Radiation-induced graft copolymerization of styrene to cellulose

The radiation-induced graft copolymerization of styrene to cellulose has been studied in vacuo at 30°C and at dose rates from (0.37 to 8.73) × 10^?2 W/kg. Dioxan was used as solvent for monomer and polystyrene homopolymer, and water (2% total volume) was incorporated as swelling agent for cellulose. The concentration of styrene in the bulk medium was varied from 0.432 to 3.46 moles/l., and the rates of both grafting and homopolymerization were shown to be proportional to [monomer] · [intensity]^1/2. The value of 3.3 × 10^?4 l. mole^?1 sec^?1 derived for k_p²/k_t in homopolymerization is similar to that for normal free-radical polymerization of styrene. However, reduced termination during grafting yielded a much higher value (58 l. moles^?1 sec^?1). Degradation of cellulose in the absence of monomer was followed viscometrically, and values of 13.5 and 24.6 were derived for G (scission) in vacuo and in air, respectively.     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. V. Studies on thermal behavior

The thermal behaviors of cellulose acetate, either grafted or ungrafted, were studied. A thermogram of cellulose acetate when grafted with acrylamide is characterized by an endothermic peak at 340°C. If, however, styrene is grafted, the thermogram shows two characteristic exothermic peaks at 330 and 420°C. A thermogram of the mixed graft comprising both acrylamide and styrene, on the other hand, is characterized by only one exothermic peak at 420°C. A consideration of various thermal data indicates that cellulose acetate when grafted is comparatively more stable than when not grafted. Again, styrene is found to be more effective than acrylamide in increasing the stability.     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. VI. Permeability of sodium chloride and sodium sulfate

Acrylamide, styrene, and mixtures of acrylamide and styrene were grafted onto cellulose acetate film. The permeabilities of sodium chloride and sodium sulfate through the ungrafted and grafted cellulose acetate films were studied. Permeability increases with the increase in the extent of grafting of acrylamide; whereas it decreases with the increase in the extent of grafting of styrene onto cellulose acetate. The same trend in permeability was observed when cellulose acetate was grafted with the binary monomer mixture. Permeability is also found to depend on the nature of the solute dissolved in water. The results were discussed in terms of free volume concept of the water-swollen films.     

Ultraviolet-radiation-induced graft copolymerization of styrene and acrylonitrile onto cotton cellulose

Photoinitiated graft copolymerization of the vinyl monomers, styrene and acrylonitrile, onto cotton cellulose was studied using uranyl nitrate and ceric ammonium nitrate as photoinitiators. Uranyl nitrate photoinitiation showed a higher level of grafting for styrene, whereas in the case of acrylonitrile ceric ammonium nitrate was found to be the better photoinitiator. Optimized conditions of grafting, when employed to cotton swollen with sodium hydroxide and zinc chloride, enhanced the graft levels for both monomers. Grafted samples were subjected to thermal analysis, as well as estimation of moisture regain and tenacity. Thermal stability increased, whereas, the moisture regain and tenacity decreased, with the increase in graft add-on in the case of both monomers. Acrylonitrile-grafted cotton showed dyeability with cationic dye that improved with the level of graft add-on. Possible explanations have been given.     

羟乙基纤维素与丙烯酸-2-羟基丙酯的反应规律

以硝酸铈铵/乙二胺四乙酸(CAN/EDTA)为引发剂,研究了羟乙基纤维素(HEC)与丙烯酸-2-羟基丙酯(HPA)的接枝共聚反应,讨论了单体浓度、引发剂浓度、反应温度、反应时间等因素对接枝率的影响,试验结果表明:在引发剂CAN和EDTA为22mmol/L,单体HPA为0.31mol/L,反应温度为40℃,反应时间为4h时,接枝率和接枝效率值最佳,并用红外光谱对接枝共聚物结构进行了鉴定。     

Effect of emulsifiers on emulsion copolymerization of styrene and n-butyl acrylate

Summary The emulsion copolymerization of styrene and n-butyl acrylate was conducted at 70°C using anionic or nonionic emulsifiers, or a mixture of both at different concentrations. The effect of the emulsifiers on the overall conversion was examined. The latex morphology with special attention to average particle diameter and particle diameter distribution was also studied. The latexes were characterized by LASER light scattering (LLS) and transmission electron microscopy (TEM).     

