Dynamics of the photo-induced orientation and relaxation of new polymethacrylates containing carbazolyl and azobenzene pendant groups

Polarized-light-induced birefringence has been investigated in copolymers of [ω-(N-carbazolyl)alkyl methacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]phenoxyalkyl methacrylate]. Optical properties of the side-chain copolymers have been compared with materials in which the azo-dye was merely dispersed in a poly[ω-(N-carbazolyl)alkyl methacrylate] matrix. Increasing the temperature of the film has a dramatic depressive effect on the maximum of photo-induced orientation near and above the glass transition temperature (T_g) region, while its effect was restricted under this temperature. Kinetics of the photo-orientation and the thermal relaxation as a function of temperature have been analysed by a biexponential model based on two rate constants. The universal Williams–Landel–Ferry (WLF) theory has been used to correlate the writing process and relaxation relative time constants with the relative temperature, i.e. T−T_g . The validity of this model for the studied materials leads to the assumption that photo-orientation and relaxation processes are mainly dependent on the free volume in the polymer matrix. This hypothesis has been assessed in the case of [11-(N-carbazolyl)undecyl methacrylate]-based materials. © 1999 Society of Chemical Industry     

Synthesis and photochemical transformations of an anthracene containing methacrylic copolymer

Summary : A new methacrylate monomer containing anthracene moiety connected with long flexible spacer was prepared and copolymerized with n-butyl methacrylate. It has been found that upon illumination in inert atmosphere photodimerization of the anthracene rings takes place to a considerable extend. The reverse decomposition of the photodimers by thermal treatment is also facilitated by the long flexible spacer. In ambient air the only photoreaction is endoperoxide formation. Received: 4 December 2000/Revised version: 21 May 2001/Accepted: 21 May 2001     

Synthesis,characterization and liquid crystalline properties of polyacrylates and polymethacrylates containing aryl ester pendant unit

Aryloxycarbonylphenyl acrylates and methacrylates were prepared by reacting 4‐acryloyloxybenzoyl chloride and 4‐methacryloyloxybenzoyl chloride with different phenols. They were homopolymerized using benzoyl peroxide as the initiator at 65°C in dimethylformamide. The polymers were characterized by IR and ¹H–NMR spectra and size exclusion chromatography. Differential scanning calorimetry and polarizing optical microscopy studies revealed that the phenyl esters of poly(4‐acryloyloxybenzoic acid) and poly(4‐methacryloyloxybenzoic acid) did not show any liquid crystalline properties, but, the para‐aryl–substituted phenyl esters did exhibit mesophase properties in the temperature range of 98–265°C depending on the nature of the aryl substituent. Polymethacrylates exhibit higher T_g, and lower T_m and T_i than the polyacrylates having the same pendant mesogen. Thermogravimetric analyses have shown that the initial decomposition temperatures of the polymers are above 230°C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 465–474, 2000     

Synthesis and characterization of photo-crosslinkable liquid crystalline copolyesters containing arylidene-keto and chalcone moieties

A series of six photo-crosslinkable thermotropic liquid crystalline copolyesters were prepared by polycondensation method at room temperature using tetra-n-butylammonium bromide as the phase transfer catalyst. The diacid chloride involved in this process was adipoyl chloride, the common diol (diol-1), also referred to as bischalcone diol, used was 3,3′-benzene-1,4-diylbis[1-(4-hydroxyphenyl)prop-2-en-1-one] and six different arylidene diols were involved as varying diols (diol-2), in the ratio 2:1:1. The common diol and the six arylidene diols were synthesized by the acid-catalyzed Claisen-Schmidt synthesis. The inherent viscosity η_inh of these six copolyesters was found between 0.35 and 0.45. The microstructure of the repeating unit present in the copolyester chain was confirmed by FT-IR, ¹H–NMR and ¹³C–NMR spectroscopic techniques. Thermal transition temperatures, resolved from the DSC thermograms, were found to be well above room temperature. Optical polarizing microscopy was employed to establish the liquid crystalline property and all the polymers were found to have nematic phase. The photo-crosslinking behaviour of these copolyesters was studied in DMF solution at different time intervals. The copolyesters having methoxy group in them absorb UV-A rays (315–400 nm) for a longer duration, which promotes them to be good candidates for UV filters and sunscreens.     

