淀粉-苯乙烯接枝共聚的分析与评定

采用悬浮聚合的方法,对淀粉进行接枝共聚改性,制得的接枝共聚物具有淀粉和单体的双重优良性能.     

Radiation-Induced Graft Copolymerization Of Some Vinyl Monomers Onto Waste Rubber Powder

Rubber powder was subjected to graft copolymerization with different vinyl monomers such as acrylamide (AAm), acrylic acid (AAc), and acrylonitrile (AN). Graft copolymerization of these monomers onto rubber powder was carried out using gamma radiation. The effects of different parameters such as monomer concentration, radiation dose, inhibitor concentration, and type of reaction solvent on the graft yield were studied. It was found that the maximum graft yield obtained is 90%, 24%, and 42% for AAc, AAm, and AN, respectively. The grafted rubber powder obtained was tested as ion exchanger for copper and lead, and its capacity for ion recovery was found to be dependent on the type of monomer and graft yield. For instance, polyacrylamide and sodium salt of polyacrylic acid grafted onto rubber powder are more efficient as ion exchangers for both copper and lead ions than polyacrylonitrile. Amidoxime derivative of polyaerylonitrile is more efficient as ion exchanger than the parent polyaerylonitrile.     

Studies on the grafting of acryloylated potato starch with styrene

An investigation of graft polymerization to determine the potential of a starch‐bonded acryloyl group as a suitable coupling agent with vinyl monomers was carried out. In this case, potassium persulfate was used as a free‐radical initiator using water as the reaction solvent for further graft polymerization. This work revealed the ability of water as a reaction medium; perhydroxyl and hydroxyl radicals were easily formed from persulfate to produce free radicals to activate the styrene monomer towards grafting with acryloylated potato starch. The graft copolymers were characterized by FT‐IR spectroscopy and further confirmed using saponification. The analysis results showed the grafted potato starch with the styryl chain afforded protection to the ester bond, which resisted the alkaline hydrolysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 452–459, 2005     

Preparation of soapless latexes by sonification of starch-based poly(isoprene–co–acrylonitrile) graft reaction mixtures

Graft copolymerization of isoprene (IP) and acrylonitrile (AN) onto gelatinized starch (S) and cationic starch having quaternary amine functionality through cerium(IV) initiation gave grafted side chains of poly(IP–co–AN). Grafts of various compositions are obtained by controlling the amounts and ratios of monomers added to starch. IP alone does not homograft onto gelatinized starch at 25° or 50°C by cerium(IV) initiation and requires the presence of an “initiator–monomer” such as AN to obtain copolymer side chains. Although cografting of IP and AN onto starch depends on AN to initiate radical chains, the ratio employed of the two monomers is critical for graft polymerization to occur. For example, at a molar ratio of IP to AN of 1 or greater, little polymer was produced; at molar ratios in the range of 0.4 to 0.67, considerable amounts of polymer were produced; and at a molar ratio of 0.13 or less, polymerization of AN was greatly retarded. Concentration of HNO₃ in the cerium(IV) reagent and reaction temperature also influence the grafting reaction. Lower HNO₃ concentrations favor grafting at 50°C, while higher acid concentrations favor grafting at 25°C. Starch graft reaction mixtures were sonified at 20 kHz to form latexes that air dry to clear pliable films. Poly(IP–co–AN) obtained by acid hydrolysis of the starch portion of the grafts failed to dissolve in either dimethylformamide or benzene, thus indicating presence of crosslinks. S–g–poly(IP–co–AN), having about one third starch and grafted side chains averaging about 2 parts polymerized IP per part of polymerized AN, was masticated on steel rolls at 100°C to a tough pliable film which was subsequently vulcanized to a rubber.     

