Polyepoxides

Poly(propylene oxide) [25322-69-4] may be abbreviated PPO and copolymers of PO and ethylene oxide (EO) are referred to as EOPO. Diol poly(propylene oxide) is commonly referred to by the common name poly(propylene glycol) (PPG). Propylene oxide [75-56-9] and poly(propylene oxide) and its copolymers, with ethylene oxide, have by far the largest volume and importance in the polyurethane (PUR) and surfactant industry compared to all other polyepoxides. Articles reviewing propylene oxide (1), poly(propylene oxide) (2—4), other poly(aIkylene oxides) (4), and polyurethanes (5—7) are cited to lead the interested reader to additional detail not in the scope of this article. 

The commercial interest in epoxide (epoxy) resins was first made apparent by the publication of German Patent 676117 by I G Farben in 1939 which described liquid polyepoxides. In 1943 P. Castan filed US Patent 2 324483, covering the curing of the resins with dibasic acids. This important process was subsequently exploited by the Ciba Company. A later patent of Castan covered the hardening of epoxide resins with alkaline catalysts used in the range 0.1-5% This patent, however, became of somewhat restricted value as the important amine hardeners are usually used in quantities higher than 5%. 

Scheme 14. Structure of brevetoxin B (1) and hypothetical polyepoxide precursors 71a and 71b.

Tandem 5-exo-oxacyclizations of polyepoxides to form polycyclic ethers are well known. In Evans s synthesis of lonomycin A, diepoxide 66 underwent the desired... 

In the synthesis of the squalenoid glabrescol (72 originally attributed structure), containing five adjacent (all cis) THF rings, the necessary precursor of the polyepoxide cascade, the pentaepoxide 71, was achieved by epoxidation of each of the trisubstituted double bonds of the known (R)-2,3-dihydroxy-2,3-dihydrosqualene (70) by the Shi epoxidation approach (Scheme 8.18) [34]. Treatment of 71 with CSA at 0 °C and subsequent purification by column chromatography provided the pure polycyclic ether 72 by a cascade process reasonably initiated by the free secondary alcohol functionality [35a]. 

As an alternative to polyepoxide cyclization, cascade cyclization of cyclic sulfates... 

Scheme 8.18 Corey s synthesis of glabrescol (72 originally attributed structure) by a polyepoxide cascade.

Lindo-rv.ff oselecli ve oxacydization of polyepoxides is less common the first ster-eospedfic tandem endo-regioselective biomimetic oxacydization of polyepoxides to fused THP rings has only recently been reported [38a], The cyclization of the hydroxy-methoxymethyl-substituted triepoxide 75 (a 1,4,7-triepoxide), promoted and directed by La(OTf)3 through an intramolecular chelation and based on a procedure originally described for a monoepoxide system [38b], afforded the tri-... 

Closely related to the polyepoxide cascade procedure for the synthesis of polycyclic systems is Corey s biomimetic-type, nonenzymatic, oxirane-initiated (Lewis acid-promoted) cation-olefin polyannulation. By this strategy, compound 96, containing the tetracyclic core of scalarenedial, was constructed by exposure of the acyclic epoxy triene precursor 95 to MeAlCl2-promoted cyclization reaction conditions (Scheme 8.25) [45]. 

Gas-filled plastics are polymer materials — disperse systems of the solid-gas type. They are usually divided into foam plastics (which contain mostly closed pores and cells) and porous plastics (which contain mostly open communicating pores). Depending on elasticity, gas-filled plastics are conventionally classified into rigid, semi-rigid, and elastic, categories. In principle, they can be synthesized on the basis of any polymer the most widely used materials are polystyrene, polyvinyl chloride, polyurethanes, polyethylene, polyepoxides, phenol- and carbamideformaldehyde resins, and, of course, certain organosilicon polymers. 

Shokal, E.C. "Sulfur-Containing Resinous Products from Polyepoxides," US Patent 2,633,458(1953). 

Essentially nonionic soil-release agents comprise polyesters, polyamides, polyurethanes, polyepoxides and polyacetals. These have been used mainly on polyester and polyester/ cellulosic fabrics, either crosslinked to effect insolubilisation (if necessary) or by surface adsorption at relatively low temperature. Polyester soil-release finishes have been most important, particularly for polyester fibres and their blends with cellulosic fibres. These finishes, however, have much lower relative molecular mass (1000 to 100 000) than polyester fibres and hence contain a greater proportion of hydrophilic hydroxy groups. They have been particularly useful for application in laundering processes. These essentially nonionic polymers may be given anionic character by copolymerising with, for example, the carboxylated polymers mentioned earlier these hybrid types are generally applied with durable press finishes. 

Bisphenol A type epoxies such as Epon 828, were also cured with the DIBF OPPI combination. When a modifier, Heloxy 505 (a low viscosity polyepoxide modifier) was added, viscosity was reduced and adhesion to the metal surface and impact resistance were improved as compared with the bisphenol A only. Surprisingly cure was faster than with the Union Carbide cycloaliphatic resins, but charring of the resin during cure was a problem. 

McDonald and coworkers studied a series of tandem endo-selective and stereospecific oxacyclization of polyepoxides by reaction with Lewis acid [92-95]. Polyepoxides, such as 50, can be obtained from the epoxidation of triene 49 with ketone 26 (Scheme 8). This cascade cyclization of polyepoxides provides an efficient method to synthesize substituted polycyclic ether structures, which are present in a number of biologically active marine natural products. 

The majority of extreme data were received from the universities. It was evident that the switch-on, inject, switch-off approach was applied (likely by the students) without critical evaluation of data produced by the computers software. The least scattered M values were obtained in the industrial laboratories, in which evidently the skilled operators performed the measurements. Better data accuracy was obtained for polyamides [154] and for oligomeric polyepoxides [155] than for the unproblematic poly(dimethyl siloxane)s and even for the most simple polymer, polystyrene likely because only experts measured the latter difficult samples. 

Polynuclear aromatics that cannot form K-region epoxides such as anthracene may be oxidized to the corresponding quinones806 by these reagents. Others, such as naphthalene and triphenylene, may be converted to polyepoxides under carefully controlled reaction conditions and workup procedures.808,809... 

Propylene oxide is one of the raw materials used to manufacture rubbery and crystalline polyepoxides. R. J. Herold and R. A. Livigni describe propylene oxide polymerization with hexacyanometalate salt complexes as catalyst. Polyphenylene oxide is made by copper catalyzed oxidative coupling of 2,6-dimethylphenol. G. D. Cooper, J. G. Bennett, and A. Factor discuss the preparation of copolymers of PPO by oxidative coupling of dimethylphenol with methylphenylphenol and with diphenylphenol. 

---