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Assembly films of a phosphocholine-based lipid and a crystalline conjugated polymer had significant CO2 selective adsorption and light absorption due to the attractive interaction of CO2 with exposed polar lipid heads and enhanced morphologies.

A thin-film deposition system was developed for the surface coating of X-ray mirrors of up to 1 m in length. With two coating process areas and four sputtering cathodes, various combinations employing a single layer, multilayered, and co-sputtered thin films are possible. Furthermore, it is possible to correct and modify the mirror surface shape by controlling the speed of the substrate stage. In this study, to evaluate the performance of the proposed coating system, the static coating distribution was measured to check the vertical direction. In a 10 mm area, a 0.9% peak-to-valley error and 0.2% root mean square error occurred. A differential deposition test was also performed for the horizontal direction (stage scan direction). In this study, arbitrary shapes were deposited on 100-mm and 400-mm-long mirrors. After removing the measurement error, the deposition error was less than 1 nm (peak-to-valley). The results demonstrate that this system can correct the surface of an X-ray mirror with ultra-high precision.

Albite is one of the major constituents in the crust. We report here that albite, when subjected to hydrous cold subduction conditions, undergoes hitherto unknown breakdown into hydrated smectite, moganite, and corundum, above 2.9 GPa and 290 °C or about 90 km depth conditions, followed by subsequent breakdown of smectite into jadeite above 4.3 GPa and 435 °C or near 135 km depth. Upon the hydration into smectite, the fluid volume of the system decreases by ~14 %, whereas it increases by ~8 % upon its dehydration into jadeite. Both the hydration and dehydration depths are correlated to increases in seismicity by 93 % and 104 %, respectively, along the South Mariana trench over the past 5 years. Moreover, the formation of smectite is accompanied by the release of OH− species, which would explain the formation of moganite and expected alkalinity of the subducting fluid. Thus, we shed new insights into the mechanism of water transport and related geochemical and geophysical activities in the contemporary global subduction system., Albite is one of the major constituents in the Earth’s crust. Here, the authors report that under hydrous cold subduction conditions, albite undergoes breakdown into hydrated smectite and other phases, which release alkaline fluids into the mantle wedge.

We assemble a film of a phosphocholine-based lipid and a crystalline conjugated polymer using hydrophobic interactions between the alkyl tails of the lipid and alkyl side chains of the polymer, and demonstrated its selective gas adsorption properties and the polymer's improved light absorption properties. We show that a strong attractive interaction between the polar lipid heads and CO

A non-invasive, image-based analytic method utilizing scattering-type scanning near-field optical microscopy (s-SNOM) is suggested to evaluate the phase separation behavior of lamella-forming polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer films. Taking advantage of the penetrability of the tip-enhanced IR signal into the films, the spatio-spectral maps of each component are constructed. Subsequently, the effect of a sole and combinatorial applications of the self-assembly procedures, such as solvent vapor annealing (SVA) and/or thermal annealing (TA), on the spatial distribution of PS or PMMA components is quantitatively assessed in terms of the areal portions of the PS domain, PMMA domain, and the mixed zone that is adjacent to the domain border. Additionally, by statistically comparing the local concentration profiles, the chemical contrast between the domains turns out to be dependent upon the annealing procedures (namely, SVA and SVA + TA). This technique can pave the way to an uncomplicated but precise investigation of the polymer nanostructure-based thin film devices whose performances are critically governed by the spatial arrangement of the chemical elements.

Self-assembled block copolymer (BCP) thin films necessarily require a distinct chemical contrast between the blocks (or microdomain homogeneity) for the purpose of high-resolution pattern transfer applications. Despite its importance, however, there has been difficulty in measuring the chemical distribution associated with the self-assembling processes, i.e. solvent vapor annealing (SVA) or thermal annealing (TA). Herein, we present a simple yet effective method to probe the chemical distribution over polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films that underwent the SVA or SVA + TA processes. An IR nanospectroscopy using scattering-type scanning near-field optical microscopy (s-SNOM), in concert with X-ray scattering analyses, provides the relative chemical concentration of the perpendicular lamellar patterns. The chemical mapping for the components based on the s-SNOM reveals that the SVA process leaves a considerable portion of the intermixed zones of PS and PMMA blocks, whereas the subsequent TA process facilitates the chain segregation towards high-contrast chemical distribution. Interestingly, such a microdomain homogeneity critically affects the quality of the unidirectional Al2O3 lines that were substituted from topographically guided lamellae. Our results substantiate an important insight into understanding the chain redistribution behavior in the self-assembled BCP films using non-destructive s-SNOM technique.

