Optimization of Carboxymethylation of Starch in Organic Solvents

A comparative study of the influence of ethanol, benzene, acetone, isopropanol, and mixtures of ethanol-acetone, ethanol-benzene, and ethanol-isopropanol as slurry media on the degree of substitution and viscosity of carboxymethyl starch during carboxymethylation is presented. It is shown that the degree of substitution increases with increasing acetone, isopropanol, or benzene content in the mixed solvent. After the same carboxymethylation steps the degree of substitution with ethanol/benzene mixture is higher than that with ethanol/isopropanol mixture.     

Experimental study on carboxymethylation of cellulose extracted from Posidonia oceanica

The production of carboxymethylcellulose (CMC) from bleached cellulose pulps obtained from Posidonia oceanica was explored. The optimal reaction conditions were studied for the carboxymethylation of cellulose in organic liquids. The carboxymethylation reaction was carried out with NaOH and monochloroacetic acid (MAC) as the reagent. Different alcohols were compared in terms of the degree of substitution (DS). The highest DS was obtained with n‐butanol. For this alcohol, the effects of the temperature, alkali concentration, and MAC concentration were studied. The reaction was also carried out in three consecutive steps. The resulting CMC had a DS of about 2.75. The functionalization of cellulose was checked using FTIR spectroscopy and ¹³C‐NMR. The X‐ray analysis showed that the crystalline structure of cellulose decreased when the DS increased and the structure was totally amorphous in high DS material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1808–1816, 2006     

Influence of quench medium on the structure and gas permeation properties of cellulose acetate membranes

Integrally skinned asymmetric cellulose acetate membranes made by the wet phase inversion for removal of CO₂ from natural gas were investigated. The membrane was cast with the membrane-forming systems of cellulose acetate–acetone and quench media, such as methanol, ethanol and isopropanol, respectively, without heat-treating and multistage exchange process. By means of evaluation on separating characteristics of the membrane for CO₂/CH₄, observation of morphologies by scanning electron photomicrographs and analysis of the phase diagrams on the membrane-forming systems, it has shown that the membrane-forming system of cellulose acetate–acetone–methanol is quite suitable to prepare integrally skinned asymmetric cellulose acetate membranes for gas separation with good selectivity CO₂/CH₄ = 30 and flux coefficient = 2.4 × 10⁻⁵ cm³/cm² − s − cm Hg. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1269–1276, 1998     

Homogenous carboxymethylation of cellulose in the NaOH/urea aqueous solution

In this work, the carboxymethylation of cellulose in the alkaline cellulose solvent, 7 wt% NaOH/12 wt% urea aqueous solution, was investigated. Carboxymethyl cellulose (CMC) samples were characterized with FT-IR, NMR, HPLC, and viscosity measurements. Water-soluble CMC with DS = 0.20–0.62 was prepared from both Avicel cellulose and cotton linters. Thus, carboxymethylation of cellulose in NaOH/urea leads to a polymer with the lowest DS value for water solubility (0.20) of CMC known. The total DS of CMC could be controlled by varying the molar ratio of reagents and NaOH to AGU and the reaction temperature. Structure analysis by means of HPLC after complete depolymerization showed that the mole fractions of the different carboxymethylated repeating units as well as those of unmodified glucose follow the simple statistic pattern. A distribution of the carboxymethyl groups at the level of the AGU in the order O-6 > O-2 > O-3 was determined. The results were similar with findings for CMC obtained by totally homogeneous reaction of cellulose in aqueous solvents such as Ni[tris(2-aminoethyl)amine](OH)₂.     

Effect of water on vapor phase photografting on cellulose and its derivatives

Effect of water on vapor phase photografting on cellulose was investigated at 60°C. An activated grafting of methyl methacrylate by water contained in the sample was observed in the experiment. The effect of water was commonly recorded irrespective of the type of cellulose derivatives such as cellulose acetate (degree of substitution, DS = 0.18 and 0.33), cellulose nitrate (DS = 0.35 and 0.75), and carboxymethl cellulose (DS = 0.19 and 0.74). Organic solvents can also be used in place of water, indicating that the percent grafting decreases in the order, water > methanol > acetone > cyclohexane. From ESR studies, water in the sample was found to contribute to the decay of cellulose radicals rather than to the radical formation. The decay was accelerated by organic solvents, and the magnitude of the effect was in the order, water ≈ methanol > acetone > cyclohexane. Based on the above investigation, it was presumed that water contained in the sample cannot contribute directly to the formation of cellulose radicals which may initiate grafting, but mostly promotes the penetration of monomer into cellulose fibers. Such penetration could lead cellulose radicals to an effective initiation of grafting.     

