淀粉接枝共聚高吸水性树脂的研究进展

分别以化学引发法和辐射引发法阐述了淀粉接枝高吸水树脂的研究进展和生产情况。介绍了化学引发接枝聚合淀粉接枝丙烯腈类树脂、淀粉接枝丙烯酸类树脂、淀粉接枝多元单体类树脂、复合型淀粉接枝脂类树脂的研究现状,对化学引发的主要影响因素进行了评述。讨论了辐射引发淀粉接枝高吸水树脂中所应用的微波辐射引发、紫外光辐射引发和γ射线辐射引发的技术优势和应用现状。指出今后淀粉类高吸水性树脂的研究应该向多元接枝共聚、制备复合型树脂和抗盐性树脂、微波固相合成、简单工艺、高效引发剂和加强理论基础研究方向发展。     

Syntheses and characterization of starch-poly(methacrylic acid) graft copolymers

Methacrylic acid (MA) was graft polymerized onto starch using Ce⁴⁺ initiator in aqueous medium. The dependence of grafting on the reaction variables, such as monomer and initiator concentration and time and temperature, was studied in detail. Acid hydrolysis and infrared (IR) spectroscopy were used for the confirmation of graft copolymer formation. Further, a representative graft copolymer was characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The solubility/swellability and the gelatinization characteristics of the copolymers are also reported. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1399–1403, 1997     

Synthesis of graft copolymers from natural rubber using cumene hydroperoxide redox initiator

The graft copolymerization of 50/50 (w/w) styrene/methyl methacrylate mixtures onto natural rubber seed latex were carried out by using cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe²⁺ as a redox initiator. The effects of the process factors such as the amount of initiator, emulsifier, and chain‐transfer agent; monomer‐to‐rubber ratio; and temperature on the grafting efficiency (GE) and grafting level (GL) are reported. The mechanism of graft copolymerization was investigated. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (¹H‐NMR) analysis. Transmission electron microscopy (TEM) was used to study the morphology of the graft copolymers. It appears that the formation of graft copolymers occurs on the surface of the latex particles through a chain‐transfer process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2993–3001, 2002; DOI 10.1002/app.2328     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003     

Synthesis and characterisation of PP-g-butyl acrylate copolymers

Butyl acrylate was grafted onto isotactic polypropylene using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time and temperature on rates of polymerization, percentage grafting and grafting efficiency were studied. The extent of grafting achieved was 2.85%. The graft copolymers were characterized by IR, thermal, viscometric and contact-angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymers.     

Synthesis and characterization of dual responsive graft copolymers composed of casein and poly(N-isopropylacrylamide)

A series of novel temperature- and pH- responsive water-soluble graft copolymers, casein-g-poly(N-isopropylacrylamide)(PNIPAAm), were prepared via a direct graft copolymerization of N-Isopropylacrylamide (NIPAAm) from casein. The polymerization was induced by tert-butyl hydroperoxide (TBHP) in water at general condition. Chemical structures of the graft copolymers were characterized by Fourier transform infrared spectra (FTIR), Thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect elements on graft copolymerization, such as concentration of initiator, reaction time, reaction temperature and ratio of NIPAAm to casein were investigated in terms of NIPAAm conversion, grafting percentage (GP) and grafting efficiency (GE), respectively. The graft copolymers are stimuli-sensitive with respect to both temperature and pH in aqueous solutions. It could self-assembly into core-shell particles in aqueous solution with collapsed PNIPAAm as core as well as inverse core-hair particles with expanded casein as core on changing temperature or pH, as indicated by transmission electron microscopy (TEM).     

黄原胶与丙烯酰胺接枝共聚反应的研究

以过硫酸铵为引发剂,在氮气保护下,研究了黄原胶与丙烯酰胺的接枝共聚反应。考察了单体浓度、引发剂浓度、反应温度和反应时间等因素对接枝率及接枝效率的影响,探讨了过硫酸铵引发黄原胶接枝丙烯酰胺共聚反应的基本规律。采用红外光谱、X射线粉末衍射对接枝共聚物的结构进行研究,用热重分析法表征了产物的热性能,并初步探讨了接枝机理。结果表明,过硫酸铵能有效地引发黄原胶与丙烯酰胺的接枝共聚反应,并且接枝率和接枝效率随单体浓度、引发剂浓度、反应温度的变化出现极大值,随反应时间的延长不断上升,直至基本不变。     