The synthesis of sandwich-shaped multinuclear silver complexes with planar penta- and tetranuclear wheel-shaped silver units and a central anion, [Agn(2-HPB)2(A-)](OTf-)n-1, nAgA, n = 4 or 5 and A- = OH- or F- or Cl-, is reported, along with complete spectroscopic and structural characterization. An NMR mechanistic study reveals that silver complexes were formed in the following order: 2Ag → 3AgH2O → 5AgOH → 4AgOH. The central hydroxides in 4AgOH and 5AgOH exhibit exotic physical properties due to the confined environment inside the complex. The size of these silver wheels can be tuned by changing the central anion or extracting/adding one silver atom. This study provides the facile way to synthesize discrete wheel-shaped multinuclear silver complexes and provides valuable insights into the dynamics of the self-assembly process.

Two-dimensional (2D) correlation analysis of in situ FTIR spectra was used to probe the thermally induced structural changes in a poly(hydroxyamide) (PHA) precursor prepared from the reaction of 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (Bis-AP-AF) with terephthaloyl chloride. Large spectral changes in the in situ FTIR spectra of the PHA precursor film were observed in the range of 200–300 °C. The thermal cyclodehydration reaction of the PHA precursor film strongly affects the spectral changes corresponding to the amide group and the adjacent phenyl ring in the Bis-AP-AF unit. The thermal cyclodehydration reaction of the PHA precursor film in the range of 240–300 °C induced the spectral changes in amide linkage before the formation of the benzoxazole ring.

Immiscible aromatic polyimide (PI) blend films and a PI blend film incorporated with thermally conductive boron nitride (BN) were prepared, and their phase separation behaviors were examined by optical microscopy and FTIR imaging. The 2,2′-bis(trifluoromethyl)benzidine (TFMB)-containing and 4,4′-thiodianiline (TDA)-containing aromatic PI blend films and a PI blend/BN composite film show two clearly separated regions; one region is the TFMB-rich phase, and the other region is the TDA-rich phase. The introduction of BN induces morphological changes in the immiscible aromatic PI blend film without altering the composition of either domain. In particular, the BN is selectively incorporated into the TDA-rich phase in this study.

Biodegradable poly-[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoates] (PHBHx) have been widely studied for their applications in potentially replacing petroleum-based thermoplastics. In this study, the effect of the high molecular weight (Mn = 3400) poly(ethylene glycol) (PEG) blended in the films of PHBHx with different ratios of PEG was investigated using chemical FTIR imaging. Chemical IR images and FTIR spectra measured with increasing temperature revealed that PEG plays an important role in changing the kinetics of PHBHx crystallization. In addition, two-dimensional correlation spectra clearly showed that thermal properties of PHBHx/PEG blend film changed when the blending ratio of PHBHx/PEG were 60/40 and 50/50. Consequently, PEG leads to changes in the thermal behavior of PHBHx copolymers.

Biodegradable poly-[(R)-3-hydroxybutyrate

The pH-induced structural changes to surface immobilized poly ( l -glutamic acid) (PLGA) films were examined by Fourier transform infrared (FTIR) spectroscopy and two-dimensional (2D) correlation analysis. Significant spectral changes were observed in the FTIR spectra of the surface immobilized PLGA film between pH 6 and 7. The 2D correlation spectra constructed from the pH-dependent FTIR spectra of the surface immobilized PLGA films revealed the spectral changes induced by the alternations of the protonation state of the carboxylic acid group in the PLGA side chain. When the pH was increased from 6 to 8, weak spectral changes in the secondary structure of the PLGA main chain were induced by deprotonation of the carboxylic acid side group.

To transfer spin-coating based high performance polymer solar cells (PSCs) to large area using roll-to-roll compatible solution process, it is important to understand effect of the processing method and materials on morphology of bulk-heterojunction (BHJ) films. We developed PBDB-T based PSCs modules using PC71BM or nonfullerene acceptor ITIC with blade coating. It is found that crystallization of ITIC and its following aggregation are significantly affected by solvent drying dynamics which is induced by thermal heating whereas PC71BM shows similar BHJ morphology regardless heating temperature. We studied mechanism and effects of acceptors on BHJ film forming during the coating. ITIC-solvent interaction makes ITIC to form high crystalline structures and but, large aggregated domains during slow solvent evaporation at room temperature. Such aggregated morphology of PBDB-T:ITIC is much improved to optimal morphology for effective charge generation and transporting with a 50 °C heating process. As a result, PBDB-T:ITIC photovoltaic module (active area 58.5 cm2) prepared at 50 °C showed much enhanced efficiency of 9.03% than 5.0% of room temperature processed one. This result is among the highest performance of large active-area PSC modules and provides research guidelines for efficient transfer of spin-coating based small cell technology to roll-to-roll based large-area PSC modules.

The thermally induced structural changes of 6FDA-ODA PAA films in the presence and absence of a base catalyst, 2,6-dimethyl piperidine, were investigated using in situ FTIR spectroscopy. In addition, principal component analysis (PCA) and 2D correlation spectroscopy (2D-COS) were applied to clarify the thermal imidization behaviors. Based on the PCA results, we can confirm the various products formed during thermal imidization. The results of 2D correlation analysis revealed the thermally induced changes in the spectra of the 6FDA-ODA PAA films. In addition, we propose that the thermal imidization of the 6FDA-ODA PAA film in the presence of a base catalyst, 2,6-diemthyl piperidine, starts at a lower temperature than it does in the absence of a base catalyst.

