Synthesis and characterization of conducting copolymers of quinoxaline derivatives

Electrochemical copolymerizations of 2,3‐di(2‐thienyl)quinoxaline (M1), 6‐methyl‐2,3‐di(2‐thienyl)quinoxaline (M2), and 2,3‐di(2‐thienyl)quinoxaline‐6‐yl)(phenyl)methanone (M3) with 3,4‐ethylenedioxy thiophene (EDOT) were carried out in CH₃CN/TBABF₄ (0.1M) solvent‐electrolyte couple via potentiodynamic electrolysis. The obtained copolymers were characterized by cyclic voltammetry (CV), Fourier transform‐infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry analyses (TGA). The conductivity measurements of copolymers and PEDOT were performed by the four‐probe technique. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of chitosan alkyl carbamates

The synthesis of chitosan methylcarbamate (ChMC) and ethylcarbamate (ChEC) is described by using a new methodology. Polymers with substitution degrees up to 63% for ChEC and 68.5% for ChMC were obtained. Derivatives with lower substitutions were acid soluble but those with higher ones were completely insoluble. This could be due to the loss in hydrophilic sites when the substitution degree increases. The reaction conditions and degree of substitution obtained for both derivatives were also described. A complete chemical characterization was carried out by spectroscopic techniques. The thermal degradation of chitosan and derivatives were studied in the range 25–500°C and both derivatives were shown to be thermally less stable than chitosan. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2742–2747, 2002     

Synthesis and characterization of PLA nanocomposites containing nanosilica modified with different organosilanes II: Effect of the organosilanes on the properties of nanocomposites: Thermal characterization

Thermal behavior of polylactic acid (PLA)/nanosilica nanocomposites prepared via bulk ring opening polymerization from lactide was investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). Both unmodified nanosilica and modified by surface treatments with different amounts of two distinct silanes were used. Samples containing pure silica show enhanced crystallization processes; with silane‐modified silica this effect is magnified, especially in the case of materials with high loadings of epoxy silane. Nonisothermal crystallization temperatures become higher and isothermal crystallization kinetics show a marked increase of Kinetic constant (K_c). TGA analyses show that, when pure nanosilica is present, nanocomposites have a thermal stability far greater than the one of standard PLA, starting their degradation at temperatures up to 70°C higher than the ones of pure PLA. When silanes are present, thermal stability lowers as silane content increases, but it is anyway higher than the one of the pure polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,characterization, and thermal degradation studies of copolymer resin derived from p-cresol,melamine, and formaldehyde

Copolymers (p-CMF) synthesized by the condensation of p-cresol and melamine with formaldehyde in the presence of an acid catalyst and using varied molar proportion of the reacting monomers. Copolymer resin compositions were determined on the basis of their elemental analysis. The number average molecular weight of these copolymers was determined by conductometric titration in nonaqueous media. Solution viscosity measurements in dimethyl sulfoxide (DMSO) were carried out to ascertain the characteristic functions and constants of the copolymer resins. The copolymer resins were further characterized byUV–visible absorption spectra in the nonaqueous medium, Infra-red (IR) spectra, and the nuclear magnetic resonance (NMR) spectra. Thermal studies of the resins were carried out to determine their mode of decomposition, the activation energy (E_a), order of reaction (n), frequency factor (Z), entropy change (ΔS), free energy change (ΔF), and apparent entropy change (S*). Thermal decomposition curves were discussed with careful attention of minute details. The Freeman-Carroll and Sharp-Wentworth methods have been used to calculate thermal activation energy and thermal stability. Thermal activation energy (E_a) calculated with these methods are in agreement with each other. The data from the Freeman-Carroll methods have been used to determine various thermodynamic parameters. The order of thermal stability of copolymers has been determined using TGA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A new Schiff base epoxy oligomer resin: Synthesis,characterization, and thermal decomposition kinetics

