Living block copolymerization of phenyl vinyl sulfoxides and characterization of a stereogradient polymer

The polymerization of phenyl vinyl sulfoxide in blocks of increasing enantiomeric excess was carried out. Portions of the polymer were removed after each charge of monomer was consumed. The poly(phenyl vinyl sulfoxide)s were characterized by gel permeation chromatography and nuclear magnetic resonance spectroscopy. Reduction of the poly(phenyl vinyl sulfoxide)s to poly(phenyl vinyl sulfide)s permitted assignment of the polymer stereochemistry and verification that stereogradient polymers were formed.     

前体法制备单分散遥爪聚乙炔

合成了苯基乙烯基亚砜 (PVSO) ,并以萘 碱金属作为引发剂、丁二酸酐作为终止剂 ,进行阴离子聚合 ,制备出单分散、端羧酸盐的苯基乙烯基亚砜的遥爪聚合物 ,聚合物的功能度基本在 1 6 0以上 .在真空加热条件下 ,聚苯基乙烯基亚砜发生侧基热消除反应 ,从而获得末端为羧酸盐的遥爪聚乙炔     

Relationship between reduction of ceric ion with poly(vinyl alcohol) and graft copolymerization

Various poly(vinyl alcohol) samples were preliminarily subjected to oxidation treatment with sodium hypochlorite, and the reduction of ceric ion and subsequently initiation in the graft copolymerization in the system containing methyl methacrylate were investigated. The reduction behavior of ceric ion could be subdivided into three parts, each of different reaction rate. In the initial stage of the reaction, there was observed rapid cleavage of the backbone chain of poly(vinyl alcohol) with ceric salts. The amount A of cleavage was proportional to the amount of ceric ion reduced at the initial fastest rate for various samples of different extents of oxidation; cleavage of 1 mole required ca. 10 moles of reduction of ceric ion. Higher carbonyl contents of the sample caused increased A. Graft polymerization was carried out in the same system with the addition of the monomer. The amounts of grafted chains produced were determined, and approximately one mole of grafted chains was obtained for per mole of cleavage. The copolymer is concluded to be blocklike in structure. The contribution of the carbonyl groups in poly(vinyl alcohol) sample to the initiation of the polymerization should be emphasized.     

Grafting of 4-vinyl pyridine onto poly(vinyl alcohol) initiated by potassium diperiodatocuprate(III)

In this article, the graft copolymerization of 4-vinyl pyridine onto poly(vinyl alcohol) via the potassium diperiodatocuprate(III)-poly(vinyl alcohol) redox system as an initiator was investigated in an alkaline medium. The graft copolymer was characterized with Fourier-transform infrared spectra analysis. A mechanism is proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, the ratio of monomer to poly(vinyl alcohol), pH, and reaction temperature and time, are investigated, and the grafting conditions are optimized. Graft copolymers with high grafting efficiency are obtained, thus indicating that potassium diperiodatocuprate(III)-PVA redox system is an efficient initiator for this graft copolymerization. Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. B, 2006, Vol. 48, No. 7, pp. 1190–1194. This text was submitted by the authors in English.     

Synthesis and characterization of graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates by atom transfer radical polymerization

Graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates were prepared by atom transfer radical polymerization. Poly(vinyl chloride) containing small amount of pendent chloroacetate units was used as a macroinitiator. The formation of the graft copolymer was confirmed with size exclusion chromatography (SEC), ¹H NMR and IR spectroscopy. The graft copolymers with increasing incorporation of butyl acrylate result in an increase of molecular weight. One glass transition temperature (T_g) was observed for all copolymers. T_g of the copolymer with butyl acrylate decreases with increasing content of butyl acrylate.     