A Fourier transform infrared (FTIR) spectro-microtomography system was used to conduct a 3-dimensional (3D) structural analysis of a Polyimide (PI) blend/boron nitride (BN) composite film, and the system was optimized by measuring materials with complex shapes, including a micrometer-sized loop and commercial PAN fiber. The results of the 3D reconstruction of the microloop and PAN fiber are in good agreement with optical and chemical images. In addition, the FTIR spectro-microtomography successfully described the phase separation behaviors of the PI blend/BN composite film in a 3D representation. Thereby, we could observe the internal structure of the blend film, which improves the thermal conduction in the out-of-plane direction.

Threshold switching is a phenomenon where the resistivity of an insulating material changes and the insulator exhibits metallic behavior. This could be explained by phase transformation in oxide materials; however, this behavior is also seen in amorphous insulators. In this study, through an ex-situ experiment using transmission electron microscopy (TEM), we proved that threshold switching of amorphous NbO2 accompanies local crystallization. The change in I-V characteristics after electroforming was examined by evaluating the concentration profile. Atom probe tomography (APT) combined with in-situ TEM probing technique was performed to understand the threshold switching in amorphous NbO2. The local crystallization in amorphous NbO2 was validated by the observed difference in time-of-flight (ToF) between amorphous and crystalline NbO2. We concluded that the slower ToF of amorphous NbO2 (a-NbO2) compared with crystalline NbO2 (c-NbO2) is due to the resistivity difference and trap-assisted recombination.

This paper reports the pH-induced structural changes in the surface immobilized poly( l -lysine) (PLL) film. Two-dimensional (2D) correlation analysis was applied to the Fourier transform infrared (FTIR) spectra of the surface-immobilized PLL film to examine the spectral changes induced by the alternations of the protonation state of the amino group in the side chain. Significant spectral changes in the FTIR spectra of the PLL film were observed between pH 7 and 8. The decrease in the protonation state of the amino group in the side chain induced spectral changes in the amino group as well as conformational changes in the alkyl group in the side chain. From pH 1–8, the spectral changes in the amino and alkyl groups in the side chain occurred before those of the amide group in the main chain of the surface immobilized PLL film.

In-situ FTIR spectroscopic measurements were used to examine the thermal imidization behaviors of 6FDA-ODA PAA films in the presence of a strong tertiary amine base, such as piperazine, N,N’-dimethyl piperazine, piperidine, and 2,6-dimethyl piperidine. Large spectral changes in the FTIR spectra of 6FDA-ODA PAA films in the presence of curing accelerators were observed in the range of 110∼190 ℃, and strong tertiary amine bases used in this study accelerate the imidization reaction. Less sterically hindered piperidine with a strong base strength led to a relatively slow imidization reaction compared to piperazine, N,N’-dimethyl piperazine, and 2,6’-dimethyl piperidine. N,N’-dimethyl piperazine and 2,6-dimethyl piperidine are effective curing accelerators similar to piperazine.

In this study, the thermal denaturation mechanism and secondary structures of two types of human insulin nanoparticles produced by a process of solution-enhanced dispersion by supercritical fluids using dimethyl sulfoxide (DMSO) and ethanol (EtOH) solutions of insulin are investigated using spectroscopic approaches and molecular dynamics calculations. First, the temperature-dependent IR spectra of spherical and rod-shaped insulin nanoparticles prepared from DMSO and EtOH solution, respectively, are analyzed using principal component analysis (PCA) and 2D correlation spectroscopy to obtain a deeper understanding of the molecular structures and thermal behavior of the two insulin particle shapes. All-atom molecular dynamics (AAMD) calculations are performed to investigate the influence of the solvent molecules on the production of the insulin nanoparticles and to elucidate the geometric differences between the two types of nanoparticles. The results of the PCA, the 2D correlation spectroscopic analysis, and the AAMD calculations clearly reveal that the thermal denaturation mechanisms and the degrees of hydrogen bonding in the spherical and rod-shaped insulin nanoparticles are different. The polarity of the solvent might not alter the structure or function of the insulin produced, but the solvent polarity does influence the synthesis of different shapes of insulin nanoparticles.

Thermally stable polyimide (PI), which has a photoreactive p-phenylenediacryloyl (PDA) moiety in the main chain with a rigid biphenyl as a side group, was prepared from a poly(amic acid) (PAA) solution using a thermal imidization process. PAA was synthesized successfully with a reasonably high molecular weight and gave high quality films with relatively good thermal stability. The photoreactions and photoalignments of PI were analyzed by ultraviolet-visible spectroscopy, and their liquid crystal (LC) alignment properties were examined. The PI in the film showed good photoreactivity to UV light irradiation. Linearly-polarized ultra-violet light (LPUVL) irradiation induced anisotropic reorientation of the polymer chains in the film due to a direction-selective photoreaction of the PDA moieties. All the films irradiated with LPUVL aligned the LCs in a direction perpendicular to the electric vector of the LPUVL. The pretilt angles of the LC molecules on the LPUVL irradiated film surfaces were controlled by th...

