Carboxymethyl guar: Its synthesis and macromolecular characterization

Guar gum was partially carboxymethylated by the reaction of the base polysaccharide with the sodium salt of monochloroacetic acid in presence of sodium hydroxide. The resulting products (carboxymethyl guar with different degrees of substitution) were characterized by a variety of material characterization techniques, such as intrinsic viscosity measurement, determination of molecular weight, elemental analysis, thermal analysis, ¹³C‐NMR spectra, and Fourier transform infrared analysis. Various grades of carboxymethyl guar gum, which were synthesized in the laboratory, were studied for their suitability as flocculants and viscosifiers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural and photooxidation studies of poly(styrene oxide) prepared with Maghnite‐H+ as cationic catalyst

The nature of irregularities and end‐groups in poly(styrene oxide) samples prepared using Maghnite‐H⁺ as a cationic catalyst were studied by ¹H‐ and ¹³C‐NMR at 200 MHz. Head‐to‐head (H‐H) and tail‐to‐tail (T‐T) irregularities are detected in all the samples studied. Secondary hydroxyl terminal groups are identified in polymers prepared with Maghnite‐H⁺. Poly(styrene oxide) was found to undergo chain scission by aging at 25°C. It was confirmed that oxidation of this type of polymers results from the important sensitivity of the polyether soft segment to oxidative degradation. For this reason, the scissions due to the oxidation of the material lead to notable quantities of low molecular weight photoproducts. Among the various structures produced by the oxidative degradation process, benzoate and secondary hydroxyl groups are identified by MALDI‐TOF‐MS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of 2‐oxazoline‐benzoxazine compound and its polymer

A novel 2‐oxazoline‐benzoxazine (POB) was synthesized with 2‐(hydroxylphenyl)‐2‐oxazoline, 1,3,5‐triphenylhexahydro‐1,3,5‐triazine and paraformaldehyde. The chemical structure of the monomer was confirmed by FTIR, ¹H‐NMR, ¹³C‐NMR, and MS. The curing behavior of the monomer was studied by DSC and FTIR, and the ring opening reaction of the monomer was found to occur from 187.5°C. The results of DMA and TGA demonstrated that the thermal properties of polymer for POB monomer (P‐m) are better than polymer for POB precursor (P‐p), because that the oligomer in benzoxazine precursor decreased the perfection of the polymer's network structure; it was also found that the thermal properties of P‐m and P‐p are much better than the common polybenzoxazine and the composite material of benzoxazine and 2‐oxazoline. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci , 2008.     

Corrosion inhibition of mild steel in 1 M HCl using Tamarindus indica extract: electrochemical,surface and spectroscopic studies

Abstract

We report, here, the corrosion inhibition of mild steel specimen in 1?M HCl by tamarind fruit pulp aqueous (TFPA) extract. The inhibition property in the presence of TFPA extract is studied using weight loss, polarization measurement and electrochemical impedance spectroscopy (EIS). The inhibitor efficiency is found to vary from 74% to 88% (weight loss method) with TFPA concentration of 100–600?ppm. The reduction in Tafel slopes shows that TFPA acts as a mixed-type inhibitor. The adsorption of the inhibitor on the metal surface follows Langmuir isotherm. The standard Gibbs free energy of adsorption value of –40?kJ/mol suggests the chemisorption of inhibitor molecules via coordinate bond. AFM results exhibit a decrease in the surface roughness of mild steel, exposed to 1?M HCl from 299?±?12 to 154?±?6.6?nm, with increasing concentration of inhibitor from 0 to 600?ppm due to the uniform coverage of inhibitor molecules on the metal surface. X-ray photoelectron spectroscopy de-convoluted high resolution profiles of C 1?s (carbon) for mild steel exposed to 1?M HCl with 600?ppm inhibitor show major peaks corresponding to sp³ C–C/C–H (284.9?eV) and oxygen bondings in C–OH, C=O, COOH with a binding energy of 285.9, 286.9, 288.5?eV, respectively, thereby confirming the adsorption of organic moieties on mild steel surface. Fourier transform infrared spectroscopy further confirms the adsorption of inhibitor molecules on the metal surface. Therefore, tamarind fruit pulp extract is a potential corrosion inhibitor for mild steel, which is cost-effective, green and non-toxic.     

