Preparation and characterization of novel main-chain azobenzene polymers via step-growth polymerization based on click chemistry

A novel α-azide and ω-alkyne A–B type azobenzene monomer, 3′-ethynylphenyl[4-(4-azidobutoxy)phenyl]azobenzene (EAPA), was synthesized and used to generate a novel polymer via step-growth polymerization using 1,3-dipolar cycloaddition reaction under the catalysis of CuSO₄·5H₂O/sodium ascorbate/H₂O (“Click” chemistry). The structure of the resultant main-chain azobenzene polymer, PEAPA, was characterized by GPC, ¹³C NMR, UV–vis and FT-IR spectra. Thermal stability and crystallinity of PEAPA powder were studied by TGA and WAXD. The photo-induced trans–cis isomerization of PEAPA and EAPA in N,N′-dimethyl formamide (DMF) solution was investigated. Furthermore, the thermal cis–trans isomerizations of PEAPA and EAPA were also observed at 60 °C in dark. Thermal stability and trans–cis–trans isomerization behavior of PEAPA was compared with its non-triazole analog, PDHA.     

新型含醛基两性聚氨酯乳液的制备与表征

以异佛尔酮二异氰酸酯(IPDI)、聚四氢呋喃醚二醇(PTMG)、2,4-二羟基苯甲醛(DDBA)、2,2-二羟甲基丙酸(DMPA)和N-甲基二乙醇胺(N-MDEA)为原料,通过加成反应制备了含醛基两性聚氨酯乳液(AAPU)。考察了r值(IPDI中的—NCO与其他原料中总羟基的物质的量的比值)以及亲水扩链剂(DMPA)用量对乳液粒径及稳定性的影响。利用紫外光谱(UV)、红外光谱(FTIR)对AAPU进行了结构表征,通过纳米粒度仪、透射电镜和Zeta电位分析仪对乳胶粒的粒径大小、形貌和带电情况进行了测定。结果表明:产物具有预期的结构。r值控制为1.20,DMPA用量为5%(以原料的总质量为基准,下同)时,所合成AAPU的平均粒径为42.6 nm,等电点为5.16,乳胶粒外形呈较规则球形;由于AAPU表现为两性,它可在非金属鞣制体系的复鞣加工中作为复鞣剂,有望提高皮革与阴离子湿整饰材料的结合能力。     

Preparation and characterization of ophthalmic polymers containing silicon nanoparticles

HEMA, MMA, NVP, EDGMA, and 3-vinylanisole were copolymerized with Si nanoparticles and silicon 2,3-naphthalocyanine bis (trihexylsilyloxide) for ophthalmic application. The physical, optical, and surface characteristics of the contact lens copolymers were investigated to examine the usefulness of the above nanomaterials as components for contact lenses. The water content and the refractive index were in the range of 26.03–37.61% and 1.435–1.479, respectively. Meanwhile, the tensile strength ranging from 0.156 to 0.802 kgf increased with increasing the addition ratio of 3-vinylanisole. Si nanoparticles reduce spectral transmittance in all wavelengths, whereas for silicon 2,3-naphthalocyanine bis (trihexylsilyloxide) the transmittance of visual light increased but the transmittance of UV and near infrared decreased. High contact angle was observed for contact lenses containing both Si nanopowder and silicon 2,3-naphthalocyanine bis (trihexylsilyloxide). The water content of contact lenses was not significantly affected by the addition of 3-vinylanisole. Nanomaterials such as Si nanoparticles and silicon 2,3-naphthalocyanine bis (trihexylsilyloxide) can be used for manufacturing hydrogel soft contact lenses with UV-blocking capabilities if the intensity and the wettability of the surface are properly controlled.     