Two-dimensional (2D) gradient mapping method and 2D correlation analysis of in situ FTIR spectra were used to probe the thermal imidization-induced spectral changes in 6FDA-ODA poly(amic acid) (PAA) films prepared by a reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′-oxydianiline (ODA) in N,N ′-dimethylacetamide. Large spectral changes in the in situ FTIR spectra of 6FDA-ODA PAA film were observed in the range, 130–230 °C. The thermal imidization of 6FDA-ODA PAA films strongly affects the spectral changes in amic acid groups in the PAA unit. The spectral change in the amic acid groups occurred before those of the imide ring. The cyclic anhydrides, isoimdes and intermolecular links are present together with the imide ring in the thermally-cured 6FDA-ODA PAA films.

This paper reports the oxidative reaction of triphenylamine (TPA)-based polyamide films. A two-dimensional (2D) gradient mapping method and 2D correlation analysis were applied to the ultraviolet–visible (UV–Vis) and infrared (IR) spectra of TPA-based polyamide films to examine the spectral changes induced by electrochemical oxidation. The benzenoid and quinoid units were present together during the electrochemical oxidation of TPA-based polyamide films. The oxidative reaction of TPA-based polyamide films strongly affects the spectral changes to the benzenoid and quinoid rings in the TPA units as well as the amide linkages adjacent to the TPA units. The oxidative reaction of TPA-based polyamide film in the range of 0–1.0 V induces spectral changes to the quinoid ring, amide linkage and benzenoid ring.

A series of transparent, 100 μm thick, polyimide (PI) composite films were prepared by a sol-gel reaction using a thermal imidization process between poly(amic acid) (PAA) and various amounts of tetraethyl orthosilicate (TEOS) in N,N-dimethylacetamide. The PAA were prepared using 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2’-bis(trifluoromethyl)benzidine (TFMB) and 3,5-diaminobenzoic acid (DABA). The chemical structure and thermal stability of the PI/silica composite films were examined in detail by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The PI/silica composite films showed high thermal stability, and the degradation behavior was found to be dependent on the amount used. In addition, the optical and thermo-mechanical properties of the films were investigated, including the haze values, yellow indices and in-plane coefficients of thermal expansion (CTE). The CTE values of the PI/silica composite film...

Soluble photosensitive polyamide, which has a photoreactive 1,4-phenylenediacryloyl (PDA) moiety in the main chain with biphenyl side groups, was synthesized with high molecular weights. The polymer produced high quality films through conventional spin-casting and dry processing with relatively good thermal stability. The photochemical reactions of the polyamide in the films were investigated by UV-Vis spectroscopy; the polymer in the film demonstrated excellent photoreactivity to UV light. Linearly polarized ultra-violet light (LPUVL) irradiation induced anisotropic reorientations of the polymer chains in the film as a result of direction-selective photoreaction of the PDA moieties. The polyamide thin films were found to have excellent unidirectional orientation ability as a result of photo-exposure with LPUVL; the direction-selective photoreaction of the PDA moiety in the main chains induced alignment of nematic liquid-crystals (LCs) on the surface. The pretilt behaviors of the LC molecules on the LPUVL...

Liquid crystals’ surface morphologies, molecular reorientation, alignment, and nematic pretilt angles on polyimide surfaces were studied. The polyimide molecules contained cinnamoyl side groups; they were treated by irradiation with linearly polarized ultra-violet light or rubbing. Root-mean-square surface roughnesses over 1.0 μm × 1.0 μm areas were 0.282, 0.260, and 2.073 nm for untreated, irradiated (1.0 J/cm2), and rubbed (strength, 65 cm) films, respectively. The optical axis of the irradiated film was perpendicular to the light's direction of polarization; in the rubbed film it was parallel to the rubbing direction. Rubbing resulted in higher retardation than irradiation. The orientations of liquid crystal molecules on the films coincided with their polymer chain orientations. Fabricating LC cells with rubbed film resulted in higher pretilt angles than using irradiated film.

The photo-degradation of poly(ethylene terephthalte) (PET) film was investigated in detail using ultraviolet–visible (UV–visible) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and two-dimensional (2D) correlation analysis. The analysis of 2D FTIR correlation spectra led to the identification of photoproducts: esters, peresters and benzoic acids. The photo-degradation of PET films strongly influences the spectral changes of the ester linkages as well as the CH2 groups adjacent to the ester groups. In addition, the spectral change of CH2 groups occurred before that of terephthalte groups.