Oligo{2,2′‐{1,4‐phenylenebis[nitrilomethylylidene]}bis(6‐methoxyphenol)} (OPNMMP) was synthesized from o‐vanillin and p‐phenylene diamine by oxidative polycondensation with NaOCl in an aqueous alkaline. Then, a new Schiff Base epoxy oligomer resin, OPNMMP–epichlorohydrine (EPC), was produced with EPC. The structures of the resulting compounds were confirmed by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, ¹H‐NMR, and ¹³C‐NMR. Further characterization processes were preformed by thermogravimetry (TG)–differential thermal analysis, gel permeation chromatography, and solubility testing. Also, the kinetics of the thermal decomposition of OPNMMP–EPC were investigated by thermogravimetric analysis. The TG curves showed that the thermal decomposition of OPNMMP–EPC occurred in one stage. The kinetic parameters related to the decomposition kinetics of OPNMMP–EPC were obtained from TG curves with the following methods: Friedman, Flynn–Wall–Ozawa, Kissinger, invariant kinetic parameter, and Coats–Redfern (CR), under an N₂ dynamic atmosphere and different heating rates (5, 10, 15, and 20°C/min). The mechanism function and pre‐exponential factor were also determined by a master plots method. The apparent activation energies of the thermal decomposition were calculated from these methods for OPNMMP–EPC. The analysis of the results obtained by the CR and master plots methods showed that the decomposition mechanism of OPNMMP–EPC in N₂ was a deceleration‐type mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of crosslinked chitosan microspheres for the colonic delivery of 5-fluorouracil

In this work, we attempted to develop a simple and inexpensive colon specific pulsatile drug-delivery system using chitosan microspheres loaded with 5-fluorouracil (5-FU) using an enteric-coated soft gelatin capsule. Chemical crosslinking by glutaraldehyde and interactions between the polymer and the drug were determined by Fourier transform infrared spectral study. Scanning electron microscopy of the microspheres revealed spherical shapes with smooth surfaces. Differential scanning calorimetry studies confirmed the molecular dispersion of the drug in the polymer matrix. Three different formulations (i.e., F1, F2, and F3) were prepared by the variation of the amount of 5-FU. Encapsulation efficiencies of 5.5, 10.8, and 17.9% for drug loadings of 10, 20, and 50%, respectively, were obtained. In vitro release studies were conducted at pH 1.2 and pH 7.4 (to simulate actual gastrointestinal fluid and gastrointestinal tract conditions, respectively). The results indicate that chitosan microspheres released 5-FU in both acidic (60%) and basic pH (40%) conditions, whereas the capsule (filled with chitosan microspheres) showed only 8–10% release in acidic media and nearly 90% in basic media within 12 h. The newly designed pulsatile capsule device could be used for targeting 5-FU to the colon. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Value‐added derivatives of soda lignin from alfa grass (Stipa tenacissima). I. Modification and characterization

Alfa grass (Stipa tenacissima) is the only raw material for manufacturing paper pulp in Algeria, Tunisia, and Morocco. Soda lignin (SL) is obtained from black liquor (BL), a byproduct of manufacturing paper from alfa grass. This work was aimed at modifying SL and using it as a polymer lubricant. Modified SL was obtained in two steps: the precipitation of BL at pH 4 with sulfuric acid (2N) followed by the modification of SL by esterification using stearic anhydride (SA) dissolved in dioxane at 50°C for 8 h. The effects of different contents of SA on the hydrophobic properties and heat stability of modified SL were evaluated with contact angle analysis and thermogravimetric analysis. A commercial stearate used in plastic processing was chosen as the reference. Its thermal properties were ascertained with thermogravimetry, and its behavior was similar to that of the modified lignins. A structural comparison study was performed with Fourier transform infrared (FTIR) spectroscopy and solid‐state ¹³C‐NMR. The FTIR and ¹³C‐NMR results showed that there were significant differences between the main structures of SL samples reacted with 10, 30, or 100% (w/w) SA. The main part of the work consisted of modifying SL, evaluating the properties of the obtained products with respect to their use as lubricants, and comparing them to industrial lubricants. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of sPS/montmorillonite nanocomposites

The present work analyzed the possibility of obtaining and producing syndiotactic polystyrene (sPS)–based nanocomposites. The work first focused on possible technology to use for intercalation from solution and melt intercalation. Using a blend of sPS with atactic polystyrene (aPS) as the matrix was also considered. Thermal analysis techniques, such as differential scanning calorimetry (DSC) and thermogravimetry (TGA), were used to study the thermal properties and stability of the nanocomposites obtained and to select the most appropriate nanocharges. The effect of the introduction of nanofillers on these properties also was evaluated. X–ray diffraction was used to investigate the degree of clay exfoliation. Finally, mechanical characterization of the nanocomposites obtained was performed and compared to that of the pure material. The tests demonstrated that nanodispersion of phyllosilicate layers improved the mechanical behavior of the polymers analyzed, especially the annealed sPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4957–4963, 2006     