New aspects of graft copolymerization of styrene onto cellulose induced by gamma rays

Graft products of styrene onto cellulose prepared by simultaneous gamma-ray irradiation under various conditions were acid-hydrolysed to recover polystyrene produced within the cellulose matrix. The polystyrene was subjected to gel permeation chromatography to determine the molecular weight (M) and further separated with a thin-layer chromatographic (t.l.c.) technique into two components, i.e. the true grafted side-chain polymer and attendant homopolymer. This t.l.c. experiment allowed an estimation of the true percentage grafting (Y). Influences of changing the reaction conditions upon the values of M and Y were thus investigated, and some newer aspects on vinyl polymerization occurring within the cellulose matrix are presented.     

Statistical experimental strategies approach to emulsion copolymerization of styrene and n-butyl acrylate

A batch emulsion copolymerization for the preparation of styrene-n-butylacrylate (St/BA) copolymer latexes is investigated. A series of n-butylacrylate-styrene copolymer latexes were obtained by emulsion copolymerization in the presence of K₂S₂O₈ (KPS) as initiator and with/without emulsifier (sodium lauryl sulfate). The effect of such preparation conditions as initiator concentration, the St/BA ratio, reaction temperature, agitation rate, and emulsifier concentration on the polymerization rate, particle size of copolymer latex, and molecular weight distribution of the resulting copolymer (∼ 80% conversion), respectively, is systematically studied using fractional factorial design methodology. Fractional factorial analysis indicates that the effects of the St/BA ratio, reaction temperature, emulsifier concentration, as well as the two-factor interaction of temperature and emulsifier concentration, are the key variables influencing the polymerization rate. At ∼ 80% monomer conversion, statistical analysis clearly isolates emulsifier concentration as the dominant factor affecting average particle size of copolymer latex; results also indicate that the effects of the St/BA ratio, reaction temperature, and emulsifier concentration are major effects influencing the polydispersity of polymer molecular-weight distribution. For 7.30 g KPS/100 g monomer and 500 rpm agitation rate, the conditions for minimizing molecular-weight distribution (∼ 80% conversion) occur for a reaction temperature, St/BA ratio, and surfactant concentration of 70°C, ∼ 3.59/1, and ∼ 2.08 g/100 g monomer, respectively, generating a minimum molecular-weight polydispersity of ∼ 3.0. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 551–563, 1998     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. IV. Studies on some physical properties and structural characterization by means of scanning electron microscopy

Binary mixtures of monomers, e.g., styrene and acrylamide in 1:1 methanol:water solution, were grafted onto cellulose acetate film by taking recourse to preirradiation grafting procedure. The surface modification of the films due to grafting was examined by means of scanning electron microscopy. The mechanical properties, e.g., tensile strength elongation at break, and elasticity as well as water vapor permeability of the grafted films, were investigated. In the case of ungrafted films or when acrylamide was grafted to a low extent, the film surfaces were smooth and hence were not modified to any significant extent. But when acrylamide was grafted appreciably, or when styrene was grafted singly or in binary mixture with acrylamide, the surfaces were found to be covered with fibrils. The pattern of the surface modification also changes with the increase of the extent of grafting. The observed properties of the grafted films were explained on the basis of the electron microscopic results.     

Studies on graft copolymerization of acrylate monomers onto casein

Poly(butyl acrylate) has been graft copolymerized onto casein using potassium peroxydisulfate–ascorbic acid as the initiating system. The proof of grafting has been obtained by ninhydrin test and IR studies. The effects of synthetic variables in the graft copolymerization have been discussed in the light of percent grafting, grafting efficiency, and the rates of polymerization.     

