Cationic polymerization of vinyl monomers initiated by 10-methylphenothiazine cation radicals

A small quantity of 10-methylphenothiazine cation radical (MPT^.+), electrochemically prepared and stocked in acetonitrile solution, initiated cationic polymerizations of n-butyl, t-butyl, and 2-methoxyethyl vinyl ethers and p-methoxystyrene, while no initiation occurred for phenyl vinyl ether, styrene, methyl methacrylate, and phenyl glycidyl ether. ¹H-NMR studies of oligomers and low molecular weight compounds isolated from the reaction mixture for the polymerization of t-butyl vinyl ether in the presence of a small amount of D₂O indicated that electron transfer from the monomer to MPT^.+ was involved in the initiation step. ¹H- and ¹³C-NMR and MO calculation implied that monomers with higher electron densities on the vinyl groups and with lower ionization potentials were more susceptible to the initiation of MPT^.+. © 1994 John Wiley & Sons, Inc.     

Cationic polymerization of styrene initiated by phosphorus oxychloride

Cationic polymerization of styrene (St) initiated by phosphorus oxychloride was carried out at 30° in dichloromethane and nitrobenzene. The rate of polymerization was proportional to (POCl₃) and (St)². The degree of polymerization of the polymer decreased with increasing conversion in the range beyond 30% and increased with increasing (St) although it was independent of (POCl₃) in both solvents. The rate and the degree of polymerization were enhanced with increasing dielectric constant of the mixed solvent composed of C₆H₅NO₂, CH₂Cl₂, and benzene. Addition of water revealed a cocatalytic effect in both systems. The molecular weight distribution (MWD) of the polymer was studied.     

Kinetics of polymerization of vinyl monomers initiated by lead tetraacetate

A systematic study of the thermal polymerization of α-chloroacrylic acid and α-bromoacrylic acid in aqueous nitric acid was carried out. The effect of variation of monomer concentration lead tetraacetate concentration, hydrogen ion concentration, ionic strength, and temperature on the rate of monomer disappearance was carried out. Based on the experimental observations, suitable reaction schemes were proposed for the polymerization of the above monomers. The rate constants and the thermodynamic parameters were evaluated.     

Radical polymerization of vinyl monomers initiated by a mono-captodatively substituted ethane

Homopolymerization of styrene and methyl methacrylate was carried out at 60–130°C in the presence of a mono-captodatively (cd) substituted ethane bearing nitrile and ethylsulfenyl substituents on the same carbon atom. It was found that the cd-ethane accelerated both styrene and methyl methacrylate polymerizations with no induction period, but the polymerization mode of methyl methacrylate was different from that of styrene. The polymerization rate of styrene was proportional to the 0.46th power of the cd-ethane concentration. However, the cd-ethane produced a reversible radical termination in the case of methyl methacrylate. The mechanism of both polymerizations is discussed in terms of the kinetic and ESR data. © 1996 John Wiley & Sons, Inc.     

Polymerization of vinyl monomers initiated by organoaluminium compounds/benzoyl peroxide systems

The free-radical polymerization of methyl methacrylate (MMA) initiated by systems comprizing benzoyl peroxide (BPO) and different organoaluminium compounds (OACs) has been studied. The influence of the type of OAC, concentration of components of the initiation system, temperature, and time on the reaction yield have been determined. Systems containing BPO and diethylaluminium chloride (Et₂AlCl) have been found to enable us to obtain, in high yields at room temperature, of homopolymers of MMA, methyl acrylate, acrylonitrile (AN), vinyl acetate, and the alternating AN/styrene (St) copolymer; they are, however, not very active in the homopolymerization of St and vinyl chloride. Factors affecting the polymerization yield have been discussed in terms of the mechanism of the reaction between BPO and OACs, reactivity of alkyl radicals formed in these systems, and catalytic effect of OAC in the propagation step.     

