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A series of liquid-crystalline (LC) diblock copolymers with an azobenzene moiety in the side chain were prepared by atom transfer radical polymerization (ATRP). Using a bromo-terminated poly(methyl methacrylate) as a macroinitiator, the obtained diblock copolymers showed well-defined structures and narrow molecular-weight distributions. Microphase-separated nanostructures with mesogenic blocks in either continuous or separated phases were observed. Owing to varied content of mesogens in the block copolymers, they showed different behavior of photoinduced alignment and holographic recording. Block copolymers with azobenzenes in the majority phases exhibited a similar performance of photoinduced alignment and refractive-index modulation to the azobenzene-containing homopolymer, but their photoinduced mass transportation was partly suppressed by the microphase separation, leading to a lower surface relief than that of the homopolymer. The photoinduced mass transfer was greatly prohibited in the block copolym...

The synthesis and photopolymerization of alkaline-developable hyperbranched polyurethane (HBPUMA-COOH) were examined. The reaction of dicyclohexylmethane 4,4‘-diisocyanate (CMDI) and trimethylolpropane (TMP) in the presence of 2-methacryloyloxyethyl isocyanate (MOI) was carried out to give the soluble hyperbranched polyurethane (HBPUMA) with terminal methacryloyl groups in satisfactory yield. After that, HBPUMA-COOH was synthesized by the reaction of HBPUMA and cis-1,2,3,6-tetrahydrophthalic anhydride (THPA). The photoradical polymerization of HBPUMA-COOH was examined in the presence of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-2-one (Irgacure 907) as a photoinitiator in the film state upon UV irradiation to afford the corresponding cured film quantitatively. It was found that the tensile strength of the resulting cured film of HBPUMA-COOH was higher than those of the HBPUMA and linear one. The negative patterning property of HBPUMA-COOH also had 5 μm line and space pattern resolution by UV irr...

Highly birefringent liquid-crystalline polymers (LCPs) containing an azobenzene group directly connected to a tolane moiety (azotolane moiety) were synthesized. Attention was focused on the effect of the position of the tolane moiety in the mesogenic azotolane group and the donor−acceptor substituent on photochemical phase transition behavior. In solution, cis−trans back-isomerization of the LCP containing azotolane moieties with a donor−acceptor was faster than that of LCPs having no acceptor groups. All the LCP films showed a homogeneous alignment and very high values of birefringence (about 0.4 at 633 nm). In the LCPs with a conventional azotolane moiety, a large change in birefringence (above 0.35) was induced repeatedly by irradiation of UV light. Furthermore, we investigated photoswitching behavior at telecommunication wavelength (1550 nm) based on the photochemical phase transition by irradiation of UV light.

[t-BuNSiMe2(2,7-t-Bu2Flu)]TiMe2 and [t-BuNSiMe2(3,6-t-Bu2Flu)]TiMe2 were synthesized and characterized by elemental analysis, 1H NMR, and single-crystal X-ray analysis. These complexes were applied for propylene polymerization using dried modified methyaluminoxane (dMMAO) as a cocatalyst at 0 and 25 °C. The introduction of tert-butyl substituents to the fluorenyl ligand improved the activity more than 3 times regardless of the position of the substituents. The postpolymerization testified that both catalytic systems conducted the propylene polymerization in a living manner at both 0 and 25 °C. The propagation rate increased linearly against the Al/Ti ratio from the range of 100−400 with keeping the number of polymer chains constant, which directly indicates that a larger amount of dMMAO enhanced the propagation rate. The introduction of tert-butyl substituents also improved the syndiospecificity: the 3,6-position was more effective than the 2,7-position, and [t-BuNSiMe2(3,6-t-Bu2Flu)]TiMe2 gave the livin...

Copolymerization of propene and norbornene (P−N) was conducted with (t-BuNSiMe2Flu)TiMe2 (1) activated by Me3Al-free methylaluminoxane (dried MAO), modified methylaluminoxane (MMAO), and Ph3CB(C6F5)4/Oct3Al at 20 °C under atmospheric pressure of propene. The 1−Ph3CB(C6F5)4/Oct3Al system showed the highest activity and gave the copolymer with the lowest molecular weight and broad molecular weight distribution. The 1−dried MAO system produced the copolymer with the narrowest molecular weight distribution. The detailed investigation of this system clarified that the norbornene content in the copolymer was almost proportional to the N/P feed ratio with a narrow polydispersity of 1.1−1.2 and the glass transition temperatures of the P−N copolymers increased linearly against the norbornene content in the copolymers, that is, 53 °C with 17 mol % of norbornene and 249 °C with 71 mol % of norbornene. The 13C NMR spectra also suggested the random distribution of the comonomers in the copolymers obtained.

