Libuše Mrkvičková

Thickening of butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid latices with an HEUR associative thickener

Thickening of acrylate copolymer latices containing various amount of 2-hydroxyethyl methacrylate (HEMA) by commercial associative thickener SER-AD FX 1070 (CONDEA Servo BV), based on hydrophobic ethoxylated urethane (HEUR), showed that the thickening efficiency decreases with the HEMA content in the latex copolymer. The strongest increase in viscosity occurred in the latex without HEMA comonomer suggesting formation of the network space structure due to the bridging of the latex particles by adsorption of hydrophobic ends of the thickener. When HEMA was incorporated into the latex copolymers, the particle surface became more hydrophilic and the association of the thickener was more significant. In this case thickening was much lower and was only a result of the hydrodynamic interaction between swollen latex particles and the thickener macromolecules or their aggregates (clusters, micelles).

Effect of alkalinization on carboxylated latices prepared with various amount of a non-ionogenic hydrophilic comonomer 2-hydroxyethyl methacrylate

Abstract Six latices of carboxylated styrene/butyl acrylate copolymers with 0–25% of 2-hydroxyethyl methacrylate (HEMA) were prepared by semicontinuous non-seeded emulsion polymerization and investigated by photon correlation spectroscopy and viscometry. Although HEMA is non-ionogenic, it profoundly affects the latex behavior after alkalinization: both methods revealed that HEMA promotes an increase in hydrodynamic dimensions of dispersed particles. The increase in viscosity due to incorporation of 10% of HEMA into the copolymers can make more than one order of magnitude at high volume fractions.

CHARACTERIZATION OF CHEMICAL HETEROGENEITY OF GRAFT COPOLYMER BY CONVENTIONAL SEC

Poly(methyl methacrylate) grafted with poly(dimethyl-siloxane) was investigated by size exclusion chromatography coupled with refractometric and low-angle laser light scattering detectors. Using successively toluene and tetrahydrofuran as eluents, a variation in chemical composition and molecular weight of individual copolymer blocks as a function of hydrodynamic volume were measured. Chemical composition distribution and heterogeneity parameters of the copolymerization product were approximated and compared with the results obtained by supercritical fluid extraction fractionation and by fractionation in demixing solvents.

Size-exclusion chromatography of low molecular weight polymers

Abstract To overcome the difficulty of the determination of the molecular-weight characteristics by size exclusion chromatography in the low-molecular-weight region (M < 104), the Sadron-Rempp relationship was used both for the construction of dependence of the universal calibration parameter on elution volume and for the tranformation of chromatographic data to molecular characteristics. Numerical values of constants of the above relation between intrinsic viscosity and molecular weight, which were calculated for some polymer-eluent systems on the basis of literature data, are given.

Structural changes of latex particles of ethyl acrylate—methacrylic acid copolymers during neutralization in the presence of methanol

Using a combination of static light scattering, potentiometry, and viscometry, structural changes of latex particles of ethyl acrylate—methacrylic acid (20–70 wt%) copolymers during neutralization in the presence of methanol were investigated. It was found that the latex particles disintegrate into small subparticles, swell, and at a high content of methacrylic acid units dissolve. Disintegration of latex particles is explained by considering the particles as agglomerates formed during polymerization by coalescence of smaller particles.

Light scattering study of structure of dispersion particles based on ethyl acrylate-methacrylic acid copolymers

Abstract Structural changes of colloid particles of ethyl acrylate-methacrylic acid (0–70%) copolymers on addition of alkali (pH∼9) or methanol were investigated. In addition to the feeding time of the monomer mixture, the content of methacrylic acid in the copolymers has been shown to influence dissolution of dispersion particles prepared by semicontinuous emulsion copolymerization. The longer the feeding time leading to higher polymer solids and the lower the acid content in the copolymer, the more limited was dissolution of disperse particles. On the basis of consistency of the results obtained in both media, this behaviour was explained in terms of a crosslinked structure of the copolymer due to chain transfer reactions.