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The grafting efficiency of dimethylaminoethylmethacrylate (DMAEMA) on to natural rubber (NR) has been studied. Grafting was by ‘topology-controlled’ emulsion polymerization, whereby polymerization is initiated by a redox couple where one component (tetraethylene pentamine) is hydrophilic and the other (cumene hydroperoxide) is hydrophobic. This should promote grafting at the interface between hydrophobic...
Protocols were examined for the measurement of rates and enthalpies of polymerization (ΔH p ) using reaction calorimetry. ΔH p was determined to be 70.2kJmol −1 for a series of seeded styrene emulsion polymerizations under typical emulsion conditions, in good agreement with literature values. However, there was a significant deviation from this value for small-particle systems,...
A means is developed for forming polysaccharide-based composites with useful material properties through use of unmodified and chemically modified natural rubber latex (NRL). Starch was used as a model for polysaccharides. The NRL was modified by grafting with dimethylaminoethyl methacrylate (DMAEMA) to form a latex with cationic water-soluble polymeric ‘hairs’ of polyDMAEMA, which should form hydrogen...
The free-radical polymerization propagation rate coefficient (k p ) of acrylic acid (AA) was calculated using transition state theory and ab initio quantum chemistry in order to shed light on the very strong solvent effects observed experimentally. Calculations were performed using a gas-phase reaction simulation, and the contribution of solvent then taken into account using the Polarizable...
The two-component redox-initiation system, cumene hydroperoxide (CHP) and tetraethylene pentamine (TEPA), was used to polymerize dimethylaminoethyl methacrylate (DMAEMA) in the presence of synthetic polyisoprene latexes. The modified latex particles are postulated to possess a ‘hairy layer’ of surface-grafted poly(DMAEMA) chains formed via an abstraction reaction between cumyloxy radicals and the...
Kinetic behavior in emulsion polymerization can be conveniently assigned as either 'zero-one' or 'pseudo-bulk'. Sufficiently small particles in emulsion polymerizations obey zero-one kinetics, where entry of a radical into a particle which contains a growing radical leads to instantaneous termination. Pseudo-bulk kinetics applies to particles in which more than one free radical can co-exist for a...
Seeded and ab initio emulsion polymerizations of isoprene using redox initiation systems were investigated and suitable reaction conditions determined to prepare polyisoprene latexes with minimal cross-linking. Polymerizations initiated with the potassium persulfate/sodium bisulfite (KPS/SBS) redox couple had a significant inhibition period and low yield. Polymerizations initiated with the tert-butyl...
Electrosterically stabilized polystyrene latexes with a poly(acrylic acid) hydrophilic layer with either perdeuterated core or perdeuterated hydrophilic layer were prepared in situ in a styrene/acrylic acid copolymerization, in a manner similar to that commonly employed industrially. Small angle neutron scattering (SANS) measurements were made over a range of contrasts for three latexes at high and...
A strategy is explored for synthesizing latex particles with polystyrene cores and poly(vinyl acetate) shells. The seed particles are poly(vinyl acetate), which theory indicates should be immune to secondary particle formation when a second-stage seeded emulsion polymerization with styrene is carried out. The objective is to form a single hydrophobic core by inversion of the second and first stages...
Strategies for avoiding secondary particle formation in seeded emulsion polymerisation, based on a simple model for particle nucleation [Macromol. Symp. 92 (1995) 13], are discussed and exemplified in the context of growing latex particles with polystyrene cores and poly(vinyl acetate) shells. With a polystyrene seed of unswollen radius 44nm, core-shell polymerisation was easily achieved. However,...
A simple model for particle formation in surfactant-free emulsion polymerisation [Macromol. Symp. 92 (1995) 13; Emulsion polymerization: a mechanistic approach, 1995], with extension to allow for induced decomposition of initiator, is explored. The object is to find conditions for secondary particle formation, especially to find conditions under which it would be possible to grow core-shell particles...
The effect of surface modifications brought about by a polymeric stabilizer on the interactions between polymer colloid particles and various substrates in aqueous media are directly measured using atomic force microscopy. The interactions of polystyrene particles with grafted hydrophilic ‘hairs’ of hydroxypropyl cellulose (denoted HPC/PS), of molecular weight ∼105, with mica, silica and graphite...
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