Free radical copolymerization of allyloxyphenylsiloxanes with some vinyl monomers

Two p-allyloxyphenyldisiloxane compounds, 1-(p-allyloxyphenyl)-1,1,3,3,3-pentamethyldisiloxane (mono-APDS) and 1,3-bis(p-allyloxyphenyl)-1,1,3,3-tetramethyldisiloxane (bis-APDS), were synthesized to study their radical copolymerizations with some vinyl monomers (styrene, methyl methacrylate, N-phenylmaleimide and maleic anhydride). The reactivities of allyl groups in mono-APDS and bis-APDS were found to be almost the same in styrene and methyl methacrylate copolymerization, as evidenced by their composition curves, and increase with the electron-accepting ability of comonomers. In the case of electron-poor monomers, such as N-phenylmaleimide and maleic anhydride, the second allyl group of bis-APDS readily took part in the crosslinking. Differential scanning calorimetry and thermogravimetry revealed that the increase of APDS contents in those copolymers led to lower glass transition temperature (T_g) and higher thermal degradation temperature.     

Grafting onto wool. VII. Ceric ion-initiated graft copolymerization of vinyl monomers. Comparison of monomer reactivities

In an attempt to compare relative reactivities of vinyl monomers toward grafting, methyl methacrylate (MMA) and acrylic acid (AAc) were grafted separately to Himachali wool in aqueous medium by using ceric ammonium nitrate (CAN) as redox initiator. Nitric acid was found to catalyze the reaction. Percent grafting was determined as a function of concentration of nitric acid, concentration of CAN, concentration of monomer, time, and temperature. Optimum conditions for maximum grafting were evaluated for each monomer and were found to depend upon the nature of the monomer. Reactivities of MMA and AAc toward grafting were compared with those of methyl acrylate (MA), ethyl acrylate (EA), and vinyl acetate (VAc) reported earlier from this laboratory and were found to follow the order MA > EA > MMA > VAc > AAc. An explanation for the observed order of reactivity of different vinyl monomers is presented.     

Graft copolymerization of vinyl monomers on cellulosic materials

Graft copolymers of acrylonitrile, ethyl acrylate, methyl acrylate, ethyl methacrylate and methyl methacrylate and of acrylonitrile/ethyl methacrylate and acrylonitrile/methyl methacrylate monomer mixtures on carboxymethylcellulose (degree of substitution 0.4–0.5) were prepared by use of ceric ion initiator in aqueous medium. The extent of graft polymer formation was measured in terms of graft level, molecular weight of grafted polymer chains and frequency of grafting as function of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight and frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen content of the acrylonitrile/alkyl methacrylate copolymer samples showed that a relativity low amount of the acrylonitrile monomeric units were incorporated into the graft copolymer even at high acrylonitrile content of the feed.     

Graft copolymerization of vinyl monomers in wool fibers

Graft copolymerization of vinyl monomers, mainly methyl methacrylate, in reduced, successively alkylated, or KCN-Treated wool fibers was performed in the redox LiBr–persulfate system without homopolymer. The reduction gives a striking effect in promoting the graft copolymerization. Methylation or ethylene recrosslinking of the reduced wool, especially the former, decreases the graft-on remarkably. By the KCN treatment in which the conversion of disulfide to lanthionine bonds occurs, the grafting is decreased in the bromide–persulfate system but promoted in the system with persulfate alone. Methylation or KCN treatment of wool as well as reduction brings about a great increase in the absorption of persulfate. The grafting of the lanthionine-containing wool in the redox system accompanied by the liberation of bromine might be retarded by the pronounced bromination of monomers over the inhibiting of homopolymerization, because the lanthionine bonds are more stable to bromine than the disulfide bonds. In general, disulfide bonds and the other easily oxidized components of wool may perhaps play an important role in regulating the bromination of monomers and in the graft copolymerization without homopolymer. The molecular weight of graft polymer is decreased distinctly with increasing extent of reduction of wool. From these results, the thiol groups on wool are considered to give predominantly graft centers by the radicalotropy from SO₄, OH·, and/or Br·.     

