Synthesis and characterization of a kind of poly(3‐butylthiophene methine) with azo side groups

To enhance the third nonlinear optical properties of poly(thiophene methine), we synthesized a new kind of poly(3‐butylthiophene methine) with azo side groups: poly[(3‐butylthiophene‐2,5‐diyl)‐p‐(N,N‐dimethylamino)azobenzylidenequinomethane] (PBTDMABQ). PBTDMABQ and its intermediate product were characterized with IR, ultraviolet–visible, and ¹H‐NMR spectroscopy. The band gaps of PBTDMABQ were calculated to be 1.94 and 2.06 eV with two different models. The thermal stability, determined by thermogravimetric analysis, indicated that PBTDMABQ decomposed above 345°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1261–1265, 2005     

Epoxy-based polymers functionalized with bisazo chromophores: Synthesis, characterization and photoresponsive behavior

In this work, two series of epoxy-based polymers bearing bisazo chromophores were synthesized from two precursor polymers (BP-AN and BP35-AN) through post-polymerization azo-coupling reactions. The polymers were prepared to contain bisazo chromophores with different electron-withdrawing groups and different numbers of methyl substituents, which were characterized by ¹H NMR, FT-IR, GPC, UV-vis, and thermal analysis. The photoinduced birefringence and surface-relief-grating (SRG) formation of the polymers were studied by irradiating spin-coated films of the polymers with laser light at three different wavelengths (488, 532, and 589 nm). The results show that the polymers containing bisazo chromophores possess broader and red-shifted absorption bands compared with ordinary azobenzene-containing polymers. The electron-withdrawing groups on the bisazo chromophores show significant effect on the absorption band positions. The behavior of photoinduced birefringence and surface-relief-grating (SRG) formation is closely correlated with the chromophore structures and excitation wavelength of the laser light. Both electron-withdrawing groups and methyl substituents on the bisazo chromophores show obvious influences on the photoinduced birefringence growth rate and SRG formation rate. The proper methyl substitution on the bisazo chromophores shows ability to enhance the photoinduced birefringence growth rate, birefringence saturation level, and SRG formation rate. The bisazo polymers obtained in this study can be further explored for applications in telecommunication, data-storage, sensors, and other optical devices.     

Influence of chromophoric electron-withdrawing groups on photoinduced deformation of azo polymer colloids

This study investigated the influence of chromophoric electron-withdrawing groups on photoinduced deformation behavior of colloidal spheres of three azo polymers. The colloidal spheres were prepared by using the epoxy-based azo polymers (BP-AZ-CA, BP-AZ-CN, and BP-AZ-NT) through gradual hydrophobic aggregation of the polymers in THF-H₂O media. The colloidal spheres were controlled to have similar average sizes by adjusting both the polymer concentrations in the initial THF solutions and water-adding rates in the preparation processes. The colloids were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The colloid deformation was investigated by irradiating the colloidal spheres in solid state with a linearly polarized Ar⁺ laser beam (488 nm, 130 mW/cm²). For comparison, the colloids were also studied by irradiation with a polarized diode solid state laser beam (532 nm, 130 mW/cm²). Upon the light irradiation, all the colloidal spheres were elongated along the polarization direction of the laser beams. The electron-withdrawing groups showed significant influence on the colloid deformation behavior related with the response to the light irradiation. The colloid deformation was more efficiently induced by irradiation with the laser beams having the intermediate wavelengths between the λ_max and the absorption band tails of the azo chromophores. When the hydrophilic carboxylic group was used as the electron-withdrawing groups, more significant deformation was induced under the same light irradiation condition, which could be attributed to the higher hydrophilicity of the polymer. Above observations can lead to a better understanding of the photoinduced deformation mechanism of azo polymer colloids.     

Main-chain azo polyaramides with high thermal stability and liquid crystal properties

Two novel main-chain aromatic polyamides containing azobenzene were synthesized by polycondensation of trans-azobenzene-4,4′-dicarbonyl chloride with various aromatic diamines under low temperature. Their molecular structures were identified to be symmetric and regular by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and elemental analysis. Polymers exhibited not only high thermal stability, but also lyotropic liquid crystal (LC) phases in N,N-dimethylacetamide solution which is due to hydrogen bonding and an ordered rigid structure. The crystal behaviours of the polymers were studied with X-ray diffraction analysis, and the photochromism was investigated with an ultraviolet–visible spectrophotometer with 365 nm ultraviolet irradiation. An abnormal change of the crystal behavior and thermal stability of polymer was found to be related with molecular structure containing ether linkage. The azo polyaramides can be applied in fields of optical techniques and potential photochromics fibres spinning in wide temperature ranges     