Optically active polymers containing side-chain benzophenone chromophores

Optically active copolymers of (—)menthyl acrylate (MtA) with 4-hydroxybenzophenone acrylate (ABP) have been prepared by radical initiation. Reactivity ratios, mean sequence lengths and the statistical distribution of the sequence lengths of both co-units have been evaluated. Chiroptical properties of the copolymers indicate that a chiral perturbation of side-chain benzophenone chromophores occurs, due to the dissymetric arrangement of the macromolecules. C.d. data in the spectral region connected with the nåπ°1 electronic transition of benzophenone chromophore, combined with statistical distribution of sequence lengths of monomeric units in the macromolecules suggest that the observed ellipticity is essentially due to the isolated ABP units, inserted in blocks of chiral MtA units.     

Preparation and characterization of green reflective films of polyaniline analogs containing azobenzene units

Pd‐catalyzed polycondensation of aniline derivatives and 4,4′‐dibromoazobenzene affords polyaniline analogs containing azobenzene units. The polymers are red in solution and in thin films state, whereas they have a green luster in thick films. Substitution of 4,4′‐dibromoazobenzene for 4,4′‐dibromostilbene changes the reflection color from green to blue, whereas the introduction of a non‐conjugated unit slightly affects the reflection color. The glossiness of the film is dependent on the smoothness of the film surface. The reflectance measurements using polarized light reveal that reflection spectra correlate well with the complex refractive index (ñ = n + ik) of the film. These results confirm that the green luster can be attributed to the uniform surface reflection of the object, which has a large refractive index and absorption coefficient at around 500 nm. The polymer films exhibit good transmission of radio frequency signals owing to the lack of free electron carriers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41275.     

Synthesis and characterization of side-chain liquid crystalline polymers and oriented elastomers containing terminal perfluorocarbon chains

Several novel chiral side-chain liquid crystalline (LC) polysiloxane resins containing epoxy groups and mesogenic components have been graft copolymerized by a one-step hydrosilylation reaction with poly(methylhydrogeno)siloxane, an epoxy monomer 2-(allyloxymethyl)oxirane, and chiral fluorinated liquid-crystalline monomers 4′-(4-(allyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate and 4′-(4-(undec-10-enoyloxy)benzoyloxy)biphenyl-4-yl 6-(perfluorooctanoyloxy)hexahydrofuro[3,2-b]furan-3-yl adipate. The synthesized epoxy resins are cured using 4,4′-diaminodiphenyl-methane in mesophase state under a magnetic field to obtain crosslinked oriented elastomers. The chemical structures, LC properties and surface morphology of the monomers, the resins and the liquid crystalline elastomers (LCEs) are characterized by use of various experimental techniques such as FTIR, ¹H NMR, EA, TGA, DSC, POM, and X-ray measurements. The mesomorphic properties of the synthesized resins and corresponding oriented elastomers are influenced by the terminal perfluorocarbon chains components effectively. The resins show chiral nematic and chiral smectic C phases (), and are frozen in their corresponding oriented elastomers. The LC phases are verified by X-ray measurements, and the orientational order parameters of the oriented LCEs are calculated as well.     

Synthesis and characterization of side-chain maleimide-styrene copolymers with new pendant azobenzene moieties

Four side-chain maleimide-styrene polymers have been synthesized from maleimide-alt-styrene copolymer (MASt) and some original azo-moieties using polymer analogous reactions. The structures have been obtained with good yields; remarkably, they showed a high chromophore load, up to ~100%. The polymers were characterized by means of SEC, FT-IR, ¹H-NMR, DSC-TGA, and elemental analysis. The side-chain polymers exhibited improved solubility and enhanced thermal stability up to 320oC, while their glass transition temperatures have been found to be as high as 210oC. The third-order NLO refraction (n₂) and susceptibility χ⁽³⁾ coefficients were measured by Z-scan technique. The results of Z-scan measurements showed that the polymers have only nonlinear refraction, the nonlinear absorption being negligible.     

