Search

The copolymerization of ethylene and a poly(propylene) macromonomer, the number-average polymerization degree (P n ) of which was about 11, was conducted with (tert-butanamide)dimethyl(tetramethyl-η 5 -cyclopentadienyl)silanetitanium dichloride (CGC-Ti) combined with methylaluminoxane. The rate of ethylene consumption is increased by adding the macromonomer when copolymerization was carried out at 40°C, whereas such rate enhancement could not be observed at 90°C. It was found that the increase of ethylene polymerization rate is accompanied by the incorporation of the macromonomer. Based on differential scanning calorimetry (DSC) and 13 C NMR measurements of the produced polymers, it was proved that the poly(propylene) macromonomer was copolymerized with the present CGC-Ti catalyst and the P n value of the macromonomer incorporated in the copolymer does not influence the conversion of the macromonomer.

Propene polymerization was conducted by a MgCl2/diisobutyl phthalate/TiCl4 catalyst combined with AlEt3 as cocatalyst. The polymerization was quenched by oxygen gas, and the polymer was fractionated into atactic and isotactic parts with boiling heptane. Each part was analyzed by 1H NMR. The spectra showed the resonances of vinylidene, vinyl, and hydroxymethylene groups, whose intensities were strongly dependent on the polymerization temperature and the stereoregularity. Raising the polymerization temperature increased the intensity of the hydroxymethylene group in both parts. The relative intensity of the hydroxymethylene to that of the vinylidene group was much higher in the atactic parts. These results suggest that the rates of β-hydrogen transfer and transfer by AlEt3 should be affected by the stereospecificity of the active species as well as polymerization conditions. Heat treatment at 120 °C in the presence of 1-octene quantitatively converted the terminal aluminum−carbon bond to a vinylidene group.

2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P 2 O 5 -MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.

The influence of the spacer structure on the photochemical phase transition behaviour was explored for azobenzene polymer liquid crystals (azo-PLCs) possessing siloxane spacers in the polymer side chain, and for analogue without the siloxane spacer. The photochemical phase transition of the azo-PLC with the siloxane spacer was found to proceed less effectively than that of the azo-PLC without the siloxane spacer. It was also confirmed that the spacer structure does not affect the trans-cis photoisomerization behaviour of the azobenzene moieties. These results were interpreted in terms of stabilization of the alignment of the mesogens in the liquid crystalline phase by the siloxane spacer, since the siloxane chain is one of the most flexible spacers and decouples the motion of the polymer backbone from that of the aligned mesogens. Furthermore, the response of the azo-PLCs in the photochemical phase transition was evaluated by means of a laser pulse. The phase transition occurred in 300 mus for both samples.

Thermotropic liquid-crystalline behavior of phosphonium salts, which are structurally simple amphiphiles with positively-charged phosphorus atoms and without rigid cores, was evaluated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. The phosphonium salts were found to show a smectic A (SA) phase in which a homeotropic structure was formed spontaneously. It is significant that the phosphonium salts possess an advantageous feature as thermotropic liquid crystals and show a stable liquid-crystalline phase and a simple phase transition behavior in comparison with commonly available ammonium analogs. For example, dimethylditetradecylphosphonium chloride showed the highest SA to isotropic (I) phase transition temperature (TSI, 187 °C) and the SA phase in the widest temperature range (119 °C on heating) among the cationic amphiphiles examined in the present study, while dimethylditetradecylammonium chloride with the same structure except the cationic part showed the...

Novel liquid-crystalline (LC) thiophene derivatives were synthesized, and their LC behavior and photoresponsive behavior were explored. Among the thiophene derivatives synthesized, 4-(4-alkylphenylazo)phenyl 2-thienylacrylates (TAn, n = 4, 5, 6, and 7) were found to show nematic (N) phase. TAn exhibited the N phase only when the azobenzene moiety in the molecule was in the trans form while no LC phase when the azobenzene was in the cis form. Photoirradiation of TA6 in a cell to bring about the trans−cis isomerization of the azobenzene moiety resulted in disappearance of the N phase. The N phase was restored when the irradiated sample was kept in the dark. Time-resolved measurements by means of a laser pulse (355 nm; 10 ns fwhm) revealed that in transmission-mode analysis the N-isotropic phase transition was completed in 8 ms, while in reflection-mode analysis it occurred in 100 μs.