The synthesis, characterization, thermal and optical properties of copper, nickel, and vanadyl complexes derived from azo dyes

Two, novel, tetradentate Schiff-base ligands, namely bis-5-phenylazosalicylaldehyde diethylenetriimine and bis-5-[(4-methoxyphenyl)azo]salicylaldehyde diethylenetriimine, as well as their Cu²⁺, Ni²⁺, and VO²⁺ complexes, were synthesized and characterized using elemental analysis, infrared and also UV–Visible spectroscopy, ¹HNMR and mass spectra. The thermal stability of the free ligands and the related metal complexes, as determined using differential scanning calorimetry and thermal gravimetric analysis, were found to be thermally stable upto 240–275 °C depending on the type of ligand and the central metal atom. The λ_max of the ligands and their transition metal complexes in the region 300–800 nm are discussed. The novel metal complexes offer potential for application as recording media owing to both their absorption spectra in the blue-violet light region and high thermal stability.     

Processable heat-resistant polymers: 14. Polyamides and polyamideimides containing azo linkages

Diamines containing azo groups were synthesized by reacting sulphanilamide or p,p′-di(aminophenyl) sulphone with aniline. These diamines were used for the synthesis of polyamides and polyamideimides by interfacial and solution polycondensation techniques. The polymers were characterized by elemental (N and S) analyses and by i.r. and u.v. spectroscopy. The physical, chemical, thermal and electrical properties of the polymers were studied. The polymers were found to be soluble in highly polar solvents. The thermal stability of polyamideimides is superior to that of polyamides. X-ray diffraction and electrical behaviour of the polymers were also reported.     

Preparation, characterization and novel photoregulated rheological properties of azobenzene functionalized cellulose derivatives and their α-CD complexes

Novel azobenzene functionalized hydroxypropyl methylcellulose (AZO-HPMC) polymers and their α-CD (α-Cyclodextrin) complexes have been prepared. FT-IR, ¹H NMR and FT-Raman spectroscopy confirm the existence of azobenzene chromophores in AZO-HPMC polymers. α-CD can improve the water solubility of AZO-HPMC by formation of inclusion complexes with azobenzene side groups. Rheological studies substantiate that both AZO-HPMC and its α-CD complex undergo thermoreversible sol-gel transitions in aqueous solutions. Viscometric measurements suggest that the association between azobenzene side groups can be eliminated by α-CD. The effect of photoirradiation on the rheological behavior shows that the gelation temperature of AZO-HPMC increases after UV irradiation, while the gelation temperature of AZO-HPMC/α-CD complex decreases after UV irradiation.     

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.     

Hyperbranched azo polyurethane synthesized through A2 + B3 scheme

A hyperbranched azo polyurethane was synthesized by one-step polymerization of an A₂ type monomer diphenylmethane-4,4′-diisocyanate and a B₃ type monomer 4-(N,N′-bis(2-hydroxyethyl))amino-2′-hydroxyethoxyl-4′-nitro-azobenzene. The azo polymer was characterized by ¹H nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) spectrum and thermal analysis. The λ_max of the polymer in dimethylformamide (DMF) solution is 488 nm. The number average molecular weight (M_n) determined by GPC is 9,300 with a polydispersion index 1.9. The glass transition temperature (T _g) of the polymer is 131°C observed from DSC thermogram. The results show that the azo polyurethane has been successfully synthesized through this scheme. Surface-relief-gratings (SRGs) were fabricated on the polymer film after being irradiated by interference pattern of Ar⁺ laser beams for 1,000 s. The surface modulation depth and the grating space period measured by AMF are 67 and 770 nm, respectively. __________ Translated from Acta Polymerica Sinica, 2007, 1: 21–25 [译自: 高分子学报]     

Stimuli-responsive polymers. 10. Photo-regulation of optical rotations in azobenzene modified poly(ester-amide)s containing highly structured,atropisomeric backbone geometries