Anionic graft polymerization of vinyl monomers initiated by metallized aromatic rings of graphite powder

Anionic graft polymerizations of methyl methacrylate (MMA) and styrene from graphite powder initiated by metallized aromatic rings on the surface were investigated. Metalation of the surface was achieved by the reaction of polycondensed aromatic rings of graphite withn-butyllithium (BuLi) in N,N,N,N-tetramethylethylenediamine (TMEDA) or hexamethylphosphorous triamide (HMPT) at 0 °C., Anionic polymerizations of MMA and styrene were initiated by metallized graphite, and these polymers were grafted onto the surface. The conversion and percentage of grafting increased by increasing the amount of BuLi used for metalation. When 0.20 g of graphite was treated with 0.4–0.5 mmol of BuLi in TMEDA, the percentage of grafting of PMMA and polystyrene reached the maximum value: PMMA 52.8% (PMMA/graphite =0.528 g/1.0 g) and polystyrene 37.2% (polystyrene/graphite=0.372 g/1.0 g). Grafting of polymers was also confirmed by infrared spectra. Although no metalation of graphite proceeded in toluene, graphite could be metallized even in toluene by the addition of crown ether as a complexing cation agent. The stability of graphite powder in organic solvent dispersion was found to be improved remarkably by grafting of polymer onto the surface.     

Cationic graft copolymerization of styrene onto poly(vinyl chloride) initiated by phosphorus trichloride

The effect of some organic halides on the cationic polymerization of styrene (St) initiated by phosphorus trichloride (PCl₃) was studied to clarify the initiation mechanism on the cationic polymerization. Addition of organic halides caused an acceleration to some extent. Further, cationic graft copolymerization of St onto poly(vinyl chloride) and polychloroprene was carried out. In each case, grafting efficiency was lower than 10%. These results in the cationic polymerization of St by PCl₃ in nitrobenzene support the assumption that the initiation step is caused by the dissociation of two molecules of PCl₃ to ion pairs.     

Cationic polymerization of redox monomers derived from monoethanolamine vinyl ether and various quinones

Cationic polymerization of redox monomers derived from monoethanolamine vinyl ether and various chlorinated quinones in aqueous-organic solutions in the presence of HCl was studied. Optimal reaction conditions were found, and the kinetic characteristics of the reactions were calculated.     

Enzymatic polymerization of vinyl monomers

The possibility of using horse radish peroxidase as a catalyst for polymerization of monomers (vinylformamide and sodium vinylsulfonate) in the presence of hydrogen peroxide and 2,4-pentanedione in aqueous medium at room temperature was studied.     

Sulfur-containing vinyl monomers. XIII. Cationic copolymerizations of vinyl sulfides with some vinyl monomers

Cationic copolymerizations of vinyl sulfides (VS) with some vinyl monomers with boron tri-fluoride-diethyl etherate catalyst were investigated to evaluate their monomer reactivities. The effects of VS on the copolymer yield and viscosity of the resulting copolymers revealed the inhibition or retardation mechanism which was explained in terms of the formation of a stable vinylsulfonium salt by the reaction between a propagating carbonium ion and VS monomer. From the results of copolymerizations of phenyl vinyl sulfide (PVS) with isobutyl vinyl ether (IBVE), β-chloroethyl vinyl ether (CEVE), α-methylstyrene (α-MeSt), and styrene (St), the relative reactivities of these monomers were found to be in the following order: IBVE > CEVE > PVS > α-MeSt > St. The relatively higher reactivity of PVS than St derivatives was explained on the basis of the conjugative and electron-donating nature of the VS monomer. The effects of alkyl and para-substituted phenyl groups in vinyl sulfides on their reactivities toward the propagating carbonium ion were correlated with polar factors and compared with those of the hydrolysis of α-mercaptomethyl chlorides. The transition state for the propagation reaction in cationic polymerization of VS was proposed to be a π-complex type structure.     

Cationic polymerization of vinyl compounds in the presence of tetra-n-butylammonium salts

The effects of salts were examined in cationic polymerization of vinyl compounds. Cationic polymerization of styrene was carried out at 0°C, with acetyl perchlorate, stannic chloride, stannic chloride–trichloroacetic acid and boron trifluoride etherate as catalysts. Tetra-n-butylammonium perchlorate, fluoroborate and iodide were used as salts. The presence of small amounts of the salts changed both the polymerization rate and the molecular weight of polymer considerably. The consideration of various effects led to the conclusion that the results are explicable principally on the basis of counterion exchange. To confirm this, the copolymerization of 2-chloroethyl vinyl ether with γ-methylstyrene was investigated at ?78°C. The copolymer composition curve when stannic chloride was used as catalyst was changed and coincided with that of polymer obtained with acetyl perchlorate catalysis when the perchlorate salt was added. This supports the concept of counterion exchange.     

