Synthesis and second-order nonlinear optical properties of hyperbranched polymers containing pendant azobenzene chromophores

Two hyperbranched polymers with methyl ester (P1) and epoxy (P2) terminal groups containing pendant azobenzene chromophores were prepared through an “A₂ + B₃” approach used for second-order nonlinear optical materials. Their chemical structures were characterized by NMR and GPC analyses. The polymers have good solubility in common organic solvents and film-forming ability. The pure films were fabricated successively without doping into other matrices. The poled films exhibit high second-harmonic generation coefficients (>50 pm/V) due to the three-dimensional spatial isolation effect resulting from their highly branched structures. The optical nonlinearity of the poled P2 film is thermally more stable than that of P1 due to the cross-linking of epoxy groups with carboxylic acid groups in the former during poling. The onset decay temperature of SHG intensity of P2 was determined to be at around 155 °C, which was 20 °C higher than that of P1.     

Synthesis and the third-order nonlinear optical properties of soluble polymers with different substituted azobenzene side chains

A series of soluble polyacrylates containing different azobenzene side chains have been synthesized via atom transfer radical polymerization (ATRP) technique, from which the side-chain nonlinear optical (NLO) polymers with controllable molecular weight and low polydispersity (1.1-1.4) have been obtained. The third-order NLO absorption and refraction coefficients were simultaneously determined by Z-scan technique. The polymerization activity of the azobenzene-containing acrylate monomers and the third-order NLO properties of the obtained polyacrylates were both dominated by the electronic effect of the different substituents in the azobenzene side chain. The results of Z-scan with and without an aperture showed that all the azobenzene-containing monomers and polymers have both nonlinear absorption and nonlinear refraction. The third-order NLO susceptibility (χ⁽³⁾) of all the azobenzene-containing samples under the laser irradiation is 1.0-5.0 × 10⁻¹¹ esu.     

Synthesis and thermal properties of polythioether‐based liquid‐crystalline polymers containing azobenzene in the side chain

BACKGROUND: Owing to the unusual structural rearrangement of polychloromethylthiirane (PCMT) at room temperature, it has not been used as the main‐chain backbone of side‐chain liquid‐crystalline polymers (SLCPs). However, it has been observed that PCMT has a relatively stable and clear structure under special conditions. Therefore, we attempted to synthesize SLCPs using PCMT as main‐chain backbone and investigated their thermal behavior. RESULTS: New polymers, poly[1‐({(4‐methoxyazobenzene‐4′‐oxy)alkyl}thio)‐2,3‐epithiopropane], in which the number of methylene units in the alkyl group is 4, 5 or 6, were prepared by means of reactions of corresponding (4‐methoxyazobenzene‐4′‐oxy)alkylthiols with PCMT. The structures of these compounds were confirmed using elemental analysis and ¹H NMR spectroscopy. The substitution ratios of the copolymers with 4, 5 and 6 methylene units in the alkyl group were 56, 75 and 80%, respectively. Differential scanning calorimetry measurements and polarized optical microscopy observations showed that the resulting copolymers exhibited thermotropic liquid‐crystalline mesomorphism with nematic phase except for the copolymer with a 56% substitution ratio. The decomposition temperature of all the synthesized copolymers was near 195 °C. CONCLUSION: This investigation has demonstrated that PCMT polymerized for 8 h has the ability to act as a suitable main‐chain backbone for SLCPs. Moreover, SLCPs could be obtained only by the reaction of PCMT with thiolate salt containing mesogenic groups. The substitution ratios increased with increasing number of methylene groups in the spacer. Copyright © 2009 Society of Chemical Industry     

Synthesis and optical properties of novel side chain NLO organic/inorganic polymers via sol-gel process

Summary Novel side chain NLO organic/inorganic polymers were developed by sol-gel process of dye-contained triethoxysilane with tetraethoxysilane. A NLO moiety based on 4-[N, N-bis(2-hydroxyethyl)amino]-4-nitrostilbene (diol-DANS) was covalently bounded to the triethoxysilane derivative. The sol-gel derived NLO polymers were analyzed by analytic techniques, including FT-IR, TGA, solid state ²⁹Si-NMR, SEM, etc. The incorporation of the DANS dye into silicon oxide networks induces high dimensional stability of dipole alignment and the easy film fabrication. They exhibited a significant improvement in the thermal stability at high temperatures exceeding 270°C. The electro-optic coefficient at 1.3 m is 4.3 pm/V for the copolymer containing 50 wt % of the dye-contained triethoxysilane system poled with corona discharge and is shown excellent long-term stability with 80% of initial value even after 3 hrs at 150°C.     

