Epoxidized polyisoprene

Synthetic polymers from alkene monomers are also a major target for epoxidizers. Polyisoprenes,26 polybutenes and polybutadienes have all been epoxidized by general in situ peracid methods. In the case of liquid polybutadienes, a wide range of types is available. Products with varying contents of 1,4-cis, 1,4-trans, and 1,2-vinyl alkene groups are available (Figure 3.6). 

Photoinitiated Ring-Opening Polymerization of Epoxidized Polyisoprene... 

From the conversion dependence of the insolubilization process, it was concluded that both inter- and intramolecular propagation reactions occur during the polymerization of the epoxy ring. Blends of epoxidized polyisoprene and difunctional vinyl ether or aciylate monomers were shown to undergo a fast and extensive cross-linking polymerization, with formation of interpenetrating polymer networks. 

THF structures have indeed been characterized by C-NMR spectroscopy in epoxidized polyisoprene exposed to UV radiation in the presence of a sulfonium photoinitiator... 

Photocross-Hnking of epoxidized polyisoprene - vinyl ether blends... 

Photocross-linking of epoxidized polyisoprene-acrylate blends... 

The photoinitiated cationic polymerization of liquid epoxidized polyisoprene is an efficient method to generate rapidly crosslinked elastomers. In the presence of a triarylsulfonium salt, the reaction develops readily upon UV exposure, with formation of both inter and intramolecular ether linkages. The formulation reactivity can be substantially enhanced by the addition of a difunctional vinyl ether or acrylate monomer, which acts as a reactive diluent and leads to the formation of an... 

When the respective component glass transition temperatures are close, the blend Tg is not a useful measure of blend homogeneity. In fact, excess mixing volumes and specific interactions can cause anomalous behavior. The Tg of such a blend can be lower (as seen in polychloroprene/epoxidized polyisoprene blends (McGrath and Roland, 1994)) or higher (as seen in polylepichlorohydrin/polyvinylmethylether blends (Alegria et al., 1995)), than Tg of either neat component. In blends of polymers having nearly equivalent... 

Low molecular weight liquid polybutadienes are epoxidized on a commercial scale to produce useful epoxide resins, which may be cross-linked by methods employed with the better known epoxide resins from epichlorhydrin using amines or acids. There is no known application of epoxidized polyisoprene or SBR although these are reported to have been prepared (Greenspan, 1964). 

The synthesis of arborescent isoprene homopolymers by coupling polyisoprenyllithium with epoxidized polyisoprene substrates as outlined in Scheme 6.6 was recently demonstrated (Yuan... 

Scheme 6.6 Synthesis of arborescent polyisoprene by grafting onto epoxidized polyisoprene.

Figure 5. Segmental relaxation times for epoxidized polyisoprene tuid polychloroprene, and two of their blends. The latter exhibit faster relaxation than the either neat components.

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