Anhydride Content Research Articles

Preparation of sugarcane bagasse hemicellulosic succinates using NBS as a catalyst

The chemical modification of native sugarcane bagasse hemicelluloses with succinic anhydride using N-bromosuccinimide as a catalyst and N, N-dimethylacetamide/lithium chloride system as solvent was studied. The parameters optimised included succinic anhydride concentration by the molar ratio of succinic anhydride/anhydroxylose units in native hemicelluloses from 1:1 to 9:1, reaction time 0.5–6 h, NBS concentration 0.5–3.0%, and reaction temperature 25–85 °C required in the process. Results were also compared with other catalysts such as pyridine, DMAP, H 2SO 4, and other two tertiary amine catalysts, N-methyl pyrrolidine, and N-methyl pyrrolidinone. The degree of substitution of succinylated hemicelluloses ranged between 0.19 and 1.39, depending on the experimental conditions. FT-IR and 1H and 13C NMR spectroscopic characterization of the esterified polymers indicated a monoester substitution. The thermal stability of the succinylated hemicelluloses decreased upon chemical modification.

Production of alkenyl succinic anhydrides from low‐erucic and low‐linolenic rapeseed oil methyl esters

AbstractFatty acid methyl esters from low‐erucic and low‐linolenic rapeseed oil were used to produce alkenyl succinic anhydrides. A second‐order Doehlert uniform network design was used to investigate the influence of the reaction temperature and the molar ratio between the maleic anhydride and the main unsaturated rapeseed oil methyl esters on the yield of alkenyl succinic anhydride from methyl oleate. Further subjects of investigation were the conversion of methyl oleate, the formation of side reaction products, the Gardner color of the product and its viscosity, and finally the content of maleic anhydride remaining in the medium after the reaction. Alkenyl succinic anhydride from methyl oleate was isolated by column chromatography and analyzed by IR, 1H‐ and 13C‐NMR and MS. The optimal reaction conditions for obtaining the maximum yield of alkenyl succinic anhydride from methyl oleate in the experimental domain (80%) were 210‐220 °C and a maleic anhydride/rapeseed oil methyl ester molar ratio of 1.5. However, the products synthesized in these conditions showed a high degree of viscosity (0.45 kg m−1 s−1), a very dark color (18 Gardner color) and a high content of undesirable side products (6%), which could hinder their industrial use. A molar ratio of less than 1.5 led to a clearer and less viscous product, although with a lower alkenyl succinic anhydride content.

Synthesis of styrene–maleic anhydride random copolymer and its compatibilization to poly(2,6‐dimethyl‐1,4‐phenylene ether)/brominated epoxy resin

AbstractStyrene–maleic anhydride random copolymer (R‐SMA7.5), with a low content of maleic anhydride (MAH) of about 7.5 mol%, has been prepared, and the copolymer was characterized by fourier‐transform infrared (FTIR) and 13C NMR techniques showing that the product contained only random copolymer without blocks. The miscibility between poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE) and R‐SMA, was investigated by differential scanning calorimetry (DSC), showing that PPE was miscible with R‐SMA synthesized in our laboratory over the entire composition with low MAH content. A blend of R‐SMA18 (MAH content is about 18 mol%) and PPE was also studied by DSC, which showed that PPE was immiscible when R‐SMA was the major component, although it was miscible with limited composition. FTIR investigation showed that R‐SMA could react with bromide epoxy (BEP) resin at high temperature (180°). The heat‐resistance and mechanical properties of R‐SMA/PPE/BEP systems were tested and analyzed, and results indicated that R‐SMA could improve the miscibility of PPE and BEP with increasing Tg of the BEP phase and decreasing the Tg of the PPE slightly, improving the breaking elongation and breaking energy, which resulted from good miscibility between PPE and BEP with R‐SMA as the compatibilizer. Finally, the properties of the composites (copper clad laminate) with R‐SMA7.5 are studied and discussed. Copyright © 2003 Society of Chemical Industry

Effects of reactive end-capper on mechanical properties of chemical amplified photosensitive polyimide

Photosensitive polyimide (PSPI) was synthesized and characterized to replace the conventional polyimide buffer layer because direct patterning with PSPI could reduce the processing procedure to the half. Since PSPI should be dissolved in alkaline aqueous solution and have good mechanical properties after imidization, low molecular weight of PSPI was synthesized with reactive end-capper, which could extend the chain length of PSPI during imidization. Therefore norbornene end-capped PSPI precursor was synthesized with various 5-norbornene-2,3-dicarboxylic anhydride (NDA) content. Although molecular weight of PSPI decrease with increasing NDA content, the elongation at break and the glass transition temperature ( T g) of PSPI films imidized at 300 °C increased with increasing NDA content. On the other hand, elongation at break of PSPI films imidized at 350 °C decreased but T g of those increased with increasing NDA content. Above T g, thermal expansion coefficient decreased dramatically by introducing NDA end-capper. From mechanical and thermal properties of PSPI, it appears that low molecular weight of PSPI can be chain-extended and crosslinked during imidization.