原位法合成聚乳酸接枝淀粉共聚物的研究与应用

首次采用阴离子开环聚合的方法,在淀粉上一步法原位接枝聚合得到聚乳酸和淀粉的接枝共聚物。采用强极性溶剂二甲基亚砜（DMSO）将淀粉溶解,然后以叔丁醇钾为引发剂,引发L-丙交酯接枝聚合,提纯后的接枝产物通过红外光谱、核磁共振、XRD等测试方法进行表征。结果表明,在聚合温度为75 ℃,时间为4 h,原料摩尔比为淀粉/丙交酯/叔丁醇钾为10/75/3条件下,接枝产物的接枝率可达83 %。将该接枝产物添加到淀粉和聚乳酸共混体系中,与未添加接枝物的共混体系相比,添加接枝物的共混体系中淀粉的分布更加均匀,性能更加均一。     

Grafting vinyl monomers onto silk fibers: Graft copolymerization of methyl methacrylate onto silk using acetylacetonate Mn(III) complex

The graft copolymerization of methyl methacrylate onto Mulberry silk fibers was studied in aqueous solution using Mn(acac)₃ as initiator. Perchloric acid was found to catalyze the reaction. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of Mn(acac)₃ up to 0.01 mol/L, decreasing thereafter. Increase of MMA concentration up to 0.56 mol/L increases graft yield, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases up to 7.5 × 10^?3 mol/L of HClO₄ concentration, and thereafter it decreases. A suitable reaction scheme has been proposed and a rate equation has been derived. The energy of activation has been calculated from the Arrhenius plot. The chain transfer constants for various chain transfer solvents have been evaluated from the average molecular weight (M?) of grafted poly(methyl methacrylate).     

RAFT synthesis of cellulose‐g‐polymethylmethacrylate copolymer in an ionic liquid

We demonstrate for the first time the feasibility in conducting the graft copolymerization of methylmethacrylate (MMA) with cellulose by the means of the reversible addition‐fragmentation chain transfer (RAFT) polymerization in an ionic liquid [1‐N‐butyl‐3‐methylimidazolium chloride] (BMIMCl). Cellulose was first converted to a macromolecular chain transfer agent to which MMA was grafted by RAFT in BMIMCl. The success of the occurrence of different reactions was validated by elemental analyses, Fourier transform infrared and nuclear magnetic resonance spectroscopies. The results demonstrate that the MMA polymer chains were grafted onto the cellulose while the use of the ionic liquid as a reaction medium enhanced the polymerization rate to a moderate extent. Gel permeation chromatography analysis of poly(MMA) chains cleaved from the cellulose by acidic hydrolysis indicated low polydispersity indices (ca. 1.3) that were consistent with the “living” nature of the RAFT. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of polyacrylonitrile pregelled starch graft copolymers using ferrous sulfate‐hydrogen peroxide redox initiation system as surface sizing agent

A graft copolymer was synthesized by graft copolymerization of starch with styrene (St) and butyl acrylate (BA), using ferrous sulfate‐hydrogen peroxide redox initiation system. The starch was pregelled in the presence of acrylonitrile (AN) in aqueous alkali at high temperature before graft polymerization. Major factors affecting the polymerization reaction were investigated. It was found that a graft copolymer with higher percentage conversion (PC), graft efficiency (GE) and graft percentage (GP) was obtained by controlling the initiator concentration, concentration, and ratio of monomers and polymerization temperature. The optimum conditions were as follows: H₂O₂ concentration, 12%; monomer concentration, 120%; St/BA ratio, 1 : 1; polymerization temperature, 65°C. Fourier transform infrared spectroscopy and NMR analyses were used to gain information on the structure of the products. It was demonstrated that St, BA, and AN had been successfully grafted onto starch and ? CN had been saponified into ? CONH₂ and ? COO^? to a certain degree when pregelling. Scanning electron microscope micrographs showed the coarse structure and broad network. The graft polymerization took place on the surface of starch granule and led to amorphization of the starch structure. Graft polymer had better thermal stability and was endowed with pseudo‐plasticity. It was observed that the starch graft copolymer offers good properties such as water resistance as surface‐sizing agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,characterization, and properties in aqueous solution of poly(starch-g-[1-amido-ethylene)-co-(sodium 1-(2-methylprop-2N-yl-1-sulfonate)amidoethylene)])