Methacrylic polymers containing permanent dipole azobenzene chromophores spaced from the main chain: synthesis and characterization

Three photochromic monomers containing a permanent dipole photochromic azobenzene group separated from the methacryloyl moiety by a polymethylene spacer, namely 4-(4-oxy-4′-cyanoazobenzene)but-1-yl methacrylate, 6-(4-oxy-4′-cyanoazobenzene)hex-1-yl methacrylate, and 8-(4-oxy-4′-cyanoazobenzene)oct-1-yl methacrylate, were synthesized in three steps starting from 4-cyanoaniline. These monomers were homopolymerized and copolymerized with an optically active monomer, (−)-menthyl methacrylate, in the presence of AIBN as a radical initiator. The polymeric materials, having a molar content of photochromic units comprised between 5 and 100% and molecular weights of about 15000, were characterized by an almost random distribution of monomeric units and a glass transition temperature ranging from 35 to 131°C. Polymer samples having a content of aromatic units larger than 75% were characterized by a thermotropic liquid crystalline structure, as evidenced by optical microscopy, X-ray diffraction and DSC measurements. Two-dimensional correlations spectroscopy (COSY) allowed an appreciable contribution by intramolecular charge transfer mesomers to the electronic distribution of the azobenzene chromophore to be highlighted. © 1998 Society of Chemical Industry     

Synthesis and characterization of H-bonded side-chain and crosslinking LC polymers containing donor/acceptor homopolymers and copolymers

Side-chain copolymers consisting of proton acceptors (stilbazoles) and proton donors (benzoic acids) connected to polyacrylate backbones with different methylene spacer lengths are prepared by tuning their donor/acceptor molar ratios. The H-bonded copolymer networks are formed once they were synthesized, and showed more homogenous phase behavior than the physical blending supramolecular networks composed of donor and acceptor homopolymers. Analogous monomer–monomer and polymer–monomer (H-bonded side-chain polymer) complexes of similar structures are also investigated. According to DSC, POM, and XRD studies, it reveals that the copolymers with various spacer lengths and donor/acceptor molar ratios show the smectic A (S_A) phase. The d spacing values of XRD results suggest that the H-bonded copolymers may be constructed by either a monolayer or an interdigitated bilayer structure. Generally, the d spacing values of copolymers (in the S_A phase) increase with higher H-bonded crosslinking density between benzoic acids and stilbazoles, i.e. decrease with higher molar ratios of benzoic acids, which may be owing to the formation of hydrogen bonds between benzoic acids from different backbones. The isotropization temperatures of the H-bonded blends and copolymers increase as the molar ratios of benzoic acids increase, while the higher H-bonded crosslinking density between benzoic acids and stilbazoles stabilizes the liquid crystalline phase.     

Synthesis and characterization of novel antimicrobial polymers containing pendent triclosan moieties

Novel antimicrobial copolymers were produced by first converting the commodity biocide, triclosan (TCS), to an epoxy-functional derivative, 2-((5-chloro-2-(2,4-dichlorophenoxy)phenoxy) methyl)oxirane (ETCS), and then reacting ETCS with polyethylenimine (PEI). While neither ETCS or PEI showed high antimicrobial activity toward either the Gram-positive bacterium, Staphylococcus epidermidis, or the Gram-negative bacterium, Escherichia coli, some the copolymers showed very high activity toward both bacteria. Antimicrobial activity for these copolymers was found to be highly dependent on both the molecular weight of the PEI utilized and the concentration of pendent groups derived from ETCS. In general, decreasing PEI molecular weight and increasing TCS pendent group concentration increased antimicrobial activity. Surface tension measurements showed that the molecular parameters affecting antimicrobial activity also affected surface activity in a similar fashion. Thus, it was speculated that the mechanism of antimicrobial activity associated with these copolymers involves interaction of the copolymers with the bacterial cell wall. A comparison of the antimicrobial activity of the most effective copolymers to TCS showed that the copolymers were more effective toward E. coli than pure TCS when compared using an equivalent TCS content (i.e. TCS pendent group content for the copolymers). This characteristic coupled with the fact that the TCS-containing copolymers are highly aqueous soluble liquids as opposed to a crystalline solid of limited solubility may afford utility of these copolymers for a variety of applications.     

