Responsive polymer latex

The theory could successfully explain the restabilization of protein-stabilized polymer latexes the increase in surface dipole density with increasing electrolyte concentration, generated by the binding of the counterions to sites of opposite charge, is in this case responsible for this effect This occurs because the repulsive force generated by the surface dipoles more than compensates for the decrease in repulsion caused by screening. 

By polymerizing poly(A -isopropylacrylamide) (PNIPAM) [55] or poly (2-(diethylamino)ethyl methacrylate) (PDEAEMA) [56] as a stimuli responsive polymer/hydrogel layer around a colored nanoparticle of PS-co-PMMA, the local refractive index and consequently the color intensity of the latex could be switched by the temperature [55] or pH [56]. 

Semiconductor particles can also be used advantageously in coating applications to provide specific optical response to the material. As an example, Kumacheva et al. recently described the synthesis of monodisperse nanocomposite particles with inorganic CdS nanocrystals sandwiched between a PMMA core and a P(MMA-co-BA) outer copolymer shell layer. The particles are prepared by emulsion polymerization in three steps (Fig. 4.21) [144]. In a first step, polymer latexes are used as host matrices for CdS nanocrystals formation [145,146]. To do so, monodisperse poly(methyl methacrylate-co-methacrylic acid) (PMMA-PMAA) latex particles were ion-exchanged with a Cd(Cl04)2 solution. The Cd + ions thus introduced into the electrical double layer were further reduced into CdS nanoclusters by addition of a Na2S solution. The CdS-loaded nanocomposite particles were subsequently recov-... 

Emulsion polymerization is among the most popular synthetic routes to prepare vinyl-based pH-responsive polymers, especially microgel systems (Rao and Geckeler, 2011). This technique employs a radical chain polymerization methodology to form latexes of narrow particle size distributions. The emulsion polymerization systems are commonly composed of monomer(s), water, water-soluble initiator and surfactant (emulsifier). Colloidal stabilizers may be electrostatic, steric or electrosteric, or display both stabilizing mechanisms. When phase separation occurs, the formation of solid particles takes place before or after the termination of the polymerization reaction. 

The first experimental proof of virtual linearity of response, up to some 80% of the aperture diameter, came from Barfield and Knight and Barfield, Wharton and Lines.27 They used spherical particles of polymer latex and the COULTER COUNTER model ZM. The experiment involved the use of different sizes of "mono-sized" latex particles measured by a range of different apertures, and therefore required no assumed or measured "real" sizes for the particles. The experiment has not been repeated for other particle shapes as no other series of suitable model particles appear to exist, so the linearity of response for other particle shapes has not yet been verified experimentally. It is reasonable to assume however, from all existing theory that no significant extra alinearity will exist for non-spherical shapes. 

Mittal, V., Matsko, N.B., Butte, A., and MorbideUi, M. 2007. Synthesis of temperature responsive polymer brushes from polystyrene latex particles functionalized with ATRP initiator. Eur. Polym. J. 43 4868-81. 

A variefy of particulate structures have been used as templates for capsule formation. These can be inorganic (carbonates such as CaCOa, MnCOa [1-3] and solid or porous silica nanoparticles [4, 5]), organic (melamine formaldehyde [6]) and polymeric (polystyrene latex [7], mesoglobules, prepared from thermo-responsive polymers [8-10]) materials, emulsion droplets [11-13], bubbles [14], and even red... 

Fig. T A shows the GPC traces obtained at wavelength 2 k and 3U0 nm for a 312 nm Dow latex sample. Note the response at 3 0 nm is at twenty-five times the sensitivity of the response at 25 nm and hence considerably exaggerated in comparison. At 25 nm two peaks are clearly noted, a polymer peak and a secondary peak whose retention volume corresponds to that of styrene monomer. At 3 0 nm, since neither monomer nor polymer absorb, the observed peak is attributable to the presence of additives such as emulsifier.

If only electrostatic effects are responsible for polymer adsorption and flocculation, our results can be explained according to the same scheme as that used by Furusawa et Al.(20) to interprete the destabilization of negatively charged latex by a cationic polymer. In a first step, the adsorption of the polymer leads to the neutralization of the particles which are no more stabilized by electrostatic repulsions and there is flocculation (we have not studied this step since in our experiments polymer was always in large excess with respect to Al(0H)3). In a second step the adsorption inverses the charge and (we have indeed measured by... 

One of the problems encountered in the entrapment of activated charcoal in a polymer matrix is the blinding-off of the pores of the charcoal, thus inactivating it. Because the pores of the carbon are responsible for its ability to adsorb organics, any pores that are filled or coated with a polymer matrix reduce its effectiveness. Conventional treatments involve blending the carbon into an acrylic latex and then applying the slurry to a reticulated foam. Upon drying, a coalescence encapsulates the carbon. 

Addition of different kinds of charged polymers (polyelectrolytes) offers one effective way to control the stability of a colloidal solution. When charged polymers adsorb on neutral colloids, the colloids repel each other for electrostatic reasons. This behavior is called electrostatic stabilization and is responsible for the long shelf-life of certain latex paints. Polymers can also stabilize a dispersion for steric reasons when they are grafted or adsorbed to the particles. If two polymer covered particles approach it will lead to a restriction on the configurational freedom for the polymers giving rise to a repulsive force. 

The free radicals produced from the fraction of initiator dissolved in the water phase are responsible for particle formation and growth in the emulsion polymerization of St initiated by AIBN. The free radicals produced in pairs in the polymer particles play almost no role in the polymerization inside the polymer particles because pairs of radicals produced within a volume as small as a monomer-swollen latex particle or a monomer-swollen micelle are very hkely to recombine. 

In latex saturation processes of preformed fiber webs, the predominant force responsible for drawing the rubber particles to fiber crossings and coagulating these particles into a coherent mass is the surface tension of the evaptxatittg water medium. Current trends are to develop latexes whose surface tension is close to water by ulibzing oligomeric emulsifiers (White, 1976) or emulsifiers polymerized into the polymer chain (Sweeney, 1958) to maximize the surface tension forces. 

Neoprene, or polychloroprene, is a synthetic rubber discovered by the Du Pont Company in 1931. It is an organic polymer composed of carbon, hydrogen, and chlorine in the ratio of 55 5 40. Its relatively high chlorine content was responsible for the early recognized resistance of the polymer to burning. Practical use of this property was not developed until procedures for making foam structures from neoprene latex were developed in the 1940 s. The U.S. Navy adapted the material to make neoprene foam mattresses that reduced the fire hazards in the crews quarters of naval vessels. For many years neoprene has been the only material to meet Navy specifications for this application. 

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