A series of soluble copoly(amic acid) precursors were synthesized with varying compositions by the conventional polycondensation of 3,3′,4,4′-biphenyltetracarboxylic anhydride (BPDA) and 3,3′-sulfonyldianiline (SDA) using 4,4′-diaminodiphenyl ether-2,2′-disulfonic acid (ODADS), a sulfonated diamine, as a third component in NMP. The synthesized precursor polymers are soluble in polar aprotic solvents. The chemical structures and inherent viscosities of the copoly(amic acid)s were determined by 1H NMR spectroscopy and viscometry, respectively. The free standing sulfonated copolyimide membranes were fabricated from solutions of the copoly(amic acid)s by a thermal imidization process and subsequent soaking in sulfuric acid solution. The chemical structure and thermal properties of the sulfonated copolyimides in the films were investigated in detail using FT-IR, DSC, and TGA. The sulfonated copolyimides show mainly three-step thermal degradation, with the degradation behavior being independent of the composition. In addition, the properties of the membranes were investigated, including their water uptake (WU), ion exchange capacity (IEC) and proton conductivity. The WU and IEC values of the sulfonated copolyimides were 8.12–38.0% and 0.18–2.05 meq/g, respectively, depending on the composition of the sulfonated diamine, and the proton conductivity of the copolyimides was dependent on the content of the sulfonated diamine. The proton conductivity values of the membranes were lower than that of Nafion 117, although their IEC values were higher.

The phenylethynyl end-capped imide model compounds 6F-PDA-PEAP and 6F-ODA-PEAP were prepared for detailed investigation of the thermal cure process. To probe the spectral changes of ethynyl C C moieties as well as imide rings and phenyl rings in PDA and ODA units during the thermal curing, we applied two-dimensional (2D) correlation analysis to the infrared spectra of 6F-PDA-PEAP and 6F-ODA-PEAP films. Thermal curing of 6F-PDA-PEAP and 6F-ODA-PEAP was influenced by molecular structure, and it induced spectral changes of C C moieties as well as imide rings and phenyl rings in PDA and ODA units. The thermal curing of 6F-PDA-PEAP and 6F-ODA-PEAP films induces the intensity changes of bands of imide and phenyl rings in PDA and ODA units before that of C C moieties.

A photosensitive polymer with azobenzene side groups was synthesized from free radical polymerization and characterized. Photoreaction and photoinduced molecular reorientation was investigated in films of poly(4-methacryloyloxyazobenzene) (PMAAz) through ultraviolet (UV) absorption spectra and two-dimensional (2D) correlation analyses of their infrared (IR) spectra. The PMAAz polymer molecules were found to undergo trans–cis photoisomerization upon UV irradiation. The fraction of the cis -isomer of azobenzene increased with an increasing UV light exposure dose. The analysis of the 2D IR correlation spectra revealed that the isomerization of azobenzene chromophores induced molecular movement of azobenzene moiety as well as alkyl main chains in PMAAz films. The mono -substituted benzene ring changed sooner than the para -substituted benzene ring for trans – cis isomerization. The azobenzene chromophores in the PMAAz film induced the molecular reorientation by photoreaction in the following sequence: mono-substituted benzene ring → N Φ bond → cis -N N → para-substituted benzene ring.

An organic solvent-soluble photosensitive polyimide (PSPI), bearing a cinnamate photoreactive moiety in its side group, was synthesized. The photochemical reactions of the PSPI in the films were investigated in detail using both UV-vis and IR spectroscopy, confirming that the cinnamate chromophores underwent photodimerization. Ultra-violet (UV) light irradiation of the polyimide thin films induced molecular reorientation of the chromophores as well as the main chain units. The molecular motions of the main chain units were induced by photoreaction before those of the photoreactive side groups in the UV irradiated films. Photo-induced molecular reorientation occurred in the following sequence: main chain → photodimerization → cinnamoyl chromophores.

Styrene monomers were grafted onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films by E-beam irradiation, controlling the degree of grafting by varying the radiation dose. In addition, polystyrene sulfonic acid (PSS) grafted FEP films were prepared by treating the polystyrene (PS) grafted FEP films with chlorosulfonic acid. The chemical mechanism of grafting, the substitution positions of the sulfonic acid, and the thermal degradation behaviors of the PS-grafted and PSS-grafted FEP films were investigated using FTIR-ATR spectroscopy, Raman Spectroscopy and TGA. Our results indicated that PS graft formation involved the removal of HF after C–C main chain scission, leading to the formation of an unsaturated structure. When heated, the PS-grafted FEP films underwent two-step thermal degradation, independent of the degree of grafting. The two degradation steps were assigned to the degradation of the PS grafts and the FEP matrix. Sulfonation of the PS-grafted FEP films was found to give rise to para-disubstituted sulfonic acid groups. The PSS-grafted FEP films were found to undergo a three-step thermal degradation, independent of the degree of sulfonation. The three degradation steps were assigned to removal of water molecules hydrogen bonded to the sulfonic acid groups, and the degradation of the PSS grafts and FEP matrix.

