Synthesis of polymer‐grafted natural rubbers by radical photopolymerization of vinyl monomers initiated from the rubber chains

The synthesis of polymer‐grafted natural rubbers (NRs) was considered through photopolymerization of vinyl monomers initiated from N,N‐diethyldithiocarbamate groups previously introduced onto cis 1,4‐polyisoprene units of NR chains. The development of the procedure was made with methyl methacrylate (MMA) as monomer. First, initiation of MMA photopolymerization was tested using a model molecule of the N,N‐diethyldithiocarbamate‐functionalized 1,4‐polyisoprene unit to verify the feasibility of the procedure considered. Then, MMA polymerization was successfully initiated from N,N‐diethyldithiocarbamate‐functionalized NR backbone used as macroinitiator, and the conditions of grafting were optimized. It was shown that MMA grafting could occur either in monomer medium, in solution in toluene, and in latex medium, and that the quantities of homopolymer formed were still low. Thereafter, grafting studies were performed with other vinyl monomers (styrene, methacrylonitrile, acrylamide, acrylic acid) showing that grafting efficiency depends essentially on the nature of the monomer. The method developed here was shown particularly well adapted for the synthesis of polymer‐grafted NR with monomers of low polarity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of cis‐1,4‐Polyisoprene Electrospun Microfibers

cis‐1,4‐Polyisoprene, a significant industrial elastomer, is electrospun into different nanostrucutures. Cis‐1,4‐polyisoprene electrospun fibers are prepared from cis‐1,4‐polyisoprene solutions in dichloromethane or chloroform and characterized by environmental scanning electron microscope and Fourier‐transform infrared spectroscopy. ESEM observation reveals that the cis‐1,4‐polyisoprene fibers show a bamboo‐like morphology with a nearly constant node distance, a diameter of 20–60 µm and a length of about 300 µm. In addition, within the individual nodes parallel grooves are clearly seen, which is very promising for their use in microprinting in the field of microelectronics. Smooth cis‐1,4‐polyisoprene fibers with a diameter of 5–8 µm can be obtained via electrospinning its chloroform solutions. In contrast to most polymers, the jet of cis‐1,4‐polyisoprene does not split during the electrospinning processes, which facilitates the collection of highly aligned fibers by using a rotating mandrel as a ground target.

     

Graft copolymerization of polyisobutylene and polychlorobutyl onto polystyrene waste

Poly(styrene-graft-isobutylene) (PS-graft-PIB) and poly(styrene-graft-chlorobutyl) (PS-graft-Cl-IIR) have been synthesized by the grafting of PIB and Cl-IIR onto polystyrene waste in conjunction with AlCl₃/HCl as catalyst. The grafting efficiency (GE) and overall graft composition have been studied. The synthesized graft polymers were purified and characterized by IR and ¹H NMR analysis. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used to study the thermal characteristics of the graft. It is shown that the grafting induces better thermal stability for polystyrene. © 1999 Society of Chemical Industry     

Poly(amide thioether)s by addition of ethanedithiol to diallylamides

The preparation of poly(amide thioether)s by addition of ethanedithiol to diallylamides in the presence or absence of peroxide catalysts is reported for the first time. Diallylamide monomers N,N'-diallyloxalamide, N,N'-diallylmalonamide and N,N'-diallylterephthalamide have been prepared by aminolysis of the corresponding esters with allylamine. The structures of the resulting polymers have been elucidated by elemental microanalysis and ¹H NMR and IR spectroscopy. The polymers obtained both as Markovnikov and anti-Markovnikov types of addition are highly crystalline compounds.     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved. __________ Translated from Acta Polymerica Sinica (China), 2007, (3): 203–208 [译自: 高分子学报]     

Architecture of nanostructured polymers by segregated domain crosslinking of block‐graft copolymer micelles