Preparation and optical performance of chiral polymers having azobenzene segments

A series of monomeric azobenzene derivatives of 6‐(4‐nitro‐4′‐oxy‐azobenzene acrylate with carbon numbers of 6 and 11, and the chiral monomer of bornyl 4‐(6‐acryloyloxyhexyloxy)‐phenyl‐4′‐benzoate were synthesized. Chiral polymers having bornyl group end‐capped pendants with azobenzene‐derived segments were prepared. Molecular structures and polymer compositions were confirmed by using ¹H‐NMR, elemental analysis, FTIR, and UV–vis analyzers. Thermodynamic properties of both monomers and polymers were investigated. Specific rotations of chiral monomers and polymers were estimated by using an automatic digital polarimeter. Liquid crystalline textures of monomers and polymers were analyzed by using a polarizing optical microscope and confirmed by a small‐angle X‐ray analyzer. The optical reflection characteristics of composite cells with chiral nematic liquid crystal and various amounts of azobenzene derivatives were evaluated by using a UV–vis spectrophotometer. The reliability and stability of the composite cells with E48/S811 and azobenzene derivatives were studied. The photoisomerization of the chiral polymer film was investigated by using SEM and AFM analyzers. It was found that the UV irradiation of a laser spot caused the shrinkage of polymer film due to the photoisomerization of azobenzene segments. The contraction of the polymer film can be recovered by heat treatment. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3693–3704, 2004     

Photo-responsive block copolymer containing azobenzene group: Synthesis by reversible addition-fragmentation chain transfer polymerization and characterization

The design and synthesis of a new azobenzene-based methacrylate monomer (Azo-IEM) was demonstrated, and its polymerization behavior during reversible addition-fragmentation chain transfer (RAFT) polymerization was investigated. Well-defined homopolymer and amphiphilic block copolymer containing Azo-IEM monomeric units were successfully prepared as evidenced by NMR and GPC analysis. Moreover, the photo-triggered reversible isomerization of polymer products in selected solvents was investigated. Finally, TEM analysis showed that there were significant differences in the nanoparticle morphologies when the block copolymer samples were irradiated with different wavelengths of light (i.e., UV and visible). The size and shapes of the p(HEMA-b-Azo-IEM) polymer capable of transitions upon changes in Vis/UV light exposure which prepared from MeOH/CHCl₃ mixture solvent. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47870.     

Preparation and characterization of novel polyimide films containing amide groups

A novel diamine monomer 4-amino-N-(4-amino-phenyl)-benzamide (DABA) containing amide group was introduced to modify the polyimide of pyromellitic dianhydride (PMDA) and 4, 4′-oxydianiline (ODA) by copolymerization. A series of homo- and co-polyamic acid were synthesized by DABA and ODA in different molar ratio with PMDA, and polyimide films were obtained by thermal imidization. The films were characterized by tensile testing, dynamic mechanical analysis (DMA), thermal gravimetry analysis (TGA), fourier transform infrared (FTIR) and wide x-ray diffraction (WAXD). All of the obtained polyimide films show excellent mechanical properties and thermal stability. With the content of DABA increasing from 0% to 100%, the tensile strength and initial modulus are highly improved from 124.72 MPa and 4.70 GPa to 286.46 MPa and 22.06 GPa respectively. The polyimides have 5% weight loss temperature in the range of 530.0–555.5 °C. The glass transition temperatures are in the range of 387.90–409.16 °C and the tanδ values decrease from 0.3721 to 0.08316. The results of WAXD and FTIR indicate that the introduction of DABA containing amide group can improve the order degree of macromolecule and form hydrogen bonds between the main chains, which results in the improvement of mechanical properties.     