Ethene−norbornene (E−N) copolymerizations were carried out by (t-BuNSiMe2Flu)TiMe2 (1) and (t-BuNSiMe2C5Me4)TiMe2 (2) activated with methylaluminoxane (free from Me3Al) under an atmospheric pressure of ethene at 40 °C. 1 showed higher activity than 2. The activity of 1 increased with increasing the feed ratio of norbornene/ethene, but the opposite trend was observed for 2. In the same feed ratio (N/E = 8), the incorporation of norbornene was higher with 1 (N = 50 mol %) than with 2 (N = 38 mol %). The 13C NMR spectrum of the E−N copolymer obtained with 1 was completely different from that with 2. The former showed the resonances of norbornene dyad and triad, whereas the latter showed only those of alternating and isolated norbornene structures. Some new signals were assigned to the rac,rac-NNN triad. The effects of activators and polymerization temperature were investigated with 1 in more detail, and the 1-Ph3CB(C6F5)4/Oct3Al system was found to show the highest activity at 80 °C and gave the E−N copolyme...

A new class of photo- and electroactive polymer materials showing an liquid-crystalline (LC) phase were designed and synthesized: four kinds of polymers with both oxadiazole and arylamine moieties as carrier-transporting groups in the side chain. Among them, the polymers with a dimethylamine and a methylcarbazole moiety show LC phases. Furthermore, all the polymers emitted strong blue fluorescence, and their fluorescent quantum yields were over 0.6. The aligned sample of the polymer with the carbazole moiety emitted polarized fluorescence at room temperature. One-layer type electroluminescent (EL) devices were fabricated by using the polymer with a triphenylamine moiety, which exhibited the highest quantum yield (∼0.82), and found to emit the EL emission at blue region.

Formation of intensity gratings was studied with two s-polarized (s+s) writing beams in polymer liquid crystals (PLCs) containing a photochromic moiety (azobenzene) and a mesogenic unit (tolane, T-AB; cyanobiphenyl, CB-AB) by means of photoinduced change in alignment of PLCs. Remarkable differences were observed between these two PLCs. T-AB showed higher values of the diffraction efficiency (η) and a faster response than CB-AB. In photoinduced alignment behavior of the PLCs, T-AB exhibited a faster change in alignment than CB-AB with the value of η about 30% in the Raman−Nath regime and the maximum value for modulation of the refractive index (Δn‘) of about 0.08. It was revealed that η and Δn‘ are dependent on the structure of the mesogenic unit. In addition, we attempted the holographic image storage of three-dimensional (3-D) objects in the T-AB films. The 3-D object was reconstructed with high resolution (>5000 lines/mm).

Propene polymerization was conducted at 0 °C by [t-BuNSiMe2Flu]TiMe2 combined with B(C6F5)3, MAO, or the MAO which had been dried in a vacuum and washed with hexane before use. The effect of cocata...

Photoinduced alignment behavior in a series of polymer liquid crystals containing different azobenzene moieties in the side chain was investigated. With increase of the strength of donor and acceptor at 4 and 4‘ positions of the azobenzene groups, the possibility of an alignment change in the polymer liquid crystals having the same methacrylic backbone decreased due to the slightly increased enthalpic stability of the mesophase and the significantly decreased concentration of cis-azobenzene, although the cis−trans isomerization rate increased. However, a high alignment efficiency was observed in polymer liquid crystal ACB-ABA6, which contained strong donor−acceptor pairs in the azobenzene moiety and exhibited low stability of mesophase, since both the rate of cis−trans isomerization and the mobility of mesogens are favorable for alignment change. Three different relaxation processes were observed in the aligned polymer liquid crystals.

Polymerization of propene was conducted by [t-BuNSiMe2Flu]TiMe2-based catalysts at −50 °C in the presence of trioctylaluminum. When B(C6F5)3 was used as a cocatalyst, polymer yield monotonically increased with increasing polymerization time. The polypropene obtained showed narrow molecular weight distribution, and the number average molecular weight of the polymer linearly increased against the polymer yield. In addition, the number of polymer chains, which was approximately a half the number of Ti used, was almost constant during the polymerization. The living nature of the [t-BuNSiMe2Flu]TiMe2 catalyst depended on polymerization temperature and cocatalyst. Deactivation occurred at 0 °C or even at −50 °C when Ph3CB(C6F5)4 was used in place of B(C6F5)3. 13C NMR analysis of the polymer indicated that the living polymerization proceeded highly regiospecifically via 1,2-insertion to give syndiotactic-rich polymer. Polymerization of 1-hexene with [t-BuNSiMe2Flu]TiMe2/B(C6F5)3 also proceeded in a living manner...

