Scale-up synthesis of vinyl polymer-grafted nano-sized silica by radical polymerization of vinyl monomers initiated by surface initiating groups in the solvent-free dry-system

For the purpose of the prevention of the environmental pollution and the simplification of reaction process, the scale-up radical graft polymerization of vinyl monomers onto nano-sized silica surface initiated by azo groups and peroxycarbonate groups previously introduced onto the surface in the solvent-free dry-system was investigated. The introduction of azo groups onto the silica surface was achieved by the reaction of surface amino groups with 4,4′-azobis(4-cyanopentanoic acid chloride). On the other hand, the introduction of peroxycarbonate groups onto the silica surface was achieved by Michael addition of surface amino groups to t-butylperoxy-2-methacryloyloxyethylcarbonate. The graft polymerization of vinyl monomers onto the surface was successfully achieved by splaying monomers to nano-sized silica having azo and peroxycarbonate groups in solvent-free dry-system. It is interesting to note that the formation of ungrafted polymer was depressed in comparison with graft polymerization in solution: the grafting efficiency was 90-95%. In addition, in the solvent-free dry-system, the grafting of copolymer having pendant peroxycarbonate groups onto the nano-sized silica surface and the radical postgraft polymerization of styrene initiated by the pendant initiating groups of the grafted copolymer chain on the silica surface was investigated.     

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerization of vinyl monomers from glass fiber surface initiated by alkylazo groups introduced onto the fiber surface. The introduction of azo groups onto the glass fiber surface was achieved by reaction of isocyanate groups which were previously attached onto the surface with two kinds of azo initiators, 4,4′-azobis(4-cyanopentanoic acid) (ACPA) and 2,2′-azobis(2-cyanopropanol) (ACP). The amounts of surface azo groups introduced by ACPA and ACP were both determined to be 1.3 × 10⁻⁵ mol g⁻¹ by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was found to be initiated in the presence of the glass fiber having surface azo groups. During the polymerization, part of resultant poly(MMA) grafted onto the fiber surface through propagation of the polymer from the surface radicals produced by the decomposition of the azo groups. The percentage of grafting of poly(MMA) reached 48.1% after 24 h. The graft polymerizations of other monomers, such as styrene, N-vinylcarbazole, and acrylic acid, were also initiated by the surface azo groups, and the corresponding polymer effectively grafted onto the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2121–2128, 1999     

Free-Radical Copolymerizations of N-Phenyl Maleimide

Free radical-initiated copolymerization of N-phenyl maleimide (NPMI) with styrene (St), vinyl acetate (VAc) and methyl meth-acrylate (MMA) at 35°C in benzene solution initiated by AIBN was studied. The copolymerization of NPMI and St yields a “nearly equimolecular” alternating copolymer, irrespective of monomer feed. Reactivity ratios of NPMI with St, VAc, and MMA were determined by a curve-fitting method which has the advantage of delivering values not involving personal judgement. Q₁ and e₁ values of NPMI were also calculated. Tentative explanations have been proposed to Interpret the “nearly alternating” copolymerization between NPMI and St. In addition, thermal stabilities of copolymers were studied by using a programmed thermo-gravimetric analysis technique. Copolymers of St, VAc, and MMA show a considerable increase in thermal stability with increasing content of NPMI. The glass transition temperatures of copolymers of NPMI with MMA and St were measured by differential scanning calorimetry. In both series of copolymers the glass transition temperature increases markedly with increasing in NPMI content. In the case of NPMI-St copolymers, the relative thermal stability as well as glass transition temperature also corroborated the nearly alternating behavior observed.     

Radical copolymerization of novel trifluorovinyl ethers with ethyl vinyl ether and vinyl acetate: Estimating reactivity ratios and understanding reactivity behavior of the propagating radical

Two novel trifluorovinyl ether (TFVE) monomers were copolymerized with either ethyl vinyl ether (EVE) or vinyl acetate (VAc) in a redox‐initiated aqueous emulsion: 1‐(2‐phenoxyethoxy)‐1,2,2‐trifluoroethene (Ph‐TFVE) and 1‐[2‐(2‐ethoxyethoxy)ethoxy]‐1,2,2‐trifluoroethene (Et‐TFVE). Previous studies demonstrated a propensity for radical hydrogen abstraction from the oligoether pendant group during the homopolymerization of Et‐TFVE with continued propagation of the resulting radical, thereby providing the rationale to investigate the copolymerization of our new TFVEs with EVE or VAc. Reactivity ratios were estimated using the error‐in‐variables model from a series of bulk free radical copolymerizations of Ph‐TFVE with EVE or VAc. The reactivity ratios were r_Ph‐TFVE = 0.25 ± 0.07, r_EVE = 0.016 ± 0.04; r_Ph‐TFVE = 0.034 ± 0.04, r_VAc =0.89 ±0.08. Partial hydrolysis of polymers containing VAc to vinyl alcohol (VA) resulted in two terpolymers: poly(Ph‐TFVE‐co‐VAc‐co‐VA) and poly(Et‐TFVE‐co‐VAc‐co‐VA), respectively. We investigated the possibility of hydrogen abstraction from VAc during polymerization by comparing the molar mass before and after hydrolysis. Abstraction from VAc was not apparent during polymerization; however, abstraction from the oligoether pendant group of Et‐TFVE was again evident and was more significant for those copolymers having a greater fraction of Et‐TFVE in the monomer feed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1344–1354, 2000     

