Pyrrole‐based narrow‐band‐gap copolymers for red light‐emitting diodes and bulk heterojunction photovoltaic cells

A series of narrow‐band‐gap conjugated copolymers (PFO‐DPT) derived from pyrrole, benzothiadiazole, and 9,9‐dioctylfluorene (DOF) is prepared by the palladium‐catalyzed Suzuki coupling reaction with the molar feed ratio of 4,7‐bis(N‐methylpyrrol‐2‐yl)‐2,1,3‐benzothiadiazole (DPT) around 1, 5, 15, 30, and 50%. The obtained polymers are readily soluble in common organic solvents. The solutions and the thin solid films of the copolymers absorb light from 300 nm to 600 nm with two absorbance peaks at around 380 nm and 505 nm. The PL emission consists mainly of DPT unit emission at around 624–686 nm depending on the DPT content in solid film. The EL emission peaks are red‐shifted from 630 nm for PFO‐DPT1 to 660 nm for PFO‐DPT50. Bulk heterojunction photovoltaic cells fabricated from composite films of copolymer and [6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) as electron donor and electron acceptor, respectively, in device configuration: ITO/PEDOT : PSS/PFO‐DPT : PCBM/Ba/Al shows power conversion efficiencies 0.15% with open‐circuit voltage (V_oc) of 0.60 V and short‐circuit current density (J_sc) of 0.73 mA/cm² under AM1.5 solar simulator (100 mW/cm²). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fluorene‐based copolymers with donor–acceptor units on the side chain and main chain: Synthesis and application in polymer solar cells

Two narrow band gap fluorene‐based copolymers with donor–acceptor (D–A) structure on the polymer side chain and/or main chain are synthesized by Pd‐catalyzed Stille coupling reactions. The two copolymers have excellent thermal stability. The effects of D–A structure on the main and side chains on the absorption and electrochemical properties are studied. The copolymer PF‐BTh‐DBT with D–A structure both on the main and side chains has broader and stronger absorption and narrower band gap than the copolymer PF‐BTh with only a pendent D–A structure. The power conversion efficiency of the assembled solar cell using PF‐BTh‐DBT as donor and PC₇₁BM as acceptor is 1.6% with open‐circuit voltage (V_oc) 0.84 V under simulated AM 1.5 G solar irradiation (100 mW/cm²). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3276–3281, 2013     

New thiophene‐based donor–acceptor conjugated polymers carrying fluorene or cyanovinylene units: Synthesis,characterization, and electroluminescent properties

Two new thiophene‐based donor–acceptor (D–A) conjugated polymers, PDTOFV and PDTOCN, are synthesized and characterized. The polymers are readily soluble in common organic solvents and exhibit good thermal stability with onset decomposition temperature (T_d) in the range 310?330°C. Cyclic voltammetry studies revealed that polymers possess low‐lying highest occupied molecular orbital (HOMO) energy levels (?5.94 eV for PDTOFV and ?5.86 eV for PDTOCN) and low‐lying lowest unoccupied molecular orbital (LUMO) energy levels (?3.35 eV for PDTOFV and ?3.55 eV for PDTOCN). The optical band gap is calculated from onset absorption edge of the polymer film. The polymers exhibit green fluorescence with fluorescence quantum yields (?_fl) of 38% and 42%, respectively, for PDTOFV and PDTOCN. Polymer light‐emitting diodes (PLEDs) are fabricated using these polymers with a device configuration of ITO/PEDOT:PSS/polymer/Al. The device based on PDTOFV emitted green light with Commission Internationale de I'Eclairage (CIE) coordinate values of (0.25, 0.39). Whereas, the device based on PDTOCN showed white light emission with CIE coordinate values of (0.32, 0.35), which is very close to the values (0.33, 0.33) of standard white light emission. The threshold voltages of the PLEDs are determined by current density‐voltage characteristics and are found to be 7.3 and 3.9 V for PDTOFV and PDTOCN, respectively. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

New low bandgap conjugated polymer derived from 2, 7‐carbazole and 5, 6‐bis(octyloxy)‐4, 7‐di(thiophen‐2‐yl) benzothiadiazole: Synthesis and photovoltaic properties