The chiral atropisomeric monomer R-(+)-2-amino-1,1'-binaphthalen-2-ol provides convenient access to a number of azobenzene modified poly(ester-amide)s having highly-ordered main-chain arrangements of their constituent monomer groups. When evaluated in dilute solution environments, each of the polymers that contain the azobenzene stimuliphore undergo photo-induced oscillations in optical rotatory power when stimulated by multiple UV light–visible light illumination cycles. Polymer behavior is strongly influenced by the particular sequence of monomer units positioned along the chiral ester-amide backbone. Periodic variants that are fashioned from R-binaphthylene, azobenzene and para-phenylene segments exhibit particularly interesting response profiles. In certain cases, their light-modulated chiroptical outputs alternate between two discrete states, fluctuating between positive and negative specific rotations, or reversibly interconverting between optically active and optically inactive endpoints. This chiroptical switching behavior is greatly influenced by the choice of solvent, providing an added means for tuning the binary outputs afforded by these structurally well-defined materials.     

Mixtures of tertiary amine functionalized azo-containing mesogens with acid-functionalized polymers

A tertiary amine functionalized 4-nitro-4′-alkoxy azobenzene mesogen with a 10 or 12 carbon spacer (azo-nN) was synthesized and complexed in equimolar proportions with poly(acrylic acid) (PA-H) and poly(sulfonic acid) (PSS-H), and investigated by thermogravimetric analysis, differential scanning calorimetry, polarizing optical microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The neat azo-nN is characterized by a partial bilayer S_A mesophase at higher temperatures, and a highly ordered phase, in which the molecules are stacked orthogonally in bilayers, at lower temperatures. As supported by infrared analysis, for the azo-nN/PA-H mixture, the complexation is partial while for the same azo-nN/PSS-H mixture, complete proton transfer occurs. When the azo-nN is blended with the PA-H, regarded as a weak acid, a biphasic system is generated and the thermotropic behavior of neat mesogen is not significantly affected. In contrast, by mixing the same mesogen with a PSS-H (regarded as a strong acid), the thermotropic behavior is significantly influenced: the complexation generated a partial or interdigitated smectic A or tilted smectic C lamellar phase.     

Study of three different families of water-soluble copolymers: synthesis, characterization and viscoelastic behavior of semidilute solutions of polymers prepared by solution polymerization

Polymer chains consisting of water-soluble polyacrylamides, hydrophobically modified with low amounts of N,N-dialkylacrylamides (N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)) have been prepared via free radical solution polymerization, using two hydrophobic initiators derived from 4,4′-azobis(4-cyanopentanoic acid) (ACVA) containing long linear chains of 12 (C12) and 16 (C16) carbon atoms. This procedure resulted in polyacrylamides containing hydrophobic groups along the chain as well as at the chain ends. This class of polymers, termed ‘combined associative polymers’, has been studied and compared with the multisticker (with hydrophobic groups along the polymer chain) and telechelic (with hydrophobic groups at the chain ends) associative polymers, which were prepared with DHAM or DOAM and with the hydrophobic initiator (ACVA) modified with alkyl chains of two different lengths. The viscoelastic properties of these different families of associative polymers were investigated using steady-flow and oscillatory experiments. The effect of type, localization and concentration of the hydrophobic groups on the viscosity of the associative polymer solution was investigated. All viscosity curves clearly show two different regimes within the semidilute range: a first unentangled regime where the viscosity increases moderately; and a second entangled regime where the viscosity varies according to a power law, proportional to C⁴. The relaxation time, T_R, and the plateau modulus, G₀, showed relatively high values which increased with the number of carbon atoms in the hydrophobic groups. The combined associative polymer (PAM-co-DHAM/ACVA12) showed relaxation times that remained relatively constant along the concentrations studied, but very high values of G₀.     

Soluble semi-conductive chelate polymers containing Cr(III) in the backbone: Synthesis, characterization, optical, electrochemical, and electrical properties

Soluble kinds of coordination polymers containing Cr(III) ion in the backbone were synthesized. Structures of the polymers were characterized by FT-IR, UV-vis, ¹H and ¹³C NMR, and size exclusion chromatography (SEC). Thermal degradation data were obtained by TG-DTA and DSC techniques. Cyclic voltammetry (CV) measurements were carried out and the HOMO-LUMO energy levels and electrochemical band gaps were calculated. Additionally, the optical band gaps (E_g) were determined by using UV-vis spectra of the materials. Electrical conductivity measurements of doped (with iodine) and undoped polymers related to temperature were carried out by four-point probe technique using a Keithley 2400 electrometer. Measurements were made by using the polymeric films deposited on ITO glass plate by dip-coating method. Also, absorption spectra of doped polymeric films were recorded by a single beam spectrophotometer showing that doping procedure causes shifting in absorption spectra. Their abilities of processing in gas sensors were also discussed. According to obtained results the synthesized chelate polymers are semi-conductors having polyconjugated structures. Also, P-2 is the most electro-conductive polymer among the synthesized, while P-1 is the most thermally stable one.     