Reaction of chlorine-containing polymers with living polymers

A graft polymer was prepared by means of the coupling reaction of chlorinated ethylene–propylene terpolymer with living polystyrene, obtained with a sodium–naphthalene complex as initiator, under various conditions; the grafting efficiency and the percentage of grafting are discussed. Poly(chloroprene), chlorinated butyl rubber, poly(vinyl chloride), poly(epichlorohydrin), and epichlorohydrin–ethylene oxide copolymer were also used as chlorine-containing polymers. The grafting efficiencies were found to be in the following order: chlorinated butyl rubber > poly(epichlorohydrin) > epichlorohydrin-ethylene oxide copolymer > chlorinated ethylene-propylene terpolymer > poly(chloroprene) > poly(vinyl chloride). A graft polymer was obtained from the reaction between chlorinated ethylene–propylene terpolymer and living poly(isoprene), with butyllithium in benzene. The undesirable metal–halogen interchange reaction was considerable.     

Influencing the morphology of polymer blends through graft copolymers

Graft copolymers have a potential as compatibilizers in two-component thermoplastic polymer blends, and also as impact-modifiers in one-component thermoplastics. The compatibility of the blocks of the copolymer (i.e. the grafts and the main chain) with the chains of the matrix polymers must be adjusted carefully. Blends of various polymers, especially of polystyrene (PS) and poly(vinyl chloride) (PVC), with graft copolymers on the basis of polybutadiene are discussed. An excellent compatibilizer, for blends PS/PVC, is a block-graft copolymer, derived from a diblock copolymer of Styrene and butadiene, with grafts of cyclohexyl methacrylate monomelic units.     

Solution behavior of [(ethylene-co-vinyl alcohol)-g-ethylene oxide] graft copolymers

The solution behavior of hydrophobic-hydrophilic water-soluble graft copolymers consisting of poly[(ethylene-co-vinyl alcohol)-g-ethylene oxide] was investigated by high-resolution NMR spectroscopy and measurements of solution viscosity in tetrahydrofuran, water, and mixtures thereof at various temperatures. A graft copolymer with a backbone containing 2.7 mole% vinyl alcohol exists in an intramolecular phase-separated conformation in aqueous solution, independent of the temperature. Graft copolymers with backbones containing 20.3 mol% vinyl alcohol exhibit an intramolecular mixed-phase conformation in which the mobility of chains in the hydrophobic region depends on temperature. The temperature dependence of the intrinsic viscosity in water shows a maximum near 50°C.     

Chemical structure of poly(ethylene terephthalate)–styrene and nylon–styrene graft copolymers prepared by radiation techniques

The graft copolymerizations of styrene onto poly(ethylene terephthalate) (PET) and nylon fibers were carried out by the mutual irradiation and preirradiation methods. True graft copolymers were isolated from the products by extraction and characterized by hydrolysis and osmometry. Among the swelling agents employed, methanol was most effective for increasing the extent of grafting onto PET. In both methods of the grafting, the molecular weight of polystyrene formed in the substrate matrix was higher than one million if no chain-transfer agent was added to the monomer solution. Similar to the case of radiation grafting onto poly(vinyl alcohol) and cellulose, the isolated graft copolymer carried only one branch per copolymer molecule in both cases. Of great interest is the particularly low extent of grafting in the case of PET–styrene. This should be attributed to the low sensitivity of PET to radiation. The grafting site on the mother polymer molecule is discussed on the basis of the solution behavior of the branch polymers separated from the backbone.     

Grafting acrylic acid monomer to poly-(vinyl alcohol) and methyl cellulose by ceric ion

A graft copolymer of acrylic acid on poly(vinyl alcohol) was prepared by use of the ceric ion–polyol redox system in aqueous medium. The graft copolymer obtained was water-soluble under the specified experimental conditions. The efficiency of grafting was determined by measuring carboxyl group content (as expected from acrylic acid unit) in the copolymer by applying the newly developed reverse dye-partition technique. The graft copolymer was also characterized by viscosity and solubility measurements. The effect of varying concentration of catalyst, monomer, and grafting time has also been determined.     

