长链烷酸接枝羟丙基纤维素相变材料的制备及其性能

采用酯化的方法将具有相变特征的长链脂肪酸接枝到羟丙基纤维素主链上, 得到了一系列性能稳定, 温度范围适宜的高分子固-固相变材料, 并利用傅里叶红外光谱(FT-IR)、核磁共振(NMR)、差示扫描量热仪(DSC)、热失重分析仪(TGA)和X射线散射等技术手段对其化学结构及相变行为进行了研究。 结果表明, 该材料呈现出可逆的固-固相转变特性, 相变温度范围可通过改变脂肪酸的长度调节。 利用棕榈酸、硬脂酸和花生酸获得的相变材料焓值达到60 J/g, 所获得的材料在250 ℃以内不发生热分解。 通过将两种长链脂肪酸混合同时接枝到羟丙基纤维素主链上, 所得产物的吸/放热温度随着混合脂肪酸组分含量的变化而变化, 同时X射线散射的结果也证明羟丙基纤维素混合酯的分子间距是位于其两种单一酯之间的。这一结果为制备一定温度范围内任意相变温度的高分子固-固相变材料提供了简便的方法。     

CERIC ION INITIATED GRAFTING ON CELLULOSE FROM BINARY MIXTURE OF ACRYLONITRILE AND METHYLACRYLATE

The Ce(IV)-ion induced grafting on cellulose from the binary mixture of acrylonitrile-methylacrylate has been investigated in heterogeneous and acidic conditions at 25 ± 0. 1°C. Various grafting parameters were evaluated as a function of molarity, feed composition, reaction time, and concentration of ceric ion at constant concentration of nitric acid in the feed. The higher fraction of acrylonitrile in the grafted chains than the feed has indicated the synergistic effect of methylacrylate taken in the feed along with acrylonitrile. IR and elemental analysis for nitrogen contents in the synthesized copolymers were used to determine the composition of the grafted copolymers. The reactivity ratios of acrylonitrile and methylacrylate have been determined by the Mayo and Lewis method and are found to be 1.45 and 0.9, respectively. The grafting parameters have shown increasing trends on varying feed composition (f_AN) from 0.25 to 0.80 and varying monomer concentration from 0. 6 to 5 4 mol dm^?3. The number of grafted moles of synthetic polymer (N_g) on cellulose were found to be dependent on molarity, feed composition, and ceric ion concentration. The experimental results have clearly indicated that maximum fraction of the feed was consumed in the formation of grafted copolymer chains in comparison to the homocopolymers and homopolymers. Estimation of ceric ion disappearance as a function of reaction time has clearly suggested that grafting on cellulose is initiated by the reactive sites generated through hydrogen ion abstraction by single electron transfer process.     

Effects of carbonyl and aldehyde groups in the graft copolymerization of methyl methacrylate on cellulose with a ceric salt

Graft copolymerization of methyl methacrylate on cellulosic materials of various carbonyl and aldehyde contents with the use of a ceric salt as an initiator was studied. It was found that the concentration of the ceric salt which gives the maximum per cent grafting is in good agreement with the equivalent of total carbonyl content in the cellulosic material, and the number of grafted chains in copolymers is roughly proportional to it. However, the molar ratio of the number of grafted chains to total carbonyl content is quite small, being approximately 1:50, and the graft copolymerization can be explained kinetically on the assumption that the number of radicals produced on cellulose by the ceric salt leading to branching is very much smaller than the number of radicals destroyed by the ceric salt, and growing radicals can be stabilized by the termination reaction with the ceric salt or with a cellulose radical. Although both aldehyde and carbonyl groups contribute to the formation of grafted chains, the former are effective mainly at low concentrations of the ceric salt; both groups participate in the production of graft copolymers showing the maximum per cent grafting.     