Bismaleimides,bisnadimides, and polyaspartimides containing ether and ester linkages and pyridine

A series of bismaleimides (BMI) and bisnadimides (BNI) containing pyridine ring and flexible linkages were prepared and the structural characterization of the resins was carried out by elemental analysis, FTIR, ¹H NMR, and ¹³C NMR spectroscopy. Their curing behavior were characterized by differential scanning calorimetry and thermal stability of the cured resins were investigated by thermogravimetric analysis. In addition, a series of polyaspartimides were prepared by the polyaddition of the bismalemide with various dimaines. The polymers were characterized by FT‐IR, inherent viscosity, and molecular weight measurements. All the polyimides were soluble in many organic solvents, the glass transition temperature of the polyaspartimides are in the range of 194–231°C, 10% weight loss (T₁₀) takes place in the temperature range of 379–482°C in N₂ and char yield in the range of 44.31–53.31%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Synthesis and characterization of biodegradable lactic acid‐based polymers by chain extension

BACKGROUND: Poly(lactic acid) (PLA), coming from renewable resources, can be used to solve environmental problems. However, PLA has to have a relatively high molecular weight in order to have acceptable mechanical properties as required in many applications. Chain‐extension reaction is an effective method to raise the molecular weight of PLA. RESULTS: A high molecular weight biodegradable lactic acid polymer was successfully synthesized in two steps. First, the lactic acid monomer was oligomerized to low molecular weight hydroxyl‐terminated prepolymer; the molecular weight was then increased by chain extension using 1,6‐hexamethylene diisocyanate as the chain extender. The polymer was characterized using ¹H NMR analysis, gel permeation chromatography, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the obtained polymer had a M_n of 27 500 g mol^?1 and a M_w of 116 900 g mol^?1 after 40 min of chain extension at 180 °C. The glass transition temperature (T_g) of the low molecular weight prepolymer was 47.8 °C. After chain extension, T_g increased to 53.2 °C. The mechanical and rheological properties of the obtained polymer were also investigated. CONCLUSION: The results suggest that high molecular weight PLA can be achieved by chain extension to meet conventional uses. Copyright © 2008 Society of Chemical Industry     

Influence of polymerization conditions on the viscosity and yield of poly(phenylene sulfide ether)

High molecular weight poly(phenylene sulfide ether) (PPSE) was successfully synthesized by reaction of 4,4′‐dihydroxy diphenyl sulfide with 4,4′‐dichloro diphenyl sulfide in N‐methyl‐2‐pyrrolidone (NMP). The influence of polymerization conditions on the intrinsic viscosity and yield of PPSE was investigated and the optimized reaction condition was concluded. Reactions at about 180°C for 6 h along with sodium benzoate as an additive and monomer concentration of 0.588 mol/L NMP were found to produce the highest intrinsic viscosity (0.55 dL/g). Longer reaction time and/or higher temperature reduced the intrinsic viscosity and yield of the resulting product, probably due to side reactions, such as reductive dehalogenation and chemical degradation. X‐ray diffraction indicated that the polymer possessed of orthorhombic cell and had a high crystallinity of 65.8%. The high molecular weight PPSE is a crystalline polymer with T_m of 252°C and T_mc of 224°C. The polymer shows good chemical resistance, but is soluble in organic amide, halo‐hydrocarbon and oxohydrocarbon solvent at a temperature over 150°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation of the surface properties of polymeric soaps obtained by ring‐opening polymerization of epoxidized soybean oil