Graft copolymerisation of vinyl monomers on modified cottons. VII. Grafting by chain transfer

Grafting of methyl methacrylate on cellulosic materials by chain transfer under the catalytic influence of azobisisobutyronitrile (AIBN) was extensively studied. The graft yield is influenced by reaction time, temperature, monomer and initiator concentration, reaction medium and nature of the substrate. In general, the grafting reaction shows an induction period after which the polymerisation proceeds rapidly. The graft yield increases and the induction period decreases by rising the reaction temperature from 50 to 70°C. This is also the case when the monomer concentration was increased from 2 to 6%. Increasing the AIBN concentration up to 0.01 M causes a significant enhancement in grafting while further increase brings about a marked fall in the graft yield. Among the reaction media studied, a water/solvent mixture containing 25% of either methanol, ethanol, propanol, butanol or acetone seems to constitute a reaction medium where the monomer and initiator are completely miscible and the swelling of cellulose by water is not hindered by the presence of these solvents. Increasing the solvent ratio in the water/solvent mixture causes a considerable decrease in the graft yield. The polymer content of the cellulosic materials, i. e. the graft yield, follows the order: partially carboxymethylated cotton > cotton treated with 12N sodium hydroxide > cyanoethylated cotton > cotton treated with 0.5 N sodium hydroxide > purified cotton. In addition, proof of grafting was provided by the fractional precipitation method.     

The “cold‐solutioning” phenomenon in cellulose triacetate–acetone mixtures

Direct mixing of cellulose triacetate (CTA) in acetone at room temperature produces only an opaque swollen gel at all concentrations. However, cycling the mixture between room temperature and ?78 ± 3°C results in a stable solution at room temperature, if the concentration is less than 6% (w/w). This process has been called “cold‐solutioning.” Such a process also produces a clear solution at concentrations between 6% (w/w) and 10% (w/w); however, in time, the solution separates slowly into at least two phases, a clear liquid and an opaque gel phase. At concentrations above 10% (w/w) and below 20% (w/w), the system exhibits two phases. A completely opaque swollen gel forms at concentrations of 20% (w/w) and above. The above‐described cold‐solutioning phenomena are shown to be the coupled kinetic and thermodynamic consequences of (1) the large thermal stresses that would result from thawing a swollen mixture of CTA and acetone, arising from the large differences in their thermal expansion coefficients; and (2) the “bimodal” composition of the cellulose derivative. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1697–1707, 2003     

淀粉的羧甲基化研究

研究了不同原料配比 (淀粉、CH2 ClCOOH及NaOH的用量 )、反应介质以及反应时间等对淀粉羧甲基化反应的影响。结果表明 ,在其它条件不变时 ,( 1)当NaOH用量不大时 ,随着NaOH用量的增加 ,取代度 (DS)和CH2 ClCOOH的反应效率(RE)亦增加 ,当NaOH与CH2 ClCOOH的摩尔比为 2 .5∶1时 ,达到最大值 ,其后随着NaOH的增加 ,DS和RE急剧下降 ;( 2 )随着CH2 ClCOOH用量的增加 ,DS和RE增加 ,其中DS在CH2 ClCOOH与淀粉中葡萄糖基的摩尔比增大到 1∶1时达到最大值 ,而RE在CH2 ClCOOH与淀粉中葡萄糖基的摩尔比为 0 .75∶1时达到最高 ;异丙醇作为反应介质优于乙醇 ;在本实验的时间范围内 ,DS随着反应时间的增长而增大     

Impact of non‐solvent on regeneration of cellulose dissolved in 1‐(carboxymethyl)pyridinium chloride ionic liquid