Preparation and characterization of novolac type phenolic resin blended with poly(dimethylsiloxane adipamide)

Phenolic resin/poly(dimethylsiloxane adipamide) (PDMSA) blends, which have been prepared, show miscibility due to intermolecular H‐bonding existing between phenolic resin and the PDMSA. The specific H‐bonding of novolac type phenolic/PDMSA blends was characterized by means of glass transition temperature behavior and Fourier Transform Infrared Spectroscopy (FTIR). The strength of intermolecular H‐bonding within the phenolic blend is a function of the H‐bonded group of the PDMSA modifier and corresponds to the deviation glass transition temperature (ΔT_g). Phenolic/PDMSA blends were completely miscible, as confirmed by the T_g study. The FTIR result is in good agreement with the inference from T_g behavior. The char yield of phenolic/PDMSA corresponds to the phenolic resin content. The molecular mobility of phenolic/PDMSA blends increases with PDMSA content in the phenolic‐rich region. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 984–992, 2002     

Synthesis and characterization of polyurethane/poly(vinylidene chloride) interpenetrating polymer networks

A series of polyurethane (PU)/poly(vinylidene chloride) (PVDC) interpenetrating polymer networks (IPNs) were synthesized through variations in the amounts of the prepolyurethane and vinylidene chloride monomer via sequential polymerization (80/20, 60/40, 50/50, 40/60, 30/70, and 20/80 PU/PVDC). The physicomechanical and optical properties of the IPNs were investigated. Thermogravimetric analysis (TGA) studies of the IPNs were performed to establish their thermal stability. TGA thermograms showed that the thermal degradation of the IPNs proceeded in three steps. Microcrystalline parameters, such as the crystal size and lattice disorder, of the PU/PVDC IPNs were estimated with wide‐angle X‐ray scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1375–1381, 2007     

Anhydride production as an additional mechanism of poly(3‐hydroxybutyrate) pyrolysis

Anhydrides production is newly proposed as an additional pyrolysis mechanism of a biopolymer, poly(3‐hydroxybutyrate) (PHB). In spite of many suggestions of multiple degradation mechanisms, simple random chain scission by β‐elimination has been accepted as an exclusive mechanism of the thermal degradation of PHB. However, a wide range of activation energy value of the degradation and the deviation from the random chain scission statistics have suggested the presence of other kinds of mechanism out of the random scission. To confirm other mechanisms out of the random scission, minor pyrolyzates from PHB were characterized with ¹H/¹³C‐NMR, Fourier transform infrared spectroscopy, and fast atom bombardment mass spectrometry. As a result, crotonic anhydride and its oligomers were detected as minor products from condensation reactions between carboxyl groups. The anhydrides production must be one reaction out of the conforming process to the random degradation statistics and contribute to the complexity of PHB pyrolysis. An expected thermal degradation pathway of PHB was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of dextrin‐grafted polypropylene

We carried out the graft copolymerization of the water‐soluble natural polymer dextrin onto preirradiated polypropylene (PP) in an aqueous medium using benzoyl peroxide (BPO) as the radical initiator. PP was irradiated by γ rays from a Co⁶⁰ source at a constant dose rate of 3.40 kGy/h to introduce hydroperoxide linkages, which served as the sites for grafting. The graft copolymerization was studied as a function of different reaction parameters, and the maximum percentage grafting (P_g; 55%) of dextrin onto PP was obtained at optimum conditions of [BPO] = 5.165 × 10⁻² mol/L, temperature = 60°C in 120 min with 15 mL of water. Different grafting parameters, such as the percentage apparent grafting, percentage grafting, and percentage true grafting have been evaluated. The graft copolymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Swelling studies were carried out in pure, binary, ternary, and quaternary solvent systems composed of water, ethanol (EtOH), dimethyl sulfoxide (DMSO), and N,N‐dimethylformamide (DMF) at different ratios. The maximum swelling percentage PP‐g‐dextrin (both composite and true graft) was observed in pure DMSO and DMF followed by EtOH and water. Water‐retention studies of PP and PP‐g‐dextrin (both composite and true graft) were investigated at different time periods, temperatures, and pH values. The maximum percentage water retention of PP‐g‐dextrin (composite, 124%) was observed at 8 h and 50°C in a neutral medium (pH 7). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of cholesteric thermotropic liquid crystalline polyesters

