Heterophase polymerization of styrene in the presence of organosilicon compounds of various natures

The heterophase polymerization of styrene has been carried out in the presence of surfactants—organosilicon compounds with different solubilities in aqueous and styrene phases and surface activities at the interface. It has been demonstrated that the stability of polymer suspensions prepared with water-insoluble organosilicon compounds is much higher than that in the presence of organosilicon surfactants soluble in organic and aqueous phases. In the former case, suspensions with narrower particle-size distributions are produced. The stability of polymer microspheres prepared at various monomer-to-water volume ratios has been tested. An increase in the monomer concentration above 25 vol % leads to the loss of system stability.     

Polymerization of styrene in the presence of monoesters of aromatic dicarboxylic acids as surfactants

The colloidal properties of monoesters of aromatic dicarboxylic acids and the heterophase polymerization of styrene in their presence have been studied. It has been shown that particles are formed from micro-droplets of the monomer. A high stability of polymer suspensions during the synthesis has been found to be provided by a strong interfacial adsorption layer formed on the surface of particles from the polymer being synthesized and a surfactant.     

Polymerization of styrene in presence of masticated rubber

The influence of the concentration of hydroperoxide (peroxide) groups in rubber (formed during mastication) and the influence of concentration of rubber on the polymerization of styrene were studied at 95, 105, 115 and 130°. The retardation effect of rubber (or non-rubber ingredients) is also due to the participation of less reactive (allylic) radicals from rubber on the termination. The derived kinetic relations allows calculation of a complex constant B* and the rate constant of decomposition of -OOH groups of rubber (k_d) at various temperatures; the latter are essentially smaller than those in masticated rubber. From kinetic analysis of experimental results, it follows that, during the polymerization of styrene in the presence of rubber, two types of rubber radicals can be formed, viz. a less reactive allylic radical and a more reactive alkyl radical.     

Polymerization of styrene in the presence of nitroxide radicals of the dihydroimidazole series

2,2,5,5-Tetramethyl-4-phenyl-2,5-dihydroimidazole-1-oxyl and 2,2,5,5-tetramethyl-4-phenyl-2,5-dihydroimidazole-3-oxide-1-oxyl have been used as regulators of chain growth in the free-radical polymerization of styrene. It has been shown that the compounds of the dihydroimidazole series function as new living polymerization agents and allow the synthesis of polymers with low polydispersity coefficients and desired molecular masses.     

Polymerization of acrylamide in various solvents in the presence of Lewis acids

The radical polymerization of acrylamide in various solvents in the presence of Lewis acids has been investigated. Considerable effects of LiBr, LiCl and CaCl₂ on the total reaction rate and the values of k_p and k₁ for polymerization in DMSO or THF have been shown. For the polymerization of acrylamide in aqueous solution, addition of the salts does not affect the kinetic behaviour of the process. The observed effect of salts arises from complexation between the salt and the monomer and/or the propagating radicals.     

Modification of styrene polymer with organosilicon groups

The homopolymer of 4‐chloromethylstyrene (P1) and its copolymers with styrene (in various mole ratios) were synthesized by bulk and solution free radical polymerizations, respectively, at 70 ± 1°C using α,α′‐azobis(isobutyronitrile) as an initiator. Lithiation of these soluble polymers in THF at −78°C was done and reacted with electrophiles such as tert‐BuMe₂Si, Et₃Si, and Me₃SiCH₂ in the presence of 4,4′‐di‐tert‐butylbiphenyl (DTBB) as a catalyst to produce modified polystyrene. In the other way, trimethylsilylmethyl lithium substitute as a nucleophile was covalently linked to the homopolymer and copolymer. The polymers were characterized by IR, ¹H NMR, ¹³C NMR, differential scanning calorimetry (DSC), and gel permeation chromatography. DSC showed that incorporation of silyl substitute in the side chains of homopolymer and copolymers increases the rigidity of the polymers and, subsequently, their glass transition temperature. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:414–420, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20314     

Polymerization of methyl methacrylate and styrene in the presence of polyimides containing aliphatic moieties in the backbone

The radical homopolymerization of methyl methacrylate and styrene in the presence of polyimide that contains aliphatic moieties and is dissolved in the monomer is studied. The viscosity characteristics, heat resistances, and thermal stabilities of the resulting polymers and their solubilities in organic solvents are examined. It is found that the products of radical polymerization are polyimide-poly(methyl methacrylate) and polyimide-polystyrene copolymers, whose properties differ from those of the respective unmodified polymerization and polycondensation polymers.     

Polymerization of styrene miniemulsions

Polymerization of styrene miniemulsions, prepared using a mixed emulsifier system comprising sodium lauryl sulfate and cetyl alcohol, was carried out using both water-soluble (potassium persulfate) and oil-soluble [2,2′-azobis-(2-methyl butyronitrile)] initiators. The effects of variation of initiator concentration, polymerization temperature, and added inhibitor on the kinetics and particle-size distributions were investigated to obtain more quantitative evidence concerning the locus of polymerization in miniemulsion systems. Experimental results for the kinetics and particle-size distributions clearly showed that monomer droplets became the main source of polymer particle formation. This was attributed to the fact that stable emulsions with droplet diameters in the range of 0.05 to 0.15 μm were produced using this mixed-emulsifier system. In this size range, droplet initiation could effectively compete with other mechanisms due to their large surface area. Their size was indeed similar to the corresponding latex particle size obtained after polymerization.     