To develop conjugated polymers with low bandgap, deep HOMO level, and good solubility, a new conjugated alternating copolymer PC‐DODTBT based on N‐9′‐heptadecanyl‐2,7‐carbazole and 5, 6‐bis(octyloxy)‐4,7‐di(thiophen‐2‐yl)benzothiadiazole was synthesized by Suzuki cross‐coupling polymerization reaction. The polymer reveals excellent solubility and thermal stability with the decomposition temperature (5% weight loss) of 327°C. The HOMO level of PC‐DODTBT is ‐5.11 eV, indicating that the polymer has relatively deep HOMO level. The hole mobility of PC‐DODTBT as deduced from SCLC method was found to be 2.03 × 10^?4 cm²/Versus Polymer solar cells (PSCs) based on the blends of PC‐DODTBT and [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) with a weight ratio of 1:2.5 were fabricated. Under AM 1.5 (AM, air mass), 100 mW/cm^?2 illumination, the devices were found to exhibit an open‐circuit voltage (V_oc) of 0.73 V, short‐circuit current density (J_sc) of 5.63 mA/cm^?2, and a power conversion efficiency (PCE) of 1.44%. This photovoltaic performance indicates that the copolymer is promising for polymer solar cells applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Visible light‐absorbing biocompatible polymers based on L‐lactide and aminosugars: preparation and characterization

Two series of polymers with low‐molecular‐weight L ‐lactide side‐arms were prepared by ring‐opening polymerization using D ‐glucosamine and N‐acetyl‐D ‐glucosamine as polymer core molecules, and methanesulfonic acid as solvent and catalyst. This simple synthetic route does not rely on the use of organometallic catalysts, and has also proven useful to the authors for chitosan grafting with lactones. NMR spectroscopy reveals a high degree of substitution (>3), and Fourier transform infrared/NMR spectra suggest the existence of three different lactate tautomers likely to be responsible for coloration. These D ‐glucosamine‐based polymers also display glass transition temperatures approximately 10 °C above that of the human body, which points to the potential of these lactone‐grafted aminosugars with tunable amphiphilic character in the design of submicrometer‐sized drug delivery vehicles. They are also viewed as interesting hydrophobic chelating agents for catalytic transition metal centers. Copyright © 2010 Society of Chemical Industry     

Synthesis and characterization of styrene–acrylic ester copolymers

Homopolymers and copolymers of styrene and different acrylic esters (i.e., acrylates) were synthesized by the free‐radical solution polymerization technique. Feed ratios of the monomers styrene and cyclohexyl acrylate/benzyl acrylate were 90 : 10, 75 : 25, 60 : 40, 50 : 50, 40 : 60 and 20 : 80 (v/v) in the synthesis of copolymers. All 6 homopolymerizations of acrylic ester synthesis were carried out in N,N(dimethyl formamide) except for the synthesis of poly(cyclohexyl acrylate) (PCA), where the medium was 1,4‐dioxane. Benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN) were used as initiators. The polymers synthesized were characterized by FTIR, ¹H‐NMR, ¹³C‐NMR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and viscosity measurements. The reactivity ratios were determined by the Fineman–Ross method using ¹H‐NMR spectroscopic data. The reactivity ratios (r) for the copolymerization of styrene (r_S) with cyclohexyl acrylate (r_CA) were found to be r_S = 0.930 and r_CA = 0.771, while for the copolymerization of styrene with benzyl acrylate, the ratios were found to be r_S = 0.755 and r_BA = 0.104, respectively. The activation energies of decomposition (E_a) and glass‐transition temperature (T_g) for various homo‐ and copolymers were evaluated using TGA and DSC analysis. The activation parameters of the viscous flow, voluminosity (V_E) and shape factor (ν) were also computed for all systems using viscosity data. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1513–1524, 2001     

Conducting systems based on styrene–butadiene‐block–copolymers: Microstructural characterization

This work reports on the preparation and structural and electrical characterization of composites consisting of HSBR, polypropylene (PP), and carbon black (CB) blends, comparing the data obtained from more or less rich PP samples. Structural analysis provided evidence of the plasticizing or crosslinked effects on the properties of composites, when CB is present in the initial system, as well as of the excellent conducting properties of CB composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 646–653, 2002; DOI 10.1002/app.10360     

Properties of nanocomposites based on maleate‐vinyl ether donor—acceptor UV‐curable systems

UV‐curable nanocomposites based on donor–acceptor crosslinking chemistry were prepared containing organically modified montmorillonites. The coatings were characterized for thermal, mechanical, and morphological properties. X‐ray diffraction and transmission electron microscopy showed that nanocomposites were formed in all samples. Results showed that an increase in the percentage of clay caused an increased modulus and glass‐transition temperature. It was also seen that tensile modulus showed dramatic improvement when compared with the unmodified polyester sample. Real time IR kinetic data showed that higher conversions were obtained at higher clay loadings. Pendulum hardness values and tensile modulus values showed different trends in properties depending on the combination of polymer matrix and organomodification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of perfluorinated acrylate–methyl methacrylate copolymers