PAA-g-PVAc Amphiphilic Graft Copolymer Synthesized by Atom Transfer Radical Polymerization

A new amphiphilic graft copolymer containing hydrophilic poly(acrylic acid) backbone and hydrophobic poly(vinyl acetate) side chains was synthesized via sequential atom transfer radical polymerization (ATRP) followed by selective hydrolysis of poly(methoxymethyl acrylate) backbone. Grafting‐from strategy was employed to synthesize PMOMA‐g‐PVAc graft copolymer (M_w/M_n=1.64) via ATRP. The final PAA‐g‐PVAc amphiphilic graft copolymer was obtained by selective acidic hydrolysis of PMOMA backbone in acidic environment without affecting the side chains. The critical micelle concentrations (cmc) in aqueous media were determined by a fluorescence probe technique. The micelle morphologies were found to be spheres.     

STUDIES ON THE OXIDATION AND GRAFT COPOLYMERIZATION OF POLYETHERS

Polyethers could form hydroperoxide under air-oxidation or photo-oxidation in the presence of H_2O_2. The scission of ether linkage induced by moderate oxidation was prevented by controlling the reaction time and hydroperoxide concentration. The oxidation rate was affected by the end groups of polyethers. The decreasing order of oxidation rate for various poly(tetramethylene ether) glycol derivatives having different end groups are as follows: poly(tetramethylene ether) glycol (PTMG)>poly(tetramethylene ether)acetate (PTMGAC) >poly(tetramethylene ether) phenyl carbamate (PTMGPC). The urethane end groups in PTMGPC increase the resistance toward oxidation. Polyether hydroperoxide reacts with ferrous ion or N,N-dimethyl toluidine (DMT) to form polymericoxy radical which then initiates the graft copolymerization of vinyl monomers at low temperature, and was devoid of homopolymerization. The copolymer after separation and purification was proved to be a graft one by IR analysis and elemental analysis.     

Gamma radiation induced graft copolymerization of vinyl monomers onto poly(vinyl alcohol)

In an attempt to modify water-soluble synthetic polymers, graft Copolymerization of methylmethacrylate (MMA) and ethyl acrylate (EA) onto poly(vinyl alcohol), PVA, has been studied by using gamma irradiation from a Co⁶⁰ source as initiator. The graft copolymerization was carried out in an aqueous medium by the mutual method in air. The effect of total dose and concentration of vinyl monomers on percentage of grafting has been determined. Water plays a significant role in the enhancement of graft copolymerization and the optimum amount of water to afford maximum grafting has been evaluated. The effect of CH₃OH on aqueous grafting of MMA and EA by radiation method has been studied. The graft copolymer has been characterized by IR spectroscopic and thermogravimetric methods.     

聚氧化乙烯和聚醋酸乙烯酯在超声波辐照下接枝反应的研究

本文分别研究了聚氧化乙烯(PEO)和聚醋酸乙烯酯(PVAc) 在苯溶液中的超声波辐照降解,PEO与PVAc在苯溶液中的超声波辐照共聚反应。实验证明,降解反应可用Ovenall方程描述。用IR、NMR和DTA分析了在超声波辐照作用下PEO与PVAc在苯溶液中生成的共聚物的结构,证明所得产物主要为接枝共聚物,将浓度为1％的(PEO-PVAc)苯溶液在频率为18.2kHz、逆变器主迥路输入电流为2.0安的超声波强度下,辐照10分钟,共聚物的产率为10.54％,接枝点密度为33.3％,平均接枝链长为17。     

Graft Copolymerization of Benzyl Methacrylate onto Poly(Acryloyl-L-valine) Microspheres by Using the Photoreaction of Side Carboxyl Groups with Lead Tetraacetate

N-Acryloyl-L-valine (ALV) was found to yield polymer microspheres when it was polymerized with a radical initiator in acetophenone. The resulting microspheres showed thermochromism in aromatic solvents such as benzonitrile, methyl benzoate, and acetophenone. Graft copolymerization of benzyl methacrylate (BzMA) onto poly(ALV) microspheres was carried out in benzonitrile by using the photoreaction of carboxyl groups in poly (ALV) with Pb(OAc)₄. The grafting efficiency was not very high (15–28%). Methyl methacrylate as the second monomer gave a higher grafting efficiency (56%) although the polymer yield was considerably lower. The resulting graft copolymer was characterized by IR spectroscopy and thermogravimetry. The grafted poly (ALV) microspheres were well dispersed in benzene. A benzene solution of grafted poly(ALV) microspheres and homopoly(BzMA) gave a film with finely dispersed poly (ALV) microspheres.     