Electroless deposition of Ni-P-nano-ZrO2 composite coatings in the presence of various types of surfactants

Ni-P-nano-ZrO(2) coatings were produced using the electroless deposition technique. To prevent agglomeration of zirconia nanoparticles in the plating bath, various surfactant additives (anionic, cationic, and nonionic) were used. The most stable bath was obtained with the addition of dodecyltrimethylammonium bromide (DTAB). The impact of this surfactant on the deposition rate, coating composition, and topography, as well as ζ potential of particles, was examined. Surface morphology and composition of the Ni-P-nano-ZrO(2) composite coatings was analyzed by various techniques including scanning electron microscopy (SEM) equipped with in situ energy-dispersive X-ray (EDX) spectroscopy. Coatings with a clearly greater amount of zirconia (21.88-22.10 wt.%) were obtained from baths containing DTAB in concentrations equal to or above its critical micelle concentration (cmc). For these surfactant concentrations, the reduction of Ni and P content was observed.     

Thermokinetics evaluation and simulations for the polymerization of styrene in the presence of various inhibitor concentrations

Styrene is an important commodity chemical that is globally applied in various polymerization processes. The aim of this study was to obtain integrated thermokinetics and safety parameters for polymerization of styrene. We mainly used differential scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative methods to investigate thermal polymerization of styrene and styrene containing various levels of 4-tertiary-butylcatechol (TBC). The results obtained included the rate constant (k), reaction order (n), apparent activation energy (E _a), frequency factor (A), and so on, from various DSC curves and simulative methods. From DSC curves, the exothermic onset temperature (T ₀) was about 105 and 132°C for styrene and styrene containing 10 ppm TBC. On the other hand, the test results from TAM indicated that styrene polymerization displays an autocatalytic phenomenon from 50–85°C. By means of this study, the intrinsic safety of a system for styrene during transportation and storage could be established.     

Studies of the polymerization of diallyl compounds. XI. Polymerization of styrene in the presence of diallyl compounds

Radical polymerization of styrene in the presence of various diallyl compounds was carried out at 60°C, with the use of 2,2′-azobisisobutyronitrile as an initiator. The chain transfer constant C_s of the styryl radical to diallyl compounds was determined graphically by solving the Mayo equation. The C_s values of diallyl esters are quite small compared to those of diallyl acetals. The polymerization mechanism of styrene in the presence of diallyl compounds was also discussed in connection with the results obtained previously.     

Polymerization of styrene and methyl methacrylate in the presence of 2,2-diethyl-4,5,5-trimethyl-2,5-dihydroimidazol-1-oxyl

The polymerization of styrene and methyl methacrylate in the presence of 2,2-diethyl-4,5,5-trimethyl- 2,5-dihydroimidazol-1-oxyl has been studied. It has been demonstrated that the nitroxyl radical makes it possible to control chain propagation in the polymerization of styrene and to synthesize polymers with relatively low polydispersity coefficients (<1.4). The polymerization of methyl methacrylate in the controlled mode cannot be performed because of the occurrence of a side reaction related to hydrogen atom transfer.     

Cyclic acetal-photosensitized polymerization. II. Photopolymerization of styrene in the presence of various monocyclic acetals

The polymerization of styrene (St) in benzene solution in the presence of 1,3-dioxane (DON), 1,3-dioxepane (DOP), trioxane (TRON), or tetraoxane (TEON) by means of photoirradiation of the system at 40°C has been studied kinetically from the standpoint of photosensitized polymerization. The rate of photosensitized polymerization R_p increased in the order: DOP < DON < TRON < TEON, as shown by the rate constant of decomposition of cyclic acetals, and then could be expressed by R_p = k[monocyclic acetal]^0.5[St]^1.0. The polymerization was confirmed to proceed via a radical mechanism.     

Polymerization of styrene in N,N-dimethylformamide

The polymerization of styrene in N,N-dimethylformamide (DMF) at 60°C has been studied both in the presence and absence of 4,4′-azobis-4-cyanopentanoic acid (ACV). Rates of polymerization were measured dilatometrically and gravimetrically, and degrees of polymerization were determined viscometrically. There was some discrepancy in the values of the transfer constant to DMF, C_s, obtained by analysis of the results. The most reliable value appeared to be 9.8 × 10^?6, from experimental data obtained in the absence of added ACV.     

Free-radical polymerization of methyl methacrylate in the presence of a ferrocenyl-containing iron(II) clathrochelate complex and initiators of various natures

Benzoyl peroxide-, lauryl peroxide-, and AIBN-initiated free-radical polymerization of methyl methacrylate has been studied in bulk and solution in the presence of macrobicyclic iron(II) bis(ferrocenyl borate) tris(nioximate). It has been found that the ferrocenyl-containing iron(II) clathrochelate forms efficient initiating systems with peroxides, whereas, in the case of AIBN, its presence has no effect on the kinetic parameters of the process and the properties of the resulting polymer. The use of clathrochelate complex-peroxide initiator systems accelerates the polymerization of methyl methacrylate and decreases the molecular mass of the polymer. The kinetic parameters of the process have been determined.     

Polymerization of styrene in the presence of carboxyl-containing polydimethylsiloxane and its mixture with oxyethylated poly(propylene glycol)

The effect of synthesis conditions, such as the phase and concentration ratios of components, on the mechanism of styrene polymerization in the presence of the water-insoluble organosilicon surfactant α,ω-bis(10-carboxydecyl)polydimethylsiloxane and its mixture with the nonionic surfactant Pluronic F-68 is studied.