Jaroslav Bartoň

Microemulsion Radical Polymerization of Alkyl Acrylates

The oil/water microemulsion polymerizations of alkyl (methyl (MA), ethyl (EA), butyl (BA), hexyl (HA) and 2-ethylhexyl (EHA)) acrylates initiated by a water-soluble (ammonium peroxodisulphate (APS)) initiator were investigated. The rate of polymerization versus conversion curve shows two inconstant intervals. The maximum rate of polymerization of MA, EA, BA and EHA is found to be proportional to the 0·53, 0·17, 0·46 and 0·59 powers of the APS concentration and to the first power of the monomer (MA, BA and EHA) concentration. Homogeneous (solution) radical polymerization is operative in the MA, BA and EHA systems. The strong rate dependence on the EA monomer concentration is assumed to be caused by both the polymerization within the micelle core and the gel effect. The particle size was observed to increase with conversion in the EA and BA runs and to decrease in the EHA and HA runs. The number of particles increased with conversion during the whole polymerization. The polymer particles grow by recruiting monomer and emulsifier from the free monomer-swollen micelles and dead particles.

Preparation of partly hydrophobized, crosslinked polyacrylamide particles by terpolymerization of acrylamide/ N,N-methylenebisacrylamide/styrene in inverse microemulsion

Free-radical polymerization of a termonomer system comprising acrylamide (AAm) N,N ′-methylenebisacrylamide (MBAAm) and styrene (S) initiated by water-soluble ammonium peroxodisulphate (APS) or by toluene-soluble dibenzoyl peroxide (DBP) in inverse microemulsion (toluene/S/AOT//water//AAm/MBAAm), leads to the formation of partly hydrophobized crosslinked polymer particles of tailored chemical composition, degree of crosslinking and polymer particle size. Styrene strongly decreases the rate of terpolymerization, while the presence of MBAAm has almost no effect on the polymerization rates observed. This conclusion is valid for both APS and DBP initiators. Increase of the S/T mass ratio (T is toluene) in inverse microemulsion leads to an increase of polymer particle diameter from about 20 nm to about 50 nm attributed to toluene swelling of the styrene-rich structural moieties of AAm-co-S copolymer located on the surface of polymer particles. Polymerization kinetics measurements pointed to the important role of exiting water soluble AAm and MBAAm monomer radicals generated by thermal decomposition of APS in water pools of inverse micelles for initiation of polymerization reactions of sparingly water-soluble S monomer in the oil-phase of the inverse microemulsion. It was shown that the polymerization and copolymerization reactions of S in the presence of AAm and/or MBAAm are effectively initiated by water-soluble APS and also by oil-soluble DBP initiators. During dialysis the polymerized single-phase water/oil Winsor IV inverse microemulsion gradually converts itself into a two-phase oil/water Winsor I dispersion system with volume fraction of aqueous phase Φaw ≈ 0.950. The water phase contains water swelled, crosslinked polymer particles of diameters 80–300 nm. During dialysis, toluene and the sodium salt of bis(2-ethyl hexyl)sulphosuccinic acid (AOT) partition between the oil phase of the dialysed dispersion system and the water dialysate. After evaporation of water from the dialysed inverse microemulsion, solid, dried, crosslinked polymer particles in the form of a transparent film, almost uncontaminated by AOT surfactant, were obtained. © 2000 Society of Chemical Industry

Aqueous polymerization of vinyl monomers in the presence of surfactants, 1. Acrylamide

The kinetics of the polymerization of acrylamide initiated by potassium peroxodisulfate in water were studied in the presence of the anion-active emulsifier sodium dodecylphenoxybenzenedisulfonate. The emulsifier was found to affect the relative molecular mass of polyacrylamide, but it showed no effect on the rate of polymerization. The transfer constants to the emulsifier and the initiator were determined and amounted to of 3,6 · 10−3 and 5 · 10−3. The ratio of rate constants of termination and propagation kt / kp2 = 6,9 · 10−2 mol · dm−3 · s, determined for the polymerization of acrylamide in the presence of the emulsifier, is almost identical with the value for the polymerization without emulsifier. Thus, propagation and termination reactions of the potassium peroxodisulfate initiated polymerization of acrylamide in water are not influenced by the emulsifier.