Modulation of light by light as stimulus has been explored by the use of liquid-crystalline (LC) materials with photosensitive moieties. Azobenzene derivatives with monomeric and polymeric forms were prepared, which show nematic (N) LC behavior in the trans form and no LC phase in the cis isomer. Photoirradiation of a very thin film of the liquid-crystalline azobenzene derivatives (∼200 nm) in the trans form resulted in the disappearance of the N phase because of trans−cis photoisomerization of each mesogen, and the N phase recovered quickly when the irradiated sample was kept in the dark in the whole temperature range where the azobenzene LCs showed the N phase because of cis−trans thermal isomerization. Time-resolved measurements by the use of a laser pulse (355 nm, 10 ns fwhm) revealed that the N-to-isotropic (I) phase transition took place in 200 μs in both monomeric and polymeric systems. This response is at least 1 order of magnitude faster than the response of nematic LCs previously reported.1,2 In...

Optical switching behavior of low-molecular-weight and polymer azobenzene liquid crystals (LCs) was explored by means of reflection-mode analysis. Reflectivity changed on pulse irradiation under va...

Optical switching and image storage have been examined by means of liquid crystals (LCs), nematic LCs and ferroelectric LCs. Photochromic molecules were incorporated either by dispersion into host LCs or covalently attached to polymer main chains. These photochromic moieties act as a photoresponsive switch which induces phase transition and change in orientation of LCs, resulting in optical switching and image storage.

Sol–gel films and monoliths were prepared by hydrolysis of tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) in the presence of 1,3-bis(9-anthryl)propan-1-ol (BAP), bis(9-anthrylmethyl)amine (BAA) and the intramolecular photodimer of BM (DBAA). The intramolecular photodimerization of these dianthryl compounds as photoprobes was examined in sol–gel glasses and compared with those in solutions as well as in poly(methyl methacrylate)(PMMA) films. The intramolecular photodimerization of both BAP and BAA was severely suppressed in sol–gel glasses and PMMA films to lead to exclusive photo-oxidization, indicating the steric restriction of these matrices. A marked difference in the matrix effect between the two solids was found in the reversible photodimerization of DBAA. Photogenerated anthryl units of DBAA disappeared upon exposure to 365 nm light faster in PMMA than in sol–gel silica, suggesting that the face-to-face conformation of photodissociated DBAA is more readily relaxed rather than in the inorganic matrix. This was supported by the fact that further exposure to 285 nm light gave a lower regeneration of anthryl units in the silica bulk material than in the PMMA matrices.

The alignment direction of liquid crystals on polyimide alignment films prepared by in situ exposure to linearly polarized light (LPL) during thermal imidization of poly(amic acid)s has been found to be parallel to the direction of polarization of the LPL, whereas the conventional method, in which the alignment layers are exposed to LPL after imidization, leads to alignment perpendicular to the direction of polarization of the LPL.

Progress for two or three decades in Pd complexpromoted alternating copolymerization of alkenes with carbon monoxide has enabled many polyketones to be synthesized with regulated structures and molecular weights.

Phosphonium salts with different alkyl chains as substituents were incorporated covalently on the surfaces of cellulose filters with silane coupling agents containing phosphonium ions, and their surface antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell-counting method in sterile distilled water. The filters incorporating phosphonium biocides showed higher antibacterial activity, and its activity strongly depended on the structure of substituents. The surface-treated filters may be used to sterilize air and water, including microorganisms. © 1994 John Wiley & Sons, Inc.

Various polymeric phosphonium salts containing long alkyl chains (C10C18) and their corresponding model compounds were prepared, which possess the same hydrophobic structure as that of the common disinfectants (quaternary ammonium salts), and their antibacterial activities were evaluated by means of the viable cell counting method against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The polymer with the decyl group exhibited a higher activity than that of the corresponding model compound, particularly against the Gram-positive strain. Furthermore, antibacterial activity of the polymers was found to decrease as the chain length increased. In contrast with the polymers, the antibacterial activity of the corresponding model compounds increased as hydrophobicity of the substituents increased. The antibacterial activity was strongly dependent on the structure, particularly on the length of the alkyl chain. © 1994 John Wiley & Sons, Inc.

Two types of homopolymers {poly[tributyl(4-vinylbenzyl)phosphonium chloride] and poly[tributyl(4-vinylbenzyl)ammonium chloride]} and copolymers, in which the compositional ratio of the phosphonium monomer to the ammonium monomer was altered, were prepared. The antibacterial activities of both the mixtures of the homopolymers in which the mixing ratio was altered and the copolymers containing positively charged phosphorus and nitrogen atoms in a single polymer chain were explored by the viable cell counting method in sterile distilled water. In the mixed system, a significant finding was the presence of an optimal mixing ratio for the antibacterial activity. The mixtures of polymeric phosphonium salt and polymeric ammonium salt clearly showed the synergistic effect on the antibacterial activity. On the other hand, the antibacterial activity of the copolymers with different cationic parts increased monotonously with increasing the phosphonium monomer units in the polymers, namely, the incorporation of two types of active moieties into a single molecule seems to be unfavorable for synergism on the antibacterial activity. © 1994 John Wiley & Sons, Inc.