Spectral properties of chalcone containing triphenylamino structural unit in solution and in polymer matrices

Novel chalcones (3-phenyl-1-phenylprop-2-en-1-ones) substituted on one end (position 3) with electron donating diphenylaminophenyl substituent and on the other end (position 1) with thiophenes with variable electronic effects (CH-1-CH-5) were prepared. The spectral properties of these molecules in solvents such as chloroform, cyclohexane, acetonitrile, methanol and incorporated into polymer matrices of polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(vinyl chloride) (PVC) were compared with those of 3-[4-(N,N-dimethylamino)-phenyl]-1-phenylprop-2-en-1-one (CH-1m) and 3-[4-(N,N-dimethylamino)phenyl]-1-(4-nitrophenyl)prop-2-en-1-one (CH-2m). The longest wavelength absorption band of model chalcones CH-1m and CH-2m was in the range of 400-420 nm and did not appear to be influenced by the medium. The fluorescence increased with the addition of acetonitrile, while it was effectively quenched in methanol. The strong electron-attracting nitro group quenched the fluorescence of CH-2m in nearly all solvents. In contrast, the fluorescence became more intense when the molecule was incorporated in a polymer matrix. The longest wavelength absorption band of novel chalcones was observed in the range of 410-450 nm in all media. The fluorescence of chalcones was red-shifted to the range of 530-575 nm and was most intense in chloroform. The quantum yield of fluorecence was the highest in chloroform for the chalcone with a methyl-thiophene (0.49) and low for the chalcone with a fluorenyl-thiophene group (0.07). The fluorescence of all chalcones (CH-1-CH-5) was effectively quenched in polar acetonitrile and methanol, and was less intense relative to chloroform when incorporated into a polymer matrix and more intense relative to other solvents. The lifetime of fluorescence was in the range of 1-4 ns. The Stokes shift was in the range of 4000-5000 cm⁻¹ in chloroform, and lower in all other media. The spectral behavior of model chalcones CH-1m and CH-2m and novel chalcones with diphenylamino substituents was similar, producing observable fluorescence in several polymer matrices. The effect of the solvent on the fluorescence is discussed in terms of negative and positive solvatokinetic effects.     

The synthesis of spherical activated carbons containing zinc and their photochemical activity

Spherical activated carbon (AC) containing photocatalyst was prepared using strong and weak acid ion-exchange resins as starting materials. These resins were treated with an aqueous solution of Zn²⁺ or [Zn(NH₃)₄]²⁺ and both treated resins and non-treated resins were carbonized and activated. The physicochemical characteristics of the AC samples were examined using XRD, SEM, EDS, BET, EPMA, ESR, compressive strength and zinc content. The photocatalytic activity was evaluated by measuring the humic acid (HA) removal efficiency using UV/photocatalyst system. When strong acid ion-exchange resins (SZ samples) were used to prepare AC containing zinc, the zinc was found to have ZnS crystal structures, whereas in case of the use of weak acid ion-exchange resins (WZ samples), the zinc was found to have ZnO crystal structure. Both the SZ and WZ samples had spherical shape except the WZ-A-900 and had a good BET specific surface area. In the HA removal test using a floating UV/photocatalyst system, the WZ samples showed higher HA removal efficiency than the SZ samples.     

Photophysical and photovoltaic properties of a PPV type copolymer containing alternated fluorene and thiophene units

The synthesis and photophysical characterization of a PPV-type copolymer containing a fluorene derivative alternated with thiophene units is presented: poly(9,9’-dioctylfluorene-thiophene) (LAPPS29). Photophysical studies demonstrated that in the solid state only preformed ground state aggregates are responsible for exciton formation. These aggregates are formed with a wide range of size distribution. The emission from isolated segments is quenched either by resonant energy transfer, or by migration processes. Also, the main photovoltaic parameters are discussed in connection with the photophysical behavior.     