Epoxidized soybean oil (ESO) was converted to a polysoap (PESO) via a two‐step synthetic procedure of catalytic ring‐opening polymerization, followed by hydrolysis (HPESO) with a base. Various molecular weights of PESO and HPESO were prepared by varying the reaction temperature and/or catalyst concentration. In addition, the counter ion chemistry was varied by changing the base used for saponification. The PESO and HPESO products were carefully characterized and identified using a combination of FTIR, ¹H‐NMR, solid state ¹³C‐NMR, and GPC. The effect of HPESO polysoaps on the surface tension of water and the interfacial tension of water‐hexadecane was investigated as a function of HPESO concentration, molecular weight, and counter ion chemistry. HPESO polysoaps were effective at lowering the surface tension of water and the interfacial tension of water‐hexadecane and displayed minimum values in the range of 20–24 and 12–17 dyn/cm, respectively, at concentration of 200–250 μM. Water‐hexadecane interfacial tension was also calculated from measured surface tension data using the Antonoff, harmonic mean (HM), and geometric mean (GM) methods. Measured values agreed well with those calculated using the HM and GM methods, but not the Antonoff method. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrochemical preparation of poly(N‐acetylaniline)/poly‐(4‐styrenesulfonic acid‐co‐maleic acid) composite film towards ascorbic acid sensing

Poly(N‐acetylaniline)/poly(4‐styrenesulfonic acid‐co‐maleic acid) (PNAANI/PSSMA) composite film was prepared by cyclic voltammetry (CV), and was characterized by FTIR and X‐ray photoelectron spectrum (XPS). The electroactivity of the composite film was high in neutral and basic solutions, and it had been used for amperometric determination of ascorbic acid (AA). Compared with pure PNAANI film, the catalytic activity of the composite film was much better. AA was detected amperometrically in sodium citrate buffer at a potential of 0.3 V (versus SCE). The response current was proportional to the concentration of ascorbic acid in the range of 4.7 × 10^?6 to 5.0 × 10^?5M and 5.0 × 10^?5 to 2.5 × 10^?3M, respectively, with the detection limit of 1.9 × 10^?6 mol L^?1 at a signal to noise ratio 3. In addition, the stability and reusability of the composite film were performed well, and it was satisfying to be used for determination of AA in real fruit juice samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Unsymmetrical α‐diimine nickel (II) complex with rigid bicyclic ring ligand: Synthesis,characterization, and ethylene polymerization in the presence of AlEt2Cl

Unsymmetrical α‐diimine ligand 1 was successfully synthesized via condensation of trimethylaluminum (TMA) metalated 2‐methyl‐6‐isopropyl‐aniline with rigid bicyclic aliphatic diketone camphorquinone. Syn‐ and anti‐stereoisomers were detected by ¹³C NMR in the condensation product. The corresponding α‐diimine nickel (II) complex 1 was prepared from the exchange reaction of (DME)NiBr₂ with the ligand 1 , and displayed high activity for ethylene polymerization in the presence of diethylaluminum chloride (AlEt₂Cl). The resultant polymers were confirmed by gel permeation chromatography and ¹³C NMR characterization to be broad molecular weight distribution polyethylene with various branches, and high degree of branching, even at low polymerization temperature ?10°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization, and biodegradation of carboxymethylchitosan‐g‐medium chain length polyhydroxyalkanoates

Grafting of medium chain length polyhydroxyalkanoates (mcl‐PHA) produced by Comamonas testosteroni onto carboxymethylchitosan (CMCH) using ceric ammonium nitrate (CAN) as an initiator was carried out under nitrogen atmosphere in aqueous medium. The grafting composition was 2 g CMCH, 0.2M CAN, and 0.5 g mcl‐PHA. The reaction was carried out at 40°C ± 1°C for 4.5 h, and reaction product was extracted by acetone precipitation. The CMCH‐g‐mcl‐PHA copolymers were characterized by Fourier transform infrared spectroscopy, Thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The data obtained showed successful grafting of mcl‐PHA onto CMCH polymer. TGA results indicated that the graft was stable up to 380°C, and the solubility studies revealed a high % grafting efficiency. Biodegradation studies of the graft in terms of microbial growth, extracellular protein concentration, and % weight loss in the graft were carried out for 30 days using a bacterial isolate Burkholderia cepacia 202 and a fungal isolate Aspergillus fumigatus 202. 93% weight loss of the graft was obtained in case of A. fumigatus 202, whereas B. cepacia 202 showed 76% loss in weight of the graft. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Emulsion polymerization of styrene with Iso‐octyl‐3‐mercaptopropionate as chain transfer agent