Gold nanoparticles modified with a newly synthesized cinnamate moiety (CI-AuNPs) were prepared using the phase method. The cinnamate moiety, which is well known for its photoreactive properties, could be reacted by means of radical attack and UV irradiation. Crosslinking of this moiety by the two reactions causes aggregation of the CI-AuNPs, which demonstrates the feasibility of fabricating self-assembled spherical structures by means of chemical crosslinking of gold nanoparticles through two distinct mechanisms, namely, photocycloaddition and radical reaction upon addition of an initiator. Both methods yielded monodispersed spherical CI-AuNPs assemblies, and especially the radical-induced system showed the ability to construct linear-chain structures. Here, we suggest the preparation of gold nanoparticles modified with a simply synthesized photoreactive group and their self-assembly via two selective strategies (photoreaction and radical reaction). We expect that this study will contribute to the strategic fabrication of self-assembled nanostructures.

A novel photosensitive polyimide, poly(4,4'-stilbenylene 4,4'-oxidiphthalimide) (ODPA-Stilbene PSPI) was newly synthesized. The most surprising feature of this PSPI is that the PSPI films irradiated with linear polarized ultraviolet light (LPUVL) can favorably induce a unidirectional alignment of liquid crystals (LCs) in contact with the film surface and further switch the director of the unidirectionally aligned LCs from a perpendicular direction to a parallel direction with respect to the polarization direction of LPUVL by simply controlling the exposure dose in the irradiation process. These LPUVL-irradiated films were found to provide high anchoring energy to LCs, always giving very stable, homogeneous cells with unidirectionally aligned LCs regardless of the LC alignment directions. In the films, the PSPI polymer chains were found to undergo favorably unidirectional orientation via a specific orientation sequence of the polymer chain segments led by the directionally selective trans-cis photoisomerization of the stilbene chromophore units in the backbone induced by LPUVL exposure. Such unidirectionally oriented polymer chains of the films induce alignment of the LCs along the orientation direction of the polymer chains via favorable anisotropic molecular interactions between the oriented polymer chain segments and the LC molecules. In addition, the PSPI has an excellent film formation processibility; good quality PSPI thin films with a smooth surface are easily produced by simple spin-coating of the soluble poly(amic acid) precursor and subsequent thermal imidization process. In summary, this new PSPI is the promising LC alignment layer candidate with rubbing-free processing for the production of advanced LC display devices, including LC display televisions with large display areas.

Poly(p-phenylene-3,6-bis(4-(n-butoxy)phenyloxy)pyromellitimide) (C4-PMDA-PDA PI), a well-defined model brush polymer composed of a rodlike polymer backbone with two bristles per repeat unit, was the first reported polyimide to align liquid crystals perpendicular to the rubbing direction at the rubbed film surface. In the present study, we used polarized infrared (IR) spectroscopy and 2D correlation analyses of the resulting IR spectra to study nanoscale films of C4-PMDA-PDA PI rubbed at various rubbing densities. The results of these studies allowed us to establish the nature and sequence of the rubbing-induced segmental reorientations that occur in the polymer molecules at the film surface. The rubbing process was found to reorient the fully rodlike polymer backbones and the n-butyl bristle end groups such that they lay parallel to the rubbing direction. In contrast, rubbing caused the phenyloxy bristle units to reorient to a direction perpendicular to the rubbing direction. These reorientations of the polymer's main chain and bristles became more pronounced with increasing rubbing density, and the rubbing process had a greater effect on the polymer's main chains than on the bristles. The rubbing-induced reorientations of the polymer segments were found to follow the sequence PDA (phenyl ring), imide ring, phenyloxy unit, imide C-N bond, and n-butyl group. It was additionally evident that the rubbing process reorients the imide rings biaxially, that is, both along the rubbing direction and out of the plane. This biaxial reorientation was found to be accompanied by a biaxial reorientation of the bristles chemically bonded to the PMDA unit that includes the imide rings. In particular, increasing the rubbing density enhanced the out-of-plane reorientation of the imide rings. In contrast, no rubbing-induced inclination of the reoriented imide rings (i.e., the polymer's main chains) was detected.

A series of well-defined brush polyimide (PI) composed of two 4- n-alkyloxyphenyloxy bristles per repeat unit on a semi-rigid poly(4,4′-methylenyldiphenylene pyromellitimide), Cm-PMDA-MDA PIs, were synthesized and their nanoscale thin films prepared by conventional spin-coating of their soluble poly(amic acid) precursor solutions and subsequent drying and thermal imidization in a nitrogen atmosphere. All the PIs were determined to be a positively birefringent polymer. The surface morphology and molecular orientation of each PI in films before and after rubbing were investigated in detail by atomic force microscopy, optical retardation analysis, and linearly polarized infrared spectroscopy. The sequence of the rubbing-induced polymer segmental orientations was further investigated in detail. In addition, the liquid crystal alignment and pretilt ability of the rubbed PI films were examined, and their thermal stability investigated. The present study provides important information on the sequence of the polymer segmental orientations induced by rubbing and additionally the mechanisms of the alignment and pretilt of liquid crystal molecules in contact with the rubbed PI film surface.