Photoactive polymers containing vanadium: 1. Preparation,characterization and photoreactions

Photoactive polymers have been prepared by reaction of VOQ₂OH (Q = 8-quinolyloxo) with polymers of types A and B carrying pendant hydroxyl groups. Type A was represented by copolymers of methyl methacrylate and 2-hydroxyethyl methacrylate and type B by a copolymer of styrene and p-vinylbenzyl alcohol. The final copolymers are designated VA, VB, respectively. The copolymers were characterized by near u.v.—visible spectra. On irradiation (λ = 365 nm) the vanadium (IV) chelate VOQ₂ is formed; this is indicated by the u.v.—visible spectral changes, and also by e.s.r. spectroscopy. The infra-red spectra of the copolymers VA, VB show important differences, notably the presence of a strong band near 960 cm^?1 (attributable to V=O stretching vibrations) in the former and its absence from the latter. From this and other evidence it is concluded that the vanadium residues have different structures in the two types of copolymer, viz. O=VQ₂OR and (HO)₂VQ₂OR in VA and VB respectively, where R is the remainder of the copolymer molecule. Irradiation (λ = 365 nm) is considered to bring about scission of VOR bonds in copolymer VA with formation of a macroalkyloxy radical OR. This is consistent with spin-trapping experiments with benzylidene nitrone. On the other hand, photolysis of copolymer VB appears to give radicals identical with those from VOQ₂OH which are most probably OH.The formation of different types of radical on irradiation of copolymers VA, VB is also indicated by spin-trapping observations with nitrosodurene in benzene solution and also the occurrence of photografting when VA (but not VB) is irradiated in a monomer. The photolysis of VOQ₂OH to which we have referred above may provide a convenient source of hydroxyl radicals in non-aqueous solution.     

Photoresponsive polymers: 2. The monolayer behaviour of photochromic polymers containing aromatic azobenzene residues

The monolayer characteristics of photochromic azo containing addition and condensationpolymers have been investigated under different conditions of illumination. Possible orientations of the polymers in the monolayers have been proposed. It was found that trans → cis photoisomerization of these materials was not always possible in the Langmuir films and photoinduced changes in monolayer area with time were followed for those polymers which showed uninhibited photoisomerization.     

Synthesis and characterization of novel aromatic condensation polymers containing rigid benzoxazole pendent groups

A new aromatic diamine monomer containing benzoxazole substituents was prepared by a multistep synthesis starting from 1,4‐dibromo‐2,5‐difluorobenzene. The diamine was polymerized with commercial aromatic dianhydride or dicarboxylic acid chloride monomers to provide several different poly(amic acid)s and polyamides with their inherent viscosities in the range of 0.24–0.46 dL/g. Thermal properties of these polymers including thermal imidization of poly(amic acid)s into polyimides were investigated by using FTIR, DSC, and TGA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 178–185, 2004     

Synthesis and characterization of poly(p-phenylene vinylene) polymers containing the quinoxaline group

Summary Novel poly (p-phenylenevinylene) polymers containing the quinoxaline group were prepared by the Horner-Wadsworth-Emmons reaction of the various diphosphonic acid diethyl ester with a dialdehyde monomer. The spectral properties of products so obtained were characterized by UV-visible and fluorescence spectroscopy. The UV-visible absorbance of these polymers showed absorption bands at ca. 432∼440 nm, which corresponding to the π-π* transition of the conjugated system. Their maximum fluorescence appeared at ca. 488 ∼ 498 nm. The resulting polymers showed greenish blue emission in solution and an orange emission in solid state. Received: 13 December 2002/Revised version: 27 February 2003/ Accepted: 1 March 2003 Correspondence to Jae Yun Jaung     

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.     

带双甲基丙烯酰基偶氮苯液晶化合物的合成与表征

合成了一毓新的带双甲基丙烯酰基偶氮苯液晶化合物,并利用元素分析、红外光谱、核磁共振谱及热台偏光显微镜等方法对其进行了不征。     

含偶氮苯8-羟基喹啉稀土配合物的合成与表征

合成了三种含偶氮苯8-羟基喹啉稀土配合物,通过元素分析、红外、紫外、荧光光谱及热分析,确定了三种配合物的组成为REL3（RE=Sm,Eu,La）,三种配合物在550～650 nm都能产生荧光,峰值（λmax）分别为569,559,552 nm。