Graft terpolymers of starch, 2-propenamide, and sodium 2-methyl-3-imino-4-oxohex-5-ene-1-sulfonate can be made by cerium-IV-initiated, free-radical polymerization of an aqueous monomer mixture on starch. Synthesis is conducted on aqueous, gelled, lintnerized potato starch at 30°C under a nitrogen atmosphere. Yields range from 50 to 100 wt % and products contain 9–52 wt % starch, 1–51 wt % 1-acidoethylene, and 18–65 wt % sodium 1-(2-methylprop-2N-yl-1-sulfonate)amidoethylene. Repeat unit ratios in the reaction product approximate monomer ratios in the reaction mixture. Fraction of starch grafted in a reaction decreases as the mole fraction of sulfonated monomer in the reaction mixture increases. No proof has been found for grafting of synthetic side chains to starch in monomer mixtures containing only sulfonated monomer. Starch graft copolymers with side chains composed of 1-amidoethylene units and a sulfonated 1-amidoethylene unit derivative, 1-(sodium[2-methylprop-2N-yl-1-sulfonate])amidoethylene, are water-soluble, thickening agents. The rheology of solutions of these copolymers is a function of the ratio of nonsulfonated to sulfonated repeat units in the synthetic chains of the molecule. Aqueous solutions of these products are shear thinning and have power law exponents which decrease 1) with increasing product concentration or 2) as the nonsulfonated to sulfonated repeat unit ratio moves toward 3/1. Limiting viscosity number of product in water decreases with increasing shear rate of measurement or with increasing salt concentration of the solvent. Formulas are derived from the theories of Kirkwood and Flory which show that for copolymers with constant molecular weight, expansion coefficient, and limiting viscosity number increase as the fraction of sulfonate-containing repeat units in the chain increase. This theoretical requirement and the limiting viscosity data for groups of samples prepared under identical synthesis conditions are used to show that molecular weight of the graft copolymer decreases as the fraction of sulfonated repeat units in the copolymer increases. Screen factor measurements show product solutions to be viscoelastic.     

Role and relevance of polarity and hindrance of vinyl monomers in graft copolymerization onto potato starch

The graft copolymerization of the vinyl monomers that were prepared by reactions of methyl acrylate and 4‐aminoazobenzene derivatives, such as 4‐aminoazobenzene, 4‐amino‐4′‐methyl azobenzene, 4‐amino‐4′‐nitro azobenzene, and 4‐amino‐3′,5′‐dinitro azobenzene, onto potato starch were carried out by the initiation of potassium persulfate. The evidence of grafted copolymers was investigated by using FTIR spectroscopy and acid hydrolysis technique. The relationship between grafting efficiency and monomer structure as well as polarity was studied. The experimental results showed that the graft copolymerization is independent of the polarity of the vinyl monomers and that the structures of monomers exhibit a marked influence on the graft copolymerization, namely, the larger the substitute is, the lower the grafting efficiency will be. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 896–899, 2002     

Flocculation characteristics of grafted and ungrafted starch,amylose, and amylopectin

Graft copolymers of starch, amylose, and amylopectin with polyacrylamide have been synthesized using a ceric-ion-initiated solution polymerization technique. In the case of amylopectin-g-polyacrylamide (Ap-g-PAM), four graft copolymers have been synthesized with variation in the number and length of grafted polyacrylamide chains. The flocculation behavior has been studied in a 0.25% kaolin suspension. It has been found that among the three graft copolymers of the starch family, Ap-g-PAM is the best flocculating agent compared to starch-g-polyacrylamide (St-g-PAM) and amylose-g-polyacrylamide (Am-g-PAM). Among the series of Ap-g-PAM, the one with fewer but longer polyacrylamide chains has been found to be the most effective flocculant. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1721–1729, 1997     

The graft copolymerization of styrene and lignin. I. Hydrochloric acid lignin

The effects of methylation of phenolic hydroxyl groups and addition of solvent on the radiation and chemically initiated graft copolymerization of styrene and hydrochloric acid softwood lignin were studied. In the radiation-induced experiments, methylation is found to increase the maximum per cent graft obtainable two or threefold, while methanol addition may increase the value tenfold. Chemically initiated experiments indicate that the main effect of methanol addition is to increase the accessibility of the lignin particles. A mechanism of graft copolymerization of polystyrene and lignin is proposed which requires the reaction to proceed primarily by chain transfer of a polystyrene chain radical to lignin and the subsequent reinitiation of polymerization (i.e., initiation of graft copolymerization) by the lignin radical. The grafting of lignin modifications is then dependent on the type of radical formation (i.e., phenoxy or benzylic) most favored, as well as the usual accessibility considerations.     