Inverse microemulsion polymerization of oil-soluble monomers in the presence of hydrophilic polyacrylamide nanoparticles

A new method for preparation of modified polymer particles in two steps was proposed. Free radical polymerization of an oil soluble vinyl monomer like butyl acrylate in inverse microemulsion containing polyacrylamide particles led to the formation of modified, partly hydrophobized, polyacrylamide particles. For the first step of the process (preparation of polyacrylamide particles in inverse microemulsion) is typical a very high polymerization rate while for the second step (polymerization of an oil soluble monomer (methyl acrylate,ethyl acrylate, butyl acrylate 2-ethylhexyl acrylate, methyl methacrylate, styrene) in the presence of polyacrylamide particles in inverse microemulsion, the reverse is true. The polymerization of an oil soluble monomer in some instances leads to the formation of 2- phase or even 3-phase disperse systems. The polymeric products obtained after precipitation of the polymer particles from the inverse microemulsions by ethanol were extracted by water and/or toluene and analyzed for acrylamide content The separated polymer product contained high content of acrylamide, AAm/oil soluble monomer (butyl acrylate BA, or styrene, S) copolymer (85 % of AAm/BA, ≃ 99 % of AAm/S) besides relatively small amounts of homopolymers of oil soluble monomers (15 % of BA, ≃ 1 % of S homopolymers).

Polymerization of vinyl monomers in separated Winsor II (w/o) and Winsor I (o/w) microemulsion phases. Part 1: preparation and characterization of polymerizable vinyl-monomer-containing microemulsions

Classical toluene-based (w/o, water in oil) single-phase Winsor IV inverse microemulsions containing toluene/(sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/acrylamide (AAm)/sodium dodecyl sulphate (SDS) and containing, besides AAm, also an oil-soluble vinyl monomer (butyl acrylate (BA), styrene (S), or ethyl acrylate (EA)) were titrated by aqueous titrating systems (TS) composed from water (TA), aqueous solutions of acrylamide (TB), aqueous solutions of sodium dodecyl sulfate (TC), and/or aqueous solution of acrylamide and sodium dodecyl sulphate (TD). The amount of TS absorbed by the inverse microemulsion during titration (i.e., before transformation of Winsor IV inverse microemulsion to the two-phase Winsor II (w/o) (microemulsion phase + aqueous phase) and/or before phase inversion to the Winsor I (o/w) (microemulsion phase + oil phase) microemulsions, depended only slightly on the nature of the oil-soluble vinyl monomer. It was found, however, that the ratios of intra-phase and inter-phase compositional parameters such as toluene/AOT and AOT/SDS of the single-phase Winsor IV (w/o) inverse microemulsions considerably affected the value of the volume fractions of the aqueous phase, Φaw2, necessary for the formation of a two-phase Winsor II (w/o) and/or Winsor I (o/w) microemulsion systems. The composition of the titrating systems TS influenced the Φaw2 values at which the phase separation, and/or phase inversion of the single-phase Winsor IV (w/o) inverse microemulsion, were observed. Thus, the following sequence TAS1 < TA ≪ TC < TB < TD of titrating systems (ordered according to the obtained Φaw2 values) was found.

Adduct of copper(II) complexes with carbon, dioxide

The reaction of carbon dioxide with the copper(II) chelates of (–)-ephedrine, ψ-ephedrine, N-ethylnor-ephedrine, and N-n-butylnorephedrine was studied; on the basis of spectrophotometric data and gravimetric and elemental analysis the formation of 1:1 adducts between carbon dioxide and these chelates is shown.

Radical Reactions Initiated by Chelate Complexes of Transition Metals. 16. Modification of Vinyl Chloride Oligomer

Abstract The reaction kinetics and characterization of the reaction products of the modification of the vinyl chloride oligomer containing CCl3 end groups by n-butyl methacrylate in the presence of copper (II) ephedrinate was studied. The reaction product contains three high molecular weight components: modi- fied poly(vinyl chloride) (copolymer), unchanged vinyl chloride oligomer, and poly(n-butyl methacrylate) homopolymer. The extent of the modification process depends on the molar ratio between the concentration of the halogen-containing groups utilizable for the reaction with metal chelate and on the concentration of metal chelate. If there is a molar excess of chelate compared with the molar concentration of CCl3 end groups in vinyl chloride oligomer, then other halogen-containing groups besides CCl3 end groups of vinyl chloride oligomer are used in the formation of modified poly(viny1 chloride). This enables incorporation of more than two poly(n-butyl methacrylate) sequences into the poly(vinyl chlo...

Initiation of vinyl polymerization by system bivalent copper-aminoalcohol-carbon tetrachloride

Abstract In this paper there are preliminary results of investigations of initiation of vinyl polymerization by the system aminoalcohol-carbon tetrachloride-copper salt. As aminoalcohol (−)-ephedrine and 2-diethylaminoethanol were used. The copper salt was represented by copper acetate, stearate and chloride. It can be inferred from the results of polymerization experiments that ephedrine is a more efficient component of the initiator in styrene polymerization than diethylaminoethanol. Between the efficiency of the copper acetate and stearate, no differences were observed. From the evaluation of ESR spectra, it appears that reduction of the bivalent copper is occurring in the initiation system. Electron transfer from the aminoalcohol to carbon tetrachloride and formation of trichloro-methyl radicals is supposed.