Graft copolymers from thiolated starch and vinyl monomers

Thiol starches of degree of substitution (D.S.) 0.005–0.162 were prepared by displacing starch tosyloxy groups with xanthate and treating the resulting xanthate esters with either sodium hydroxide or sodium borohydride. Acrylonitrile, styrene, acrylamide, acrylic acid, and dimethylaminoethyl methacrylate were grafted onto the thiol starches with hydrogen peroxide as initiator. The peroxide caused both grafting of monomer and coupling of thiol groups to disulfide. Treating graft copolymers with sodium borohydride regenerated thiol groups from disulfide groups so that the grafting sequence could be repeated. By regenerating the thiol groups and repeating the grafting steps, high add-on and high-frequency starch graft copolymers were prepared. During four grafting sequences, acrylonitrile reacted with D.S. 0.162 thiol starch to give graft copolymers that contained increasing amounts of polyacrylonitrile (46.0–66.5%). Grafting frequency increased from 183 to 71 anhydroglucose units (AGU)/graft, while molecular weights of the grafted chains ranged between 20,000 and 25,200. The final product was hydrolyzed with potassium hydroxide solution to a copolymer, which absorbed up to 400 ml water per gram. Styrene was grafted onto thiol starch to give products containing 34.4–69.5% polystyrene with 986–3520 AGU/graft and having molecular weights of grafted chains between 276,000 and 364,000. Graft copolymers containing 48.9% polyacrylamide, 21.2% poly(acrylic acid), and 77.7% poly(2-methacryloyloxyethyldimethylammonium acetate) were obtained under similar conditions.     

Improved synthesis of poly(MAA)–starch graft copolymers

Graft copolymerization of methacrylic acid (MAA) onto starch using a potassium persulfate/sodium thiosulfate redox initiation system was investigated. Emphasis was placed on the promotion of graft formation while minimizing homopolymerization. This could be achieved through a thorough investigation into the major factors affecting the polymerization reaction such as the state of the starch, redox ratio of the initiator, monomer and initiator concentrations, time and temperature of polymerization, and material-to-liquor ratio. The results obtained imply that the magnitude of the polymer yield including total conversion, graft yield, and homopolymer are determined by these factors. The yield is favored under the influence of higher temperature, longer time, short liquor, and increased monomer and initiator concentrations. A poly-(MAA)–starch graft copolymer is the main product of the polymerization reactions only when starch was preswelled (through cooking prior to grafting). Moreover, this grafted product could be precipitated by more dilution with water and easily separated by filtration. Hence, the results of the current work formed the basis of a novel method for the synthesis of poly(MAA)–starch graft copolymers. The mechanisms involved in the synthesis are reported. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1709–1715, 1998     

微波辐射下淀粉-丙烯酰胺接枝共聚物的合成

以硝酸铈铵作为引发剂、丙烯酰胺为单体,用微波辐射法合成了淀粉接枝丙烯酰胺共聚物。探讨了反应时间、引发剂浓度、单体和淀粉质量比和反应温度等因素对接枝反应的影响。正交实验确定的最优工艺条件为:反应时间20 m in,引发剂浓度4 mmol/L,丙烯酰胺和淀粉质量比2.5∶1,反应温度55℃,最高接枝率和接枝效率分别达到211.6%和74.3%。     

超声-微波共辐射法合成纤维素-MMA接枝共聚物

引言纤维素作为一种天然的可再生高分子材料,存在于丰富的绿色植物中,是自然界取之不尽用之不竭的清洁资源。因此,在煤、石油、天然气的储量日益减少的今天,纤维素可作为一种可持续发展的绿色资源来研究和开发。而且天然植物纤维资源丰富、价格低廉,并且具有较好的生物可降解性,在     

ESR studies of the photodegradation of cellulose graft copolymers

Ultraviolet light induced free radicals in cellulose and cellulose graft copolymers were studied by means of ESR spectroscopy. At least six kinds of free radicals were formed in cellulose when the polymer was irradiated with ultraviolet light. Polystyrene and poly(methyl methacrylate) are more resistant to ultraviolet light than cellulose; however, the cellulose graft copolymers of polystyrene and poly(methyl methacrylate) were degraded by ultraviolet light. ESR studies revealed that photoinduced free radicals in cellulose graft copolymers were formed at the grafting branches of the copolymers rather than the cellulose backbone. The mechanisms of light stabilization and energy transfer reactions of cellulose and cellulose graft copolymers are discussed.     

