Interfacial cationic polymerization

Cationic polymerization can also be performed in direct miniemulsion in the presence of water. p-Methoxystyrene (p-MOS) was polymerized using the inisurf (= initiator - - surfactant) dodecylbenzenesulfonic acid with a monomer [91]. In the presence of ytterbium triflate, inverse systems were formed [92]. Although the rate of polymerization was found to be slower than for direct systems, the molecular weights obtained were shown to be larger. The polymerization was initiated by l-chloro-l-(p-methoxyphenyl)ethane (p-MOS-HCl), and catalyzed by trisdodecyl sulfate ytterbium, which served simultaneously as a surfactant and as a Lewis acid [93]. The Lewis acid surfactant did not play the expected role, however, as the p-MOS-HCl was hydrolyzed. The resulting hydronium protonated the SDS surfactant, which then served as an inisurf in the interfacial cationic polymerization process. 

Development of a imagewise film-deposition technique via photoinitiated interfacial cationic polymerization. 

Figure 2. Photoinitiated interfacial cationic polymerization imaging process sequence.

As indicated above, an extraordinary range of compositions can be synthesized in a relatively simple way that will encompass surfactant properties that depend on composition and use temperature. Virtually no other polymer system can span this range of interfacial or surfactant properties. The polymerization mechanisms and procedures used are described earlier in this chapter and though most often anionic-step polymerization is used, it is possible to prepare the block copolymers by cationic polymerization. 

An analogous mechanism should also produce polymers on irradiation of epoxies. Crivello s recent mechanistic suggestions [29] are consistent with the mechanisms given above. One can conclude that radiation-induced polymerization of epoxies can proceed via several mechanisms. However, further work is needed to determine the relative contributions of the different mechanisms, which might vary from one epoxy to another. As part of the Interfacial Properties of Electron Beam Cured Composites CRADA [37], an in-depth study of the curing mechanism for the cationic-initiated epoxy polymerization is being undertaken. 

Poly(s-caprolactone) Poly(e-caprolactone) is a semicrystalline polymer synthesized by anionic, cationic, free-radical, or ring-opening polymerization [94]. It is available in a range of molecular weights and degrades by bulk hydrolysis autocatalyzed by the carboxylic acid end groups. The presence of enzymes such as protease, amylase, and pancreatic lipase accelerates polymer degradation [95], The various methods of preparation of poly(e-caprolactone) nanoparticles include emulsion polymerization, interfacial deposition, emulsion-solvent evaporation, desolvation, and dialysis. These methods and various applications are extensively reviewed [94],... 

In a recent work, PE-MMT nanocomposites with strong interfacial interactions were synthesized by a similar approach. " The authors carried out the polymerizations using a metallocene catalyst in the presence of modified MMT after sodium exchange with a polymerizable surfactant undecenylammonium cation. For the sake of comparison, dodec-ylammonium chloride-modified MMT was also used for in situ ethylene polymerization. The MMT content was 1 wt% in both PE nanocomposites. NMR spectra pointed out the success of linking fhe polymerizable surfacfanf to PE backbone. TEM images revealed that modified MMT wifh fhe polymerizable surfacfant was better dispersed in the PE matrix than long alkyl chain-modified MMT. 

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