Stabilization latex particle

Salt effects in polyelectrolyte block copolymer micelles are particularly pronounced because the polyelectrolyte chains are closely assembled in the micellar shell [217]. The situation is quite reminiscent of tethered polymer brushes, to which polyelectrolyte block copolymer micelles have been compared, as summarized in the review of Forster [15]. The analogy to polyelectrolyte brushes was investigated by Guenoun in the study of the behavior of a free-standing film drawn from a PtBS-PSSNa-solution [218] and by Hari-haran et al., who studied the absorbed layer thickness of PtBS-PSSNa block copolymers onto latex particles [219,220]. When the salt concentration exceeded a certain limit, a weak decrease in the layer thickness with increasing salt concentration was observed. Similar results have been obtained by Tauer et al. on electrosterically stabilized latex particles [221]. 

Increase of ionic strength reduces the stability of electrostatically stabilized latex particles and causes them to coalesce at sufficiently high values. However the difference in the effects of potassium octadecanoate and sodium dodecyl benzene... 

Fig. S.9. The dependence of the CFV and LCFT upon stabilizer surface coverage for poly(12-hydroxystearic acid) stabilized latex particles in n-heptane (after Napper, 1968b).

Fig. I3.I. The distance dependence of the steric interaction free energy for polystyrene stabilized latex particles in toluene 1, experimental results 2, theoretical mixing term 3, theoretical elastic term 4, total theoretical terms (after Doroszkowski and Lamboume, 1973).

Fig. 16.4. The reciprocal of the stability ratio of poly(oxyethylene) stabilized latex particles in the presence of free poly(oxyethylene) of different molecular weights curves 1,300000 2,10000 3, 4 000 4, 600 5, 200 (after Cowell et al., 1978).

Fig. 16.7. The three component diagram at 25 °C for poly(oxyethylene) stabilized latex particles (L) in aqueous (S) poly(oxyethylene) (P) solutions (a) stabilizer POE 750 with 10 000 free POE in water (b) same as (a) but in 0-065 M MgSO., same as (a) but with 1500 free POE (d) same as (a) but with 400 free POE. The numerals I and II denote dispersed particles only and dispersed particles plus floes respectively (after Cowell et al., 1978).

The most common method of stabilizing latex particles is by addition of mixed anionic and nonionic surfactants. The key property of a siufactant is that it possesses chemically dissimilar groups one hydrophobic and one hydrophilic. The hydrophobic group is physically adsorbed onto the polymer latex particle while the hydrophilic portion extends into the aqueous phase. It is the hydrophilic groups that provide the stabilization. 

Fig. 1.24 The three intervals of a typical emulsion polymerization reaction, showing surfactant molecules ( "), large monomer droplets, micelle (indicated by clusters of surfactant molecules within Interval 1), radicals (R ), initiator (1) and surfactant-stabilized latex particles (Reprinted from Thickett and Gilbert [274]. Copyright 2009, with permission from Elsevier)...

For initiation in the aqueous phase to produce a monodisperse latex, the primary particles generated early in the reaction must act as nuclei to capture all primary radicals formed thereafter and these nuclei must grow without flocculation until the end of the polymerization. Therefore, the emulsifier must adsorb rapidly enough to stabilize these initial nuclei but not so rapidly as to stabilize the primary particles formed later in the reaction. This condition may be met if the emulsifier concentration is relatively low or if the emulsifier is omitted the sulfate endgroups introduced by the persulfate initiator are often sufficient to stabilize latex particles at relatively low monomer-water ratios (30). Table III gives the increase in particle size and surface charge resulting from the flocculation of the primary particles described in... 

Weiss, A., N. Dingenouts, M. Ballauff, H. Senff, and W. Richtering, "Comparison of the Effective Radius of Sterically Stabilized Latex Particles Determined by Small-Angle X-ray Scattering and by Zero Shear Viscosity". Langmuir 14, 5083-5087, (1998). 

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