醋酸纤维素/PET接枝共聚物的制备及性能

以低数均分子量的聚对苯二甲酸乙二醇酯(PET)、二醋酸纤维素(CDA)为原料,异孚尔酮二异氰酸酯(IPDI)为接枝剂,二月桂酸二丁基锡(DBTDL)和离子液体1-丁基-3-甲基咪唑氯盐为催化剂制备得到新型的接枝共聚物CDA-g-PET。对接枝过程进行了优化,研究了催化剂种类与接枝剂用量对接枝过程的影响,利用红外分析和广角X射线衍射分析探究了接枝机理。同时对CDA-g-PET膜进行力学性能测试,探讨了PET的加入量对CDA-g-PET膜力学性能的影响。结果表明:PET通过化学键连接接枝到CDA上,接入的PET降低了CDA的结晶性;采用DBTDL与离子液体作为联合催化剂,接枝时间由7d缩短至8h;当接枝剂IPDI的加入量,即n(IPDI)/n(PET)为1.05~1.10时CDA-g-PET无交联;随着PET含量的增加,CDA-g-PET膜与CDA膜相比拉伸强度仅降低6.55%~27.24%,断裂伸长率增加149.89%~177.81%。     

Studies of the graft copolymerization of methyl methacrylate by means of the photochemical reduction of ceric ion adsorbed on cellulosic materials

It was observed that the rate of reduction of ceric ion adsorbed on cellulose was remarkably accelerated by irradiation with ultraviolet light, and this behavior depended upon the kind of cellulose. When the graft copolymerization of methyl methacrylate on cellulose with adsorbed ceric ion was carried out by irradiation with ultraviolet light, the percent grafting decreased for softwood, bleached sulfite pulp and increased for hardwood semichemical pulp. The average molecular weight of the grafts was observed generally to decrease. If it is assumed that the ceric ions, which are reduced at an accelerated rate in the early stages of reaction with SCP, do not participate in the graft formation, a relation is observed between the modified amount of reduced ceric ion and the number of grafted chains formed, and the molar ratios of these quantities are 12:1 without irradiation and 75:1 to 100:1 with irradiation. Even when the rate of reduction of ceric ion is accelerated, the increase in the number of grafted chains is found to be very small.     

Graft polymerization of acrylic monomers onto starch fractions. IV. Effect of reaction time on the grafting of butyl acrylate onto amylose

Studies were carried out on the grafting of butyl acrylate (BA) to amylose by the ceric ion method. After removing the homo-PBA with THF and toluene, and the ungrafted amylose with 0.5NNaOH, the PBA content of the graft copolymers was determined by acid hydrolysis with 1N HCl. The influence of reaction time on the grafting yields was determined and the largest values were: 82% for the grafting efficiency, 246% for the percent grafting, 62% for the grafted amylose, 48% for the grafted PBA, and 64% for the total conversion.     

Preparation and Antibacterial Function of Quaternary Ammonium Salts Grafted Cellulose Fiber Initiated by Fe2 +-H2O2 Redox

The surface contact disinfecting technique is a newly developed method for water sterilization. In this paper, the grafted quaternary ammonium salts (QAS) antibacterial fibers were prepared and designed to apply for the surface contact disinfecting process in water treatment. The antibacterial fibers were directly prepared by grafting methacryloxylethyl benzyl dimethyl ammonium chloride (DMAE-BC) onto cellulose fiber using thiocarbonate-H₂O₂ redox system. All kinds of factors in the grafting reactions, such as reaction time, reaction temperature, monomer concentration, initiator concentration, which influence the percentage of grafting, were studied and optimized. The modified cellulose fibers were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope(SEM). The effects of the percentage of grafting of the grafted cellulose fibers on bactericidal activity were also studied. The spread plate method was used to characterize the bactericidal activity. The disinfection process was further investigated by directly observing the morphology of the bacterial cells adsorbed on the antibacterial fibers with SEM and measuring extracelluar total protein concentration in suspension. The poly(DMAE-BC)-grafted cellulose ?ber was found to exhibit particularly high activity against E.coli.     

Synthese et etude de celluloses echangeuses d'ions. Leur emploi dans l'epuration des eaux residuaires de l'industrie textile—1: Synthese d'une cellulose greffee par des chaines poly (acide acrylique) et d'une cellulose renfermant des fonctions ammonium quaternaire

For use as ion exchangers and particularly as purification agents for textile industrial effluents, cellulose grafted with polyacrylic acid and cellulose substituted by quaternary ammonium functions have been prepared. For both syntheses, the influences of experimental parameters have been studied in detail and the optimum conditions for large-scale preparation have been determined. Large amounts of modified cellulose have been obtained and tested in industry (cf. part III). The grafting by acrylic acid has been carried out by the ceric-ion method; the quaternary ammonium cellulose has been obtained by condensation of cellulose with epoxy propyl triethyl ammonium chloride. Synthesis of this salt in the presence of cellulose has been achieved so that the quaternary ammonium cellulose can be obtained from cellulose and epichlorhydrin in one step.     