Polystyrene‐block‐polyisoprene (PS‐block‐PI; high 3,4‐structure) diblock copolymer was prepared by living anionic polymerization. For transfer into a reactive intermediate, the hydroxylation of the double bonds of PI block was achieved by hydroboration, followed by oxidation. Esterification of the hydroxy‐derivative with stearoyl chloride or decanoyl chloride resulted in block‐graft copolymers composed of PS (flexible chain)‐grafted long alkane (stretched chains). After partial chloromethylation of PS block copolymer, photofunctional N,N‐diethyldithiocarbamate (DC) groups were introduced into such pendant sites by reaction with the corresponding sodium salt. We studied the self‐assemblies of photofunctional block‐graft copolymers in a selective solvent, such as heptane, and constructed nanostructured polymers by crosslinking PS cores under UV irradiation. © 2001 Society of Chemical Industry     

异戊二烯和四氟乙烯—丙烯共聚物的光化学接枝反应

在紫外光作用下,二苯甲酮、蒽醌和安息香能通过夺氢反应使异戊二烯在四氟乙烯-丙烯共聚物中接枝,接枝反应按三重态自由基引发机理进行,接枝率随光照时间的增长而增加,但不会超过40％。和异戊二烯的自由基聚合反应不一样,接枝物中聚异戊二烯接枝链的微结构以3,4-和1,2-聚合为主,而前者以1,4-聚合为主。Ce~(+4)及Fe~(+2)-H_2O_2等氧化还原体系对该接枝反应不产生作用.极性溶剂四氢呋喃的加入,对接枝链微结构的影响很小。     

Greffage Anionique de Polyisoprene par Desactivation sur les noirs de Carbone Porteurs de Groupes Esters. Taux Limite de Greffage

Anionic grafting of polyisoprene and polystyrene by desactivation of a living polymer on the ester groups previosly introduced on the carbon black surface has been followed as a function of the molecular weight of the polymer. The desactivation reaction is limited. A correclation between the grafting ratios and the molecular weights exists. If we assume the macromolecule to behave like spheres having a radius identical to the gyration radius calculated from the viscosity measurement, we will be able to determine the surface coverage of the solid sample. A constant value equal to 1,5 is thus obtained for all the polymers having molecular weights ranging from 4 000 to 135 000. A surface coverage of 1 would correspond to ellipsoids showing axes ratios in close agreement with those calculated statistically by KUHN .     

Microwave-assisted synthesis and characterization of polyacrylamide grafted co-polymers of <Emphasis Type="Italic">Mimosa</Emphasis> mucilage

Response surface methodology was applied to optimize the microwave-assisted graft co-polymerization of acrylamide on Mimosa pudica seed mucilage. The effect of variables, microwave power and time of exposure, concentrations of acrylamide, mucilage and ammonium persulfate on grafting efficiency of graft co-polymerization was screened using Plackett–Burman experimental design. The results revealed that the concentration of acrylamide and mucilage are the most significant variables, which were further optimized using, a central composite design. A second-order polynomial equation fitted to the data was used to predict the response in the optimal region. The optimal grafting parameters provided graft co-polymer with grafting efficiency close to the predicted values. The proposed mathematical model is found to be robust and accurate for graft co-polymerization of acrylamide and Mimosa mucilage consistent with goals of maximizing grafting efficiency. The results of FT-IR, DSC, XRD, and SEM studies confirmed the formation of graft co-polymer of acrylamide and Mimosa mucilage.     

Amylose graft polymers made by 60Co gamma-irradiation

Model products were needed to elucidate structure–property relationships in a starch graft polymer research program. Simultaneous irradiation of amylose and acrylamide in oxygen-free, dilute aqueous solutions gave graft polymers with maximum add-on of about 16%. The graft polymers were separated from homopolymer and subfractionated by incremental additions of nonsolvent (methyl or ethyl alcohol) to irradiated aqueous reaction media. The graft polymers were fairly homogeneous in graft content. Effects were determined of ratios of monomer to substrate, dose rate, and total dose on yield, graft content, intrinsic viscosity, and homopolymer characteristics. Under some conditions, crosslinks probably formed between graft side chains. Large differences in solution properties of a synthetic mixture of separately irradiated amylose and acrylamide and an irradiated solution of amylose and acrylamide indicated that grafting had occurred. Further evidence for true grafting was based on the action of a selective precipitant, n-butyl alcohol, on graft polymer solutions.     