Long-lived polymer radicals. IV. Reactions of poly(N-methylacrylamide) and poly(N-methylmethacrylamide) radicals with binary mixtures of vinyl monomers

N-methylacrylamide (NMAAm) and N-methylmethacrylamide (NMMAm) were polymerized to give polymer microspheres containing living propagating radicals. The microsphere polymer radicals were allowed to react with some binary mixtures of vinyl monomers including alternating copolymerization combinations. The reaction processes were investigated by ESR spectroscopy. In the poly(NMMAm) radical/methyl methacrylate (MMA)/styrene (St) system, the propagating radical from MMA was mainly observed at the higher MMA concentration, while polySt radical prevailed at the lower MMA concentration. In the poly(NMMAm) radical/α-methylstyrene (α-MeSt)/diethyl fumarate system, the α-MeSt radical was exclusively observed, while the maleic anhydride (MAn) radical was predominantly observed in the α-MeSt/MAn system. In the MAn/diphenylethylene system, the propagating radicals from both monomers were observed at comparable concentrations. The poly(NMAAm) microsphere radical behaved differently in the reaction with the MMA/St mixture. The poly(NMAAm) microsphere was found to incorporate preferentially St, leading to formation of the St radical. The St preference was enhanced in the St/cyclohexyl methacrylate (CHMA) system. These results were in agreement with those of block copolymerization via the reaction of poly(NMAAm) radical with the MMA/St or CHMA/St mixture, where the compositions of the resulting polymers were analyzed by pyrolysis gas chromatography.     

Cationic Grafting of Vinyl Polymers onto a Carbon Whisker,Initiated by Acylium Perchlorate Groups Introduced onto the Surface

Abstract

The cationic graft polymerization of vinyl monomers onto a carbon whisker, vapor-grown carbon fiber, initiated by acylium perchlorate groups introduced onto the surface, was investigated. The introduction of acylium perchlorate groups onto a carbon whisker was achieved by the treatment of a carbon whisker having acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride, with silver perchlorate in nitrobenzene. It was found that the cationic polymerization of vinyl monomers, such as styrene, indene, N-vinyl-2-pyrrolidone, and n-butyl vinyl ether, is initiated by acylium perchlorate groups on a carbon whisker. In the polymerization, the corresponding vinyl polymers were grafted onto a carbon-whisker surface based on the propagation of polymer from the surface: the percentage of grafting of polystyrene and polyindene reached 42.5 and 100.3%, respectively. The percentage of polystyrene grafting decreased with increasing polymerization temperature because of preferential chain transfer reactions at higher temperatures. Polymer-grafted carbon whisker gave a stable colloidal dispersion in a good solvent for grafted polymer.     

Graft polymerization of methyl methacrylate initiated by pendant azo groups introduced onto γ-poly(glutamic acid)

The grafting of poly(methyl methacrylate) (PMMA) onto biosynthesized γ-poly(glutamic acid) (γ-PGA) initiated by pendant azo groups introduced onto γ-PGA was performed. The introduction of pendant azo groups onto γ-PGA was achieved by the reaction of carboxyl groups of γ-PGA with azo initiators having hydroxyl or amino groups, such as 2,2-azobis[2-(hydroxymethyl)propionitrile] (AHP), 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (AMHP), and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP), using N,N′-dicyclohexylcarbodiimide. The amount of pendant AHP groups introduced onto γ-PGA was estimated to be 0.15 mmol/g. Untreated γ-PGA failed to initiate the polymerization of MMA. On the contrary, the polymerization of MMA was found to be initiated in the presence of γ-PGA having azo groups: the polymerization rate was proportional to the square root of the concentration of γ-PGA having pendant azo groups. During the polymerization PMMA was grafted onto γ-PGA; the percentage of grafting of PMMA onto γ-PGA obtained from the graft polymerization initiated by pendant AHP, AMHP, and AIP groups was evaluated to be 65.0, 53.1, and 29.0%, respectively. Differential scanning calorimetric analysis shows that the endotherm transition point of γ-PGA at 220°C disappears by the grafting of PMMA onto the polymer. © 1993 John Wiley & Sons, Inc.     