Synthesis and characterization of novel polyampholyte and polyelectrolyte polymers containing imidazole,triazole or pyrazole

Novel soluble and non-soluble polymers based on methacrylic acid, ethylene glycol diglycidyl ether and pyrazole, triazole or imidazole were obtained by a one-spot synthetic strategy. The new materials were characterized by spectroscopic techniques (FT-IR, and solution- and solid-state NMR). Evidence on the covalent binding of the different heterocycles to the non-soluble matrix was given by the unequivocal assignment of the ¹³C solid-state NMR spectra. Proton relaxation times in the rotating frame and two-dimensional wideline separation (¹H-¹³C WISE) NMR spectra were used to assess their molecular dynamics. The higher synthetic yield of polyampholytes bearing triazole or pyrazole correlated with a lower molecular motion and a higher cross-linking degree. The polyelectrolyte effect of these materials was exhaustively explored through the acid-base properties, swelling and zeta potential. The quaternization of heterocyclic residues, responsible for adsorptive properties, was studied taking into account that these materials are attractive for analytical, environmental and biotechnological processes.     

Synthesis of side-chain liquid crystalline polyacrylates,polymethacrylates and polysiloxanes containing 4-cyano-biphenyl 4-alkanyloxybenzyl ether side groups

Summary The synthesis and characterization of side-chain liquid crystalline polyacrylates, polymethacrylates and polysiloxanes containing 4-cyanobiphenyl 4-alkanyloxybenzyl ether side groups are presented. All polymers display respectively a smectic A mesophase. The influence of the polymer backbone flexibility on the phase transition temperatures of the synthesized side-chain liquid crystalline polymers is discussed. The results demonstrate that flexible backbones enhance the decoupling of the motions of the side chain and main chain. Therefore, among three kinds of polymer backbones which contain the same mesogenic side groups, the most flexible one, i.e., polysiloxane, reveals a highest isotropization temperature and a widest temperature range of mesophase.     

Synthesis and properties of polyesterimides containing a bicyclo-octene ring

New polyesterimides containing a bicyclo-octene ring were synthesized by the polycondensation reaction of N,N′-dicarboxymethyl(bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid diimide)dimethylester and N,N′-dicarboxyphenyl(bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid diimide)dimethylester with various aliphatic diols. These polymers thus obtained are soluble in m-cresol, dimethylformamide (DMF), dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO) except those from ethylene glycol. The polymers showed thermal stability above 350°C.     

Synthesis and characterization of soluble copolyimides containing chalcone and phosphine oxide moieties in the main chain

The functional diamines 3,3′‐diaminochalcone and bis(3‐aminophenyl)‐3,5‐bis(trifluoromethyl)phenyl phosphine oxide were successfully prepared by simple and convenient procedures with short reaction times, and the overall yields were 78 and 70%, respectively. Copolyimides prepared from 3,3′‐diaminochalcone, bis(3‐aminophenyl)‐3,5‐bis(trifluoromethyl)phenyl phosphine oxide, and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride exhibited excellent solubility in several organic solvents, such as dimethyl sulfoxide, N,N‐dimethylformamide, N‐methyl pyrrolidone, tetrahydrofuran, and acetone. They also showed very good thermal stability even up to 450°C for 5% weight loss (by thermogravimetric analysis) in nitrogen and a high glass‐transition temperature up to 274°C (by differential scanning calorimetry) in nitrogen. The copolymers' adhesive and photoreactive properties were also investigated, and it was confirmed that the copolyimide containing chalcone and phosphine oxide moieties in the main chain had good adhesiveness and photoreactivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization, and photochemical properties of chromophores containing photoresponsive azobenzene and stilbene