Preparation of alkenyl succinic anhydrides from vegetable oil FAME

AbstractSunflower oil and oleic motif‐enriched sunflower oil methyl esters were used to prepare alkenyl succinic anhydrides. A classic batch reactor was selected to carry out the synthesis. The range in which the temperature, reaction time, and molar ratio between the number of moles of maleic anhydride and the equivalent number of double bonds present in the unsaturated vegetable oil methyl esters (the most influential factors in the process) varied was determined in a preliminary study. A secondorder Doehlert uniform network design was used to investigate the influence of the temperature and molar ratio for all the methyl esters on the yield of alkenyl succinic anhydride from methyl oleate, the conversion of methyl oleate, the formation of side reaction products, the Gardner color of the product, and viscosity. The optimal reaction conditions for obtaining the maximal yield (around 95%) of alkenyl succinic anhydride from methyl oleate were 235°C, a molar ratio of 1.5, and a reaction lasting 8 h. However, the products synthesized under these conditions showed high viscosity (215 cP), a very dark color (18+ Gardner color), and a high content of undesirable side products (4%), which hindered their direct industrial use. The increase in the product viscosity was probably due to the formation of side reaction products. A molar ratio of less than 1.5 led to a less viscous product, although with a lower alkenyl succinic anhydride content.

Rapid preparation of starch esters by high temperature/pressure reaction

This study was undertaken to determine if starch esters of moderate to high degree of substitution (DS) could be prepared more rapidly, efficiently and with fewer byproducts. The method selected was to heat mixtures of dry corn starch, glacial acetic acid and anhydrides under pressure in small (60 μl) stainless steel sealed pans. Starch acetates of DS 0.5–2.5 were prepared at temperatures of 160–180 °C in 2–10 min. Reaction efficiencies were essentially 100%. Reaction rates increased with increasing acetic acid concentration and decreased with increasing acetic anhydride concentration. The acetic acid remaining in the samples could be completely removed by vacuum stripping at 120–190 °C. Starch succinates of DS 1.0–1.5 were prepared at temperatures and times similar to those for starch acetates above. Longer reaction times (20–60 min) were required for the preparation of starch octenylsuccinates and dodecenylsuccinates having moderate DS values (∼0.5). Significant acetylation due to esterification of starch with acetic acid also occurred in these systems for long heating times (>20 min). This results in release of water and probably accounts for some of the apparent degradation (reduction in viscosity, browning) seen at long heating times.

Dielectric Relaxation and Compatibility Investigation of Polystyrene/Polyvinyl Chloride Blends

A systematic dielectric study over a frequency range 100 Hz up to 100 kHz was carried out on polystyrene/polyvinyl chloride (PS/PVC) blends with different concentrations of maleic anhydride (MA) ranging from 0–20%. After subtraction of the losses resulting from DC conductivity, the dielectric data were fitted in the frequency domain by two Fröhlich regions. The first absorption region in the lower frequency range, which is found to be unchanged by increasing either blend ratio or the content of maleic anhydride, could be ascribed to the Maxwell Wagner effect because of the difference in the permittivities and conductivities in polymeric materials. The relaxation time associated with the second absorption region, which involve the rotation of various segments of the side group, is found to increase by increasing both the PS and MA content in the blend. The compatibility study undertaken by using either dielectric or viscosity techniques led to the conclusion that PS/PVC blends free from MA and those containing 5% MA are incompatible. On the other hand, the addition of MA with concentration 10% and 20% could solve to some extent the problem of phase separation (i.e., improve the compatibility of PS/PVC blends).

Modification of Styrene-Containing Oligomer Based on Bottoms from Toluene Distillation in Production of Polybutadiene

Chemical modification of styrene-containing oligomer with maleic anhydride was studied. The process conditions and content of maleic anhydride were optimized.