Hexavalent-chromium-initiated graft copolymerization of methyl methacrylate onto cellulose

Graft copolymerization of methyl methacrylate (MMA) onto cotton–cellulose has been carried out using hexavalent chromium Cr(VI) as initiator. Aqueous-methanolic solution of perchloric acid has been chosen as the reaction medium. The effect of monomer, initiator, acid, reaction medium, and temperature on the graft percentage has been found out. The reactions have also been carried out in the presence of polymerization, inhibitors, and retarders, such as hydroquinone and transition metal salts like CuSO₄, FeCl₃, etc. The grafted samples, after exhaustive separation of homopolymers and purification, were subjected to various chemical, mechanical, and thermal testings. The results of various analyses have been compared with the reference, and the improvement in the graft has been evaluated. A suitable mechanism for the grafting processes has been suggested, in accordance with the experimental results.     

苯乙烯-异戊二烯-丁二烯橡胶接枝苯乙烯聚合动力学

以自制的4种苯乙烯-异戊二烯-丁二烯橡胶(SIBR)为增韧组分,采用本体聚合工艺,以过氧化苯甲酰为引发剂进行苯乙烯接枝聚合以制备高抗冲聚苯乙烯,考察了用量、相对分子质量及分子链结构不同的SIBR对苯乙烯聚合速率的影响,并比较了用不同橡胶改性聚苯乙烯时的聚合动力学行为。结果表明,SIBR的用量越大聚合速率越小,相对分子质量越大则聚合速率越大;按SIBR分子链序列结构的不同聚合速率还呈现出从大到小依次为线型嵌段SIBR、线型无规SIBR、星形嵌段SIBR及星形无规SIBR的规律。用不同橡胶增韧聚苯乙烯时的聚合速率从大到小依次为SIBR、丁苯橡胶及顺丁橡胶。苯乙烯的表观接枝率随着SIBR用量或其相对分子质量的增大而减小,且远大于使用顺丁橡胶。     

Simulation and optimization of cellulose and styrene graft copolymerization process

Graft polymerization of styrene into cellulose was investigated using Ceric ions redox systems as initiator. A mathematical model with the D-optimal design combined with the least squares method was applied to the system. The variables considered in the model are the reactant variables i.e. monomer and initiator concentrations and the processing variables i.e. reaction time, temperature and agitation rate. The optimal composition and processing conditions were determined using a three dimensional space analysis.     

纤维素醚的乳接枝共聚合

在水溶性聚合物羟丙基甲基纤维素（ＨＰＭＣ０存在下进行丙烯酸酯的乳液支共聚合,研究了引发剂加料方式,用量和ＨＰＭＣ用量对接枝率的影响,结果表明,引发剂质量分数和引发与纤维素的预接触时间对接枝率有显著影响,增大ＨＰＭＣ质量分数导致表观接枝率和真实接枝率明显下降。     

Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F_AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10^?2 to 60.0 × 10^?2 mol L^?1, whereas the composition of the grafted chains (F_AAm) was found to be dependent on feed composition (f_AAm) and reaction temperature. The effects of ceric(IV ) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10^?3 mol L^?1 concentration of CAN at a feed molarity of 30.0 × 10^?2 mol L^?1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10^?3 mol L^?1) at a constant concentration of nitric acid (5.0 × 10^?2 mol L^?1). The composition of the grafted chains (F_AAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r₁) and ethyl acrylate (r₂) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r₁ = 0.54 and r₂ = 1.10, respectively, and hence the sequence lengths of acrylamide (m?M₁) and ethyl acrylate (m?M₂) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r₁ × r₂) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔE_a) of graft copolymerzation was found to be 5.57 kJ mol^?1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry     

Photoinitiated graft copolymerization of hydroxyethyl methacrylate onto cotton cellulose