Graft copolymers of starch with mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate

Mixtures of acrylamide and the nitric acid salt of dimethylaminoethyl methacrylate (DMAEMA·HNO₃) have been graft polymerized onto unmodified wheat starch with ferrous ammonium sulfate–hydrogen peroxide initiation. Graft polymerizations were carried out with both unswollen starch granules and granules that had been swollen by heating in water to 60°C. Ungrafted synthetic polymers were removed from graft copolymers by cold-water extraction and were characterized by their M?_n and DMAEMA·HNO₃ content. Graft copolymers were characterized with respect to per cent add-on, M?_n and DMAEMA·HNO₃ content of grafted polymer, and grafting frequency. Ungrafted synthetic polymers contained a mole percentage of DMAEMA·HNO₃ equal to or greater than that present in the initial monomer mixtures; whereas in most grafted polymers the mole-% DMAEMA·HNO₃ in the grafted branches was less than that in the starting monomers. At all monomer ratios examined, polymer grafted to swollen starch granules contained a higher percentage of DMAEMA·HNO₃ then polymer grafted to unswollen starch. The influence of starch granule swelling on the molecular weight and frequency of grafted branches was correlated with the composition of the initial monomer mixture. It was determined that the effect of granule swelling on graft copolymer structure would be minimal when 25–30 mole-% DMAEMA·HNO₃ was used. In an acetonitrile–water solvent system, reactions with 20 and 50 mole-% DMAEMA·HNO₃ produced graft copolymers with less DMAEMA·HNO₃ in grafted branches than corresponding graft polymerizations run in water. The flocculation of 3% aqueous suspensions of diatomaceous silica was examined with selected starch graft copolymers.     

聚羧酸接枝共聚物的合成工艺研究

通过无皂乳液聚合反应和接枝反应合成一类主链带羧基、支链带聚氧乙烯基醚的聚羧酸减水剂。考察了聚合反应温度、聚合反应时间、引发剂含量、马来酸酐(MAn)与甲基丙烯酸(MA)物质的量比等对共聚反应的影响,比较了共聚物在有机溶剂和水溶液中反应的产率,还研究了温度和时间对接枝率的影响,并利用红外光谱表征其结构。结果表明,共聚反应在n(MAn):n(MA)=1:1,w(引发剂)=3%,反应0.5h条件下,产率可达80%以上。接枝反应的最佳温度和时间分别为120℃和6h,接枝率达30%。     

淀粉丙烯酰胺表面控制反应机理及接枝产物结构表征

以木薯淀粉和丙烯酰胺为主要原料,采用反相乳液聚合方法合成淀粉丙烯酰胺接枝共聚物,并通过红外光谱、电镜扫描、X射线衍射、热分析等手段对接枝共聚产物进行结构分析和聚合机理探讨。实验结果显示,淀粉与丙烯酰胺的反应主要发生在淀粉团粒表面,符合表面控制反应机理;接枝共聚物中含有淀粉和丙烯酰胺成分;共聚反应改变了原淀粉的聚集形态,接枝产物基本上为无定形的聚集态结构;但对淀粉的热稳定性影响不显著。     

Grafting. III. Copolymerization of methyl methacrylate and methacrylic acid

The method of graft copolymerization of methyl methacrylate on halogen-containing polymer has been utilized for grafting of methyl methacrylate–methacrylic acid monomer pair onto poly(vinyl chloride) and chlorinated rubber. Substantial grafting could be obtained by using the method reported earlier. However, the compositions of the grafted chains are found to deviate appreciably from the compositions calculated from r₁ and r₂ values reported in literature. The reactivity ratios for this pair of monomers have been therefore evaluated using azobisisobutyronitrile and n-butane thiol–dimethyl sulfoxide as initiators. The anomalies of the grafted chain compositions have been discussed and an explanation presented on preferential solvation.     

