Latex particles physical surface functionalization

Posttreatment for Physical Surface Functionalization of Latex Particles. 269... 

There are two synthesis methods for physical surface functionalization of latex particles. In the first approach, the surface modifier is directly added to the reaction mixture (in situ). This approach is used to extend the latex particle application by using a predesigned molecule or macromolecule that plays a role in the particle-formation process and also in the particle surface functionalization. The second method includes two steps (the synthesis of the latex particles and a posttreatment) since the latex particle is functionalized once the nanoparticle is formed. 

The microemulsion polymerization and copolymerization of amphiphilic monomers and macromonomers can produce the fine polymer latex in the absence of emulsifier [98-100], The surface active block or graft copolymer stabilizes the latex particles. The chemically bound emulsifier (surface active copolymer) onto the particles surface is known to be much more efficient emulsifier than the emulsifier physically adsorbed onto the particle surface and, therefore, very stable and fine polymer latexes are formed. The similar behavior is expected with the transferred emulsifier radicals. For example, the surface-functionalized nanoparticles in the 12 - 20 nm diameter range can be prepared by a one-step or two-step microemulsion copolymerisation process of styrene (and/or divinylbenzene (DVB)) with the polymerisable macromonomer (Fig. 7) [93, 101]. 

The viscoelastic behavior of concentrated (20% w/w)aqueous polystryene latex dispersions (particle radius 92nm), in the presence of physically adsorbed poly(vinyl alcohol), has been investigated as a function of surface coverage by the polymer using creep measurements. From the creep curves both the instantaneous shear modulus, G0, and residual viscosity, nQ, were calculated. 

The colloidal properties of latex products are of great importance from both academic and industrial points of view. Some representative charaeteristics include the particle size and particle size distribution, the particle surface charge density (or zeta potential), the particle surface area covered by one stabilizer molecule, the conformation of the hydrophilic polymer physically adsorbed or chemically couplet onto the particle surface, the type and concentration of functional groups on the particle surface, the particle morphology, the optical and rheological properties and the colloidal stability. 

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