Grafting of Methyl Acrylate onto Cellulose by Ceric Ion

Abstract

Methyl acrylate was grafted onto dissolving pulp by ceric ion in aqueous sulfuric acid under oxygen-free argon. At a low Ce(IV) concentration (up to 1 mmol/L), the rate of polymerization (R_p ) is proportional to [Ce]^0.5 [MA]¹ [cellulose]¹. At higher concentrations of cericion (1–20 mmol/L), R_p is proportional to [Ce]⁰ [M] ^1.5 [cellulose]¹. The mechanism of grafting is consistent with a kinetic scheme involving initiation by primary radicals and termination by growing polymer radicals. Above 20 mmol/L of ceric salt, the data are consistent with the linear termination mode.     

Controlled grafting of MMA onto cellulose and cellulose acetate

Homogeneous graft copolymerization of methyl methacrylate onto cellulose and cellulose acetate was carried out in various solvents and solvent systems taking ceric ammonium nitrate, tin (II) 2-ethyl hexanoate [Sn(Oct)₂] and benzoyl peroxide as initiators. The effect of solvents, initiators, initiator and monomer concentration, on graft yield, grafting efficiency and total conversion of monomer to polymer were studied. Formation of Ce³⁺ ion during grafting in presence of CAN enhances the grafting efficiency. Methylene blue was used as a homopolymer inhibitor and controlled the molecular weight of the grafted polymer and its effect on grafting was also studied. In presence of MB, amount of PMMA homopolymer formation reduced and consequently grafting efficiency increased. The number average molecular weights and polydispersity indices of the grafted PMMA were found out by gel permeation chromatography. The products were characterized by FTIR and ¹H-NMR analyses and possible reaction mechanisms were deduced. Finally, thermal degradation of the grafted products was also studied by thermo-gravimetric and differential thermo-gravimetric analyses.     

Graft Copolymerization on to Cellulose Using Binary Mixture of Monomers

The graft copolymerization of acrylonitrile (AN) and ethyl acrylate (EA) comonomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 35±0.1°C. The addition of ethyl acrylate as comonomer has shown a significant effect on overall and individual graft copolymerization of acrylonitrile on cellulose. The graft yield (%G_Y) and other grafting parameters viz. true grafting (%G_T), graft conversion (%C_G), cellulose number (Ng) and frequency of grafting (G_F) were evaluated on varying the concentration of comonomers from 6.0–30.0×10^?1 mol dm^?3 and ceric (IV) ions concentration from 2.5–25×10^?3 mol dm^?3 at constant feed composition (f_AN 0.6) and constant concentration of nitric acid (7.5×10^?2 mol dm^?3) in the reaction mixture. The graft yield (%G_Y) and other grafting parameters were optimal at 15×10^?1 mol dm^?3 concentration of comonomers and at 10×10^?3 mol dm^?3 concentration of ceric ammonium nitrate. The graft yield (%G_Y) and composition of grafted chains (F_AN) was optimal at a feed composition (f_AN) of 0.6. The energy of activation (Ea) for graft copolymerization has been found to be 16 kJ mol^?1. The molecular weight (Mw) and molecular weight distribution (Mw/Mn) of grafted chains was determined by GPC and found to be optimum at 15×10^?1 mol dm^?3 concentration of comonomer in the reaction mixture. The composition of grafted chains (F_AN) determined by IR method was used to calculate the reactivity ratios of monomers, which has been found to be 0.62 (r₁) and 1.52 (r₂), respectively for acrylonitrile (AN) and ethyl acrylate (EA) monomers used for graft copolymerization. The energy of activation for decomposition of cellulose and grafted cellulose was determining by using different models based on constant and different rate (β) of heating. Considering experimental observations, the reaction steps for graft copolymerization were proposed.     