Radiation-initiated graft copolymerization of binary monomer mixtures containing acrylonitrile with cotton cellulose

By the use of the cobalt 60 postirradiation grafting technique, purified cotton cellulose fibers were graft-copolymerized with binary mixtures of acrylonitrile and other monomers, including styrene, 1,3-butylene dimethacrylate, vinylpyrrolidone, vinylidene chloride, and methyl, butyl, lauryl, glycidyl, and allyl methacrylates. The irradiated cotton fibers were immersed in solutions of the monomers at 25°C to initiate graft copolymerization. Solvents were water, methanol, dimethyl sulfoxide, and methyl ethyl ketone, alone or in several combinations. The extent of graft copolymerization and the composition of the grafted copolymer depended on the composition of the binary mixtures of monomers and on the solvent or mixtures of solvents used. For example, addition of styrene, 1,3-butylene dimethacrylate, or vinylpyrrolidone to acrylonitrile increased the extent of graft copolymerization to a maximum value; addition of vinylidene chloride or allyl methacrylate to acrylonitrile did not greatly affect the extent of graft copolymerization; and addition of methyl or glycidyl methacrylate to acrylonitrile increased the extent of graft copolymerization without passing through a maximum value. The proportion of acrylonitrile in the grafted copolymer was generally less than that in the binary mixtures. As the reaction time was increased, the extent of graft copolymerization increased to a maximum value; however, the composition of the grafted copolymer did not change significantly. Generally, the addition of water to the solutions increased the extent of graft copolymerization. The mechanisms of these graft copolymerization reactions are discussed.     

Cationic graft polymerization of polymers from carbon fiber initiated by acylium perchlorate groups introduced onto the surface

The cationic graft polymerization of several monomers initiated by acylium perchlorate groups introduced onto the carbon fiber surface was investigated to modify the surface. The introduction of acylium perchlorate groups was successfully achieved by the reaction of silver perchlorate with acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride. It was found that the cationic polymerization of styrene is initiated by acylium perchlorate groups on the carbon fiber. In the polymerization, polystyrene was grafted onto the carbon fiber surface through the propagation of polystyrene from the surface. Ungrafted polymer was also formed by the chain transfer reaction of growing polymer cation to the monomer. The acylium perchlorate groups have the ability to initiate cationic ring-opening polymerization of tetrahydrofuran (THF) and ε-caprolactone (CL), polyTHF and polyCL being grafted onto the carbon fiber surface, respectively. Polyacetals, such as poly(1,3-dioxolane) and polyoxymethylene, were able to graft onto the carbon fiber by cationic ring-opening polymerization of the corresponding monomers.     

Graft polymerization of acrylic acid onto polyphenylene sulfide nonwoven initiated by low temperature plasma

Graft copolymerization of acrylic acid (AA) onto polyphenylene sulfide (PPS) nonwoven initiated by low temperature plasma was studied. The effects of various conditions on graft reaction and the grafting rate were investigated. SEM images showed that PPS nonwoven was grafted, and the graft copolymerization only occurred on the surface of PPS. It may be due to the chain transference going with the graft copolymerization. It was found that with the increasing of plasma power, treatment time, space between electrodes, monomer concentration, and temperature of graft polymerization, the grafting rate increased at first, went to the top, and then decreased. The PPS nonwoven surface graft reaction could be optimized by the following processing conditions: 120 s of plasma treatment time, 50 W of plasma power, 1.5 cm of space between electrodes, 30% (w/w) of monomer concentration, and 50°C of temperature of graft polymerization. Measurement of XPS showed that the peak of C1s of graft polyacrylic acid was existed, and the peak area increased with the increase of the grafting rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5884–5889, 2006     

Influence of starch granule swelling on graft copolymer composition. A comparison of monomers

Seven monomers, which varied widely in water solubility and ionic charge, were graft polymerized onto both unswollen starch and starch that had been swollen by heating in water to 60°C. Polymerizations were initiated with ferrous ammonium sulfate hexahydrate–hydrogen peroxide and, where applicable, with ceric ammonium nitrate. Graft copolymers were freed of ungrafted homopolymer by solvent extraction and were characterized by weight percentage of synthetic polymer incorporated in the graft copolymer, molecular weight of grafted branches, and grafting frequency. The influence of starch granule swelling on graft copolymer structure varied with the monomer used and could not be predicted on the basis of water solubility of monomer or its resulting polymer. With acrylonitrile and acrylamide, swollen starch gave higher molecular weight and less frequent grafts than unswollen starch. However, methyl methacrylate, N,N-dimethylaminoethyl methacrylate · HNO₃, N-t-butylaminoethyl methacrylate. HNO₃, and 2-hydroxy-3-methacryloyloxypropyltrimethylammonium chloride produced less frequent graft of higher molecular weight when starch was unswollen. With acrylic acid, graft molecular weight was independent of starch granule swelling, although grafting was less frequent when swollen starch was used.