Anionic Graft Copolymers. III. Hydrogenation of Polydienes Grafted with Vinylaromatics

A new method is described to prepare graft copolymers of polystyrene and polyvinylcyclohexane on polyethylene and poly (ethylene, butene-1). Hydrogenation of the butadiene moieties of graft copolymers of polystyrene on poly-1, 4-butadiene and high vinyl polybutadiene forms graft copolymers of polystyrene on polyethylene and on poly (ethylene, butene-1). Graft copolymers of polyvinylcyclohexane on polyethylene and on poly (ethylene, butene-1) are prepared by completely hydrogenating graft copolymers of polystyrene on poly-1, 4-butadiene and on high vinyl polybutadiene. The physical properties of these polymer systems depend on composition and graft level, resulting in either tough polymers or elastomers.     

Graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel by gamma-ray irradiation

Poly(methylvinylsiloxane)-bonded silica gel was synthesized by condensation reaction between silica gel and the hydrolysis product of methylvinyldichlorosilane. Graft polymerization of styrene or indene onto poly(methylvinylsiloxane)-bonded silica gel was carried out by gamma-ray irradiation and compared with that onto silica gel. Homopolymer was found to be formed through a radical mechanism concurrently with an ionic mechanism in the graft polymerization. Probably genuine graft polymers are formed in the graft polymerization onto poly(methylvinylsiloxane)-bonded silica gel, while the product formed in the graft polymerization onto silica gel may be apparent graft polymers.     

Stabilizing bicontinuous nanophase segregation in piCP-C60 donor-acceptor blends

The synthesis and thin film properties of a conjugated polymer bearing graft chains that are compatible with a fullerene, chemically modified with a similar motif, are described. The graft copolymer, obtained by nitroxide-mediated radical polymerization of a vinyl triazole onto a postfunctionalized poly(3-hexylthiophene) (P3HT) backbone, is blended with a fullerene modified with a pendant triazole functionality (TAZC60). For a given ratio of polymer:TAZC60, graft copolymer (P3HT-g-PVTAZ:TAZC60) blends exhibit substantially reduced photoluminescence compared to P3HT:TAZC60 blends, while TEM analysis reveals the graft polymer undergoes extensive mixing with the fullerene to form bicontinuous 10 nm phase domains. Graft polymer blends annealed for 1 h at 140 degrees C retain their nanometer phase separation as evidenced by TEM, UV-vis, XRD, and photoluminescence analysis, and phase purity was enhanced. In contrast, P3HT:TAZC60 blends exhibit micron-sized phase-segregated morphologies before and after annealing. The chemical similarity of the triazole functionality attached to P3HT and the fullerene leads to the formation of films with uniform, stable, nanophase morphologies. This strategy may prove a useful strategy for controlling the extent of phase segregation in electron donor and acceptor blends of pi-conjugated polymers (piCPs) and fullerenes.     

Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.     

STUDIES ON ULTRASONIC GRAFTING OF POLY(VINYL ACETATE) WITH POLY(ETHYLENE OXIDE)

The ultrasonic degradation of poly(ethylene oxide) and poly(vinyl acetate) in benzene solution, and grafting reaction of poly(vinyl acetate) with poly(ethylene oxide) were studied. It is found that the chain-scission reactions follow the course suggested by D. W. Ovenall. The structure of the copolymer was identified by IR, NMR and DTA, showing that the copolymer prepared is a graft copolymer mainly. The copolymer formed by irradiating 1% PEO/PVAc solution (PEO/PVAc:1/1 by weight) for a period of 10 rain at 18.2 kHZ, with 2.0 A input current on reversed main circuit, amounts to 10.5%.