Cellulose dissolved in ionic liquid (1‐(carboxymethyl)pyridinium chloride)/water (60/40 w/w) mixture is regenerated in various non‐solvents, namely water, ethanol, methanol and acetone, to gain more insight into the contribution of non‐solvent medium to the morphology of regenerated cellulose. To this end, the initial and regenerated celluloses were characterized with respect to crystallinity, thermal stability, chemical structure and surface morphology using wide‐angle X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. According to the results, regardless of non‐solvent type, all regenerated samples have the same chemical structure and lower crystallinity in comparison to the initial cellulose, making them a promising candidate for efficient biofuel production based on enzymatic hydrolysis of cellulose. The reduction in crystallinity of regenerated samples is explained based on the potential of the non‐solvent to break the hydrogen bonds between cellulose chains and ionic liquid molecules as well as the affinity of water and non‐solvent which can be evaluated based on Hansen solubility parameter. The latter also determines the phase‐separation mechanism during the regeneration process, which in turn affects surface morphology of the regenerated cellulose. The pivotal effect of regenerated cellulose crystallinity on its thermal stability is also demonstrated. Regenerated cellulose with lower crystallinity is more susceptible to molecular rearrangement during heating and hence exhibits enhanced thermal stability. © 2019 Society of Chemical Industry     

Carboxymethylation of cellulosic material (average degree of polymerization 2600) isolated from cotton (Gossypium) linters with respect to degree of substitution and rheological behavior

Carboxymethylation of cellulosic material (average degree of polymerization 2600) containing 76.5% cellulose and 23.6% xylose isolated from cotton (Gossypium) linters was studied under varying reaction conditions with respect to maximum degree of substitution (DS). The influence of reaction conditions on the apparent viscosity of the prepared derivatives was also studied. The conditions optimized were sodium hydroxide concentration 3.75M, monochloroacetic acid concentration 2.05 mol/AGU, carboxymethylation time 3.5 h, and temperature 55°C, to yield carboxymethyl cellulose of DS 0.77. Rheological studies of 1 and 2% solutions of the optimized product revealed their non‐Newtonian pseudoplastic behavior. Repeating units of the optimized product were also determined by HPLC after complete depolymerization of the polymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1477–1482, 2005     

Variables affecting the methylation reactions of cellulose

Solubility of methyl cellulose (MC) depends on the degree of substitution (DS), the average degree of polymerization (DP), and the distribution of methoxyl groups. Of these, the DS appears to be the most important. The DS of the MC depends on the conditions of preparation. The conditions studied in this work revealed that the DS of the MC increased as the concentration of sodium hydroxide increased from 10 to 50%. This result is attributed to the increase in the extent of formation of alkali cellulose II as a result of the increase in the alkali concentration and hence the increase of the DS of the MC. Decreasing both the ratio of dimethyl sulfate: cellulose and the liquor ratio increased the DS. High DS was achieved within a period of 2 and 3 h. However, the DS increased as the time increased. The decrease of the DS as the liquor ratio increased may be attributed to the sol–gel transition due to the interaction of the hydrophobic methoxyl groups within the polymer chains. To reveal the effect of the thermal sol–gel transition, the reaction was carried out in nonaqueous medium and the results obtained showed an increase of the DS with the increase of the solvent ratio until a maximum. This result may be contributed to the breakdown of the hydrogen bonding in the presence of solvents that transfer the reaction medium to the sol-form and hence more methylating reaction takes place. The degree of the solvation of the methyl groups into the solvents also plays a role. © 1994 John Wiley & Sons, Inc.     

纤维素在离子液体AmimCl中的均相苯甲酰化反应

酱油渣中可以提取到纤维素等生物资源,但由于纤维素不溶于水和一般溶剂,难以进行衍生化应用,因此常常遭到浪费。而离子液体对纤维素呈现出较好的溶解性,可作为纤维素衍生化的良好溶剂。本文利用提取过油脂和半纤维素的酱油渣为原料进一步提取纤维素,并对以离子液体为溶剂,无催化剂条件下纤维素的均相苯甲酰化进行了研究。重点考察了离子液体种类对均相苯甲酰化的产率和取代率的影响,反应温度、时间、苯甲酰氯与葡萄糖单元摩尔比对均相苯甲酰化的取代率的影响。研究结果发现以离子液体AminCl（1-烯丙基-3甲基咪唑氯盐）为溶剂时有最优的产率。在最优反应条件为温度80℃、时间90min、苯甲酰氯与葡萄糖单元摩尔比4：1时,可得到最高取代率0.72。     