The photoinitiated graft copolymerization of hydroxyethyl methacrylate (HEMA) onto cotton cellulose was studied using uranyl nitrate (UN) and ceric ammonium nitrate (CAN) photoinitiators. Optimization of various parameters of the graft-copolymerization reaction viz., time, temperature, initiator, and monomer concentration, was carried out. The optimized conditions of grafting were employed to cotton samples swollen in zinc chloride as well as sodium hydroxide. Graft add-on was found to be dependent on the nature of substrate and the concentrations of monomer and photoinitiator. UN was found to be the better photoinitiator, giving higher grafting with HEMA. The grafted samples showed initially decrease and then marginal increase in the moisture regain with increase in graft add-on. The dye uptake of both direct and reactive dyes decreased with increase in graft add-on.     

Gamma radiation-induced graft copolymerization of divinylbenzene onto cellulose fabric

The extent of DVB grafting onto cellulose fabric increases with total gamma radiation dose up to 10–15 kGy while it decreases with the radiation dose rate. A quantitative analysis of DVB grafting has been attempted by means of IR spectroscopy using the baseline method. Characteristic bands were selected in the spectra of copolymers, namely, the cellulose band at 1160 cm^?1 and DVB band at 798 cm^?1. The former band decreased and the latter increased with the degree of copolymerization, and the values were in accordance with the calibration straight line. An attempt to graft DVB onto cotton fabric previously grafted with styrene showed greater extent of copolymerization than with pure fabric.     

Corona-induced graft polymerization of ethyl acrylate onto cellulose film

Ethyl acrylate was readily grafted from an aqueous solution onto cellophane film previously treated in a corona discharge at atmospheric pressure. The effect was found when the corona treatment was carried out not only in air but also in pure nitrogen. The observed grafting was not promoted but depressed by the presence of ferrous ion, which indicated that peroxide radicals were not initiating the graft. A high grafting efficiency was obtained, and the grafted surface was covered with a smooth uniform layer of polymer.     

Homogeneous graft copolymerization of styrene onto cellulose in a sulfur dioxide–diethylamine–dimethyl sulfoxide cellulose solvent

Graft copolymerization of styrene onto cellulose was studied in a homogeneous system (SO₂–DEA–DMSO medium) by γ-ray mutual irradiation technique. At the same time, homopolymerization of styrene was also examined separately in DMSO, SO₂–DMSO, DEA–DMSO, and SO₂–DEA–DMSO media by the same technique. Polymerization of styrene hardly occurs on concentrations above 10 mole SO₂–DEA complex per mole glucose unit. Maximum percent grafting was obtained in concentrations of 4 mole, after which it decreased rapidly. Total conversion and percent grafting increased with the irradiation time. The value (=0.55) of the slope of the total conversion rate plotted against the dose was only a little higher than the 1/2 which was expected from normal kinetics. No retardation in homopolymerization of styrene in DMSO, SO₂–DMSO, and DEA–DMSO was evident, while the retardation of homopolymerization in the SO₂–DEA–DMSO medium was measurable. Sulfur atoms were detected in the polymers obtained in both of SO₂–DMSO and SO₂–DEA–DMSO solutions. All of the molecular weights of polymers obtained in the present experiment were very low (3.9 × 10³?1.75 × 10⁴).     

Effect of wavelength region on photo-induced graft copolymerization onto cellulose

The effect of wavelength region of ultraviolet light was examined on the unsensitized photo-induced graft copolymerization of methyl methacrylate onto cellulose. When the quartz tube system was compared to the glass tube system, there was no induction period of copolymerization, the rate of reaction was a little larger, the homopolymerization of methyl methacrylate was increased causing interference with graft copolymerization, and the depolymerization of grafts and the scission reaction of cellulose chains occurred easily. The number of grafts was hardly improved by varying the reaction conditions, and the copolymers obtained generally exhibited low per cent grafting and contained grafts with lower degree of polymerization.