Cholesteric liquid crystalline polyesters were successfully synthesized from isosorbide, methyl hydroquinone, and isophthaloyl chloride. Homo/copolyesters were synthesized by the solution polycondensation method, for which a mild organic base such as pyridine was employed. Inherent viscosities of polyesters P‐3–P‐5 were in the range of 0.31–0.39 dL/g at 25°C in chloroform, and polyesters P‐1 and P‐2 were insoluble in chloroform. Homo/copolyesters based on isosorbide, methyl hydroquinone, and isophthalic acid had thermal stability at more than 300°C on the basis of 10% weight loss. The thermotropic liquid crystalline properties were examined by differential scanning calorimetry and polarizing optical microscopy. Wide‐angle X‐ray diffraction study demonstrated that polyesters P‐1, P‐2, and P‐3 were semicrystalline, whereas the degree of crystallinity of polyesters P‐4 and P‐5 was less than 5%. Copolyester P‐4 showed formation of a yellow iridescent streak at 209°C on heating and development of a Grandjean texture at 270°C on heating. These are typical textures of the cholesteric liquid crystalline phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1232–1237, 2007     

Synthesis and characterization of new polyureas derived from 4‐(4′‐Methoxyphenyl)urazole

4‐(4′‐Methoxyphenyl)urazole (MPU) was prepared from 4‐methoxybenzoic acid in five steps. The reaction of monomer MPU with n‐isopropylisocyanate was performed at room temperature in N,N‐dimethylformamide solution, and the resulting bis‐urea derivative was obtained in high yield and was finally used as a model for polymerization reaction. The step‐growth polymerization reactions of monomer MPU with hexamethylene diioscyanate, isophorone diioscyanate, and toluene‐2,4‐diioscyanate were performed in N,N‐dimethylacetamide solution in the presence of pyridine as a catalyst. The resulting novel polyureas have an inherent viscosity (η_inh) in a range of 0.07–0.21 dL/g in DMF and sulfuric acid at 25°C. These polyureas were characterized by IR, ¹H‐NMR, elemental analysis, and TGA. Some physical properties and structural characterization of these novel polyureas are reported. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1141–1146, 2002     

Synthesis of a novel curing agent containing organophosphorus and its application in flame‐retarded epoxy resins

A novel amine‐terminated and organophosphorus‐containing compound m‐aminophenylene phenyl phosphine oxide oligomer (APPPOO) was synthesized and used as curing and flame‐retarding agent for epoxy resins. Its chemical structure was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (¹H NMR), ¹³C nuclear magnetic resonance, and ³¹P nuclear magnetic resonance. The flame‐retardant properties, combusting performances, and thermal degradation behaviors of the cured epoxy resins were investigated by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. The EPO/APPPOO thermosets passed V‐1 rating with the thickness of 3.0 mm and the LOI value reached 34.8%. The thermosets could pass V‐2 rating when the thickness of the samples was 1.6 mm. The cone calorimeter test demonstrated that the parameters of EPO/APPPOO thermosets including heat release rate and total heat release significantly decreased compared with EPO/PDA thermosets. Scanning electron microscopy revealed that the incorporation of APPPOO into epoxy resins obviously accelerated the formation of the compact and stronger char layer to improve flame‐retardant properties of the cured epoxy resins during combustion. The mechanical properties and water resistance of the cured epoxy resins were also measured. After the water‐resistance test, EPO/APPPOO thermosets still remained excellent flame retardant and the water uptake was only 0.4%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41159.     

Organic‐soluble chitosan/polyhydroxybutyrate ultrafine fibers as skin regeneration prepared by electrospinning

In the present contribution, the ultrafine fiber membranes of polyhydroxybutyrate (PHB) and organic‐soluble chitosan(O‐CS) was prepared by electrospinning. The structure and thermal stability were studied by infrared (FTIR) and thermogravimetric analysis (TG). The surface properties of ultrafine fibers were estimated by contact angle measurements using water. The morphology was observed by scanning electron microscopy (SEM). The cytotoxicity assessment with mouse fibroblast cells (L929) was also investigated. Cell culture results showed that it benefits promoting the cell attachment and proliferation. The results showed it could be as tissue engineering for skin regeneration. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of new polyureas based on 4‐(4′‐aminophenyl)urazole and various diisocyanates