Stimuli-responsive conjugated polymers. Synthesis and chiroptical properties of polyacetylene carrying l-glutamic acid and azobenzene in the side chain

A glutamic acid- and azobenzene-containing novel N-propargylamide, (S)-CHCCH₂NHCOCH(CH₂CH₂CO₂CH₂C₆H₅)NHCO₂CH₂CH₂-p-C₆H₄NNC₆H₅ (1) was synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] as a catalyst to obtain the corresponding polymer [poly(1)] with the moderate number-average molecular weight of 12,200 in 93% yield. The chiroptical studies revealed that poly(1) took a helical structure in THF, CHCl₃, CH₂Cl₂ and toluene. Poly(1) underwent solvent and heat-driven helix-helix transition. The trans-azobenzene of the side chain isomerized into cis upon UV-irradiation, accompanying decrease in helicity. The cis-azobenzene moiety reisomerized into trans upon visible-light irradiation, while the polymer did not recover the original helicity.     

Synthesis, thermal and optical properties of liquid crystalline terpolymers containing azobenzene and dye moieties

The synthesis, thermal properties and photochemical and photophysical studies of new azopolymers are described. These polymers contain three different types of monomer, each of which is mainly responsible for a particular function: A mesogenic benzanilide, a photochromic azobenzene and a dye unit (a benzoxazole, an anthracene or a stilbene derivative). This approach provides liquid crystalline terpolymers with different spectral properties and with the potential ability to be photoaligned by irradiation and thermotropic self-organization. The polymers have been prepared by random radical polymerisation of the corresponding methacrylate-fucntionalised units. All of the materials show good thermal stability and liquid crystalline behaviour, displaying smectic A or nematic mesophases. Optical properties of the polymers in solution display additive bands in the absorbance spectrum and luminescent properties in the emission region of the individual dye monomers. However, films of these polymers are not luminescent. A study of the absorption and redox properties of the dyes has been performed in order to evaluate the quenching process in the polymers.     

Dielectric and optical properties of liquid crystalline side chain polymers. A MNDO-analysis

Semiempirical quantum mechanical MNDO-calculations were performed on side chain liquid crystalline polymers to predict their electronic properties and thus their anisotropic dielectric and optical properties. These predictions are compared with the corresponding experimental results. The conclusion is that the predictions are sufficiently accurate, which suggests to use such methods for screening potentially interesting polymer liquid crystals prior to synthesizing them.     

Optical anisotropy and non-linear optical properties of azobenzene methacrylic polymers

Photoinduced optical anisotropy has been studied in several methacrylic copolymers, either amorphous or liquid crystalline, with cyano azobenzene chromophores in the side chain. Illumination with linearly polarised 488 nm light gives rise to high and stable values of birefringence and dichroism, mainly in liquid crystalline films. Both dichroism and birefringence decrease with the azo content in the copolymer series while some increase can be achieved by the incorporation of biphenyl molecules to the copolymers. Photoinduced anisotropy disappears above the glass transition temperature in amorphous polymers, whereas it increases in liquid crystalline polymers (LCP) due to a thermotropic self-organisation.The non-linear optical (NLO) properties of the films have been studied by second harmonic generation (SHG) measurements. The intensity of the harmonic signal from in situ corona poled polymeric films has been measured. The effect of 488 nm light irradiation on the azo chromophores orientation and consequently on the NLO response of the films was investigated at different temperatures. The intensity and thermal stability of the second harmonic signals obtained after the two different (thermal and photoassisted) corona poling processes have been compared.     

Synthesis and properties of novel vinyl polymers bearing azacrown ether side chain

Summary Novel vinyl polymers bearing monoazacrown ether-type side chains with a number average molecular weigh of over 5000 were radically synthesized from the 16-membered α-methylenemacrolide monomers. The obtained polymers possessed a Na⁺ or K⁺ selective extraction ability, whereas K⁺ was preferentially extracted by the monomers. The polymer having the N-(2-naphthoyl)azacrown ether pendant groups showed a selective UV-responsive complexation with Li⁺ in 1,2-dichloroethane-CH₃CN.     

Synthesis of third-order nonlinear optical polyacrylates containing an azobenzene side chain via atom transfer radical polymerization

A series of polyacrylates containing different substituted-azobenzene chromophores were synthesized and polymerized via atom transfer radical polymerization. Nonlinear optical homopolymers containing an azobenzene side chain, of controllable molecular mass and low polydispersity (1.1–1.4) were obtained. In addition, side-chain copolymers were prepared in which the composition of the copolymers was controlled by using different feed ratios of the azobenzene monomer and methyl methacrylate. The third-order nonlinear optical properties of azobenzene monomers and their polymers were measured using the degenerated four-wave mixing technique. Each of the polymers displayed a high χ⁽³⁾ of about 10^?11 esu and rapid response time in femto-second magnitude. The effect of substituents on the azobenzene group and the composition of the polymer chain on the third-order nonlinear optical properties of the polymers were investigated.     

