Polymerization of epichlorohydrin

Other polymerizations of commercial interest are the polymerizations of epichlorohydrin with aluminum or zinc alkyls with... 

The cationic ring-opening polymerization of epichlorohydrin in conjunction with a glycol or water as a modifier produced hydroxyl-terminated epichlorohydrin (HTE) liquid polymers (1-2). Hydroxyl-terminated polyethers of other alkylene oxides (3 4), oxetane and its derivatives (5 6), and copolymers of tetrahydrofuran (7-15) have also been reported. These hydroxyl-terminated polyethers are theoretically difunctional and used as reactive prepolymers. 

HTE liquid polymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) in the presence of water or ethylene glycol (EG) as a modifier (1). Cyclic oligomers were removed by extraction. After extraction, the liquid polymers were essentially free from cyclic oligomers as determined by gel permeation chromatography (GPC) (Figure 1). 

Frankel and coworkers at Rocketdyne [108] first synthesized PECH-triol by polymerization of epichlorohydrin (ECH) with glycerol as initiator followed by synthesis of GAP-triol [Structure (4.16)] as in Scheme 4.2. 

Another type of activation of aluminum alkyl was found in the asymmetric-selective polymerization of epichlorohydrin (ECH) with an optically active cobalt-salen type complex [Co (II)]. The structure of the salen-type cobalt complex was shown previously (13, 14). In a benzene solution of the binary system consisting of [Co (II)] and AlEt, no evolution of ethane or ethylene was observed at room temperature. The NMR signals of the methyl protons for AlEt shifted down field on mixing with [Co (II)]. These observations together with a circular dichroism study indicated that AlEt and [Co (II)] formed a molecular complex in benzene, none of Al-Et bonds being cleaved by this complexation. 

Cationic Ring-Opening Polymerization of Epichlorohydrin in the Presence of Ethylene Glycol... 

These systems, as well as the cationic polymerization of epichlorohydrin (ECH) (next section) represent the best examples of the cyclooligomerization and competition between linear growth and cyclization ... 

Epoxy resins are a class of polymers that can be crossllnked to yield materials with a wide range of physical and chemical properties. Usually, linear, low-molecular weight products, known as pre-poljnners or first-stage polymers are polyethers with reactive epoxide endgroups. The most commonly used prepolymer is prepared by the condensation or step-growth polymerization of epichlorohydrin and bisphenol A as shown by the following equation ... 

This procedure has been adapted to transformation reactions however, most of the reported transformations were achieved from AM polymerization of cyclic ethers to conventional radical polymerization by using thermal or photochemical activation. For instance, AM polymerization of epichlorohydrin (ECH) was performed in the presence of 4,4 -azobis(4-cyanopentanol) yielding polymers with azo linkages in the main chain. Polymerization was conducted under typical conditions, that is, by slow addition of ECH to the solution of initiator containing catalyst. The reaction was considerably slower than in the presence of simple diols (e.g., EO) and only 28% conversion was achieved under conditions sufficient to reach complete conversion in the polymerization initiated by EO. Poly(epichlorohydrin) (PECH) prepared this way was consequently used in the polymerization of St to produce block polymer (Scheme 59). This polymerization yielded PSt with PECH segments at each end since termination occurs through radical-radical combinations. 

Okamoto [92] has studied the cationic polymerization of epichlorohydrin in the presence of ethylene glycol, using as initiator triethyloxonium hexafluoro-phosphate, and proposed a propagation mechanism similar to living polymerization. 

The epoxy prepolymer is prepared by step-growth polymerization of epichlorohydrin with a diol (OH—R—OH), which is normally bisphenol-A. After some time of polymerization, the reaction mass consists of the following ... 

Allyl Glycidyl Ether. This ether is used mainly as a raw material for silane coupling agents and epichlorohydrin mbber. Epichlorohydrin mbber is synthesized by polymerizing the epoxy group of epichlorohydrin, ethylene oxide, propylene oxide, and aHyl glycidyl ether, AGE, with an aluminum alkyl catalyst (36). This mbber has high cold-resistance. 