Photografting of vinyl polymers onto ultrafine inorganic particles: Photopolymerization of vinyl monomers initiated by AZO groups introduced onto these surfaces

The photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain. © 1994 John Wiley & Sons, Inc.     

Block Copolymerization of Vinyl Monomers with Macroiniferer

Abstract

Block copolymers composed of a polyether, such as poly(oxytetra-methylene), and vinyl polymers, such as polystyrene, poly(methyl methacrylate), poly(butyl acrylate), and poly(vinyl acetate), were prepared by photopolymerizations of vinyl monomers initiated with a polyether macroiniferter, α - (diethyldithiocarbamylacetyl) - ω - (diethyldithiocar-bamylacetoxy)-poly(oxytetramethylene). ESR spectroscopy and end-group analysis of diethyldithiocarbamyl indicated that block copolymers should be predominantly ABA-type copolymers. The block copolymers were characterized in detail by NMR, GPC, and DSC analysis.     

二元单体在棉纤维上的γ辐射接枝

在氮气气氛下用γ射线辐照的方法在棉纤维上接枝苯乙烯/马来酸酐、苯乙烯/甲基丙烯酸二甲胺乙酯、苯乙烯/醋酸乙烯酯二元单体. 研究了溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响, 并探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响. 结果表明决定二元接枝生成物结构比例的是二元单体的比例及其竞聚率. 接枝产物的红外、热重分析进一步佐证了竞聚率对不同二元单体体系接枝生成物结构的影响. X射线衍射结果表明棉纤维素上接枝不同的二元单体后均引起结晶度的下降, 而且结晶度随接枝率的增加而降低, 证明二元接枝反应是从纤维素无定型区通过第三相向结晶区逐步扩展的.     

Preparation and properties of biocompatible polymer-grafted silica nanoparticle

Grafting of biocompatible polymer onto the surface of silica nanoparticles was achieved by radical graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC), initiated by azo groups previously introduced onto the surface or by a system consisting of Mo(CO)₆ and trichloroacetyl groups on the silica surface. Both of these systems have the ability to initiate graft polymerization of MPC, resulting in the formation of poly(MPC)-grafted silica, but the percentage of poly(MPC) grafting for the latter initiating system was much higher than that of the former. The amount of moisture that could be adsorbed onto the silica surface was found to increase with increasing poly(MPC) grafting. This indicates that grafting of poly(MPC) onto the silica surface markedly increases the hydrophilic nature of the surface. The contact angle of water in composites prepared from poly(vinyl alcohol) and poly(MPC)-grafted silica was found to decrease with increasing poly(MPC)-grafted silica content. When poly(MPC)-grafted silica was added to water containing a small amount of chloroform, it was found to act as stabilizer for droplets of chloroform. In addition, according to tests by the Lee-White method, poly(MPC)-grafted silica shows non-thrombogenic characteristics.     

Synthesis of Vinyl Polymer—Poly (α-Amino Acid) Block Copolymers by End-Reactive Oligomers

In order to synthesize block copolymers consisting of segments having dissimilar properties, vinyl polymer - poly (α-amino acid) block copolymers were synthesized by two different methods. In the first method, the terminal amino groups of polysarcosine, poly(γ-benzyl L-glutamate), and poly(γ-benzyloxycarbonyl-L-lysine) were haloacetylated. The mixture of the terminally haloacetylated poly (α-amino acid) and styrene or methyl methacrylate was photoirradiated in the presence of Mo (CO)₆ or heated with Mo(CO)₆, yielding A-B-A-type block copolymers consisting of poly(α-amino cid) (the A component) and vinyl polymer(the B component). The characterization of block copolymers revealed that the thermally initiated polymerization of vinyl compounds by the trichloroacetyl poly(α-amino acid)/Mo(CO)₆ system was most suitable for the synthesis of vinyl polymer - poly-(α-amino acid) block copolymers. In the second method, poly (methyl methacrylate) and polystyrene having a terminal amino group were synthesized by the radical polymerization in the presence of 2-mercaptoethylammonium chloride. Using these polymers having a terminal amino group as an initiator, the block polymerizations of γ-benzyl L-glutamate NCA and e-benzyloxycarbonyl-L-lysine NCA were carried out, yielding A-B-type block copolymer. By eliminating the protecting groups of the side chains of poly(α-amino acid) segment, block copolymers such as poly(methyl methacrylate) with poly(L-glutamic acid) or poly(L-lysine) and polystyrene with poly(L-glutamic acid) and poly(L-lysine) were successfully synthesized.     