4‐(4′‐Aminophenyl)urazole (AmPU) was prepared from 4‐nitrobenzoic acid in six steps. The reaction of monomer AmPU with n‐isopropylisocyanate was performed in N,N‐dimethylacetamide solutions at different ratios, and the resulting disubstituted and trisubstituted urea derivatives were obtained in high yields and were finally used as models for polymerization reactions. The step‐growth polymerization reactions of AmPU with hexamethylene diisocyanate, isophorone diisocyanate, and toluene‐2,4‐diisocyanate were performed in N‐methylpyrrolidone solutions in the presence of pyridine as a catalyst. The resulting novel polyureas had inherent viscosities of 0.11–0.18 dL/g in dimethylformamide at 25°C. These polyureas were characterized with IR, ¹H‐NMR, elemental analysis, and thermogravimetric analysis. Some physical properties and structural characterization of these novel polyureas are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2692–2700, 2003     

Effect of glycerol on electrical conducting of chitosan/polyaniline blends

Chitosan (Cs) and polyaniline (PANI) were studied in this article for possible application as conductive and flexible films. Cs is a biodegradable polymer, that presents interesting properties as film applications. Otherwise, PANI is a semiconductor polymer with a wide range of applications. The films were produced by casting adding 30% glycerol and glutaraldehyde. The morphology, thermally, chemical structure, and electrical properties of films were obtained. Results showed the casting technique becomes possible to obtain self-standing films, with a chemical structure identical to precursor materials. Glutaraldehyde reacted to amine groups of terminal PANI chains, acting in the increase of electric conductivity and decrease of sheet resistance. The plasticizing effect of glycerol increased the spacing between Cs chains and facilitated the PANI dispersion. Therefore, glycerol and glutaraldehyde proved to be extremely efficient in increasing the electrical conductivity of blends.     

Synthesis,characterization, and thermal properties of copolymers of behenyl acrylate and behenyl fumarate

Radical copolymerization of behenyl (systematic IUPAC nomenclature: n‐docosyl) acrylate and behenyl fumarate has been carried out in toluene at 70°C using benzoyl peroxide as initiator. Gel permeation chromatography was used to determine molecular weights (MW) and molecular weight distribution (MWD) of behenyl acrylate–behenyl fumarate (BA‐BF) copolymers. ¹H NMR and carbon analysis was used to determine the composition of BA‐BF copolymers. Monomer reactivity ratios for high conversion polymerization were calculated by conversion‐extended Kelen‐Tudos plot. Differential scanning calorimetric (DSC) measurements shows sharp melting peaks at about 64°C. Thermal stability studies were performed with thermogravimetric analyzer (TGA). By using these DSC and TGA data in several nonisothermal methods, the activation energies were calculated. X‐ray diffraction studies show the linearity of the copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2721–2726, 2003     

Synthesis and characterization of new optically active segmented poly(amide imide urethane)s based on different diacids via an isocyanate route

A new class of optically active poly(amide imide urethane)s (PAIUs) was synthesized via a two-step diisocyanate route. In the first step, 4,4′-methylenebis(phenyl isocyanate) (MDI) was reacted with different diacids to produce an isocyanate-terminated oligo(amide imide). The chain extension of the previous hard segment with poly (ethylene glycol) diols with a molecular weight of 400 was the second step for furnishing a series of new PAIUs. N-Trimellitylimido-L -leucine was used as a diacid monomer for polycondensation reactions. Polymerization reactions were performed without any catalysts or with pyridine or dibutyltin dilaurate as a catalyst. The optimized reaction conditions were used for the reaction of N-trimellitylimido-L -isoleucine, N-trimellitylimido-L -methionine, N-trimellitylimido-S -valine, and N-trimellitylimido-L -phenylalanine as diacid monomers with MDI. The resulting multiblock copolymers had inherent viscosities of 0.25–0.78 dL/g. These multiblock copolymers were optically active, thermally stable, and soluble in amide-type solvents. All these polymers were fully characterized with Fourier transform infrared spectroscopy, ¹H-NMR and ultraviolet–visible spectroscopy, specific rotation measurements, and thermal analyses. Some structural characteristics and physical properties of these new optically active PAIUs were examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008