Two series of brush polyimides (PIs) with various lengths of the bristles were studied as thin films using atomic force microscopy, optical retardation and linearly polarized infrared spectroscopy before and after rubbing, and their nematic liquid crystal (LC) aligning abilities were investigated: poly(p-phenylene 3,6-bis(4-(n-alkyloxy)phenyloxy)pyromellitimide)s (Cn-PMDA-PDA PIs: n = 4, 6, 7 and 8) and poly(4,4′-methylenyldiphenylene 3,6-bis(4-(n-alkyloxy)phenyloxy)pyromellitimide)s (Cm-PMDA-MDA PIs: m = 1, 4, 8 and 12). For all the PI films, the rubbing process was found to create microgrooves in the films along the rubbing direction, and to orient the polymer main chains and the n-alkyl bristle end groups along the rubbing direction, but to orient the phenyloxy bristle units perpendicular to the rubbing direction. The LC molecules on the rubbed film surfaces of Cn-PMDA-PDA PIs with n = 4, 6 and 7 were found to be aligned perpendicular to the rubbing direction. In contrast, rubbed films of Cn-PMDA-PDA PIs (n = 8) and Cm-PMDA-MDA PIs (m = 1, 4, 8 and 12) induced LC alignment parallel to the rubbing direction. These results collectively lead a conclusion that LC alignment on the rubbed PI film is determined by a play-off between the directionally anisotropic interactions the LC molecules with all possible factors associated at the film surface.

Films of poly(4-vinylpyridine) (P4VP) and poly(2-vinylpyridine) (P2VP) were characterized before and after they were rubbed with a rayon velvet, and their liquid crystal (LC) aligning abilities were investigated. Atomic force microscopy images showed that microgrooves developed along the rubbing direction in the surfaces of the rubbed films of both polymers. Retardation and linearly polarized infrared spectroscopy analyses revealed that in both polymers the vinyl backbones are oriented along the rubbing direction, while the pyridine side groups are oriented perpendicular to the rubbing direction; the para -directions of the pyridine rings in the P4VP film have a tilt angle of about 45° in the plane perpendicular to the rubbing direction but the para -directions of the pyridine rings in the P2VP film align nearly in the film surface. These rubbed films were found to induce uniform, homogeneous LC alignment along the rubbing direction. Both LC alignments were, however, found to have low anchoring energies that are due to the inherently weak interactions of the LCs with the film surfaces. Moreover, LC cells prepared using these films were found to have only limited stability. These results lead to the conclusion that the microgrooves generated along the rubbing direction play a critical role in governing the alignment of LCs that weakly interact with the parallel oriented vinyl main chains in competition with the perpendicularly oriented pyridine side groups, despite their dimensions, which are larger than the LC molecules and thus limit their effectiveness. In addition, the zero degree pre-tilting behavior of the LCs on these films was investigated in detail, taking into account both the rubbing-induced orientations of the polymer segments and their anisotropic interactions with the LC molecules.

To characterize the reorientations of molecular segments in polymer films treated by rubbing, which is critical information for understanding the effects of the rubbing process, the surface structu...

We have investigated the surfaces of rubbed polystyrene (PS) films in detail using atomic force microscopy and have discovered a previously unknown surface feature: submicroscale meandering groove-like structures composed of gravel-like grooves in tens of nanometers are present, oriented perpendicular to the rubbing direction. This unusual surface morphology is a significant departure from the surface topographies observed so far for rubbed PS and other polymer films, for which grooves are usually only found parallel to the rubbing direction. We also conclude from retardation analysis and linearly polarized infrared (IR) spectroscopy that the phenyl side groups of the PS chains are reoriented perpendicular to the rubbing direction, with para-directions that are nearly normal to the film plane, whereas the vinyl backbones of the PS chains are reoriented along the rubbing direction. This is the first time IR spectroscopic techniques have been used to determine the three-dimensional reorientation geometry o...

Poly{p-phenylene-3,6-bis[[4-(n-octyloxy)phenyl]oxy]pyromellitimide} (C8-PMDA-PDA PI), a model brush polymer with a fully rodlike backbone, was determined to be positively birefringent by prism coupling analysis. Films of the PI were examined in detail by optical retardation and polarized infrared spectroscopy before and after mechanical rubbing with a velvet fabric. In addition, the alignment behavior of liquid crystal (LC) molecules in contact with rubbed films of the model polymer was investigated. Atomic force microscopic imaging revealed that rubbing caused microgrooves, as well as fine grooves (around 100 nm in size) with a surface morphology that resembled ground-beef, to develop parallel to the rubbing direction. The morphologies of these grooves are attributed to the structure of the fabric fibers and the shear deformation characteristics of the polymer. At the rubbed surface, the polymer main chains and the n-octyl end groups of the bristles were determined to be oriented parallel to the rubbing ...