Anhydride prodrugs for nonsteroidal anti-inflammatory drugs.

The objective of this study was to synthesize anhydride prodrugs for prolong action to shield the carboxylic acid group from irritative effects and to temporary hydrophobize the drug so that it becomes accessible to aqueous media when the anhydride residue is hydrolyzed. Ibuprofen, a nonsteroidal anti-inflammatory agent, was used as a representative drug for anhydride derivatization. Mixed anhydrides of ibuprofen with fatty acids of different chain length were prepared by reacting acid chloride derivatives with the corresponding acid in the presence of acid acceptor and two-phase reaction. Mixed anhydrides were also prepared by dehydration reaction using acetic anhydride and anhydride interchange of symmetric anhydrides. The analgesic effects of mixed anhydride prodrugs were tested using nonsteroidal anti-inflammatory drug rat paw edema model. In vitro degradation of mixed anhydrides and drug release were monitored by high-performance liquid chromatography. Ibuprofen was bound to aliphatic and aromatic acids via an anhydride bond in high reaction yields (>85%) with high mixed anhydride content (>80%). The mix anhydride was purified by chromatography and stored at 4 degrees C to minimize conversion into the symmetric anhydride. These anhydride derivatives hydrolyzed at different time intervals depending on the hydrophobicity of conjugated acid. In vivo testing of the ibuprofen anhydride derivatives for analgesic effect indicated an extended action of the drug for over 24 h as a function of the fatty acid chain length. This study demonstrates the promise of anhydride prodrugs for extending drug action and shielding the carboxylic acid group.

H-Atom abstraction by C-centered radicals from cyclic and acyclic dipeptides. A theoretical and experimental study of reaction rates

Using the pulse radiolysis and other radiation chemical techniques, the reaction kinetics of ˙CH3 and ˙CH2OH radicals with alanine anhydride, glycine anhydride and sarcosine anhydride were examined in aqueous solution. The second order rate constant of reaction of ˙CH3 with alanine anhydride has been determined at 2 × 105 dm3 mol−1 s−1. A very similar value (8 × 104 dm3 mol−1 s−1) has been obtained by measuring the methane and ethane yields as a function of the alanine anhydride concentration at different dose rates and evaluation of these data by computer analysis. Similar experiments carried out with glycine anhydride and sarcosine anhydride yielded identical rate constants of 4 × 104 dm3 mol−1 s−1 for these compounds. It was found that ˙CH2OH radical does not react with alanine anhydride at an appreciable rate (k < 2 × 102 dm3 mol−1 s−1). The reactions of ˙CH3, ˙CH2OH, and ˙C(CH3)2OH with both cyclic anhydrides and acyclic glycine and alanine peptides were studied by means of theoretical calculations at the B3LYP/6-311+G(d,p) level of theory. Free energies in the gaseous phase were determined in the classical harmonic oscillator–rigid rotator model, and used to estimate rates of H-transfer reactions at the αC-site of the peptides. The effects of aqueous solution on the activation enthalpies were estimated by the SCIPCM procedure. Using the experimental A-factor for the methyl radical + D,L-alanine anhydride reaction, modified experimental Arrhenius A-factors were obtained for the reactions of the other species, and used to calculate solution-phase rate constants. The reactions are discussed in terms of the charge and spin polarisation in the transition state, as determined by AIM analysis, and in terms of orbital interaction theory. Rate constants, calculated by transition state theory are in good agreement with the available experimental data.

Kinetics of 4-acetoxybenzoic acid synthesis

High-temperature polymers have found a wide range of uses in recent decades. 4-Acetoxybenzoic acid (PABA) is used as a monomer for the polymerization of one such thermotropic polymer. Information on polycondensation of already prepared PABA is available in the literature. However, information in the literature concerning the kinetics of PABA synthesis by acetylation of 4-hydroxybenzoic acid (PHBA) using acetic anhydride is limited. The reaction between PHBA and acetic anhydride in a carrier solvent, Therminol-66 (T-66), was investigated. Aspects of the global reaction mechanism and the dependence of the reaction rate on acetic anhydride concentration were determined. Nuclear Magnetic Resonance (NMR) spectrometry and gravimetric analysis were used to analyze the samples collected from a 3 l batch reactor. The specific rate constant and the activation energy of the reaction were determined and a rate equation for the reaction suggested.

