Other Functional-group Latices

Other Functional-group Latices.—There is considerable overlap here with the use of emulsion polymerization for the preparation of model colloids. Ahmed et al. have described the preparation of monodisperse sulphonated and sulphated polystyrene latices by surfactant-free emulsion copolymerization. The functional group monomers were sodium styrenesulphonate, sodium vinyltoluenesulphonate, sodium sulphoethyl methacrylate, and a commercial acrylic sulphate. Chonde and Krieger have described a procedure for the detection and removal of water-soluble oligomers in styrene-sodium styrenesulphonate copolymer latices produced by surfactant-free emulsion copolymerization. The essential step of the 

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A widely used self-condensable monomer is N-methylol acrylamide. This monomer undergoes a self-condensation reaction as well as reactions with hydroxyl and carboxyl moieties. The methylol functional groups can also react with epoxides or other methylol or methylol ether groups. Typically, N-methylol acrylamide is employed at concentrations of 3-7 wt% in latex coatings formulations [Daniels and Klein, 1991]. 

The efect of crosslinking on the dynamic mechanical properties of polymers has been studied for many years. But one should note a clear distinction in the case of film formation from disposions of crosslinked latex particles. Each particle is a microgel. The crosslinks are confined to the particle itself without any additional ctosslinking across the particle boundaries [68]. Of course in some systems, like those formed from butadiene-containing latexes or from other latexes containing reactive functional groups, cross-boundary crosslinking can occur subsequent to film formation. 

Different types of water-based emulsions are used in EPI adhesives. The most common are poly(vinyl acetate) (PVAc) emulsion, ethylene vinyl acetate (EVAc) emulsion, vinyl acetate-acrylate copolymerized (VAAC) emulsion, acrylic-styrene (AcSt) emulsion or styrene-butadiene rubber (SBR) latex or modified versions of these emulsion types [1, 8, 9], It has also been reported that tri- or ter-polymer emulsions like vinyl acetate-butyl acrylate-hydroxypropyl methacrylate or emulsions with different combinations of block copolymers can be used [4], Emulsion polymers containing cross-linking functional groups are especially well suited [4,6, 9]. The choice of emulsion(s) will, to a large extent, influence the adhesive properties such as setting time, bond quality, heat resistance, and moisture resistance. EPI adhesive systems are, however, very complex and the total composition (including the choice of cross-linker) and the interaction between the different components will determine the properties of the adhesive. Due to this it is difficult to describe in detail the effect of choosing one type of emulsion over the other. 

Like anion exchangers, cation exchangers are divided into polymer-based cation exchangers (PS-DVB, EVB-DVB, polymethacrylate, and polyvinyl copolymers), latex-agglomerated cation exchangers, silica-based, and other (e.g., crown ether, aluminia materials).Modern cation exchangers contain sulfonic, carboxylic, car-boxylic-phosphonic, and carboxylic-phosphonic-crown ether functional groups. 

The preparation of a synthetic latex is shown to be a very complex process that is affected by the monomers selected, surfactants, initiators and the polymerisation process. The semi-continuous process is the one most frequently used as it provides control of the polymerisation heat removal, as well as control of the composition of the copolymers comprising several types of monomer units. Some aspects of copolymerisation in emulsion and particle growth in the case of the semi-continuous process are discussed. The copolymers usually comprise 4 to 5 comonomers, some of them with functional groups. The functional groups serve as loci for crosslinking, improve colloid stability, increase polarity, improve adhesion and cause alkali-solubility and/or alkali swellability. High value polymer latices with special particle morphology, composition and other... 

The filming properties for example, of the four latexes described above are quite different. Other practical uses of the power feed technique include the control of particle swelling, the location of functional groups within particles, and control of molecular weight distributions (23). 

The advantage of the low Cex RCTAs is that latexes with controlled particle size distributions using seeded polymerisations can be made. These latex particles in a second stage polymerisation can be further reacted with other monomers to make block copolymers with core-shell particle morphology or even latex particles in which the second block has functional groups, that is, reactive latexes (Monteiro de Barbeyrac, 2002). 

Using heterofunctional polymeric peroxides (HFPP), the surface [119] of various polymeric coUoidal systems such as emulsions, latexes, polymer-polymer mixtures, and so on, was modified. HFPP are carbon chain polymers, which have statistically located peroxidic and highly polar functional groups such as carboxylic, anhydride, pyridine, and others along the main chain. The reactions of the functional groups provide chanical bonding of the macromolecules to the interfacial surface. The activation of latex particles surface by surface-active HFPP is of special interest. 

ATRP-functionalized polymer particles are generally synthesized by emulsion polymerization, where the functionalizing monomer (e.g., benzyl halides and a-halo carboxylates carrying the terminal acrylic or methacrylic gronps) is polymerized onto polymer-seed polymer latex particles [157-166]. The process is formally achieved in two different steps, where the polymer seed is formed first with the desired characteristics and the functionalizing monomer is polymerized afterward on the surface. On the other hand, ATRP initiator can be introduced onto particle surface by a chemical reaction between the ATRP initiator and a reactive functional group attached previously at the latex particle surface [167-172]. 

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