Turbulent drag effectiveness and shear stability of xanthan-gum-based graft copolymers

A number of graft copolymers of xanthan gum and polyacrylamide have been synthesized by grafting acrylamide onto xanthan gum using the ceric-ion-initiated solution polymerization technique. The effects of various synthesis parameters such as amount of catalyst, reaction time, and ratio of xanthan and acrylamide on drag reduction effectiveness of the graft copolymers have been studied. The scaling up of grafting reaction has been accomplished in 40-L reactor. The drag reduction effectiveness of the graft copolymers is investigated over a wide range of concentrations and Reynolds numbers. It is shown that the maximum drag reduction obtainable in xanthan gum solutions above 300 ppm can be obtained in solutions of graft copolymers at concentrations of 100–150 ppm. The grafting also improves the shear stability at higher Reynolds numbers. The shear stability of the graft copolymers at constant wall stress has been found to be superior to polyacrylamide and the mixtures of polyacrylamide and xanthan gum. In general, the shear stability of graft copolymers and polyacrylamide is shown to increase with concentration. The drag reduction characteristics and shear stability have been discussed in terms of structural features of the graft copolymers. The drag reduction characteristics of the graft copolymers are found to be similar to those of flexible polymers.     

Development and assessment of the advanced graft copolymers obtained from Hibiscus sabdariffa biomass

In this article, the morphological transformation in Hibiscus sabdariffa stem fiber through graft copolymerization with effective ethyl acrylate (EA) and its binary vinyl monomeric mixtures using ceric ammonium nitrate—nitric acid initiator system has been reported. Different reaction parameters such as temperature, time, initiator concentration, monomer concentration, and pH were optimized to obtain the maximum graft yield (117.3%). The optimized reaction parameters were then used to screen the additive effect of EA with n‐butyl acrylate (BA), acrylic acid (AA), and 4‐vinyl pyridine (4‐VP) in binary vinyl monomer mixtures on percentage grafting, properties, and the behavior of the fiber. The graft copolymers were characterized by FTIR, SEM, XRD, TGA, and DTA techniques and evaluated for physico‐chemical changes. With increase in the P_g a significant physico‐chemico‐thermal resistance, miscibility in organic solvents, hydrophobicity were found to increase, whereas crystallinity, crystallinity index, dye‐uptake, and hydrophylicity decreased, however, the cellulose form I remained unchanged. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of poly(lactic acid) based graft copolymers

This review summarizes recent developments in the preparation and characterization of grafting of poly(lactic acid) or polylactide (PLA). PLA is the most expansively researched and utilized biodegradable, biocompatible, compostable, recyclable and renewable thermoplastic polyester. The graft copolymers of PLA have been synthesized and characterized by different spectroscopic techniques, including FTIR spectra and NMR data. The graft copolymers of PLA have been analyzed critically by taking different monomers/polymers; such as chitosan, cellulose, starch, polyethylene glycol, vinyl based polymers, lignin, dextran, methyl methacrylate, maleic anhydride and graphene oxide. In the first part of this review, the grafting of PLA and applications of grafted PLA has been discussed briefly. The second part, the major objective of this paper, focuses on the synthesis and characterization of different PLA based graft copolymers. For few cases, where useful properties, such as high molecular weight, narrow PDI, or stereocontrol, have been observed, a more detailed examination of the graft copolymers is provided.     

Synthesis and characterization of butyl acrylate graft sodium salt of partially carboxymethylated starch

Graft copolymers were synthesized by graft copolymerization of butyl acrylate (BA) onto sodium salt of partially carboxymethylated starch (Na‐PCMS). Ceric ammonium nitrate (CAN), a redox initiator, was used for initiation of graft copolymerization reaction. All the experiments were run with Na‐PCMS having degree of substitution, DS = 0.35. The grafting reaction was characterized by parameters such as % total conversion (%Ct), % grafting (%G), % grafting efficiency (%GE), and % add‐on. Graft copolymers were characterized by infrared spectral analysis and scanning electron microscopy. Variables affecting graft copolymerization reaction such as nitric acid concentration, reaction time, reaction temperature, and ceric ion concentration were investigated. The results revealed that 0.3M CAN as initiator, 0.3M HNO₃, with reaction time 4–4.5 h at 25–30°C were found as suitable parameters for maximum yield of graft copolymerization reaction. © 2006 Wiley Periodicals, Inc. JAppl Polym Sci 102: 3334–3340, 2006     

Chemically induced graft copolymerization of acrylonitrile onto lignocellulosic fibers