Hybrid copolymerization of alkyl vinyl ethers with glycidyl ethers

Homopolymerization and copolymerization experiments of isobutyl and dodecyl vinyl ether with propylene oxide, and some glycidyl ethers have been carried out by using both conventional cationic initiators (BF₃, BF₃·OEt₂) and 4-chlorophenyldiazonium tetrafluoborate as cationic photoinitiator. Conventional polymerization experiments performed under vacuum at low and room temperature gave rise to a mixture of the two homopolymers, indicating that the epoxide and vinyl ethers are incompatible with respect to chemical reactivity and that apparently no hybrid copolymerization occurs. Analogous results were obtained in parallel photoinitiated polymerization experiments.     

Grafting onto wool. XX. Graft copolymerization of vinyl monomers by use of redox initiators. Comparison of monomer reactivities

Methyl methacrylate (MMA) and ethylacrylate (EA) have been graft copolymerized onto Himachali wool in aqueous medium by using a ferrous ammonium sulfate–hydrogen peroxide (FAS? H₂O₂) system as redox initiator. Percentage of grafting has been determined as functions of concentration of monomer, molar ratio of [FAS]/[H₂O₂], time and temperature. Percentage of grafting is found to depend upon the molar ratio of [FAS]/[H₂O₂]. An attempt has been made to compare the reactivities of the acceptor monomer (MMA and EA) with that of the donor monomer (VAc) toward grafting onto wool.     

Chemically induced graft copolymerization of vinyl monomers onto cotton fibers

We investigated the chemically induced graft copolymerizations of acrylic acid (AA), acrylamide, crotonic acid, and itaconic acid (IA) onto cotton fibers. Benzoyl peroxide was used as an initiator. The effects of grafting temperature, grafting time, and monomer and initiator concentrations on the grafting yields were studied, and optimum grafting conditions were determined for the sample material. The maximum grafting yield value obtained was 23.8% for AA. Swelling tests, Fourier transform infrared spectroscopy, and scanning electron microscopy analyses of grafted and ungrafted fibers were also performed to characterize fiber properties. IA‐grafted fibers were measured as the most swollen fibers, with a swelling value of 510%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2343–2347, 2006     

Relative reactivities and graft distributions of polystyrene Macromers® in vinyl chloride copolymerization

Polystyrene macromonomers terminated with methacrylate, vinyl ether, or maleic half ester functionalities were evaluated in free radical initiated copolymerizations with vinyl chloride in aqueous suspension polymerization. Macromers® (M₁) terminated with methacrylate disappeared very rapidly in copolymerization with vinyl chloride (M₂). The relative reactivity ratio, r₂, was determined to be 0.05 in good agreement with literature values of about 0.04. Vinyl ether-terminated Macromers® had unexpectedly uniform reactivity with vinyl chloride in early conversion samples, but macromonomer conversion was incomplete. Macromers® having maleic half ester functionality were incorporated rapidly in vinyl chloride copolymerization at pH 2.5 (r₂ = 0.13). However, at pH 10 these Macromers® had reduced reactivity (r₂ = 0.34), which improved graft polymer uniformity. These Macromer® copolymerization relative reactivities are shown to be useful in predicting and controlling graft densities and graft polymer heterogeneity which influence morphology, processing, and mechanical properties.     

Photoinitiated radical copolymerization of vinyl ether and maleate system

The photoinitiated radical copolymerization of difunctional vinyl ether/unsaturated polyester containing maleate has been studied by differential photocalorimetry. The copolymerization kinetics were found to be affected by various factors, such as the composition, the photoinitiator concentration, the light intensity and the presence of oxygen. No temperature effect on the copolymerization was found. The mixture of vinyl ether and unsaturated polyester containing maleate was studied by fluorospectrophotmetry and the existence of a complex of electron donor‐acceptor was detected. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3541–3547, 1999     