Polymeric phosphonium salts with different side-chain length between the main chain and the active group, poly[4-2-tributyl-phosphonioethyl)styrene chloride-co-4-(2-chloroethyl)styrene] and poly[4-(3-tributylphosphoniopropyl)styrene chloride-co-4-(3-chloropropyl)styrene], were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were examined by the viable cell counting method in sterile distilled water. The antibacterial activity was found to decrease as the side-chain length increased. The most significant finding is a peculiar concentration dependence of the antibacterial activity, which demonstrated the presence of an optimal concentration. The observed specific effects of the side chain length and the concentration on the antibacterial activity seem to be ascribed to the state of aggregation of the polycationic biocides in aqueous solution. © 1994 John Wiley & Sons, Inc.

Alkoxysilane with phosphonium biocides as coupling agents were covalently attached to cotton-fiber surfaces, and the antibacterial activity of the surface-treated fibers against Staphylococcus aureus and Escherichia coli was evaluated by the viable cell counting method in sterile distilled water. These fibers with phosphonium salts were found to exhibit high antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity increased as hydrophobicity of the substituents bonded directly to phosphonium ions increased. Furthermore, morphological changes of the cells of S. aureus and E. Coli in contact with the fibers were evaluated by scanning electron microscopy. It was found that the fiber with the phosphonium biocides exhibited bacteriostatic as well as bactericidal activity against both strains, which was evident from observation of normal and deformed cells of these species in contact with the fibers. © 1994 John Wiley & Sons, Inc.

Various phosphonium salts possessing single or double alkyl chains of various lengths (C10 to C18) were prepared as cationic biocides, and their antimicrobial activities against 11 typical strains of microorganisms including methicillin-resistant Staphylococcus aureus (MRSA) were evaluated. The phosphonium salts with long alkyl chains were found to show high levels of antimicrobial activity. Their activities depended strongly on the molecular structure, and a correlation between antimicrobial activity and molecular structure was observed. In the alkyltrimethylphosphonium salts, the bactericidal activity against S. aureus and Escherichia coli increased with increasing alkyl chain length, and the compound with the longest alkyl chain (C18) killed all the bacterial cells (ca. 10(7) cells per ml) within 30 min of contact at concentrations of 2.8 and 28 microM, respectively. In contrast, the bactericidal activity of dialkyldimethylphosphonium salts was found to decrease as the chain length of the substituents increased. It is significant that the phosphonium biocide containing double decyl groups exhibited the broadest spectrum of activity against microorganisms tested and showed the greatest bacteriostatic activity against MRSA (MIC = 0.78 micrograms/ml). Furthermore, we systematically investigated differences in bactericidal activity between the phosphonium salts and commonly available ammonium salts with the same hydrophobic structure. It was observed that the phosphonium salts showed an advantage over the corresponding ammonium salts in bactericidal activity and killing rate. For example, tetradecyltrimethyl- and didecyldimethylphosphonium chlorides killed all S. aureus organisms (ca. 10(7) cells per ml) within 60 and 30 min of exposure at 28 and 2.8 microM, respectively, while tetradecyltrimethyl- and didecyldimethylammonium chlorides which are representative of the existing cationic disinfectants did not kill all the bacteria even at the longest exposure time (120 min).

Octadecylesters of L -1-naphthylalanine and L -1-pyrenylalanine were synthesized. Both compounds form stable condensed monolayers at the air-water interface and can be transferred onto solid plates by the vertical dipping and horizontal lifting methods to give the alternating Y-type and non-alternating X-type films respectively. The orientation and packing of the aromatic rings depend upon the deposition methods and the surface pressures, as indicated by UV, circular dichroism and fluorescence spectra. Poly-amino acids containing the π-electron systems as a side group could be obtained in the LB films. For the Y-type films, the oligomer was obtained in the first step at 25°C, and then the poly-amino acid with a random coil was produced by increasing the temperature to 40°C, as suggested by the amide I bands at 1690 and 1650 cm −1 . The conversion in the X-type film was very low compared with that in the Y--type film. It is considered that the interlayer reaction propagates by “sewing up” the amino and the ester groups facing each other at the adjacent layers in the Y-type films.