Synthesis and characterization of high molecular weight side chain liquid crystalline/photoactive polymers

Various liquid crystalline and photoactive azobenzene monomers were synthesized and attached to copoly(methyl methacrylate‐glycidyl methacrylate) [copoly (MMA‐GMA)] to get high molecular weight side chain liquid crystalline (LC)/photoactive copolymers. Further, spacers are generated in situ and reactive groups are obtained after the modification. All monomers and polymers were thoroughly characterized by FTIR, ¹H and ¹³C NMR, UV‐VIS spectrophotometry, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy. All side chain LC polymers showed higher thermal stability than that of copoly(MMA‐GMA). Three LC and one azo monomer exhibited characteristic nematic mesophase where as one LC monomer has shown nematic and sanded smectic‐A texture. The rate of trans‐cis isomerization of polymer was lower than that of the monomer and both monomers and polymers showed slow back isomerization. Present approach offers convenient way to synthesize high/desired molecular weight photoactive LC polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,thermal, and photo alignment behavior of polyethylene imines having nitro substituent azobenzene side chain group

Polyethylene imines having nitro substituent azobenzene side chain group with different methylene spacer groups (PEImN) were successfully synthesized and characterized by differential scanning calorimetry, polarized optical microscopic, and X‐ray diffraction analysis. All synthesized polyethylene imines showed liquid crystalline properties and the glass transition temperature (Tg) of PEImN decreased as the number of methylene spacers increased. Melting temperatures (Tm) of synthesized PEImN showed an odd‐even effect. Photochemical, thermo‐optical, as well as photo alignment behavior of PEImN were investigated and out‐of‐plane orientational behavior of polymeric films was dependent on number of methylene spacers and polyethylene imines having higher number of methylene spacers (six or more) showed high order parameter values that revealed the well pronounced tendency for the development of out‐of‐plane order from random state on annealing. And the molecular orientation of PEImN between random and out‐of‐plane structures has been achieved by the combination of thermal and photochemical processes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characteristic properties of cutting fluid additives derived from the derivatives of ricinoleic acid polymers

A number of esters were prepared from the reaction of acid chlorides with ricinoleic acid polymers and screened for anti-rust properties and antimicrobial activity in spent coolants of water-based cutting fluids. Aqueous solutions of triethanolamine salts with decanoic acid, undecanoic acid and oleic acid esters of ricinoleic acid dimer, trimer, tetramer and hexamer showed good anti-rust properties for water-based cutting fluids. Dehydrates of ricinoleic acid polymers also showed good anti-rust properties for water-based cutting fluids.     

Synthesis and properties of carbazole-based hyperbranched conjugated polymers

Carbazole-based novel hyperbranched conjugated polymers linked with triphenylamine and benzene moieties were synthesized by Sonogashira coupling polycondensation of N-octadecyl- and N-octyl-3,6-diethynylcarbazoles with tris(4-iodophenyl)amine and 1,3,5-tribromobenzene. Solvent-soluble polymers with number-average molecular weights in the range of 3500-21,000 were obtained in 48-66% yields. The UV-vis absorption bands of the polymers were red-shifted compared to that of carbazole, indicating the extension of conjugation length. The polymers emitted blue-green fluorescence with high quantum yields up to 67% in CHCl₃. Poly(1/3) containing triphenylamine units emits visible light and shows unique solvatochromism. The polymers were electrochemically redox-active.     

Synthesis and characterization of bulky side chain methacrylate polymers

The synthesis, and dilute solution behavior of poly(2,4-dimethylphenyl methacrylate) (2,4DMP), poly(2,5-dimethylphenyl methacrylate) (2,5DMP), and poly(3,5-dimethylphenyl methacrylate) (3,5DMP) is described. Comparison is made with results reported for other bulky side chain polymers. The Kuhn-Mark-Houwink-Sakurada (KMHS) relationships were established. The unperturbed dimensions 〈r²〉 ${}_{\text{½}}^{\text{0}}$ , the rigidity factor σ, the characteristic ratio C_∞, and the thermodynamic parameters were determined, using the Stockmayer-Fixman equation, from viscometric data in good solvents. The high rigidity observed for these polymers is explained assuming that these polymers behave as kinked-chains.     

