Admicellar polymerization

Barraza, H.J. Admicellar-Polymerized Thin Elastomeric Coatings for Engineered Interfaces for Enhanced Composite Performance. Ph.D. dissertation, University of Oklahoma, 2003. 

Alternative approaches involving molecules that combine the properties of a monomer with those of a surfactant (so-called polymerizable surfactants) have also been reported. For example, quaternary alkyl salts of dimethyl aminoethyl methacrylate (CnBr) surfactants were used to promote polymer encapsulation of silica gels in aqueous suspension [43, 44]. The polymerizable surfactant formed a bilayer on the silica surface, the configuration of which enabled the formation of core-shell particles. The CnBr amphiphilic molecule was either homopolymer-ized or copolymerized with styrene adsolubilized in the reactive surfactant bilayer. This concept of admicellar polymerization is detailed in Sect. 3.1. In the recent... 

For NR nanocomposite filled with silica, it has always been known that the hydrophilicity-hydrophobicity issue is a challenge since silica is hydrophilic and NR is hydrophobic. The usual method to overcome this issue is by adding coupling agent. In 1987 Wu and coworkers introduced admicellar polymerization where a thin polymeric film will be formed on the silica s surface. This process yields a thin film of polymer on the silica which can further enhance the adhesion between the surfaces of silica and rubber. The steps involved in admicellar polymerization are outlined in Scheme 7.7. In principle, a bilayer of surfactant, i.e. the admicelle, is first formed on the surface of the silica. Monomer will then penetrate the admicelle, i.e. the adsolubilization of monomer. Upon addition of initiator to the reaction system, in situ polymerization occurs in the admicelles. Finally, the surfactant is removed by washing with water and an ultrathin polymer layer is formed on the surface of the silica. The polymerization of the monomer in the admicelles can be induced by thermal process, chemical initiators or radiation. ... 

Table 7.2 summarizes recent works reported on silica admicellar polymerization of polyisoprene. The silica modified by admicellar polymerization was reported by researchers as having superior performance compared to those reinforced with unmodified silica or silica modified with typical silane coupling agents. Studies also showed that the use of surfactant can influence performance of the rubber composite. ... 

Scheme 7.7 Schematic diagram representing steps involved in admicellar polymerization (adapted from ref. 41).

Table 7.2 Summary of some silica modified via admicellar polymerization in NR- or polyisoprene-based nanocomposites.

A comparative studied on the radiation-induced admicellar polymerization with the traditional thermal process. ... 

Effects of silica modifled by radiation- and thermal-induced admicellar polymerization on the mechanical properties i.e. tensile properties and tear strength of the reinforced polyisoprene were compared with those of the typical silica filled polyisoprene with and without TESPT. "... 

Effect of 3 different type of surfactants cetyltrimethyl ammonium bromide (CTAB), dodecyltrimethyl ammonium bromide (DTAB) and tetradecyltrimethyl ammonium bromide (TTAB) to silica modified by both thermal admicellar polymerization and radiation induced admicellar polymerization. 

Polyisoprene-coated silica was prepared by admicellar polymerization technique. ... 

Sample modified by CTAB showed highest degradation rate, followed by those modified with DTAB and TTAB for both thermal- and radiation-induced admicellar polymerization. 

CTAB is shown to be the most effective surfactant for modifying the silica surface via admicellar polymerization. 

NR is one of the world s important natural resources and sihca is considered environmentahy friendly upon disposal. Thus, in terms of sustainability development, development of sihca-fihed NR nanocomposites opens new opportunities for producing green materials/products such as tyres. Traditionally, carbon black is preferred over sihca as fiber in tyres due to the challenge in dispersing sihca in rubber compounds. With the new development, e.g. in situ sol gel silica, admicellar polymerization and polymer-encapsulated sihca, the applications of nano-silica in NR and modified NRs are widened. 

J. Maity, P. Kothary, E.A. O Rear, C. Jacob, Preparation and comparison of hydrophobic cotton fabric obtained by direct fluorination and admicellar polymerization of fluoromono-mers, Ind. Eng. Chem. Res. 49 (13) (2010) 6075-6079. 

PPy is a conductive polymer with several biomedical applications owing to its good biocompatibility and the ability of cells to attach, differentiate and proliferate on its surface [148,149]. In one study, the attachment, proliferation and differentiation of rat MSCs on PPy surfaces was shown to be comparable to those of regular tissue culture plastic surfaces [150]. The synthesis of PPy involves either electrochemical or chemical polymerization, with the admicellar polymerization technique enabling the uniform deposition of thin PPy films from a few to 100 nm thick [151]. Moreover, the attachment of cells to the PPy surface can be improved, for example, via the adsorption of fibronectin or the incorporation of Arg-Gly-Asp (RGD)-containing peptides [152]. Immobilization of the glycosaminoglycans heparin and hyaluronic acid on PPy surfaces was also shown to maintain bone marrow-derived MSC cultures and to induce differentiation successfully into mature osteoblasts [153]. 

Castano H, O Rear EA, McFetridge PS, Sikavitsas VI. Polypyrrole thin films formed by admicellar polymerization support the osteogenic differentiation of mesenchymal stem cells. Macromol Biosci 2004 4 785-94. 

FIG U R E 4 Magnetic nanoparticle encapsulation through admicellar polymerization. 

Preparation of magnetic nano-carriers possessed tmiform core/sheU/shell nano-stmcture composed of 40 run magnetite particles/poly(styrene-co-glycidyl methacrylate (GMA))/polyGMA, which was constracted by admicellar polymerization was reported by Honda et al.[65]... 

The admicellar polymerization concept was also applied to the synthesis of thermosensitive magnetic latex particles based on V-isopropylacrylamide (NIPAM) [66,67]. In this case, however, the polymerization cottld be better defined as seeded precipitation polymerization owing to the water solirbility of this monomer. 

Tragoonwichian S, O Rear EA, Yanumet N (2008) Broad ultraviolet protection by copolymerization of 2-3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl ethyl methacrylate and 2-hydroxy-4-acryloyloxybenzophenone on cotton via admicellar polymerization. J Appl Polym Sd 108(6) 4004- 013. doi 10.1002/app.28049... 

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