Functional groups, determination styrene—methacrylate

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. 

This technique has been used extensively for the determination of functional groups, in polymers and copolymers (Chapter 3) and in comonomer analysis (Chapter 4). Both these aspects are concerned with the determination of polymer structure. For example the distinction between free and combined vinyl acetate in vinyl chloride - vinyl acetate copolymers (Section 3.4.4) or the elucidation of the structure of methylmethacrylate (MMA) - glycidyl methacrylate copolymers (Section 3.6.1) or the elucidation of the various types of unsaturation occurring in styrene - butadiene copolymers (Sections 3.9.3, 3.9.4). Typical infrared (IR) spectra of copolymers are shown in Figures 6.1 to 6.4. 

In a copolymerization of styrene and methyl methacrylate under CCT conditions, the fraction of unsaturated styrene end groups is proportional to the fraction of styrene in the monomer feed.368 Due to the stability of styrene radicals, the relative fraction of propagating styrene radicals is large over the whole range of monomer feed compositions.432 433 This feature complicates the determination of radical reactivity ratios but may be compensated for by measuring the average transfer rate coefficient as a function of monomer feed composition. 

Carboxy- and amino-functionaUzed polystyrene nanoparticles have been synthesized by the miniemulsion process using styrene and the functional monomers acrylic acid (AA) or 2-aminoethyl methacrylate hydrochloride (AEMH) as functional comonomers [30,31]. By changing the amount of the comonomer, different surface densities of the charged groups could be realized. Since a fluorescent dye was incorporated inside the nanoparticles, the uptake behavior of different cell Unes could be determined as a function of the surface functionalization [30,31]. It was found that, in general, the uptake of the nanoparticles into the cells increases with increasing functionality on the particle s surface. For HeLa cells, for example, the internalized particle amount was up to sixfold better for carboxy-functionaUzed polystyrene (PS) nanoparticles than for non-functionalized PS particles. For amino functionalized PS nanoparticles, an up to 50-fold enhanced uptake could be detected. In order to investigate the actual uptake pathway into HeLa cells, positively... 

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