Graft Polymerization of Vinyl Monomers Onto Carbon Black by Use of the Redox System Consisting of Ceric Ions and Carbon Black Carrying Alcoholic Hydroxyl Groups

The radical graft polymerization of vinyl monomers onto carbon black initiated by a redox system consisting of ceric ion and carbon black having alcoholic hydroxyl groups was investigated. The introduction of alcoholic hydroxyl groups onto the carbon black surface was achieved by the reaction of carbon black with alcoholic hydroxyl radicals, formed by the reaction of alcohol with benzoyl peroxide. The rate of the polymerization of acrylamide (AAm) initiated by the redox system was found to increase in the following order of hydroxyl groups: 1-hydroxyoctyl < 1-hydroxypropyl < 1-hydroxyethyl < hydroxymethyl < 1-hydroxy-1-methylethyl. In the redox polymerization, poly-AAm was effectively grafted onto carbon black by propagation of the polymer from the radical formed by the reaction of ceric ions with the alcoholic hydroxy groups. The percentage of grafting increased with increasing conversion. By use of this redox system, poly(acrylic acid), polyacrylonitrile, and poly(N-vinyl-2-pyrrolidone) could be grafted onto carbon black, but poly(methyl methacrylate) and polystyrene could not be so grafted. The graft polymerization of AAm by use of a redox system consisting of ceric ion and PVA-grafted carbon black was also investigated.     

含磺酸基单体在炭黑表面接枝共聚合

近年来,炭黑粒子在水性体系中的分散稳定性倍受人们关注。研究认为影响炭黑分散稳定的主要因素为炭黑颗粒之间的相互作用力（包括电磁力、静电排斥力和空间位阻力等）和炭黑粒子与分散介质之间的相互作用力。目前,实现炭黑在水性体系中良好分散所采用的方法主要有炭黑氧化法、分散剂法和炭黑高分子接枝法,其中以炭黑高分子接枝方法效果最佳。     

Graft polymerization of vinyl monomers onto starch by use of tetravalent cerium

Grafting of acrylonitrile onto starch showed slightly higher yields when using soluble rather than insoluble starch, for reaction times < 1.5 hr. Beyond this time, the rate of grafting onto the soluble starch levels off, while that for grafting onto the insoluble starch proceeds leading to prograssive increase in the grafting yield. Momomer reactivity was in the following order: acrylonitrile > ethyl acrylate? methyl methacrylate. For the first two monomers, the order of reactivity is the reverse of that found for grafting onto cellulose; extremely low grafting yields resulted from grafting of ethyl acrylate rather than acrylonitrile onto starch. This result was attributed to the jelly nature of the polyethyl acrylate grafted starch, preventing diffusion of the monomer into the starch granules. This view was supported by the higher consumption of ceric ions at the start of the reaction, on grafting ethyl acrylate instead of acrylonitrile. As the reaction proceeds, the reverse takes place. Increase of ceric salt concentration, as well as the liquor to starch ratio, led to increased grafting yields.     

Water-Soluble Copolymers. II. Synthesis and Characterization of Model Dextran-g-Acrylamides by Ce(lV)/HNO3-lnduced Initiation

In order to develop polymers useful as mobility control agents in enhanced oil recovery processes, water-soluble acrylamide grafted polysaccharide copolymers have been synthesized in water at 25° C using a ceric ammonium nitrate/nitric acid system. The effects of varying concentrations of ceric ion, monomer, and substrate on conversion, graft length, and molecular structure of the reaction products have been examined. The crude reaction products were purified by fractional precipitation and then were analyzed for nitrogen content using a micro-Kjeldahl method. The chemical structures of the graft copolymers were studied by selective hydrolysis of the carbohydrate backbones. Intrinsic viscosity and grafting length data were used to predict solution behavior of the graft copolymers prepared under controlled conditions. Aqueous size exclusion and viscosity studies showed direct correlations between hydrodynamic volume and length of the polyacrylamide side-chain grafts.     

Optimization of Preparation Process for Allylamine-bacterial Cellulose via Graft Copolymerization by Response Surface Methodology

In order to improve the efficiency of new adsorbent, grafting-allylamine bacterial cellulose（al-BC）, response surface methodology（RSM） was used for the optimization of preparation process. Three factors affecting the yield of grafting reaction are the amount of allylamine, the concentration of ceric ammonium nitrate（CAN） and the concentration of nitric acid. Based on the regression coefficient analysis in the Box-Behnken design, a relationship between the preparation variable and grafting yield was obtained. Square error analysis on main factors, and multi-variable interactions were employed for studying grafting yield. The results show that at the conditions of CAN of 23.00 mmol/L CAN, 0.17 mol/L nitric acid, adding an amount of grafting-allylamine bacterial cellulose of 26.49 mL/L made grafting rate reach maximum of 24.25% at 40℃ after the reaction for 4 h. The experimental results are in good agreement with the calculation values via proposed regression equation, indicating that the equation could be used to nredict and optimizate the preparation of grafting al-BC.     