Polymers from renewable resources: Kinetics studies of the radiochemical graft copolymerization of styrene onto cellulose extracted from pine needles and the effect of some additives on the grafting parameters in an aqueous medium

In an attempt to develop an alternative to petro‐based polymers, we graft‐copolymerized cellulose isolated from the needles of Pinus roxburghii with styrene in a limited aqueous medium in air by simultaneous irradiation using gamma rays as the initiator. The optimum conditions for obtaining maximum grafting were determined as a function of monomer concentration, total dose of irradiation, and amount of water. Maximum percentage of grafting (P_g; 79.9) was obtained at a total dose of 1.152 × 10⁴ Gy with 1.325 × 10^?4 mol of styrene. The effect of methanol, LiNO₃, Cu(NO₃)₂, Mohr's salt, H₂SO₄, HNO₃, and AcOH on P_g was studied. All the additives were found to decrease graft yield, contrary to some reported studies. Total percentage conversion and rates of polymerization, grafting, and homopolymerization were evaluated. Evidence of grafting was provided by the characterization of cellulose and its graft copolymers by Fourier transform infrared spectroscopy, thermogravimetry, and observation of the swelling behavior in some solvents. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1490–1500, 2002     

Synthesis and Thermothickening Behavior of Graft Copolymers Based on poly(N,N-Diethylacrylamide-co-N,N-Dismethylacrylamide) Side Chains

A new type of thermothickening graft copolymer was synthesized through free radical copolymerization and grafting onto technique in aqueous solution. Their molecular structure combines a hydrophilic backbone based on poly(acrylicacid-co-2-acrylamido-2-methylpropane sulfonic acid and thermosensitive side chains based on N,N-diethylacrylamide and N,N-dimethylacrylamide (DMAA). The lower critical solution temperature of poly(N,N-diethylacrylamide) was increased easily by copolymerizing with hydrophilic monomers DMAA. The results demonstrate that the polymers in aqueous solution exhibit a significant increase in viscosity with the temperature rising and their thermothickening behavior is related to various physicochemical parameters such as the concentration of the polymer, shear rate, chemical composition of side chains, salt concentration, and pH value.     

Surface functionalization of Si3N4 nanoparticles by graft polymerization of glycidyl methacrylate and styrene

To improve dispersibility and interfacial interaction of nano‐Si₃N₄ particles in epoxy‐based composites, graft of glycidyl methacrylate (GMA) and styrene (St)/GMA onto the nanoparticles' surface was carried out in terms of emulsion polymerization method. The grafting polymers proved to be chemically attached to the nanoparticles via the double bonds introduced during the coupling agent pretreatment. The factors affecting the graft parameters, such as monomer concentration, initiator consumption, reaction time, etc., were investigated. It was shown that higher concentrations of monomer and initiator are favorable for the graft polymerization. When St/GMA was employed as the grafting monomer, the nanoparticles were found to play the role of polymerization loci. The grafted nanoparticles exhibit greatly improved dispersibility in cured epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 992–999, 2006     

Synthesis and characterization of well-defined comb-like branched polymers

Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig reaction. The resulting comb-like branched polymers were characterized by IR, ¹H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups. Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved.     

Polyisoprene modified poly(alkyl acrylate) foam as oil sorbent material

Biorenewable polyisoprene latex obtained from natural rubber, Hevea brasiliensis, was used to prepare the reusable polyisoprene–poly(alkyl acrylate) foam for petroleum‐based liquid absorption. The foam was produced via latex vulcanization and cured by steaming. The effect of various types of poly(alkyl acrylate) such as poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), and poly(butyl acrylate) (PBA) on oil sorption capacity of the foam were studied. Scanning electron microscope (SEM) images showed interconnected open‐cell macrostructure with the foam porosity greater than 75% and good compression set. The oil sorption capacity of the foam was in the range of 2.0–16.6 g g^?1. The addition of poly(alkyl acrylate) enhanced hydrophobicity and oil sorption capacity of the foam. The absorbed oil was easily recovered by squeezing and the foam can be reused up to 30 sorption–desorption cycles and still preserve high quality sorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42688.     

