Monomer sequence distribution, emulsion

The microstructure of acrylamide-sodium acrylate copolymers was determined by NMR (36). The monomer sequence distribution was found to conform to Bernouillian statistics and the reactivity ratios of both monomers were close to unity. These results which differ from those obtained for copolymers prepared in solution or emulsion (37) confirmed a polymerization process by nucleation and interparticular collisions. 

Figure 6.1 presents some important microstructural features of the emulsion polymers. They include copolymer composition, monomer sequence distribution (MSD),... 

It is useful to compare the detailed monomer sequence distribution in SBRs obtained with emulsion free-radical and n-BuLi systems with the SBRs prepared with Ba/Mg/Al. We will begin by discussing how styrene incorporation varies with extent of conversion, then examine reactivity ratios and sequence distribution information obtained by proton NMR. 

In addition to determining monomer composition in the range 30-85% styrene in copolymer, this method has been used in sequence distribution studies. With emulsion copolymers, the mole fractions of styrene triplets (FSSS) is much smaller and the mole fraction of acrylate-styrene-acrylate units (FASA) is much higher than for the corresponding FSSS and FASA values for bulk copolymers. 

Copolymerization of a water-soluble monomer and a surfactant monomer can be performed in organic solution or in aqueous media in the presence or absence of noiqrolymeriz le surfactants (19,38-41). In aqueous media, micelle or emulsion polymerization may occur, by which copolymers with a blocky sequence distribution of tte surfactant comonomer unit may be obtained (19,22,38-40,42). In contrast, homogeneous polymerization in organic solution may yield copolymers with a random distribution. The association behavior of the copolymer depends strongly on the sequence distribution of surfactant comonomer units (19,20,26,39,43,44). To obtain copolymers with a random distribution of and DEmMA (Chart 1), homogeneous solution polymerization... 

Random copolymer—Distribution of the monomer units does not follow any definite sequence. These are produced in bulk, aqueous, suspension, or emulsion using free radical initiators of the peroxide type or redox systems. 

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