A novel principle for photochemical control of optical properties of ferroelectric liquid crystal (FLC) is presented, which is based on photochemically induced switching of polarization of FLC triggered by photoisomerization of azobenzene derivatives doped in FLC. At the irradiated sites of the azobenzene/FLC mixtures, flip of polarization was induced, causing the change of the optical properties. The process was found to be fast, reversible, and repeatable

The photomechanical behavior of cross-linked azobenzene-containing liquid-crystalline polymer films was investigated by means of simultaneous measurement of their optical and mechanical properties. The connection between photoisomerization of the azobenzene moieties, photoinduced change in molecular alignment, photoinduced stress generation, and macroscopic bending was analyzed. Upon UV irradiation, the films exhibited bending due to gradient in cis-azobenzene content, and subsequent unbending when cis-azobenzene content became uniform throughout the film. The maximum photoinduced stress was generated in the same time scale as the time required to reach photostationary state in the cis-azobenzene concentration. The maximum values of photogenerated stress strongly depended on the crosslinker concentration, even if the azobenzene concentration and the cis-azobenzene content in the photostationary state were similar for all the polymer films. The stress is connected to the initial Young's modulus and also to the photoinduced change in birefringence of the polymer films. In addition, a significant photoinduced decrease in Young's modulus was for the first time observed in cross-linked azobenzene-containing liquid-crystalline polymers, which is likely to be an important factor in dictating their photomechanical behavior.

A novel principle for photochemical control of optical properties of ferroelectric liquid crystal (FLC) is presented, which is based on photochemically induced switching of polarization of FLC triggered by photoisomerization of azobenzene derivative doped in FLC. At the irradiated sites of the azobenzene/FLC mixtures, flip of polarization was induced, causing the change of the optical properties. The effects of the structures of host FLCs on the photochemical flip of polarization are discussed.

Polymers with phosphonium salts and different alkyl spacers in the main chain were prepared, and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. The antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds against each strain, and the effect of the molecular weight on the antibacterial activity was also observed for the compounds with the same spacer length. The antibacterial activity of the polymer samples bonded with different spacer lengths was found to increase with increasing the spacer length against both strains. © 1993 John Wiley & Sons, Inc.

Polyesters were prepared which retained phosphonium biocides as counter ions of sodium sulfonate moieties incorporated into the polymers, and surface antibacterial activity of the polyester films against Staphylococcus aureus and Escherichia coli was explored. These films exhibited a high surface antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity was affected by the structure and the compositional ratio of the phosphonium salts. Amount of the released phosphonium salts was very small, so that liberation of the phosphonium biocides can be expected to occur over a long period. Morphological changes of the cells of S. aureus and E. coli in contact with the polyester films were evaluated by scanning electron microscopy. It was found that the surface antibacterial activity of the polyester films was rather bacteriostatic than bactericidal as evidenced by no morphological changes of the bacterial cells in contact with the phosphonium biocides © 1993 John Wiley & Sons, Inc.

Sol-gel glass thin films were prepared from tetraethyl orthosilicate in the presence of 4-methoxy-4′-(2-hydroxyethoxy)azobenzene (MHAB), 4-methoxy-4′-(N-(3-triethoxysilylpropyl)carbamoylmethoxy)azobenzene (MTAB) and 4,4′-bis(N-(3-triethoxysilylpropyl)carbamoylmethoxy)azobenzene (DTAB). The optical absorption spectra of the three azobenzenes entrapped in the films were investigated. The trans-cis photoisomerization and the thermal reversion of the azobenzene moiety were studied in the glass films and compared with those in solutions as well as in polymethyl methacrylate (PMMA) thin films. Triethoxysilyl groups linked with the azobenzene moiety had no effect on isomerization reactions. The cis fraction of the three azobenzenes in a photostationary state in PMMA was quite similar to that in solution whereas the photoisomerization was strongly suppressed in sol-gel films due to the rigidity of the matrix. The introduction of one triethoxysilyl group has a slight effect on both photoisomerization and thermal reversion in sol-gel films. Photoisomerization of DTAB with two silylating units was depressed in a sol-sol film because both sides of the azobenzene moiety were fixed to the sol-gel glass matrix.

Copolymers of 2-(3-methacryloyloxypropyl)-4,5-diphenyloxazole (3) with various monomers were prepared. It was observed that the oxazole rings attached to the copolymer backbone are converted efficiently to the corresponding triacylamino residues by photooxidation using meso-tetraphenylporphin as a photosensitizer in solution and in a thin film of the polymer. This photoinduced transformation in a copolymer 5c having N-isopropylacrylamide as a comonomer was found to be applicable to a positive working photoresist by development with an aqueous solution of amines to dissolve the exposed areas of the film. A new system for positive image formation by visible light is presented.