In this article, we describe the synthesis of two azobenzene and two stilbene‐based diacetylene chromophores containing terminal electron‐donating (? OCH₃) and electron‐withdrawing (? NO₂) terminal groups with esterification reactions. The target compounds were characterized by NMR, X‐ray diffraction (XRD), absorption, and photoluminescence spectroscopies. We investigated the structural effects of these photochromic compounds on the E–Z photoisomerization and 1,4‐addition under UV irradiation. 4‐[(4‐Nitrophenyl)‐diazenyl]phenyl pentacosa‐10,12‐diynoate, incorporating the electron‐withdrawing nitro group (? NO₂), underwent the fastest rate of Z‐to‐E isomerization in darkness via a rotation mechanism. Our results demonstrate that self‐assembled azobenzene Z isomers exhibited enhanced fluorescence under UV irradiation. XRD spectroscopy identified bilayer packing by the polydiacetylene films after 1,4‐addition. Chromophores comprising the diacetylene group presented moderate photochromic stability upon 1,4‐addition, changing from their original yellowish color to form a blue phase. These synthesized compounds may be useful in the development of new and unique functional materials that exhibit bistable photochromism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

含多取代嘧啶环的乙氧甲酰硫脲的合成及除草活性

合成了6种新的N－乙氧甲酰基－N（4,5,6－三取代－2－氨基嘧啶）硫脲化合物。进行了IR、^1HNMR和元素分析表征。初步的除草活性测定表明,部分目标化合物对单子叶植物的生长有较好的抑制活性,对双子叶植物稳定,表现出较好的选择性。     

A comparison of triazole cross‐linked polymers based on poly‐AMMO and GAP: Mechanical properties and curing kinetics

Triazole cross‐linked polymers based on poly(3‐azidomethyl‐3‐methyl oxetane) (poly‐AMMO) and glycidyl azide polymer (GAP) were prepared using bis‐propargyl‐1,4‐cyclohexyl‐dicarboxylate (BPHA) as curing agent, respectively. Swelling tests demonstrated that cross‐linking densities of the resulted polymers both increased with the increase of BPHA. Triazole cross‐linked polymers based on poly‐AMMO showed superior tensile strength and elongation at break than those of GAP at comparable stoichiometry. The curing kinetics was also investigated by FTIR, and GAP exhibited faster reaction rate when reacted with BPHA than that of poly‐AMMO. In addition, with the increase of cross‐linking density, the glass transition temperature (T_g) of as‐prepared polymers significantly increased, and poly‐AMMO‐based polymers showed stronger T_g‐raising effect than GAP‐based polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43341.     

Polymer thin film photodegradation and photochemical crosslinking: FT-IR imaging, evanescent waveguide spectroscopy, and QCM investigations

Photodegradation and photocrosslinking of benzophenone blended polystyrene (PS) thin films were investigated primarily using Fourier transform infrared (FT-IR) imaging, evanescent waveguide spectroscopy (WS), and quartz crystal microbalance (QCM) methods. The main objective is to observe the changes (spectral and chemical) indicative of these competitive processes in an ultrathin polymer film. This also serves as a model study in the application of combined spectroscopic, optical, and acoustic methods towards understanding crosslinking and degradation phenomena within the same time frame of observation. To induce photocrosslinking, 1,12-dodecanediylbis(oxy-4,1-phenylene)] [bis[phenylmethanone] (2BP12), a small molecule with two benzophenone groups, was blended with PS in solution, spincast onto glass and silicon substrates, and irradiated with ultraviolet light. Photodegradation and benzophenone-mediated crosslinking were observed both directly via functional group spectroscopies and indirectly via their effects on thin film surface properties and morphologies. Atomic force microscopy (AFM) and QCM were used to elucidate local morphology change and mass-uptake kinetics in the presence of O₂ in air, respectively. All results correlated well with the two photoprocesses occurring simultaneously and competitively on these films with the refractive index, thickness, and mass change differing with the presence of 2BP12. Crosslinking was observed to cause an increase in thickness while photodegradation gave a decrease. Both processes resulted in an increase in the refractive index and mass. While various methods have separately identified these observations, this is the first instance that the in situ chemical, optical, and structural dimensionality of the photodegradation and photocrosslinking phenomena in a thin polymer film is correlated within the same time frame of observation.     