A novel perfluorinated acrylic monomer 3,5‐bis(perfluorobenzyloxy)benzyl acrylate (FM) with perfluorinated aromatic units was synthesized with 3,5‐bis(perfluorobenzyl)oxybenzyl alcohol, acryloyl chloride, and triethylamine. Copolymers of FM monomer with methyl methacrylate (MMA) were prepared via free‐radical polymerization at 80°C in toluene with 2,2′‐azobisisobutyronitrile as the initiator. The obtained copolymers were characterized by ¹H‐NMR and gel permeation chromatography. The monomer reactivity ratios for the monomer pair were calculated with the extended Kelen–Tüdos method. The reactivity ratios were found to be r₁ = 0.38 for FM, r₂ = 1.11 for MMA, and r₁r₂ < 1 for the pair FM–MMA. This shows that the system proceeded as random copolymerization. The thermal behavior of the copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). The copolymers had only one glass‐transition temperature, which changed from 46 to 78°C depending on the copolymer composition. Melting endotherms were not observed in the DSC traces; this indicated that all of the copolymers were completely amorphous. Copolymer films were prepared by spin coating, and contact angle measurements of water and ethylene glycol on the films indicated a high degree of hydrophobicity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of a novel high‐oil‐absorbing resin

A high‐oil‐absorbing resin, which was a low crosslinking resin, was synthesized by conventional suspension copolymerization in this study. The effects of the monomer ratio, crosslinker, initiator, ratio of water to oil, and defined optimum reaction conditions were studied. The highest oil absorptivity of the resin was about 11.5 g/g in diesel and the oil‐absorption saturation time was 3 days when the best process conditions were as follows: ratio of styrene to ethylene–propylene–diene terpolymer = 40/60 w/w, amount of crosslinker divinylbenzene = 1.0 wt %, amount of benzoyl peroxide = 1.0 wt %; proportion of gelatin to calcium phosphate = 0.2 g/0.1 g, stirring speed = 500 r/min, and proportion of water to oil = 15 : 1. By using such methods as infrared spectroscopy, thermogravimetric analysis, and other methods, we studied the oil‐absorbing resin structure, oil‐absorption rate, oil‐absorption saturation time, and oil‐absorption rate twice. The oil‐absorbing resins were used repeatedly through the extraction of ethanol. The experiment results show little effect on the oil‐absorption properties. The oil‐absorption rate constant was evaluated for diesel, and the oil‐absorbing process obeyed the first‐order kinetics equation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of methacrylic acid–ethyl acrylate copolymers

Copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed in aqueous medium in the presence of an emulsifier with MAA as the major component (53.7–82.3 mol %). Emulsion stability was studied as a function of concentration and the nature of the emulsifier (ionic or nonionic). Copolymers were characterized using IR and ¹H-NMR spectroscopy. ¹³C-NMR spectra of MAA–EA copolymers have been discussed in terms of their triad monomer sequence distributions. Reactivity ratios of the MAA–EA pair were determined using a nonlinear least-square errors in variables method. Partition of the monomers in aqueous and organic phases was studied using a gas chromatographic technique. A two-loci polymerization mechanism was proposed on the basis of this partition behavior and the calculated composition of the oligomeric radicals formed in the initial stages of polymerization. © 1994 John Wiley & Sons, Inc.     

Synthesis and properties of some novel,soluble and light‐coloured,aromatic poly(amide–imide) copolymers

A new type of tetraimide‐dicarboxylic acid (I) was synthesized starting from the ring‐opening addition of m‐aminobenzoic acid (m‐ABA), 4,4′‐oxydiphthalic anhydride (ODPA) and 4,4′‐methylenedianiline (MDA) at a 2:2:1 molar ratio in N‐methyl‐2‐pyrrolidone (NMP), followed by cyclodehydration to the diacid I. A series of soluble and light‐coloured poly(amide–imide–imide)s (III_a–j) was prepared by triphenyl phosphite‐activated polycondensation from the tetraimide‐diacid I with various aromatic diamines (II_a–j). All films cast from DMAc had cutoff wavelengths shorter than 400 nm (376–393 nm) and had b* values between 20.46 and 40.67; these polymers were much lighter in colour than those of the corresponding trimellitimide series. All polymers were readily soluble in a variety of organic solvents such as NMP, N,N‐dimethylacetamide, dimethyl sulfoxide, and even in the less polar m‐cresol and pyridine. Compared with those of corresponding ODPA–MDA polyimide, the solubilities of poly(amide–imide–imide)s III_a–j were greatly improved. Polymers III_a–j afforded tough, transparent, and flexible films, which had tensile strengths ranging from 82 to 105 MPa, elongations at break from 8 to 14%, and initial moduli from 2.0 to 2.2 GPa. The glass transition temperature of polymers were recorded at 255–288 °C. They had 10% weight loss at a temperature above 540 °C and left more than 60% residue even at 800 °C in nitrogen. © 2002 Society of Chemical Industry     