Nanoconjugates of methacrylic polymers: Synthesis,characterization, and immobilization to leather

Imparting superhydrophobicity to surfaces has direct implications for developing water-repellent materials. Most hydrophobic materials cannot be applied directly to specific surfaces like leather because of noncompatibility. Although methacrylic polymers are compatible to leather, their inherent hydrophilic characteristics make it challenging to use for introducing hydrophobicity or superhydrophobicity. In this article, we present a strategy of introducing hydrophobicity in various degrees as well as superhydrophobicity to different surfaces, particularly leather and glass surfaces by using conjugates of methacrylic polymers and various carbon nanomaterials. The covalent functionalization of methacrylate polymers with carbon nanotubes and fullerenes was performed by radical polymerization in the presence or absence of chain transfer agents (CTAs). CTA was used during polymerization to introduce carboxylic acid group, necessary for chromium-assisted binding to leather to avoid leaching. A balance between the compatibility of the polymer nanoconjugates with the leather and the amount necessary for coating stabilization was studied by a rheometer. While water contact angle measurement indicated the mild hydrophobicity in most cases, we were delighted to observe superhydrophobicity in one case presumably due to increased roughness because of the presence of specific nanomaterial to overcome inherent hydrophilicity of methacrylic polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48627.     

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     

Water soluble poly(ethylene glycol) prodrug of silybin: Design,synthesis, and characterization

Silybin, the main component of silymarin, is an antihepatotoxic agent. But it presents numerous challenges associated with its poor aqueous solubility which has been realized as the major problem in its dosage form development and clinical application. The objective of our study was to solubilize silybin by designing and synthesizing its aqueous soluble prodrug using high aqueous soluble polymeric carrier—poly(ethylene glycol) (PEG). A novel soluble silybin prodrug was synthesized with a linear PEG and succinic ester linkage, and was extensively characterized using proton NMR, FTIR, and TOF‐MS. Furthermore, the prodrug was evaluated for its drug loading capability which was 6.65% and the solubility was 800 mg/mL. The results indicate significantly higher solubility of the prodrug in comparison with silybin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization and rheological properties of three different microstructures of water-soluble polymers prepared by solution polymerization

Three different structures were synthesized via solution free radical polymerization. Polyacrylamides hydrophobically modified with small amounts of two different N′N-dialkylacrylamides [N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)] and two different N-alkylacrylamides [N-dodecylacrylamide (DAM) and N-hexadecylacrylamide (HDAM)] have been synthesized using two linear hydrophobic initiators with 12 (ACVA₁₂) and 16 (ACVA₁₆) carbon atoms and two di-substituted hydrophobic initiator with two chains of 6 (ACVA_di6) and 8 (ACVA_di8) carbon atoms derived from 4′4-azobis(4-cyanopentanoic acid) (ACVA). The polymers obtained were telechelic, multisticker and combined. The initiators, monomers and polymers synthesized were characterized by ¹H NMR and light scattering (LS). The rheological properties of these three different associative polymers were investigated using steady-state experiments. The effect of location and structure (linear or di-substituted) of the hydrophobic groups upon the viscosity of the polymer in solution was studied.     

Perfluoropolyether polymers by UV curing: design,synthesis and characterization

Perfluoropolyether (PFPE) structures can be functionalized with acrylic groups using appropriate hydrogenated acrylic monomers: the macromers obtained are highly reactive under UV irradiation, and fluorinated polymers can be obtained. In the first part of this work is described the synthesis of new PFPE (meth)acrylic oligomers by extending OH‐terminated fluorinated chains with urethane groups and reactive acrylic functions. The photopolymerization reaction of each product is then reported followed by the characterisation of the main thermal, mechanical and surface properties of UV‐cured coatings. The polymers have good thermal resistance and fair mechanical and chemical resistance. More interestingly they show very low refractive index and low surface tension. For these latter properties the products can be advantageously used in highly demanding applications such as photonic devices and nano‐patterning. Copyright © 2011 Society of Chemical Industry