铈离子氧化还原引发体系与铈离子引发接枝或嵌段共聚合研究的新进展

本文介绍Ce⁴⁺/酰胺引发体系;Ce⁴⁺/聚酰胺、带酰苯胺侧基的聚合物引发接枝共聚合;Ce⁴⁺/氨基甲酸酯引发体系;Ce⁴⁺/聚醚氨酯引发接枝共聚合;Ce⁴⁺/羰基化合物引发体系;Ce⁴⁺引发嵌段共聚合6个方面的研究新进展.     

Vinyl Polymerization. 371. Polymerization of Methyl Methacrylate Initiated by the System of Polyvinylferrocene and Carbon Tetrachloride

The polymerization of vinyl monomers initiated with the system of polyvinylferrocene (PVFc) and carbon tetrachloride (CCl₄) was carried out in dark. Methyl methacrylate (MMA) and acrylonitrile (AN) could be polymerized, while styrene (St) was hardly polymerized under the conditions used. The polymerization proceeded through a free-radical mechanism and was concluded to be initiated by attack of vinyl monomer, having a polarized vinyl group, on the charge-transfer complex of PVFc/CCl₄. In the polymerization of MMA, the initiating ability of PVFc was much larger than that of ferrocene (Fc-H) or poly(ferrocenylmethyl methacrylate) (PFMMA) and was comparable to that of polyferrocenylenemethylene (PFM). The overall activation energy was estimated to be 34.2 kJ/mole.     

Comparison of the different emulsion polymerization routes between acrylic and vinyl acetate monomers using poly(vinyl alcohol) as the sole stabilizer

The emulsion polymerization of acrylic and vinyl acetate monomers using poly(vinyl alcohol) (PVA) as protective colloid has been studied for a long time, whereas rare reports ranged over the lateral comparison of the two systems and the reason for the unstability of the PVA/MMA polymerization system was still indistinct. Here in this paper, a collection of experiments of methyl methacrylate (MMA) and vinyl acetate (VAc) were performed respectively with varied amount of PVA as the sole stabilizer. The grafting extent of the polymerisate was characterized through the fraction and FTIR and it was found that the grafted amount of PVA was even larger in the PVA/MMA copolymers than PVA/VAc copolymers, so the grafted mode of PVA was considered. Based on the kinetics, the slower initiation rate of sulfate radical towards MMA was found to be responsible for the unstability of corresponding colloids accompanied with the relatively quicker hydrogen abstraction of radical to PVA, which resulted in “layer-by-layer” grafting structure inside and the particle surface-grafting density was lowered thereof. This was proved with TEM and static contact angle measurements and a pseudo-homopolymer model was employed to describe the relationship of colloidal stability and the PVA density on surfaces.     

Grafting onto Wool. XV. Graft Copolymerization of MA and MM A by Use of Mn(acac)3 as Initiator

Graft copolymerization of acceptor monomers MA and MMA onto Himachali wool fiber in an aqueous medium was studied by using Mn(acac)s as initiator. Nitric acid was found to catalyze the graft copolymerization. Percentage of grafting and percent efficiency have been determined as functions of the concentration of chelate, nitric acid, monomer, time, and temperature, Under optimum conditions, MMA produced a maximum grafting of 82.5% while MA afforded maximum grafting to the extent of 27.5%. Relative reactivities of MA and MMA toward grafting have been compared with those of EA, BA, and VAc reported earlier from this laboratory. Different vinyl monomers were found to follow the following reactivity order toward grafting onto wool fiber in the presence of Mn(acac)₃: MMA > EA > BA > MA > VAc. An attempt has been made to explain the observed reactivity pattern shown by different vinyl monomers in graft copolymerization reactions.     

Biobased Polymers via Radical Homopolymerization and Copolymerization of a Series of Terpenoid-Derived Conjugated Dienes with exo-Methylene and 6-Membered Ring

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, such as methyl acrylate (MA), acrylonitrile (AN), methyl methacrylate (MMA), and styrene (St), resulting in copolymers with comparable incorporation ratios of bio-based cyclic conjugated monomer units ranging from 40 to 60 mol% at a 1:1 feed ratio. The monomer reactivity ratios when using AN as a comonomer were close to 0, whereas those with St were approximately 0.5 to 1, indicating that these diene monomers can be considered electron-rich monomers. Reversible addition fragmentation chain-transfer (RAFT) copolymerizations with MA, AN, MMA, and St were all successful when using S-cumyl-S’-butyl trithiocarbonate (CBTC) as the RAFT agent resulting in copolymers with controlled molecular weights. The copolymers obtained with AN, MMA, or St showed glass transition temperatures (T_g) similar to those of common vinyl polymers (T_g ~ 100 °C), indicating that biobased cyclic structures were successfully incorporated into commodity polymers without losing good thermal properties.     