Copolymers from tert-butyl methacrylate and itaconic anhydride––reactivity ratios and polymer analogous reactions

Free radical copolymerisation of tert-butyl methacrylate ( 1) and itaconic anhydride ( 2) has been investigated and reactivity ratios r 1 =0.272±0.08 and r 2 =0.301±0.09 have been obtained. Peak temperature of the endotherm and the enthalpy of the cis-elimination of the tert-butyl ester show a linear dependence on the content of anhydride in the copolymer. Alcoholysis of the anhydride with methanol resulted in complete formation of monomethyl itaconate, whereas the reaction with isopropanol in the presence of N, N-dimethyl-aminopyridine as catalyst stopped at lower conversion. Re-formation of the anhydride takes place around 100 °C in case of the monoisopropyl itaconate and at 120 °C for the monomethyl ester. This offers the possibility to adjust polymer properties, e.g. glass transition temperatures and solubility by controlled polymer analogous reaction. The copolymers can be used in photoresist processing, where adhesion and solubility can be adjusted during processing by alcoholysis and baking steps.

Chemical Modification of Jack Bean ( Canavalia ensiformis ) Starch by Succinylation

Canavalia ensiformis native starch was succinylated and the functional properties of the succinylated starch evaluated. Reaction conditions investigated included: pH (8.0-8.5 and 9.0-9.5), succinic anhydride concentration (3 and 4%), temperature (20 and 30 °C) and reaction time (1 and 3 h). When starch was succinylated with 4% succinic anhydride, at pH 8.0-8.5, at 30 °C for 1 h, 1.58% succinylation was obtained. Compared to native Canavalia starch, these succinylated products exhibited increasing paste and gel clarity, solubility (36%), swelling power (46.2 g water/g starch), and viscosity (86.5 mPas). Gelatinization temperature range was reduced to 67-73 °C and retrogradation was eliminated. The use of succinylated Canavalia starches as thickening and stabilizing agents in ice creams, fruit jellies, baked products, sauces and frozen foods is suggested.

Modification of cassava starch by using propionic anhydride and properties of the starch-blended polyester polyurethane

Chemical modification of the cassava starch was conducted through acylation by using propionic anhydride as an esterifying reagent. The reaction was carried out in the presence of a pyridine catalyst and the effects of reaction variables such as the anhydride content, reaction time and reaction temperature on the degree of acylation were investigated. Results from Fourier transform infrared spectroscopy suggested that the hydroxyl groups in the starch molecules were converted into ester groups, accompanied by an increase in water stability of the starch. The propionyl content was found to be non-linearly dependent with the reaction variables. Scanning electron micrographs of the modified starch-blended polyurethane showed a better interfacial adhesion than the normal starch-blended polyurethane. However, results from the soil burial test showed that the modified starch experienced a slower biodegradation than the normal starch.

Transient kinetics of n‐Butane oxidation to maleic anhydride over a VPO catalyst

AbstractTransient reaction kinetics is usually needed to model the reactor system operated under unsteady‐state mode to improve the performance of the catalyst packed in such a reactor system and to match operating conditions of different reaction steps in this system. The transient reaction kinetics of n‐butane oxidation to maleic anhydride over a commercial VPO catalyst was systematically studied, using online MS/GC measurements, transient response, and forced periodic operation methods. A simplified scheme with respect to the reaction network is proposed based on the previous studies and the observations in this work. Combining the results on the roles of lattice and adsorbed oxygen in the reaction process with the data obtained in transient response experiments, a transient kinetic model taking account of the oxygen storage and diffusion in the bulk‐phase of the catalyst was introduced and its parameters were estimated. The model was examined by the transient response experimental data and time‐average concentrations of butane and maleic anhydride under forced unsteady‐state operation.

Bulk modification of styrene–butadiene–styrene triblock copolymer with maleic anhydride

AbstractThe bulk modification of SBS rubber with maleic anhydride in a mixing chamber of a Haake rheomixer was studied. The effect of temperature, maleic anhydride, and benzoyl peroxide concentrations on the grafting efficiency was evaluated. High grafting efficiency was achieved when the ratio of peroxide and maleic anhydride concentration was high. On the other hand, on this condition high insoluble fraction was generated. The addition of a diamine, 4,4′‐diaminediphenylmethane to the reaction mixture minimizes the amount of insoluble polymer. However, the grafted MAH content also decreases. The graft copolymer was characterized by infrared spectroscopy and the grafting extension was determined by titration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2953–2960, 2002; DOI 10.1002/app.10355