Studies in the graft copolymerization of vinyl monomers on cellulosic materials

Graft copolymerization of acrylonitrile, methyl methacrylate, and vinyl acetate on bleached holocellulose initiated by ceric ions in aqueous medium was studied at 29°C. The extent of graft copolymer formation was poly(methyl methacrylate) > polyacrylonitrile > poly(vinyl acetate), indicating the influence of polarity of monomer on graft copolymerization. It was found that, although the molecular weights of the grafted polyacrylonitrile copolymer were lower than the values obtained for poly(methyl methacrylate), the latter was less frequently incorporated on the cellulosic backbone polymer than the polyacrylonitrile grafts. The marked reductions in graft level associated with thiolation of the cellulosic material suggest that hydrogen abstraction reactions from carbon atom carrying hydroxyl groups may not be important in graft copolymer formation.     

Kinetic analysis of radiation-initiated copolymerization reactions of water-soluble vinyl monomers with cellulose

A kinetic analysis of the radiation-initiated copolymerization reactions of 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), and methacrylic acid (MAA) from water, methanol (MeOH), N,N-dimethylformamide (DMF), dimethysulfoxide (DMSO), and combinations of these solvents with irradiated fibrous cellulose I and II was made. The maximum extent of copolymerization of HEMA and HPMA with irradiated cellulose occurred from water solutions. When organic solvents were added to the water solution, while the concentration of monomer was kept constant, the extent of copolymerization decreased. The maximum extent of copolymerization of MAA with irradiated cellulose occurred from mixtures of MeOH (15–30 vol-%) and water (85–70 vol-%) solutions rather than from water. After initiation of the copolymerization reactions, they were apparently diffusion controlled and exhibited second-order kinetics. The relative concentrations of grafted polymer and homopolymer formed with irradiated cellulose from aqueous solutions depended primarily on the concentration of water in the solutions. From MeOH (60 vol-% or less)–water (40 vol-% or more) solutions, about 60% of poly(MAA) formed was apparently grafted polymer; from solutions containing less water, the fraction of grafted polymer decreased to about 40%.     

Graft copolymerization of vinyl monomers on modified cotton. IV. Ceric-induced grafting on vinyl monomers on cellulose bearing different substituents

The influence of introducing various functional groups into the cellulose molecule on its susceptibility toward grafting with vinyl monomers such as acrylonitrile and methyl methacrylate using the Ce(IV)–cellulose redox system was studied. While cellulose bearing either cyanoethyl or carboxymethyl groups showed higher graft yields, cellulose bearing both groups showed lower yields. Presence of acrylamidomethyl groups in the cellulose molecule reduced its reactivity to grafting. The same holds true for cellulose bearing acrylamidomethyl groups along with carboxymethyl groups. On the other hand, introducing carbamoylethyl groups in the cellulose molecule enhances significantly the susceptibility of cellulose toward grafting. This is also observed with cellulose bearing cyanoethyl and carboxyethyl groups. Treating cellulose with N-methylolacrylamide in alkaline medium seems to produce a crosslinked cellulose with lower reactivity to grafting. The results obtained with the different substrates were discussed on the basis of the change in the physical and/or chemical structure of cellulose brought about during its modification as well as on the nature of the substituent groups introduced. The mode of Ce(IV) attack on cellulose was also clarified.     

Controlled radical copolymerization of vinyl acetate and dibutyl maleate by iodine transfer radical polymerization