Four batch and unseeded emulsion polymerizations of styrene were investigated, which included isooctyl 3‐mercaptopropionate (iOMP) as chain transfer agent (CTA). This compound was analyzed by ¹³C NMR and GC/MS, resulting in a mixture of over 10 isomers. Because of different reactivities of the CTA isomers, the produced polystyrenes presented broad and bimodal molecular weight distributions (MWDs). A mathematical model was adjusted to the measurements, and the measured MWDs were adequately predicted when assuming the CTA as a binary mixture of high but different reactivities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal Damage on LX‐04 Mock Material and Gas Permeability Assessment

RM‐04‐BR, a mock material for the plastic‐bonded HMX‐based explosive LX‐04, is characterized after being thermally damaged at 140 °C and 190 °C. We measured the following material properties before and after the thermal experiments: sample volume, density, sound speed, and gas permeability in the material. Thermal treatment of the mock material leads to de‐coloring and insignificant weight loss. The sample expanded, resulting in density reductions of 1.0% to 2.5% at 140 °C and 190 °C, respectively. Permeability in the mock samples was found to increase from 10⁻¹⁶ to 10⁻¹⁵ m², as the porosity increased. The permeability measurements are well represented by the Blake‐Kozeny equation for laminar flow through porous media. The results are similar to the gas permeability in PBX‐9501 obtained by other researchers [1, 2].     

Ethylene/α‐olefin copolymerization using diphenylcyclopentadienyl‐phenoxytitanium dichloride/Al(iBu)3/[Ph3C][B(C6F5)4] catalyst systems

Copolymerization of ethylene with 1‐octene and 1‐octadecene using constrained geometry catalysts 2‐(3,4‐diphenylcyclopentadienyl)‐4,6‐di‐tert‐butylphenoxytitanium dichloride (1), 2‐(3,4‐diphenylcyclopentadienyl)‐6‐tert‐butylphenoxytitanium dichloride (2), 2‐(3,4‐diphenylcyclopentadienyl)‐6‐methylphenoxytitanium dichloride (3), and 2‐(3,4‐diphenylcyclopentadienyl)‐6‐phenylphenoxytitanium dichloride (4) was studied in the presence of Al(ⁱBu)₃ and [Ph₃C][B(C₆F₅)₄](TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was also examined. The 1 /TIBA/B catalyst system exhibits high catalytic activity and produces high molecular weight copolymers. The melting temperature and the degree of crystallinity of the copolymers show a decrease with the increase in the comonomer incorporation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Residual compressive behavior of alkali‐activated concrete exposed to elevated temperatures

This paper reports the effect of elevated temperature exposures, up to 1200^°C , on the residual compressive strengths of alkali‐activated slag concrete (AASC) activated by sodium silicate and hydrated lime; such temperatures can occur in a fire. The strength performance of AASC in the temperature range of 400–800^°C was similar to ordinary Portland cement concrete and blended slag cement concrete, despite the finding that the AASC did not contain Ca(OH)₂ , which contributes to the strength deterioration at elevated temperatures for Ordinary Portland Cement and blended slag cement concretes. Dilatometry studies showed that the alkali‐activated slag (AAS) paste had significantly higher thermal shrinkage than the other pastes while the basalt aggregate gradually expanded. This led to a higher thermal incompatibility between the AAS paste and aggregate compared with the other concretes. This is likely to be the governing factor behind the strength loss of AASC at elevated temperatures. Copyright © 2008 John Wiley & Sons, Ltd.     

Controlled radical polymerization of poly(methyl methacrylate‐g‐epichlorohydrin) using N,N‐dithiocarbamate‐mediated iniferters

Poly(epichlorohydrin) (PECH) with pendent N,N‐diethyl dithiocarbamate groups (PECH‐DDC) was prepared by reaction of PECH with sodium N,N‐diethyl dithiocarbamate (DDC) in anhydrous ethanol, before being used as a macrophotoinitiator for the graft polymerization of methyl methacrylate. Photopolymerization was carried out in a photochemical reactor at a wavelength greater than 300 nm. Controlled radical polymerization was confirmed by the linear increase of the molecular weight of polymers with conversion. The polydispersity remained at 1.4–1.6 during polymerization. The formation of PMMA‐g‐PECH copolymer was characterized by GPC, ¹H‐NMR, FTIR spectroscopy, and DSC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of new cardo poly(bisbenzothiazole)s from 1,1‐bis(4‐amino‐3‐mercaptophenyl)‐4‐tert‐butylcyclohexane dihydrochloride