两组元乙醇基混合工质振荡热管的传热性能

通过实验研究乙醇中分别加入少量水、丙酮、甲醇,体积比分别为2：1、4：1,加热功率从10 W到100 W,充液率为45%、55%、62%、70%、90%时振荡热管的热阻特性,并与纯乙醇工质振荡热管相比较。结果表明,45%充液率时,乙醇中加入水可以改善烧干,混合工质较乙醇、水纯工质振荡热管热阻小;55%充液率时,乙醇-丙酮混合工质较乙醇、丙酮纯工质振荡热管热阻小;大充液率62%～90%时,两组元乙醇基混合工质振荡热管传热性能略不如各纯工质振荡热管。混合工质对振荡热管的影响主要与物性、分子间相互作用、溶液汽液相平衡及相变特性、传质阻力有关。     

Cellulose graft copolymers. IV. Graft copolymerization of methacrylonitrile with γ-irradiated cellulose from DMSO–, acetone–, and methanol–water systems

Methacrylonitrile was graft-copolymerized from DMSO–, acetone–, and methanol–water systems with γ-irradiated, purified cotton cellulose. The relative extents of scavenging of the free radicals in the irradiated cellulose after immersion in the solvents for 3 min at 25°C, as determined by electron spin resonance spectroscopy, were: methanol (77%) > water (70%) ? acetone (5%) > DMSO (0%). After immersion of irradiated cellulose in the solvents for 60 min at 25°C, the relative extents of scavenging of the radicals were: methanol, water (80–85%) > DMSO (80%) > acetone (62%). From these data, it would appear that the overall rates of diffusion of methanol and water into the fibrous macrostructure were greater than the rates of diffusion of DMSO and acetone into the structure. The relative radiochemical yields of the graft copolymerization reactions of methacrylonitrile with irradiated cellulose in the different solvents were: water ? DMSO > methanol ? acetone. The addition of water to the systems increased the yields of the reactions.     

共反应剂法合成金刚烷甲酸纤维素酯

In order to develop a novel bioactive material utilizing cellulose resource, adamantane carboxylic acid esters of cellulose were synthesized through in-situ activation of the adamantane carboxylic acid using N,N-dimethylacetamide/LiCl as solvent, p-toluenesulfonyl chloride as co-reagent.The structure and properties of adamantane carboxylic acid esters of cellulose were characterized by means of IR, ¹H NMR, TG,etc.The esterification conditions were investigated in detail.The results showed that the degree of substitution was influenced by reaction temperature, reaction time and mole ratios of repeat units of cellulose/adamantane carboxylic acid/p-toluenesulfonyl chloride.Under the optimized reaction conditions, the highest degree of substitution (DS) was 1.9.TG analysis revealed that the thermal stability of cellulose esters was improved with the increase of DS due to the incorporation of adamantane carboxylic acid into chains of cellulose.The products are soluble in various organic solvents, depending on the DS.     

A green route to prepare cellulose acetate particle from ramie fiber

A novel procedure for synthesizing cellulose acetate particles from ramie fiber was developed. The optimum conditions for preparing cellulose acetate (CA) by reaction of ramie fiber with acetic anhydride under an acidic condition were determined. Reaction was carried out in a ratio of ramie fiber to acetic anhydride of 1:6 (w/w) at 80 °C for 0.5–1 h. When CA was added to a mixture of water and acetone, CA particles with a well-distributed diameter ranging from 5 to 15 μm were obtained. The difference of the CA particle surface was resulting from different washing methods of CA particles with water or aqueous sodium bicarbonate. The highest degree of substitution (DS) of 2.50 for CA by titration method was achieved. A new adsorbent was prepared from CA, which is an excellent sorption regent for organic waste in water. The scanning electron microscopy (SEM) and particle size distribution results showed that the average size of CA particles is about 5–15 μm in diameter. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to determine the stability of ramie fiber and CA particle.     