The grafting of vinyl monomers is an important method for replacing hydrophilic hydroxyl groups present on the surface of natural fibers by hydrophobic polymer chains. It improves the compatibility of natural fibers with polymer matrixes during the fabrication of natural‐fiber‐reinforced polymer composites. This article deals with the graft copolymerization of acrylonitrile onto Agave americana fibers in air in the presence of ceric ammonium nitrate as a redox initiator. A maximum percentage grafting of 24% was obtained after the optimization of various reaction parameters, including the reaction time, temperature, and concentrations of nitric acid, initiator, and monomer. The graft copolymers obtained under the optimum conditions were then subjected to the evaluation of different physicochemical properties, including swelling behavior in different solvents, moisture absorption behavior under different humidity levels, and chemical resistance. The graft copolymers were further characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermal analysis (thermogravimetric analysis/differential thermal analysis), and X‐ray diffraction techniques. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of mica—vinyl graft copolymers

Graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto mica was carried out by the ceric ion method. Experiments were carried out both in the presence and absence of oxygen; oxygen has some detrimental effect in the grafting of AN onto mica. Mica—vinyl graft copolymers were characterized using infrared spectra after purifying the crude graft copolymers for the removal of the occluded homopolymers. The percent grafting, grafting efficiency and the ratio of R_g/R_h were determined. Mica—graft copolymers were saponified by treating with aqueous alkali to convert the nitrile groups to carboxyl groups with a view to utilize these groups for coupling to collagen substrates. Since in a chrome-tanned leather there are available coordination sites due to fixed chromium, the mica—graft copolymer could get bound, thereby resulting in a well filled-up leather.     

Synthesis of poly(styrene-co-isopropenyl acetate) -g-polyisobutylene graft copolymers via combination of radical polymerization with cationic polymerization

Random copolymers of poly(styrene-co-isopropenyl acetate) (SIPA) with an average number of 9 initiating sites per chain were synthesized by free radical copolymerization of styrene with a small amount of isopropenyl acetate using 2,2′-azo-bis-(isobutyronitrile) as an initiator at 70 °C. SIPA copolymer could be further used as macroinitiator for the grafting cationic polymerization of isobutylene (IB) from SIPA chain in CH₂Cl₂ at ?40 °C to produce graft copolymers of SIPA-g-PIB. The effect of SIPA concentration ([SIPA]), TiCl₄ concentration ([TiCl₄]) and IB concentration ([IB]) on initiation efficiency of macroinitiator, grafting efficiency of initiating sites, average length of PIB branches of the resulting graft copolymers were investigated. It can be found that almost all of the initiating sites of IPAc units on SIPA chains were active for the cationic polymerization of IB and both initiation efficiency and grafting efficiency were close to 100% at sufficient molar ratio of TiCl₄/IPAc. This synthetic route presents quantitative grafting efficiency and possibility to control length of PIB branches. The graft copolymers of SIPA-g-PIB with average 9-branched PIB chains having terminal functional tert-chlorine groups could be successfully obtained. The average molecular weight of PIB branches in SIPA-g-PIB graft copolymers could be mediated from 3900 to 47,300 g mol^?1 by changing the ratios of macroinitiator to monomer and concentration of TiCl₄.     

Synthesis and applications of reactive carbohydrates. III. Preparation and methylolation of polyacrylamide-carboxymethyl cellulose graft copolymers

Carboxymethyl cellulose (CMC) was treated with HCl at 80°C for different time periods (15 – 60 min). The hydrolyzed CMC samples as well as the original sample were graft copolymerized with acrylamide using K₂S₂O₈ as initiator. It was disclosed that the increasing duration of acid hydrolysis is accompanied by a progressive increment in the copper number of CMC, meanwhile its carboxyl content decreases. Acid hydrolysis enhances significantly the susceptibility of the CMC toward grafting. The latter reduces the copper number of the hydrolyzed CMC samples most probably via conversion of the aldehydic to carboxylic groups under the action of K₂S₂O₈ during grafting. Grafting also reduces the carboxyl content of the original CMC sample while increasing those of the hydrolyzed CMC samples. Methylolation of the polyacrylamide-CMC graft copolymers results in reactive finishes. When the latter were applied to cotton fabric according to the conventional pad-dry-cure method followed by a thorough washing, the fabric retained ca. 86% of the finish derived from the copolymer of CMC and 92% of finishes derived from the copolymers of hydrolyzed CMC.