical interface between a polycrystalline Pt electrode and an ionic liquid 1-butyl-3-methylimidazolium trifluoromethane sulfonate ([bmim]OTf) has been studied by in situ sum frequency generation (SFG) spectroscopy. Potential dependent adsorption and desorption processes of OTf anion as well as [bmim] cation have been observed. A double-layer model of the interface structure has been suggested based on the behavior of both the anion and the cation in the electrochemical potential window. Hysteresis effect has been observed during the desorption and the re-adsorption processes of both the anion and the cation on the Pt surface. ©The Electrochemical Society.

The vibrational sum frequency generation ( SFG) spectra of the air - liquid interface of H2SO4 - H2O solutions over a wide range of concentrations are measured in the SO stretching region ( 1000 - 1300 cm(-1)). The analogy of the concentration dependence of Raman and SFG is indicative of a nearly identical behavior of the first acid dissociation at the air - liquid interface as in the bulk.

Surface structures of organic-in organic hybrid coatings of polyvinylalcohol (PVA) /polyacrylicacid (PAA)-silica, which have high gas barrier properties, have been investigated using X-ray photoelectron spectroscopy (XPS) and sum frequency generation spectroscopy (SFG). The cross-linked PVA/PAA surfaces show that these polymers are well mixed homogeneously even at the surface regions. In contrast, the backbones of the PAA preferentially appear at the surfaces of the PVA/PAA-silica hybrid films. The SFG spectral changes suggest that the topmost surfaces of the PVA/PAA-silica hybrid films are almost covered with the PAA. This observation is due to the polymers and silica being mixed homogeneously even at the surface region. No significant changes of the SFG spectra are observed under highly humid conditions, which suggests that the surface structures of the polymer-silica hybrid coatings do not affect the gas permeability.

The air/liquid interface of a room temperature ionic liquid, 1-butyl-3-methylimidazolium trifluoromethane-sulfonate ([bmim]OTf), is investigated using infrared-visible sum frequency generation (SFG) spectroscopy. The SFG spectra clearly show low-frequency modes [CF3-symmetric stretching (ss) mode and SO3-symmetric stretching (ss) mode] of the OTf anion, demonstrating the existence of anions polar oriented at the interface. The amplitude of the CF3-ss peak of the OTf anion has the opposite sign with respect to that of the SO3-ss peak, indicating that OTf anions at the surface have polar ordering where the nonpolar CF3 group points away from the bulk into the air, whereas the SO3 group points toward the bulk liquid. The line width of the SFG peak from the submerged SO3 group is appreciably narrower than that from IR absorption, suggesting the environment of the surface OTf anions is much more homogeneous than that of the bulk. The vibrational calculations also suggest that the anions and the cations form a more specific aggregated configuration at the surface as compared to the bulk.

Sum-frequency generation vibrational spectroscopy was used to study the molecular structure of surface-grafted poly(N-isopropylacrylamide) (PNIPAM) in air and in D2O. It was found that the side chains of the PNIPAM were nearly standing at the air/PNIPAM interface, owing to the hydrophobic nature of the isopropyl groups. Total internal reflection geometry was employed to obtain SFG spectra of the D2O/PNIPAM interface. When the water temperature was increased, red shifts of the SFG peaks were observed. This can be explained by the dehydration of the alkyl groups at the water interface. From the quantitative analysis of the molecular orientation, restructuring of the main chain due to the dehydration occurs at the water/PNIPAM interface is suggested.

Surface-immobilized poly(N-isopropyl acrylamide) (poly(NIPAAm)) surfaces and water/poly(NIPAAm) interfaces have been investigated by using sum-frequency generation (SFG) spectroscopy. The change of the surface wettability vs. temperature is attributed to different conformations taken by the side chain of the polymer.

Surface segregation of a block copolymer of polystyrene (PS) and 2-[2-(2-methoxyethoxy) ethoxy]ethyl methacrylate (PME3MA) has been investigated by using sum-frequency generation (SFG) spectroscopy. SFG reveals that the side chain of PME3MA segregates at the surface regardless the low volume fraction of PME3MA block in PS. The quantitative orientational analysis for the terminal CH3 was performed. The segregation of the block copolymer to the surfaces is strongly influenced by the presence of methoxy group at the end of the side chains.