Graft polymerization of methyl methacrylate onto gelatin

In order to extend the application of grafting for the modification of natural polymers, the graft polymerization of methyl methacrylate onto gelatin by radical initiators was studied in aqueous solution at temperatures between 60°C and 80°C. Among the initiators used (peroxy-sulfates, α,α′-azobisisobutylonitrile, and benzoyl peroxide), potassium peroxysulfate was found to be the most efficient initiator in this particular graft polymerization. From the kinetic data with this initiator, it was shown that (1) efficiency of grafting is higher at lower temperature; (2) a sharp increase in the efficiency of grafting occurs at the later period of the polymerization at high temperature, which is attributable to the combination between homopolymer and backbone gelatin; and (3) generally, the number of branches was small and the molecular weight of the branch polymer was high in this polymerization.     

An example of free radical graft polymerization where the mechanism from-to applies

Free-radical grafting on natural and synthetic polymers is a method widely used to modify these polymers chemically. A number of these chemical systems show an unexpected behaviour of the polymerization rate when the monomer concentration is sufficiently high: it decreases and sometimes it increases afterwards. Here, the effect of varying the monomer concentration on the graft yield when grafting methyl acrylate, vinyl acetate and a mixture of both monomers onto cellulose initiated by ceric ions is discussed, considering a three-component mechanism of grafting (mechanisms from, onto and from-to). It is suggested that the unexpected behaviour indicated above is accounted for by the presence of the grafting mechanism from-to. Some knowledge about the copolymer structure can be reached by using this mechanistic approach.     

Synthesis and characterization of graft copolymer (guar gum–g–N‐vinyl‐2‐pyrrolidone) and investigation of metal ion sorption and swelling behavior

Graft copolymer of N‐vinyl‐2‐pyrrolidone with guar gum was synthesized and its reaction conditions were optimized for better yield using potassium peroxymonosulfate (PMS) and glycolic acid (GA) as a redox initiator. The effect of PMS, GA, hydrogen ions, guar gum, and N‐vinyl‐2‐pyrrolidone (NVP) along with reaction time and temperature were studied by determining the grafting parameters: grafting ratio, efficiency, conversion, add‐on, homopolymer, and rate of grafting. It was observed that the maximum yield occurred at with a time of 120 min at a temperature of 45°C and a guar gum concentration of 0.4 g/L concentration. The graft copolymer was characterized by infrared spectroscopy and thermal analysis. The activation energy for the grafted and ungrafted gum was calculated. It was observed that the graft copolymer was thermally more stable than the pure gum. The swelling and metal ion sorption behavior of guar gum and guar gum‐g‐N‐vinyl‐2‐pyrrolidone also were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2480–2489, 2006     

Self‐driven graft polymerization of vinyl monomers on poultry chicken feathers in the absence of initiator/catalyst

An efficient and simple method for graft copolymerization of powdered chicken feather (CF) with vinyl monomers without any free radical initiator is reported. Various vinyl monomers such as glycidyl methacrylate (GMA), styrene (S), and methyl methacrylate (MMA); (20–60 wt % with respect to CF) were successfully grafted to chicken feather (CF) by using sodium dodecyl sulfate (SDS, 0.086–0.5 mmol) in the absence of any catalyst or initiator. Most likely, the hydrophilicity, hydrophobicity, and complex forming properties of chicken feather keratin with surfactant molecules were responsible for efficient grafting of polymers on CF surface. The effect of polymerization conditions, such as monomer concentration, temperature, and time of reaction, on the grafting parameters such as monomer conversion, grafting efficiency, and molar grafting ratio were studied. The described method showed a good potential of using low cost, easily accessible poultry chicken feathers as grafting material and self catalyzing agent for graft copolymerization with vinyl monomers to produce low cost commodity plastic for various end uses. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44645.     

液体聚异戊二烯的结构表征

通过傅立叶变换红外光谱、核磁共振、不饱和度测定、凝胶渗透色谱、热重分析和动态流变分析等手段对液体聚异戊二烯（LIR-50）的结构及其基本性质进行了研究.结果表明,LIR-50的链节化学组成与天然橡胶完全相同,但二者的空间结构有明显区别.LIR-50的顺-1,4、反-1,4和3,4结构含量分别为70.8%、24.4%、4.8%,而天然橡胶的顺-1,4结构高达98%.LIR-50的数均分子量为42000,多分散指数为1.24,其动态粘度对温度敏感,对剪切速率不敏感.