淀粉接枝衣康酸/丙烯酸高吸水材料制备与性能

旨在为降低吸水材料成本、拓宽原料来源、提高生物降解性、减少对石油化工产品的依赖提供指导,以水溶液接枝共聚法制备了淀粉接枝衣康酸/丙烯酸高吸水材料（S/IA/AA）,讨论了淀粉糊化条件、中和度、单体含量、反应温度等因素对材料吸水性能的影响,采用FTIR、SEM、EDX等对吸水材料进行表征。研究表明：淀粉糊化最佳条件为糊化温度80℃,糊化比为10 g•g^-1,糊化时间30 min;吸水材料合成最佳条件为中和度50%,衣康酸40%,淀粉20%,引发剂为4×10^-3 mol•L^-1,交联剂0.075%,反应温度50℃;利用40％衣康酸替代丙烯酸所制S/IA/AA同S/AA相比,其吸水性能有一定提高且保水性能优良。     

New multifunctional sulfonamide-containing azobenzene chromophores: Synthesis and photochromic properties

The work presents synthesis and characterization of novel sulfadimethoxine and sulfabenzamide azo derivatives as well as the kinetic study of their trans-cis-trans isomerization. Spectral properties and kinetic constants were determined for the chromophores dispersed in poly(methyl methacrylate-co-butyl methacrylate) deposited on glass substrates in form of transparent, thin films. The maximum absorption bands were observed within wavelength in range of 446-457 nm for N-disubstituted aminoazobenzene derivatives and 361-362 nm for phenolic chromophores. For the phenolic azo derivatives of sulfadimethoxine and sulfabenzamide the photoisomerization induced with UV light followed the first order kinetics, while for other compounds the process combined of two parallel reactions with different rate constants was observed. The rate constants of thermal relaxation in the dark were usually few times smaller than those determined for photoinduced trans-cis isomerization. The change of real part of refractive index upon illumination determined by ellipsometry was within the range of 0.0043-0.0138.     

Thermal properties of acrylonitrile/itaconic acid polymers in oxidative and nonoxidative atmospheres

Thermal stabilization of polyacrylonitrile (PAN) fibers is an indispensable process in the manufacture of carbon fibers. The effects of acidic comonomers on the thermal properties of PAN have attracted much attention because of their importance in the fibers spinning and heat treatment process. In this study, oxidative and nonoxidative atmospheres are adopted in differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) test to disclose the key effects of oxygen on the thermal properties of PAN/itaconic acid (IA) polymers. The DSC results under oxidative atmosphere are consistence to the reports by previous researchers: the exothermic curves of copolymers containing 0.6 wt % and 1.0 wt % IA exhibit lower initiation temperature and more broaden shapes than that of PAN homopolymer, indicating that IA facilitates both cyclization and oxidation reactions. However, copolymers containing the same content of IA shows no apparent improving effect on the thermal properties under inert atmosphere, which has not been mentioned in the published literature. TGA indicates that oxygen remarkably increases the thermal stability of AN/IA copolymers structure, and will bring high carbon yield in the eventual carbon fibers. The influential mechanisms of oxidative and nonoxidative atmospheres on thermal stabilization reactions of PAN were discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,characterization and photovoltaic properties of two-dimensional conjugated polybenzodithiophene derivatives appending diketopyrrolopyrrole units as side chain

Two side-chain donor-acceptor (D-A) narrow-band-gap two-dimensional (2D) conjugated polymers of POBDTDPPs and PTBDTDPPs with benzodithiophene (BDT) as D unit and appending diketopyrrolopyrrole (DPP) as A unit were designed and synthesized. The optical, thermal, electrochemical and photovoltaic properties have been investigated. It was found that both polymers exhibit better solution processability and a deeper HOMO energy level relative to its corresponding main-chain conjugated polymers (PBDT-DPP). Moreover, the PTBDTDPPs with an additional di(alkylthiophene)- substituted BDT unit shows a deeper HOMO energy level than the POBDTDPPs with a dialkoxy- substituted BDT unit. Using PTBDTDPPs as an electron donor and [6,6]-phenyl-C₇₁-butyric acid methyl ester as an electron acceptor, the resulting polymer solar cells (PSCs) exhibited meliorative photovoltaic properties with a power conversion efficiency (PCE) of 2.92% and open circuit voltage (V_oc) of 0.94 V. The PCE and V_oc levels are 1.52–2.92 and 1.14–1.18 times higher than those in the PBDT-DPP- and POBDTDPPs-based PSCs, respectively. This work demonstrates a good example for tuning energy level and photovoltaic properties of the polymers by the application of 2D conjugated structure.