Anionic polymerization of methacrylate monomers initiated by lithium dialkylamides

The anionic polymerization of methacrylate monomers has been investigated with lithium dialkylamides as initiators in THF and toluene, respectively. Theoretical arguments and previous studies of mixed aggregates of lithiated organic compounds support the complexity of these systems. Lithium diisopropylamide (LDA) shows the highest initiation efficiency (e.g., f = 75% in THF at −78°C). Interestingly enough, lithium chloride has a remarkable beneficial effect on the methacrylates polymerization in THF at −78°C, due to the formation of 1 : 1 mixed dimer with LDA, which promotes a well-controlled anionic polymerization (M_w/M_n = 1.05) with a high initiation efficiency (94%). The less bulky lithium–diethylamide (LDEA) is much less efficient (f = 26%), essentially as a result of some associated “dormant” species and side reactions on the carbonyl group of MMA. Although various types of ligands have been screened, no remarkable improvement of LDEA efficiency has been observed. Lithium bis(trimethylsilyl)amide (LTMSA) has also been used to increase the steric hindrance of the initiator. This compound is, however, unable to initiate the methacrylates polymerization, more likely because of a too low basicity and a too strong Li—N bond. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3637–3644, 1997     

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.     

Preparation and polymerization of some vinyl monomers containing the 1,3-dioxolane group

The synthesis and structure determinations of (2,2-dimethyl-1,3-dioxolan-4-yl)-methyl acrylate, 4-(2,2-dimethyl-1,3-dioxolan-4-yl)methyl itaconate, and [(2,2-dimethyl-1,3-dioxolan-4-yl)methyl] methyl fumarate are described. Reactivity ratios in the copolymerization of these monomers with other comonomers are reported and the Alfrey-Price Q and e values calculated. The post-polymerization study of the effects of ultraviolet light and heat on these polymers and copolymers is presented. The 1,3-dioxolane group when appended to the polymer chain performs as an internal ultraviolet sensitizer. A mechanism is offered to explain the crosslinking behavior of these polymers when treated with ultraviolet light.     

Cationic polymerization of isobutyl vinyl ether initiated with transition‐metal ate complexes

The cationic polymerization of isobutyl vinyl ether was examined with transition‐metal ate complexes with trityl cation as initiators. The initiators were generated by the reaction of triphenylmethyl chloride [trityl chloride (TrCl)] with ate complexes of Nb, Mo, and W with lithium cation, which were obtained in situ by the reaction of the transition‐metal halides with anionic reagents (organolithium or lithium amide). When the polymerization was initiated with a mixture of TrCl and Li⁺[NbH₅(NnBuPh)]^?, the resulting poly(isobutyl vinyl ether)s had narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.13–1.20). Although the polymerization was supposed to be initiated by the electrophilic attack of the trityl cation, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the resulting poly(isobutyl vinyl ether)s revealed the presence of H at the α‐chain end. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2636–2641, 2006     

Photoinitiated polymerization of vinyl monomers by benzophenone t-butyl peresters

Benzophenone peresters undergo efficient photodecomposition when irradiated at 366 nm. This article reports peresters derived from benzophenone p,p′-dicarboxylic acid 1 which may produce radicals at two different centers in the same molecule. These peresters represent a unique new example of an efficient photoinitiator for acrylate and styrene polymerization.      

Kinetics of polymerization initiated by peroxides containing heterocyclic groups. I. Kinetics of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide

The rate and degree of bulk polymerization of styrene and vinyl acetate initiated by difuroyl peroxide and, for comparison, by dilauroyl and dibenzoyl peroxides were measured at several temperatures as a function of the initiator concentration. Also the rates of initiation were determined by the inhibition method with Banfield's radicals. The rate of polymerization initiated by difuroyl peroxide appears to be lower than could be expected from the rate of initiation determined by the inhibition method and from the decomposition of difuroyl peroxide. In the case of polymerization of vinyl acetate there are significant deviations from the proportionality between R_p and the square root of the initiator concentration, which follows from the conventional kinetic scheme. The degrees of polymerization are also low, and the plots of P _n^?1 versus R_p are not linear. These deviations can be accounted for by postulating a retardation effect of the furan cycle and chain transfer to difuroyl peroxide.