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1H n.m.r. relaxation data, determined via either wide-line 1 H n.m.r. or high-resolution solid-state 13 C n.m.r., were used to analyse the existence and extent of interphasic regions in dimethylsiloxane-styrene block copolymers. Results thus obtained have shown that copolymers having very short blocks possess relatively large interphases characterized by intermediate mobility...
In the copolymerization of styrene-butadiene and styrene-isoprene, a novel rare earth catalyst system (CF 3 CO 2 ) 3 Ln/R 3-n AlH n /(CH 3 ) 3 CCH 2 Br (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; R = Me-, Et-, i-Bu-, and Oct-; n = 0 and 1) has been studied. The 1,4 unit contents in the copolymers obtained...
Network formation during copolymerization of styrene with a model bismaleimide, p-maleimidobenzoic anhydride, or with mixtures of p-maleimidobenzoic anhydride and methyl p-maleimidobenzoate was studied. The concentrations of pendent double bonds in copolymers, calculated from the consumption of monomers and copolymer composition, follow the general trend typical for vinyl-divinyl copolymerizations...
The rate of monomer loss during the n-butyllithium-initiated anionic polymerization of styrene in ethylbenzene has been measured using Raman spectroscopy. Gel permeation chromatography measurements on the reaction products have been used as an indirect method of obtaining the concentrations of the propagating species involved in the reaction. The rate of propagation for styrene polymerization has...
The concept of the critical chain length for radical entry Z was used for modelling the rate of carboxylation between the particle surface and particle core. An average Z value was computed by a semi-empirical method from the individual Z values for homopolymers. Grafted, buried and water soluble polymerized acid could be computed as well as the molecular weight of the grafted and water soluble...
The initiation steps in the copolymerization of styrene and acrylonitrile with t-butoxyl radicals have been investigated using the nitroxide trapping technique. t-Butoxyl radicals add to styrene five times more rapidly than to acrylonitrile whereas methyl radicals, formed by β-fragmentation of t-butoxyl radicals, add to acrylonitrile about four times faster than to styrene. Acrylonitrile also reacts...
The mixed SDS/NP-40 (anionic/nonionic) surfactants were used to examine the generality of Smith-Ewart theory which was originally proposed for emulsion polymerization systems containing anionic surfactants. Our results are consistent with Smith-Ewart theory only when the wt% of NP-40 in the surfactant mixture ([NP-40]) is less than 30%. However, the reaction system deviates from Smith-Ewart theory...
High temperature, polymeric, structural foams were prepared using a high internal phase emulsion (HIPE) to copolymerize styrene with maleimide based monomers. In this work, N-ethylmaleimide and a bismaleimide (BMI) monomer, bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane, were successfully free-radically copolymerized with styrene in a water-in-oil HIPE to produce polymeric foams with glass transition...
Monomer reactivity ratios in free radical copolymerization of styrene and butyl acrylate monomers at 80°C in toluene solution under reduced pressure were determined for low and high conversions. Mayo-Lewis, Finemann-Ross, inverted Finemann-Ross, Kelen-Tudos, extended Kelen-Tudos, Tidwell-Mortimer and Mao-Huglin methods for low conversion and extended Kelen-Tudos and Mao-Huglin methods for high conversion...
An examination has been made of the effects of 1-phenyl-1-propene, (β-methylstyrene) (BMS), 3-phenyl-1-propene (allylbenzene) (AB), 1,2-diphenyl-1-propene (1,2-DPP) and 1,3-diphenylpropene (1,3-DPP) on the radical polymerizations of methyl methacrylate (MMA) and styrene (STY) at 60°C. Transfer constants have been found by the method depending on analyses of polymers for end-groups derived from the...
This paper deals with the effects of initiator concentration ([I]) on the styrene (STY) emulsion polymerisation stabilised by the mixed anionic/nonionic surfactants, sodium dodecyl sulfate (SDS)/nonylphenol polyethoxylate with an average of 40 ethylene oxides per molecule (NP-40). The reaction system stabilised only by SDS ([NP-40] = 0 wt%) results in an increase in the rate of polymerisation (R ...
Electron spin resonance (e.s.r.) spectroscopy should be useful for the measurement of propagation rate coefficients (k p ) in free radical polymerisations, since the propagating radical concentration can be directly observed. However, in previous studies, k p values have generally been inconsistent, and disagreed with data from other accepted experimental techniques, such as pulsed...
Diblock and triblock copolymers were synthesized, under standard conditions, by sequential anionicpolymerization of styrene and 2,3-epoxypropyl methacrylate or glycidyl methacrylate (GMA). In both cases, suitable initiators were selected. The ‘living’ carbanions originating from the polymerization of styrene are able to attack GMA. The reverse reaction (attack of styrene monomer by poly (glycidyl...
Relatively stable styrene (ST) miniemulsions were prepared by using a water-insoluble, low molecular weight blue dye as the cosurfactant. The data of the monomer droplet size, creaming rate and phase separation of the monomer as a function of time, were used to evaluate their shelf stability. The dye concentration in toluene can be determined by UV absorbance at 678 nm. This makes the dye molecule...
UNIFAC--group contribution method for determination of local monomer concentrations and the simplex method for determination of reactivity ratios were used to describe the terminal and penultimate models of copolymerization in the styrene-acrylonitrile monomer system in bulk at 333.15 K. Results show that the procedure is applicable for prediction of the kinetic behaviour of the comonomer pair. ...
The influence of three N-substituted maleimides on the processing, thermal, and mechanical performance of high internal phase emulsion (HIPE) polymerized foams are investigated. N-propylmaleimide, N-butylmaleimide, and N-cyclohexylmaleimide were copolymerized with styrene and crosslinked with either divinylbenzene or bis(3-ethyl-5-methyl-4-maleimide-phenyl)methane in a HIPE polymerization process...
The synthesis of poly(styrene-dimethylsiloxane) block and graft copolymers is described. Commercially available difunctional poly(dimethylsiloxane) (PDMS) containing either vinylsilyl or hydrosilyl terminal species was reacted with the corresponding hydrosilyl or vinylsilyl attachable initiators containing the benzyl chloride species. The attachment of the initiators to PDMS was achieved by hydrosilation...
The reaction of DNBP (2,4-dinitro-6-sec-butylphenol) with toluene, ethylbenzene or styrene and tert-butylperoxide at 110°C leads to 7-sec-butyl-5-nitro-2-phenylbenzoxazole. This benzoxazole was also detected in the residues of an industrial styrene fractionation still in which DNBP was routinely used as the polymerisation retarder. The formation of this product from either ethyl benzene or from...
The use of reactive solvents provides a unique opportunity to extend the processing characteristics of both intractable and standard (tractable) polymers beyond existing limits. The polymer to be processed is dissolved in the reactive solvent (monomer) and the solution is transferred into a mould. Upon polymerisation, phase separation and phase inversion occur and the originally dissolved polymer...
An extensive model is given for the particle size distribution (PSD), particle number, particle size and amount of secondary nucleation in emulsion polymerisations. This incorporates what are thought to be all of the complex competing processes: aqueous phase kinetics for all radical species arising from both initiator and from exit (desorption), radical balance inside the particles, particle formation...
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