The mechanism of chemical modification reactions of PS were determined using toluene as a model compound with EC in the presence of BF3-0(C2H5)2 catalyst and the kinetics and mechanism of the alkylation reaction were also determined under similar conditions [53-55]. The alkylation reaction of toluene, with epichlorohydrin, underwent polymerization of EC in the presence of Lewis acid catalysis at a low temperature (273 K) as depicted in Scheme (9). 

It has been shown for many metal halides and monomers that binary mixtures of these can be prepared (usually in a solvent) without any polymerization taking place. Such a quiescent mixture can be made to react by the addition of a suitable third compound, which is called the co-catalyst. This term is preferable to the word promoter , because in certain contexts a substance is called promoter which enhances the rate or yield of a reaction that will also go in the absence of the promoter herein lies the true distinction between promoter and co-catalyst [28]. (For example, small quantities of epoxides or epichlorohydrin act as promoters in the cationic polymerization of tetrahydrofuran.) I will take it that in the above quotation the word promoter was inadvertently used in place of co-catalyst , for only thus does it become really meaningful. 

The reaction actually involves the sodium salt of bisphenol A since polymerization is carried out in the presence of an equivalent of sodium hydroxide. Reaction temperatures are in the range 50-95°C. Side reactions (hydrolysis of epichlorohydrin, reaction of epichlorohydrin with hydroxyl groups of polymer or impurities) as well as the stoichiometric ratio need to be controlled to produce a prepolymer with two epoxide end groups. Either liquid or solid prepolymers are produced by control of molecular weight typical values of n are less than 1 for liquid prepolymers and in the range 2-30 for solid prepolymers. 

Potassium carboxylate groups introduced onto the surface of carbon fibers initiated anionic polymerization of epoxides (e.g., styrene oxide, epichlorohydrin, and glycidyl phenyl ethers) and cyclic acid anhydrides (e.g., maleic anhydride, succinic anhydride, and phthalic anhydride) in the presence of 18-crown-6 [41]. 

Polyethers are prepared by the ring opening polymerization of three, four, five, seven, and higher member cyclic ethers. Polyalkylene oxides from ethylene or propylene oxide and from epichlorohydrin are the most common commercial materials. They seem to be the most reactive alkylene oxides and can be polymerized by cationic, anionic, and coordinated nucleophilic mechanisms. For example, ethylene oxide is polymerized by an alkaline catalyst to generate a living polymer in Figure 1.1. Upon addition of a second alkylene oxide monomer, it is possible to produce a block copolymer (Fig. 1.2). 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

Rozenberg et al. (24) have also studied the kinetics of polymerization of THF initiated by triethyl oxonium tetrafluoroborate. They generated their catalyst in situ from epichlorohydrin and the boron trifluoride-ether cofnplex and carried out their polymerizations in bulk and in... 

Several dyes have been found to sensitize the cationic polymerization of cyclohexene oxide, epichlorohydrin, and 2-chloroethyl vinyl ether initiated by diaryliodonium salts (109,110). Acridinium dyes such as acridine orange and acridine yellow were found to be effective sensitizers. One example of a benzothiazolium dye (setoflavin T) was also reported, but no other class of dye nor any other example of a dye absorbing at longer wavelengths were discovered. Crivello and Lam favored a sensitization mechanism in which direct energy transfer from the dye to the diaryliodonium salt occurred. Pappas (12,106) provided evidence that both energy transfer and electron transfer sensitization were feasible in this system. 

In the preparation of commercial DGEBPA, an excess of epichlorohydrin is used in order to minimize polymerization of the reactants to higher molecular-weight species. Nevertheless, the typical viscous final product usually contains ca 80% by weight of the monomeric (n = 0) DGEBPA as determined by gel-permeation chromatography (gpc). The manufacture of liquid epoxy resins in a batch process has been described in some detail (9). 

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