Iodine transfer radical homo‐ and copolymerization of vinyl acetate (VAc) with dibutyl maleate (DBM) were carried out in the presence of ethyl iodoacetate (EtIAc) and 2,2′‐azobis(isobutyronitrile) (AIBN) as chain transfer agent and initiator, respectively, at 60 °C. Molecular weight and its distribution and (co)polymer structure (i.e. copolymer composition and chain end groups) were analysed using gel permeation chromatography and ¹H NMR spectroscopy, respectively. Homo‐ and copolymerization reactions proceed via a controlled characteristic with predetermined molecular weight and relatively narrow molecular weight distribution. The presence of DBM in the reaction mixture decreases the consumption rate of EtIAc as well as the polymerization rate. This is attributed to the effect of DBM on the transfer constant to the EtIAc and probably on the iodine exchange rate constant between the growing chains. The effect of the concentration of AIBN, EtIAc and overall monomers on the conversion, molecular weight and its distribution was studied. Simultaneously high conversion and molecular weight with a relatively narrow molecular weight distribution can be achieved only when equimolar and intermediate concentration of EtIAc and AIBN is used in the reaction mixture. End‐group analysis by ¹H NMR reveals that iodinated VAc end groups in the (co)polymer chains are unstable, resulting in aldehyde end groups. Thermogravimetric analysis shows that the thermal stability of the VAc‐based polymer increases on incorporating DBM units into the copolymer chains. © 2013 Society of Chemical Industry     

Radiation induced graft copolymerization of vinyl monomers and their binary mixture onto rayon fibre

Ethyl acrylate (EA), Vinyl imidazole (VI), and their binary mixture have been copolymerized onto rayon in aqueous medium by mutual method using γ-radiation. The graft yield has been determined as a function of different reaction parameters such as total dose, concentration of vinyl monomers, and amount of water. Effect of surfactant (1-octane sulfonic acid, sodium salt) has been studied on the percentage of grafting of EA, VI, and (EA + VI). A plausible mechanism has been suggested to explain the observed behavior of the surfactant on grafting. Water retention and moisture regain of the grafted film was determined at appropriate relative humidity. The graft copolymers have been characterized by IR spectroscopy and scanning electron microscopic methods. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion

Graft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.     

Grafting of vinyl monomers onto silk fibers: Trivalent-manganese-initiated graft copolymerization of acrylamide onto silk fibers

Graft copolymerization of acrylamide (AM) onto silk fibers, using Mn(III)–sulphate as initiator, has been investigated, in aqueous sulphuric acid in the temperature range of 30–55°C. Grafting reaction has been studied by varying the concentration of monomer, Mn(III), sulphuric acid, temperature, and also with the modified silk. The graft yield increases significantly with increase of monomer concentrations to the extent of 0.85M, after which the rate falls. With increase in Mn(III) concentration and H⁺ ion concentration the graft yield increases, but after an optimum concentration a depression in the graft yield is noticed. The rate of the reaction is temperature-dependent; with increase of temperature the graft-on increases. Among the solvent composition studied a solvent/water mixture containing 10% of the solvent seems to constitute the most favorable medium for grafting, and a further increase of solvent composition decreases the graft yield. The effect of various additives such as transition metal salts, aromatic and heterocyclic amines on grafting reaction has been studied. A suitable mechanism for grafting has been proposed. Finally physical characterization such as thermal analysis (TGA) of the grafted samples has been carried out in order to ensure grafting and to study the change in the properties of the fibers.     

溶液丁苯的偶联反应--乙烯基单体为偶联剂的偶联反应研究

以n-BuLi为引发剂，四氢呋喃（THF）为调节剂，环己烷或抽余油为溶剂，采用4种含可聚合基团的亲电试剂（丙烯酰氯，甲基丙烯酰氯，甲基丙烯酸缩水甘油酯，烯丙基氯）对丁二烯－苯乙烯活性阴离子共聚物进行偶联，结果表明，丙烯酰氯为偶联剂对活性丁苯聚合物进行偶联可以制得含有星型聚合物的溶液丁苯，而采用甲基丙烯酰氯，甲基丙烯酸缩水甘油酯，烯丙基氯等偶联活性丁苯聚合物主要得到双偶联产物，结合偶联剂的分子结构对所得结果进行了分析。     

Half-sandwich ruthenium complexes for the controlled radical polymerisation of vinyl monomers

Ruthenium complexes of the type [RuX(Cp^#)(PPh₃)₂] (X=Cl and H; Cp^#=Cp, Cp*, indenyl, and carboranyl) catalyse the radical polymerisation of styrene and n-butyl acrylate, and both the catalyst activity and the degree of control of the polymerisation strongly depend on the Cp^# ligand and the monomer.