Synthesis and characterization of novel thermo‐ and pH‐responsive copolymers based on amphiphilic polyaspartamides

Novel amphiphilic, thermo‐ and pH‐responsive polyaspartamides showing both double‐responsive (pH and temperature) behavior and a sol‐gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized by the successive aminolysis reactions of polysuccinimide using both hydrophobic N‐alkylamine (laurylamine, octylamine, hexylamine) and hydrophilic N‐isopropylethylenediamine. The composition of each component was analyzed by ¹H NMR. At the intermediate composition range, the system showed a lower critical solution temperature behavior in water. The transition temperature (pH dependent) could be modulated by changing the alkyl chain length and graft composition. The temperature dependence of the nanoparticle size distribution of the polyaspartamide derivatives was also examined. The critical micelle concentration of the copolymers in a phosphate‐buffered saline (pH 7.4) solution ranged from 6 to 20 μg/L. In addition, physical gelation, i.e., a sol‐gel transition, was observed in a concentrated solution. These novel double‐responsive and injectable hydrogels have potential biomedical applications such as drug delivery systems and tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of gelatin‐polydimethylsiloxane graft copolymers

Gelatin‐polydimethylsiloxane (PDMS) graft copolymers were prepared through the reaction between gelatin and α‐[3‐(2,3‐epoxypropoxy)propyl]‐ω‐butyl‐PDMSs. The copolymers were characterized by FTIR and ¹H‐NMR spectra. As proved by wide angle X‐ray analysis, a new characteristic crystalline peak appeared after the bonding of PDMS to gelatin chains. The microstructure and the elemental identification of gelatin and copolymers were followed through scanning electron microscope with energy dispersive spectrometer. The glass transition temperature of gelatin and copolymers were obtained by differential scanning calorimetry analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of temperature‐responsive poly(vinyl alcohol)‐based copolymers

A poly(vinyl alcohol) (PVA)/sodium acrylate (AANa) copolymer was synthesized to improve the water solubility of PVA at the ambient temperature. Furthermore, a series of temperature‐responsive acetalyzed poly(vinyl alcohol) (APVA)‐co‐AANa samples of various chain lengths, degrees of acetalysis (DAs), and comonomer contents were prepared via an acid‐catalysis process. Fourier transform infrared and ¹H‐NMR techniques were used to analyze the compositions of the copolymers. The measurement of the turbidity change for APVA‐co‐AANa aqueous solutions at different temperatures revealed that the lower critical solution temperature (LCST) of the copolymers could be tailored through the control of the molecular weight of the starting PVA‐co‐AANa, DA, and comonomer ratios. Lower LCSTs were observed for APVA‐co‐AANa with a longer chain length, a higher DA, and fewer acrylic acid segments. In addition, the LCSTs of the APVA‐co‐AANa aqueous solutions appeared to be salt‐sensitive. The LCSTs decreased as the concentration of NaCl increased. Moreover, atomic force microscopy images of APVA‐co‐AANa around the LCST also proved the temperature sensitivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New anthracene‐containing phenylene‐ or thienylene‐vinylene copolymers: Synthesis,characterization, photophysics,and photovoltaics

Four new conjugated alternating vinylene‐copolymers, PAP6 , PAT , PA , and TAT , incorporating anthracene rings along the backbone were synthesized by Heck coupling. They were very soluble in common organic solvents and absorbed at the range of 300–500 nm with optical band gaps of 2.38–2.47 eV. They behaved in solution as green emitters, with maximum photoluminescence at 455–518 nm. Finally, these soluble copolymers were used as donor material to realize bulk heterojunction solar cell with (6,6)‐C₆₁‐butyric acid methyl ester as the acceptor. More efficient photovoltaic cells were obtained from the copolymer that carried hexyloxy than dodecyloxy side groups. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of heat‐resistant N‐phenylmaleimide–styrene–maleic anhydride copolymers and application in acrylonitrile–butadiene–styrene resin

