Epichlorohydrin cationic molecular weight

Cationic polymerization of the unsubstituted oxirane (ethylene oxide) leads to the mixture of relatively low molecular weight (M < 103) linear polymer and up to >90% of cyclic oligomers, predominantly cyclic dimer (1,4-dioxane) 191,102]. The same behavior was observed for polymerization of substituted oxiranes, propylene oxide [103], epichlorohydrin [104], and other oxiranes having one or more substituents in the ring, although the distribution of cyclic fraction varied, depending on the structure of monomer. 

Reten 205 [Aqualon], TM for a strongly cationic, high molecular weight, synthetic, water-soluble polymer. A finely divided white powder, dissolves in either hot or cold water to produce clear, smooth, viscous, nonthixotropic solutions available in a variety of viscosity grades and cationic functionality. Reten 763 is an aqueous solution of a modified polyamide-epichlorohydrin resin. 

The high thermodynamic polymerizability of oxiranes (due to the relatively large ring strain) and the availability of monomers such as ethylene oxide (EO), propylene oxide (PO) or epichlorohydrin (ECH) led to considerable efforts directed toward the preparation of high molecular weight polymers. Both cationic and anionic polymerizations were explored and it soon became clear that for several monomers only anionic polymerization gives high polymers. 

The treatment of this lower molecular weight polyamide with epichlorohydrin, principally by reaction at these secondary amine sites, to form the key cationic, reactive functionality 3-hydroxyazetidinium chloride and to develop further the molecular weight of the PAE resin... 

Although butyl rubber is by far the most important commercial elastomer to be synthesized by cationic polymerization, several heterocyclic monomers provide useful elastomeric materials via this mechanism also. Epichlorohydrin can be polymerized to high molecular weight using a complex catalyst formed from a trialkylaluminum compound and water as shown in Eq. (58) [64, 130-132], For copolymerizations with ethylene oxide, a catalyst formed from a trialkylaluminum compound, water, and acetylacetone is useful [64,130], The mechanism proposed for these polymerizations is... 

Epoxide adhesives comprise epoxy resin, many of which are prepared from phenols and epichlorohydrin, for example, the diglycidyl ether of bis-phenol A or bis-phenol F usually, these resins are a mixtnre of molecular weights blended to fit the applications. The most-common cnratives for epoxy resins are polyanfines (used in stoichiometric amounts), usually a chain-extended primary aliphatic amine, for example, diethylene triamine or triethylene tetraamine or chain-extended equivalents, which react rapidly with the epoxy resin at room temperature. Aromatic amines react slowly at room temperature but rapidly at higher temperatures. Most epoxide adhesives also contain catalysts, typically, tertiary amines. Dicyanimide is the most-common curative for one-component high-temperature-cured epoxide adhesives. Mercaptans or anhydrides are used as curatives for epoxide adhesives for specialist applications, for example, for high-speed room-temperature cures or for electronic applications. A smaller number of epoxide adhesive are cured by cationic polymerization catalysed by Lewis acids photogenerated at the point of application. Lewis acid photoinitiators include diaryliodonium and triarly sulphonium salts. See Radiation-cured adhesives. 

---