Oxidized cellulose esters: I. Preparation and characterization of oxidized cellulose acetates — a new class of biodegradable polymers

Oxidized cellulose acetates (OCA), with a degree of substitution (DS) value ranging between 1.1 and 2.3 and a free carboxylic acid group content of 20% (w/w), have been prepared by reacting oxidized cellulose (OC, COOH content 20% w/w) with a mixture of acetic acid and acetic anhydride in the presence of sulfuric acid as a catalyst. The DS of OCA, in general, increased with increasing reaction temperature, reaction time, and concentration of acetic anhydride in the reaction mixture. The yield of OCA, in contrast, increased with increasing concentration of acetic anhydride and decreased with increasing reaction time and temperature. The intrinsic viscosity of OCA varied between 0.100 and 0.275, depending on the reaction conditions used during its preparation. In general, an increase in reaction temperature and the use of a prolonged reaction time decreased the intrinsic viscosity of OCA. No correlation was found between DS and intrinsic viscosity of OCA. The apparent pKa of OCA is 3.7-3.9. The new OCA polymers are practically insoluble in water and slowly dissolve in pH 7.4 phosphate buffer solution. They are, however, soluble in a range of organic solvents (e.g. ethyl acetate, acetone, acetone/water, chloroform/methylene chloride, dimethylsulfoxide, dimethylformamide, and/or chloroform/methanol).

Water-Blown Expandable Polystyrene. Improvement of the Compatibility of the Water Carrier with the Polystyrene Matrix by in Situ Grafting

The compatibility of starch with the polystyrene matrix in the synthesis of water-blown expandable polystyrene (WEPS) was improved by making use of maleic anhydride. The foam morphology on the contrary is significantly changed after pre-expansion as the content of maleic anhydride is increased. It has been found that starch is grafted during the polymerization with styrene-maleic anhydride copolymer. Partial immscibility of polystyrene matrix and styrene-maleic anhydride grafts formed at higher concentrations of maleic anhydride causes the agglomeration of starch. Consequently, water, as the blowing agent, cannot be finely dispersed in the matrix, which is the reason of the irregular foam morphology. Different methods for the improvement of the compatibilization are discussed.

Water-blown Expandable Polystyrene. Improvement of the Compatibility of the Water Carrier with the Polystyrene Matrix by in Situ Grafting

In the synthesis of water-blown expandable polystyrene, granular starch as a carrier of water, the blowing agent, was grafted with polystyrene by radical initiated polymerization. Organic peroxides, such as tertbutyl perbenzoate or dibenzoyl peroxide were used as free radical initiators. The graft polymerization reaction was confirmed by FT-IR spectroscopy and SEM. The reaction leads to low level grafted starch. However, the amount of grafted polymer can be significantly increased using maleic anhydride in the monomer feed. The effect of concentration of maleic anhydride was studied. The reaction mechanism was proposed.

Effect of maleic anhydride content on the rheology and phase behavior of poly(styrene-co -maleic anhydride)/ poly(methyl methacrylate) blends

We investigated the thermo- rheological behavior of high glass transition, high molecular weight and small dynamic asymmetry blends of poly(styrene-co-maleic anhydride) (SMA) and poly (methyl methacrylate) (PMMA) with varying amounts of maleic anhydride (MA) content, namely 8 wt%, 14 wt% and 32 wt%, in the SMA component. The phase separation (binodal) temperature of each blend was determined rheologically using a combination of dynamic frequency and temperature sweeps in parallel plate geometry; it was marked by a change in slope of the elastic modulus and the occurrence of a peak in tan δ in temperature sweeps. Failure of the time-temperature superposition principle and observation of two peaks in the Cole-Cole plots corroborated these findings. The blends displayed lower critical solution temperature (LCST) behavior with the critical temperatures exhibiting a non-monotonic dependence on the MA content. From rheological and thermal measurements it was concluded that SMA/PMMA blends containing 14% MA were more miscible than those containing 8% or 32% MA, a finding attributed to the compositional dependence of the interplay between SMA-SMA and SMA-PMMA interactions in the different samples. MA also influenced the dynamic asymmetry and pretransitional concentration fluctuations. The phase diagrams corresponding to each blend were modeled using a two-parameter temperature dependent interaction parameter, based on the concept of generalized Gibbs free energy of mixing. The fitted values of interaction parameter were in good agreement with values calculated explicitly using the Flory-Huggins theory.