Surfmers Structures

In common with conventional surfactants, Inisurfs and Transurfs, Surfmers form micelles in aqueous solutions above the CMC. The organized monomer aggregates of colloidal dimension are microscopically heterogeneous and may affect polymerization kinetics and polymer structure and properties. 

Non ionic Surfmers. The alkoxylation of polymerizable substrates has been for many years a source of building blocks for innovative surfactant species as well as for the synthesis ofhigh performance Surfmers. Some of the early experimental prototypes have evolved into commercial products and the growing understanding of structure-performance relationships... 

A lot of mechanistic problems remain to be solved. It is not so clear, at the moment, why most of the inisurfs studied up to now have such a low efficiency, whatever their structure. On the other hand it is quite remarkable that, even with that low efficiency, they are able to allow the preparation of stable latexes under acceptable experimental conditions. Another problem is the control of the nucleation both with inisurfs and transurfs, there are indications that the particle number and size may not very sensitive to the amount of reactive surfactants, and more dependent on the amount of monomer used. Such behavior, up to now, has not been explainal Very few studies have been devoted to the reactivity of these surfactants, i.e., reactivity ratios for the surfmers, transfer constants for the transurfs and initiator efficiency for the inisurfs. Both the reactivities and the partition coefficient between the water and the organic phase have to be determined. In addition the reactivities may dependent on the other components of the recipe, for instance due to the effect of the ionic strength on the cmc. 

Figure 15.4 Chemical structures of surfmers for radical polymerization in miniemulsion.

Two polymerizable cationic surfactants were synthesized to produce thermally stable organoclays (ll-acryloyloxyundecyl)dimethyl(2-hydroxyethyl)ammonium bromide (called hydroxyethyl surfmer), and (ll-acryloyloxyundecyl)dimethylethylammonium bromide (called ethyl surfmer (Table 3.5) [63]. PS nanocomposites were produced by bulk polymerization and by free radical polymerization using these organoclays. Exfoliated structures were obtained with the ethyl surfmer-modified clay, whereas a mixed exfoliated/ intercalated structure was obtained using the hydroxyethyl surfmer-modified clay. The nanocomposites exhibited enhanced thermal stability and an increase in the glass transition temperature, in addition to improved mechanical properties relative to polystyrene. However, intercalated structures were obtained when nanocomposites were prepared in solution, because of competition between the solvent molecules and monomer in penetrating the clay galleries. Enhanced thermal stability was also obtained in the solution polymerization case. 

Polymerizable surfactants (surfmers) [224-231] are of current interest because of their potential application in drug delivery [232], in paints, in polymerization processes, for surface modifications, as well as for studies of polymerizable micelles [224,225,230]. Stabler and co-workers [224,225,230] prepared polymerizable surfactants with the structures... 

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