Synthesis and characterization of poly(arylene ether ketone)s containing triazole units through click chemistry

In order to develop a novel process for poly(arylene ether ketone)s with high thermal and chemical stability, a series of poly(aylene ether ketone)s containing triazloe moieties were synthesized via the click chemistry of 4,4′-bis(azidomethyl) diphenyl ketone (BADPK) and bisethynyl compounds (BEAE1-5). The resulting polymers were characterized by using IR and ¹H NMR techniques. The solubility data showed that samples possessed good solubility in highly polar solvents. Molecular mass of these samples was determined by GPC which indicated they exhibited reasonable molecules weights and relatively small polydispersity. Furthermore, thermal stability of the samples was evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), which indicated that they possessed good thermal stability and high T _g (100–140 °C). All the polymers were amorphous confirmed by DSC and X-ray diffraction (WAXD).     

NMR investigations on molecular transport in ZSM-5 type zeolites containing structural defects

NMR spectroscopy is used to study the transport properties in ZSM-5 type zeolites containing structural irregularities. Using methane as a probe molecule, the structural distortions in polycrystalline aggregates are found to lead to an enhanced molecular mobility. After coking, molecular mobility is more reduced than in the monocrystalline specimen. This finding is explained by a preferential coke deposition in the secondary pore system. A variation of the concentration of non-acidic OH groups (silanol groups) indicating non-intact Si---O---Si bonds as structural defects of the pentasil structure, leads to characteristic changes in the sorption and diffusion properties of water. Bronsted acid sites are probed by methane self-diffusion measurements after chemisorption of ammonia and pyridine.     

Photophysical properties and potential application in photocurrent generation of porphyrin-[60]fullerene polymer linked by metal axial coordination

Porphyrin-[60]fullerene polymers linked by metal axial coordination of fullerenoacetic diacids e-isomer with dihydroxo Sn(IV) porphyrin have been prepared and characterized. The polymers display the regular one-dimensional linear arrays with lengths exceeded 200 nm and show good thermal stability. The efficient photoinduced electron transfer from singlet excited porphyrin to fullerene in the polymer has been achieved resulting in the formation of charge separation state with a lifetime as long as 140 μs in benzonitrile. The long-lived charge separated state is very useful for photoelectric conversion system. The photocurrent generation in organic photovoltaic device was described further, and a steady and rapid cathodic photocurrent response was produced at the irradiation of λ_ex = 429 nm light. The polymers are expected to provide novel photonic or electronic functions in organic solar cell.     

Thermoanalytical and infrared spectroscopy investigations of some mineral pastes containing organic polymers

The interaction in the presence of water between organic polymers [two polyvinyl alcohol acetate (PVA1 and PVA2)-, one polyvinyl acetate (PVAc)-, and one acryloethyl-metacrylomethyl (R)-type copolymers] and inorganic materials (3CaO·Al₂O₃+CaSO₄·2H₂O, 12CaO·7Al₂O₃, and CaO·Al₂O₃) was investigated using complex thermal analyses and infrared (IR) spectroscopy. The DTA curves of the 1-to 28-day-hydrated organo-mineral composite samples showed some significant differences in comparison with those of the hydrated inorganic materials. The most important differences consist in the presence of some exothermic peaks that are not attributable to the pure organic polymers. More than that, none of the specific effects of the pure organic polymers are evidenced on the DTA curves of the hydrated organo-mineral composite materials. This, in connection with their IR spectra, which clearly evidence the disappearance of some investigated polymers specific IR bands, can be considered as an indirect evidence of the cross-linking of polymer chains via metal ions.