Vinyl polymerization. 410. Polymerizations of vinyl monomers initiated by poly(styrene-co-sodium acrylate) or poly(methyl methacrylate-co-sodium methacrylate). A verification of the concept of hard and soft hydrophobic areas and monomers

It was found that the copolymers of sodium acrylate (AA-Na) with styrene (St) and of sodium methacrylate (MAA-Na) with methyl methacrylate (MMA) could polymerize vinyl monomers in an aqueous phase without the usual initiator. Interestingly, there was a definite composition of the copolymer for the polymerization of a given monomer; for example, when poly(St-co-AA-Na) was used, St, MMA, vinyl acetate, ethyl acrylate, methyl acrylate, and acrylonitrile were polymerized by the copolymer having mole ratios of AA-Na:St of 0.61:0.29, 0.47:0.53, 0.38:0.62, 0.30:0.70, 0.24:0.76, and 1.00:0, respectively. The copolymers of various compositions can form hydrophobic areas (HAs) in the water phase. As has been repeatedly reported, the polymerization proceeds in the HAs, and the following new hypothesis was recently proposed that the hard (the less hydrophilic) HA prefers to incorporate the hard monomer and the soft (the less hydrophobic or the more hydrophilic) HA prefers to incorporate the soft monomer. The results mentioned above support this hypothesis.     

Ternary microemulsions of vinylic and acrylic monomers

Ternary systems consisting of sodium dodecyl sulfate (SDS) as surfactant, water and several vinyl and acrylic monomers [vinyl acetate (VAc), acrylonitrile (ACN), ethyl acrylate (EtA), butyl acrylate (BuA), 2-ethylhexyl acrylate (EHA), methyl methacrylate (MMA), butyl methacrylate (MMB) and styrene (St)] were studied. The solubilization of monomer in aqueous solutions of SDS was found to be dependent on its structure and concentration. The molar specific solubility was observed to decrease with hydrophobicity and increase with polarity of monomer, that is, it was lowest for St, EHA and highest for MMA, EtA. The NMR and fluorescence studies indicate that solubilization occurred at a different domain of the interfacial layer. The hydrophobic monomers are solubilized toward the hydrocarbon interior of the micelles whereas the hydrophilic ones, toward the hydrated tail of the surfactant. The penetration of monomers into the oil-in-water interface is limited because the screening of charged ions of emulsifier is not operative. A relationship between the persulfate initiator decomposition rate and the lability of the α-hydrogen linked to the substituted carbon of the double bond was established. The initiator productivity was the highest for MMA (lacking such α-hydrogen) and the lowest for VAc and St, the monomers in which the C-H_α bond is the most reactive.     

Radical Graft Polymerization of Vinyl Monomers Initiated by A20 Groups Introduced Onto a Carbon Black Surface: Effect of azo Groups on Graft Polymerization

The radical graft polymerization of vinyl monomers from carbon black initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto carbon black surface was achieved by three methods: the reaction of 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP) with (1) epoxide groups, which were introduced by the reaction of carbon black with chlorometh-yloxirane; (2) acyl chloride groups, which were introduced by the reaction of carboxyl groups on the surface with thionyl chloride; and (3) 3-chloroformyl-1-cyano-1-methylpropyl groups, which were introduced by the reaction of carbon black with 4,4′-azobis(4-cyanovaleric acid) and then thionyl chloride. The amount of azo groups introduced onto the surface by the above methods was determined to be 0.07-0.19 mmol/g. The graft polymerization of methyl methacrylate was found to be initiated by azo groups introduced onto the carbon black surface. During the polymerization, poly(methyl methacrylate) was effectively grafted onto carbon black through propagation of the polymer from the radical produced on the surface by the decomposition of the azo groups. The percentage of grafting using carbon black having azo groups introduced by method 1 increased to 40%. It was also found that the graft polymerization of several vinyl monomers such as styrene, acrylonitrile, and acrylic acid was initiated by the azo groups introduced onto the surface and the corresponding polymer was effectively grafted onto the surface. Furthermore, the effect of the amount of carbon black having azo groups on the graft polymerization was investigated.