The heat‐resistant copolymer of N‐phenylmaleimide (NPMI)–styrene (St)–maleic anhydride (MAH) was synthesized in xylene at 125°C with di‐tert‐butyl diperoxyterephthalate as an initiator. The characteristics of the copolymer were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (¹H‐NMR and ¹³C‐NMR), gel permeation chromatography, and elemental analysis. The ¹³C‐NMR results show that the copolymer possessed random sequence distribution; this was also supported by the differential scanning calorimetry experiment, in which a single glass‐transition temperature (T_g) of 202.3°C was observed. The thermal stability and degradation mechanism of the copolymer were investigated by thermogravimetric analysis. Using the Kissinger equation and Ozawa equation, we proved a nucleation controlling mechanism with an apparent activation energy of 144 kJ/mol. Blends of acrylonitrile–butadiene–styrene with the NPMI–St–MAH copolymer with various contents were prepared with a twin‐screw extruder processes. The mechanical and thermal properties of the materials, such as the tensile and flexural strength, T_g's, and Vicat softening temperatures, were all enhanced with the addition of the modifier, whereas the melt flow index decreased. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and properties of fluorenyl–pyridinyl alternatingcopolymers for light‐emitting diodes

A novel series of well‐defined alternating poly[2,7‐(9,9‐di(2‐ethylhexyl)fluorenyl)‐alt‐pyridinyl] (PDEHFP) copolymers were synthesized using palladium(0)‐catalyzed Suzuki coupling reaction in high yields. These polymers were characterized using ¹H NMR, UV‐visible and fluorescence spectroscopies, gel permeation chromatography, thermal analysis and cyclic voltammetry. The optical properties of the copolymers, including photoluminescence (PL) and electroluminescence (EL), were studied. The difference in linkage position of pyridinyl units in the polymer backbone has significant effects on the electronic and optical properties of polymers in solution and in film state. Meta‐linkage (3,5‐ and 2,6‐linkage) of pyridinyl units in the polymer backbone is more favorable for pure blue emission and prevention of aggregation of polymer chains. PDEHFPs with 2,6‐ and 3,5‐linkage of pyridinyl units have relatively high PL efficiency of 37 and 44% in the film state. In comparison with homopolymer PDEHF, the copolymers with pyridinyl units possess low lowest unoccupied molecular orbital energy levels for easy electron injection from a cathode. Strong EL is observed and light‐emitting diodes (LEDs) exhibit typical rectifying characteristics. The emission intensity starts to increase at around 12 V. The emission peak wavelengths of the polymers roughly coincide with those of PL. This series of fluorene–pyridine‐based alternating copolymers seem to be candidates for polymeric LEDs. © 2013 Society of Chemical Industry     

Synthesis,characterization, and properties of two‐component amphiphilic polyoxyethylene–containing multiblock copolymers

Amphiphilic (oxyethylene–oxypropylene) and (oxyethylene–styrene) multiblock copolymers, both with high molecular weights, were synthesized by coupling poly(ethylene glycol) (PEG) with poly(propylene glycol) (PPG) or with telechelic dihydroxy polystyrene using 2,4‐toluene diisocyanate as a coupling agent, respectively. The polymerization conditions were investigated. The products were purified and characterized by IR, ¹H‐NMR spectroscopy, and membrane osmometry and identified as multiblock copolymers. Crystallinity of the two kinds of multiblock copolymers was determined by DSC. They showed good emulsifying properties. Their complexes with LiClO₄ showed high room‐temperature conductivities from 3 × 10⁻⁵ to 4 × 10⁻⁴ S/cm at 30°C. High molecular weight (oxyethylene–oxypropylene) multiblock copolymers, at a weight ratio of PEG/PPG = 6/4, behave like thermoplastic elastomers. The (oxyethylene–styrene) copolymer functions as a good compatibilizer for the blend of chlorohydrin rubber and polystyrene. An amount of only 3 wt %, based on the blend, is needed to increase the tensile strength of the blend almost sixfold. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1295–1301, 2005     

Synthesis and characterization of silicone-modified vinyl acetate–acrylic emulsion copolymers

The triethoxyvinylsilane (TEVS) containing vinyl acetate (VAc)/2-ethylhexylacrylate (2-EHA) copolymers were prepared by emulsion copolymerization. The polymerization was performed with methacrylic acid (MAA) and auxiliary agents at 80 °C in the presence of ammonium peroxodisulfate (APS) as the initiator. Alkyl phenol ether sulfate and Arkupal N-300 were used as anionic and nonionic emulsifiers, respectively. The resulting copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of copolymers was also investigated by scanning electron microscopy (SEM) and then the effects of temperature, agitation speed, initiator and silicone concentrations on the properties of the silicone-modified VAc–acrylic emulsion copolymers were discussed. The obtained copolymers have high solid content (53%) and can be used in emulsion paints as a binder. The calculations of monomer conversion versus time histories and monomer conversion indicate that by increasing the TEVS concentration, the polymerization rate and the number of polymer particles decrease, respectively.