Photoreaction and photoinduced molecular reorientation in nanoscaled films of poly[oxy(4-n-alkyl-3,5-benzoate)oxy-1,4-phenylenediacryloyl] (PPDA-CnBZ), which contains n-alkyl side groups and photosensitive 1,4-phenylenediacryloyl (PDA) units in the main chain, were in detail investigated by linearly polarized infrared (IR) and ultraviolet (UV) absorption spectroscopy and optical retardation analysis. The PPDA-CnBZ polymer molecules were found to undergo mainly photodimerization upon UV light irradiation. However, the occurrence of trans−cis photoisomerization in the PPDA-CnBZ film could not be detected. In addition, irradiation with linearly polarized UV light (LPUVL) induced selective photoreaction of the PDA chromophores positioned parallel to the polarization direction of the LPUVL, which caused the molecular reorientation of the polymer chains. In the irradiated films the unreacted PDA chromophores were found to anisotropically distribute in a direction perpendicular to the polarization direction of t...

This paper demonstrates the use of two-dimensional (2D) correlation spectroscopy in the characterization of the sodium molybdate structures that include and are intermediate between the hexagonal and orthorhombic forms; this series of sodium molybdates is produced by varying the preparation conditions, particularly the acid concentration and the heat-treatment temperature. In order to verify the assignments of the vibrational modes of hexagonal sodium molybdate, 2D correlation analysis was applied to the acid concentration-dependent Raman spectra. We can confirm from 2D Raman correlation analysis that this series of preparation conditions results in a series of sodium molybdates including and intermediate between the hexagonal and orthorhombic forms. Furthermore, 2D Raman correlation analysis elucidates the sequence of the structural transformation of hexagonal sodium molybdate into the orthorhombic form. With progression within the series from the hexagonal to the orthorhombic structures, the intensities of the oxygen–molybdenum stretching bands in sodium molybdate change in the following sequence: 973 cm−1 (terminal OMo in the hexagonal structure, decrease in intensity) 996 cm−1 (terminal OMo in the orthorhombic structure, increase in intensity) (897, 881) cm−1 (corner OMo2 in the hexagonal structure, decrease in intensity) 664 cm−1 (edge OMo3 in the orthorhombic structure, increase in intensity) 820 cm−1 (corner OMo2 in the orthorhombic structure, increase in intensity) 692 cm−1 (edge OMo3 in the hexagonal structure, decrease in intensity). This sequence implies that the changes in the corner OMo2 and edge OMo3 structures along the series of sodium molybdates are strongly correlated. Copyright © 2003 John Wiley & Sons, Ltd.

Photoreaction and photoinduced molecular reorientations in nanoscaled films of poly(methyl 4-(methacryloyloxy)cinnamate) (PMMCi) were investigated through two-dimensional (2D) correlation analyses of their infrared (IR) and ultraviolet (UV) absorption spectra. In the PMMCi film the presence of three distinct chromophore types was evident: isolated trans-isomeric cinnamoyl moieties and parallel and end-to-end cinnamoyl aggregates. Their photoinduced reorientations take place in the following sequence: isolated trans isomeric chromophores → parallel chromophore aggregates → end-to-end chromophore aggregates. It turns out that they react photochemically at different rates. The PMMCi polymer molecules were found to undergo both photoisomerization and photodimerization upon UV irradiation, with the trans−cis isomerization of the isolated trans isomeric cinnamoyl moieties occurring more rapidly than the photodimerization of the cinnamoyl aggregates. Of the photodimerization processes, the reorientation of the...

Nanoscaled films of poly{p-phenylene 3,6-bis[4-(n-butoxy)phenyloxy]pyromellitimide} (C4-PMDA-PDA PI), a well-defined brush polyimide (PI) composed of aromatic−aliphatic bristles set into a fully rodlike polymer backbone (two bristles per chemical repeat unit of the polymer backbone), were studied by atomic force microscopy, optical retardation, prism coupling, and linearly polarized IR spectroscopy before and after mechanical rubbing with velvet fabric, and their liquid crystal (LC) aligning abilities were investigated. Uniform, homogeneous LC alignment was achieved at the rubbed film surfaces of PIs with positively birefringent characteristics. Surprisingly, however, the LC alignment director for this PI is perpendicular to the rubbing direction as well as to the reorientation direction of the polymer main chains. This is the first time that LCs on a PI surface have been induced to align in the direction perpendicular to the rubbing direction, a significant departure from the LC alignment observed for al...

New polyesters with the main-chain cinnamoyl group, but with the different length of alkyl side-chain have been investigated their photoreactivity and photoalignment characteristics using UV–VIS absorption and FTIR spectra. In the case of Cn-polyesters, chromophores in cinnamoyl group are found to involve in the (2+2) cycloaddition reaction. The remained chromophores demonstrate a preferred orientation in the direction perpendicular to the exposure direction of the linearly polarized UV light, whereas photodimers do not display any anisotropy.