Oxazole rings attached to a copolymer backbone, which was composed of 2-[3-(methacryloyloxy)propyl]-4,5-diphenyl-1,3-oxazole and N-isopropylacrylamide, were transformed efficientlytothe corresponding N,N-dibenzoylcarboxamide derivatives in a thin film by photooxidation using various dyes as photosensitizers. This photo induced transformation was found to be applicable to a panchromatic photoresist with positive tone by development with an aqueous solution of amines to dissolve the exposed areas of the fiilm. The photooxidation had the quantum efficiency for generation of singlet oxygen in the range 0.2-0.7 depending upon the sensitizers used in the system

Various poly[tributyl(4-vinylbenzyl)phosphonium salt]s with different counter anions were prepared and their antibacterial activities against Staphylococcus aureus were explored by the viable cell counting method in sterile distilled water. Antibacterial activity was found to be affected by the structure of the counter anions. The activity was low for a counter anion which tends to form a tight ion-pair with phosphonium ion, while it was high for those facilitating ionic dissociation to free ions. Furthermore, the molecular weight dependence of the antibacterial activity was investigated for poly[tributyl(4-vinylbenzyl) phosphonium chloride] with various molecular weights against S. aureus. Antibacterial activity was found to increase with molecular weight. Various copolymers were prepared in which the compositional ratio of tributyl(4-vinylbenzyl)phosphonium chloride to acrylamide, N-vinyl-2-pyrrolidone, or styrene was altered, and the effect of the positive charge density on the antibacterial activity was investigated against S. aureus. Antibacterial activity of the copolymers was much higher than that of the low-molecular-weight model compound and enhanced with the molar fraction of the phosphonium units in the copolymers. © 1993 John Wiley & Sons, Inc.

Immobilized polycationic biocides with phosphonium salt on the surface of poly (propylene) film were prepared by surface photografting. These films with phosphonium salts were found to exhibit high antibacterial activity against S. aureus and E. coli-particularly against E. coli. Furthermore, morphological changes of the cells of S. aureus and E. coli in contact with the immobilized phosphonium salt were estimated by SEM. It was found that the immobilized biocides exhibited surface bactericidal activity against both strains as evidenced by shrunken and deformed cells of these species in contact with the immobilized biocides

The role of the ground-state morphology on excimer formation has been explored for five kinds of polymer liquid crystals (PLCs) [CH 2 CH(COO[CH 2 ] m OPhPhCN)] n (m= 2,3,5,6,11). In PLCs with a short alkyl spacer such as PACB2 and PACB3, excimer formation is depressed in the neat film in comparison with PACB5 and PACB6. This may be explicable by the strong coupling of the mesogenic moieties with the main chain, which results in a lower mobility of the cyanobiphenyl moieties. PACB11 showing a smectic phase also exhibited the depression of excimer formation. In this case, diffuision of the cyanobiphenyl moieties is highly suppressed owing to the restricted mobility of mesogens in the smectic phase

Various polymeric phosphonium salts and the corresponding low-molecular-weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part

Switching behaviors of ferroelectric polymer liquid crystal (FPLC), poly(2-methylbutyl 4′-(10-acryloyloxydecyloxy) biphenyl-4-carboxylate), were successfully modulated reversibly by photochemical reaction of photochromic guests (azobenzene derivatives) doped in the FPLC. Chiral azobenzene (ABchi) possessing the same structure as the host FPLC at the chiral part was found to enhance the transmitted light intensity through a pair of crossed polarizers on the trans to cis photoisomerization, while the other achiral azobenzene derivatives reduced the transmitted light intensity on photoisomerization. This difference in photoresponsiveness has been attributed to the different effect of the trans-cis photoisomerization on the host mesogens, the change in molecular shape for the achiral azobenzenes and the change in dipole moment for ABchi.

The trans to cis photoisomerization and cis to trans thermal isomerization of azobenzene derivatives molecularly dispersed in liquid crystal polyacrylates (PLC) [CH 2 CH(COOR)] n (R= (CH 2 ) n OPhCOOPhOMe n= 3,6) were investigated with reference to the inner free volume of the PLC matrices. The size distribution and the fluctuating nature of the inner free volume were examined, and it was found that the nematic phase posesses more inner free volume than the smectic phase

Superelasticity — a form of elasticity that involves a phase transition — has been observed for the first time in a pure organic crystal. The material could find applications in microfluidics.

The thermal stability of alignment of a nematic liquid crystal (LC) on three polyimide (PI) films exposed to linearly polarized light at 366 nm was investigated. Polarizing optical microscopy analysis indicates that the thermal stability of the LC alignment on the PI film without significant structural change was higher than that with obvious structural change.