A new monomer 1,1‐bis(4‐amino‐3‐mercaptophenyl)‐4‐tert‐butylcyclohexane dihydrochloride, bearing the bulky pendant 4‐tert‐butylcyclohexylidene group, was synthesized from 4‐tert‐butylcyclohexanone in three steps. Its chemical structure was characterized by ¹H NMR, ¹³C NMR, MS, FTIR, and EA. Aromatic poly(bisbenzothiazole)s (PBTs V) were prepared from the new monomer and five aromatic dicarboxylic acids by direct polycondensation. The inherent viscosities were in the range of 0.63–2.17 dL/g. These polymers exhibited good solubility and thermal stability. Most of the prepared PBTs V were soluble in various polar solvents. Thermogravimetric analysis showed the decomposition temperatures at 10% weight loss that were in the range of 495–534°C in nitrogen. All the PBTs V, characterized by X‐ray diffraction, were amorphous. The UV absorption spectra of PBTs V showed a range of λ_max from 334 to 394 nm. All the PBTs V prepared had evident fluorescence emission peaks, ranging from 423 to 475 nm with different intensity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2000–2008, 2006     

Synthesis,characterization, and properties of silylene–acetylene preceramic polymers

A series of silylene–acetylene preceramic polymers 3a–e were synthesized by polycondensation reaction of dilithioacetylene with dichlorosilane (H₂SiCl₂) or/and methyldichlorosilane (MeSiHCl₂). Their structures were confirmed by infrared spectra (IR), and ¹H and ²⁹Si NMR spectroscopies. Differential scanning calorimetry (DSC) diagrams show exotherms centered at 200 to 233°C temperature range, attributed to crosslinking reaction of the acetylene and Si? H groups. After thermal treatment, the obtained thermosets 4a–e possess excellent thermal stability. Thermogravimetric analysis (TGA) under nitrogen show the T_d5s (temperature of 5% weight loss) for all the thermosets are above 600°C, and the overall char yields are between 95.62% and 89.67% at 900°C. After pyrolysis at 1200°C, the obtained ceramic residues 5a–e exhibit good thermo‐oxidative stability with final weight retention between 98.76% and 91.66% at 900°C under air. In particular, perhydroploy(silylene)ethynylene 3a , which has the highest Si/C ratio in silylene–acetylene polymers, has the highest char yield, and the derived ceramic material 5a displays the best thermo‐oxidative stability. Based on Scanning electron microscopy and its associated energy‐dispersive X‐ray microanalysis (SEM EDX) and ¹³C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis, ceramic 5a contains the highest SiC content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Liquid‐phase sintering of highly Na+ ion conducting Na3Zr2Si2PO12 ceramics using Na3BO3 additive

Na₃Zr₂Si₂PO₁₂ (NASICON) is a promising material as a solid electrolyte for all‐solid‐state sodium batteries. Nevertheless, one challenge for the application of NASICON in batteries is their high sintering temperature above 1200°C, which can lead to volatilization of light elements and undesirable side reactions with electrode materials at such high temperatures. In this study, liquid‐phase sintering of NASICON with a Na₃BO₃ (NBO) additive was performed for the first time to lower the NASICON sintering temperature. A dense NASICON‐based ceramic was successfully obtained by sintering at 900°C with 4.8 wt% NBO. This liquid‐phase sintered NASICON ceramic exhibited high total conductivity of ~1 × 10^?3 S cm^?1 at room temperature and low conduction activation energy of 28 kJ mol^?1. Since the room‐temperature conductivity is identical to that of conventional high‐temperature‐sintered NASICON, NBO was demonstrated as a good liquid‐phase sintering additive for NASICON solid electrolyte. In the NASICON with 4.8 wt% NBO ceramic, most of the NASICON grains directly bonded with each other and some submicron sodium borates segregated in particulate form without full penetration to NASICON grain boundaries. This characteristic composite microstructure contributed to the high conductivity of the liquid‐phase sintered NASICON.