Carboxymethylation of dextran in aqueous alcohol as the first step of the preparation of derivatized dextrans

Carboxymethyldextrans (CMD) with a degree of substitution of carboxymethyl groups DS > 0.9 are precursors for the synthesis of derivatized dextrans termed CMDBS, which present heparin-like biological properties. Syntheses of CMD in water/organic solvent mixtures using monochloroacetic acid (MCA) and strong alkaline conditions allowed to obtain highly substituted CMD with good reproducibility and high yields. The influences of, respectively, individual concentrations of reactants, composition and temperature of reaction medium, and allowed reaction time have been examined. The most favorable conditions for dextran carboxymethylation were obtained with 3.8 M NaOH and a [MCA]/[dextran] ratio of 2.5, allowed to react at 60°C for 90 min, in a reaction medium consisting of a tert-butanol/water (alternatively isopropanol/water) 85 : 15 (v/v) mixture. A DS of about 1.0 was obtained in one step, as compared to a DS less than 0.6 when using aqueous conditions. Improvements on overall CMD substitution levels (up to DS of 1.47) were achieved by merely repeating the reaction i. e. using the CMD products of the first reaction as substrate in the second.     

Solubility measurement and thermodynamic properties of sulfamonomethoxine in pure solvents and sulfamonomethoxine hydrate in acetone + water binary solvent at different temperature

The experimental solubility of sulfamonomethoxine in six different pure solvents (methanol,ethanol,1-propanol,l-butanol,ethyl acetate and acetone) and sulfamonomethoxine hydrate in acetone + water mixture solvents were measured from 294.55 K to 362.15 K by a laser dynamic method under atmospheric pressure.Experimental results indicated that the solubility data of sulfamonomethoxine increased with temperature increasing in pure solvents and the solubility followed this order:acetone ＞methanol ＞ ethanol ＞ ethyl acetate ＞ 1-propanol ＞ 1-butanol,but solubility in ethyl acetate was not affected significantly by temperature.In acetone + water mixture solvent,the solubility of sulfa-monomethoxine hydrate increased with temperature and the acetone concentration.Thermodynamic equations were applied to correlate solubility data of sulfamonomethoxine and sulfamonomethoxine hydrate including the modified Apelblat equation,λh equation,Wilson equation,NRTL equation,Van't Hoff-Jouyban Acree equation and modified Apel-Jouyban-Acree equation.Furthermore,thermodynamic properties △Gd,△Hd and △Sd of sulfamonomethoxine and sulfamonomethoxine hydrate in dissolution process were obtained and discussed with the modified Van't Hoff equation and Gibbs equation.     

Investigation of biocatalytic properties of soybean seed hull peroxidase

Soybean seed hull peroxidase (SBP) is an inexpensive oxidoreductive enzyme and could potentially be used to oxidise/polymerise various organic pollutants present in the industrial and petrochemical wastes. SBP is able to retain its catalytic properties under wide ranges of pH and at elevated temperatures. In this study, a systematic evaluation of the biocatalytic properties of SBP was carried out. The optimal pH for SBP activity is pH 6.0 and significant activity was observed between 2.2 and 8.0. SBP also showed three times higher activity at an elevated temperature of 80°C and at pH 6.0 when compared to the activity at room temperature. The pH and temperature of the reaction mixture were found to significantly influence the SBP activity. SBP is fairly active in organic solvents. The enzyme exhibited highest activity in the presence of 16.67% (w/v) ethanol followed by acetone, methanol and acetonitrile. The enzyme activity was reduced with an increase in concentration of the organic solvent. SBP also showed maximum activity at different concentrations of acetone using a phosphate buffer, pH 6.0 than with the other pH buffers. Benzene/acetone mixture seems to be another better solvent system for SBP where it showed about 65% of its activity at 16.67% (w/v) concentration.     

EFFECTIVE DIFFUSION COEFFICIENT OF ACTIVE SOLVENTS IN COMPOSITE POLYMERIC MATERIALS

ABSTRACT

A method and a device for determination of the effective diffusion coefficient of active solvents in composite polymeric materials (CPM) based on cellulose derivatives are proposed and examined. This method accounts for anomalous mass transfer phenomena, considerable shrinkage and changes of sorption capacity of the CPM specimen allowing selection of the rational technological regime. Results of experimental studies on diffusion of acetone and ethanol in cellulose nitrate with various degrees of substitution are given as examples.