Graft copolymerization of cellulose initiated by ceric salts: Effect of reaction conditions on the consumption of ceric ion

A soluble monomer [methyl acrylate (MA)] and an insoluble monomer [butyl methacrylate (BMA)] were grafted onto cellulose by three types of ceric salts under both oxygen-free conditions and in the presence of oxygen. For comparison, Ce(IV) consumption during cellulose oxidation was also determined under similar reaction conditions. Slightly more Ce(IV) was consumed during cellulose oxidation in the presence of oxygen. During graft copolymerization of MA under oxygen-free conditions, the consumption of Ce(IV) was much lower than during cellulose oxidation regardless of the type of ceric salt employed. The opposite was observed in the presence of oxygen: much more Ce(IV) was consumed during grafting than during cellulose oxidation. The consumption of Ce(IV) in the graft copolymerization of BMA by ceric sulfate was nearly independent of reaction conditions and it was approximately the same as in cellulose oxidation. In the reaction initiated by ceric ammonium nitrate under oxygen-free conditions, less Ce(IV) was once again used up during grafting than during cellulose oxidation. However, the difference was much smaller than in the case of MA.     

Grafting acrylonitrile and methyl methacrylate on holocellulosic materials

Graft copolymers of acrylonitrile and methyl methacrylate on bleached holocellulose and thiolated holocellulose were obtained by the use of ceric ions in aqueous medium at 29°C. The level and efficiency of grafting on the bleached holocellulose were significantly higher than on the thiolated holocellulse, but the molecular weights and number of grafted copolymer chains on both the unmodified and thiolated holocellulose were similar. The graft level and molecular weight of acrylonitrile graft copolymer were significantly lower than those for methyl methacrylate at comparable ceric ion and monomer concentrations. These results indicate the significance of the influence of the polarity of monomer on the extent of graft copolymer formation and lead to the suggestion that graft copolymerization may not result entirely from radicals generated on the cellulose substrate.     

WATER-SOLUBLE AMPHOLYTIC GRAFTED POLYSACCHARIDES. 1. GRAFTING OF THE ZWITTERIONIC MONOMER 2-(2-METHACRYLO-ETHYLDIMETHYLAMMONIO) ETHANOATE ONTO HYDROXYETHYL CELLULOSE

Novel ampholytic grafted polysaccharides were prepared by grafting the Zwitterionic monomer 2-(2-methacryloethyldimeth-ylammonio) ethanoate onto hydroxyethyl cellulose. Ethylenediamine tetraacetic acid was used in combination with ceric ammonium nitrate as the redox initiator. The effects of various factors such as initiator amount, monomer concentration, reaction temperature and time on the grafting were studied and the optimum reaction conditions to obtain maximum degree of grafting were found. The resulted graft copolymer was characterized by IR and thermal analyses.     

The mechanism of consumption of ceric salt with cellulosic materials

Efforts were made in the present study to elucidate the mechanism of graft copolymerization of cellulose in the presence of a ceric salt as initiator. When cellulose is treated with an aqueous solution of the ceric salt, ceric ion is consumed in a roughly first-order reaction in the oxidation of cellulose and in the adsorption on cellulose, and the ratio of the rate constants of oxidation and adsorption is about 1:3 in the case of sulfite pulp. Ceric ion is adsorbed so strongly on cellulose as not to be readily desorbed by treatment with water, dilute acid, or dilute alkali. The number of moles of adsorbed ceric ion was approximately equal to the number of moles of the total carbonyl groups in the cases of cotton and sulfite pulp, which are low in hemicellulose content, and was several times as large in the cases of kraft pulp and semichemical pulp, which contain about 22% hemicellulose. In these samples, however, it was interesting to note that the amount of the adsorbed ceric ion was roughly equal to the amount consumed in oxidation. Cellulose on which ceric ion is adsorbed reacts with methyl methacrylate to yield graft copolymers; a higher molecular weight of grafts, smaller number of grafts, and lower graft efficiency than in a standard polymerization were observed. Since the stability of the adsorbed ceric ion is high, a contribution of the adsorbed ceric ion to the graft copolymerization appears small, and the oxidation reaction, which proceeds slightly more slowly than adsorption, seems more important to the graft copolymerization.