Polydomain films of liquid crystalline polymer (MACB-AB6) with low content (6 mol %) of azobenzene units were prepared and irradiated with linearly polarized light at 366 nm, thus inducing an alignment of the photochromic side groups as well as the nonphotoactive mesogens, the cyanobiphenyl groups. An induced order parameter, S, was obtained from polarized UV and IR spectroscopy, and it increased with increase in temperature at first and then decreased due to phase transition. The effect of light intensity on the alignment behavior has been investigated in detail. Alignment change can take place even for a low intensity (0.7 mW/cm2) of irradiation light. Irradiation light at high intensity induced alignment as well as a phase transition at relatively low temperature. A higher saturation order parameter and faster achievement of the order parameter were obtained, since a higher concentration of cis-azobenzene was produced when the film was exposed to polarized light with a higher intensity. This is due to ...

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.

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.

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

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

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

Liquid crystal (LC) polymers [CH 2 CH(COOR)] n (R= (CH 2 ) 3 OPhCOOPhOCH 3 , (CH 2 ) 3 PhPhCN) doped with azobenzene derivatived and LC copolymers [CH 2 CH(COOR)] x [CH 2 CH(COOR')] y (R= (CH 2 ) 3 OPhCOOPhOCH 3 ) were studied. Using a nanosecond pulsed laser, it was found that the relaxation time required for the nematic (N) to isotropic (I) phase transition was in a time range of 10 (copolymer)-100 ms (homopolymer doped with azobenzene) at T/T NN = 0.999, which was comparable to that of low molecular weight LC. Effects of temperature, laser power and structure of guest molecule were discussed

Etude du polyacrylate (CM 2 -CHCO 2 R 1 ) n -(CH 2 ) m -O-Ph-Ph-CW) dope par le 4-butyl 4'-methoxyazobenzene et du copolymere [(CH 2 -CHCO 2 R 1 -) x (CH 2 -CHCO 2 R 2 ) y ] n (R 2 =-(CH 2 ) m -O-Ph-N=N-Ph-OMe) L'irradiation des films de polymere entraine l'isomerisation reversible trans-cis qui induit la transition nematique → isotropique. L'efficacite de la transition depend de la valeur de m de la masse moleculaire du polymere et de l'ordre orientationnel initial du polymere

Comparison of PMMA end-labeled by 4-(N,N-dimethylamino) benzoate (DMAB) groups with monomer model compound (ethyl 4-(N,N-dimethylamino) benzoate; EtDMAB) and PMMA bearing a trace amount of DMAB on the side chain revealed that the twisting motion at the polymer end group was more facile than that of the polymer side chain and comparable to that of EtDMAB. When the degree of polymerization is increased, the end-group motion is suppressed slightly in a good solvent and strongly in a poor solvent

Etude de la transition de phase induite par la photoisomerisation dans les polyacrylates de ω-[methoxy-4' phenoxycarbonyl-4 phenoxy] alkyle dopes par un compose mesogene photoisomerable et dans les copolymeres du meme acrylate avec un acrylate de ω-(methoxy-4 phenylazo-4 phenoxy] alkyle. Relation avec la vitesse de la transition et la longueur de l'espaceur alcoxy et l'ordre orientationnel initial du polymere. Evaluation du polymere comme materiau de stockage d'image

Determination par DSC des parametres thermodynamiques des transitions nematique-isotrope et des parametres d'ordre orientationnel de polyacrylates de ω-[methoxy-4' phenoxycarbonyl-4 phenoxy] alkyle et de copolymeres du meme acrylate avec un acrylate de ω-[methoxy-4 phenylazo-4 phenoxy] alkyle en fonction de la longueur de la chaine alkyl

Etude par spectrometrie d'absorption et de fluorescence des polyacrylates (CH 2 CHCO 2 R) n (R=(CH 2 ) 6 -O-PhPh-CN, n=2, 3, 5, 6, 11) en solutions diluee et concentree dans le THF. Discussion de la formation d'excimeres inter- et intramoleculaires et de la formation possible d'agregats

A liquid-crystalline polymer of 6-[4-(4-ethylphenyl)diazenylphenyloxy]hexyl methacrylate and copolymer of the azobenzene monomer with 4‘-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl were cast as t...

Etude comparee du poly(vinyl-9 carbazole), du poly(([carbazolyl-9]-2 cyclobutyl-1)-9 vinyl-2 carbazole) et de son copolymere avec le vinyl-2 ethyl-9 carbazole. La mobilite plus importante dans les polymeres contenant 2 motifs carbazole est due a la concentration en sites de piegeage beaucoup moins elevee que dans le poly(vinyl-9 carbazole) ou le poly(ethyl-9 vinyl-2 carbazole)