Crosslinked epoxides

The UV-radiation curing technology is not restricted to the synthesis of clay-acrylate nanocomposites, but it can be extended to other types of polymer systems, such as crosslinked epoxides, vinyl ethers and interpenetrating polymer networks, as well as to other types of layered nanoparticles, such as superconductive nanofillers and magnetic particles. Future work should be... 

Cycloahphatic diamines react with dicarboxyUc acids or their chlorides, dianhydrides, diisocyanates and di- (or poly-)epoxides as comonomers to form high molecular weight polyamides, polyimides, polyureas, and epoxies. Polymer property dependence on diamine stmcture is greater in the linear amorphous thermoplastic polyamides and elastomeric polyureas than in the highly crosslinked thermo set epoxies (2—4). 

Epoxy resins have a wide range of molecular weights (=1,000-10,000). Those with higher molecular weights, termed phenoxy, are hydrolyzed to transparent resins that do not have the epoxide groups. These could he used in molding purposes, or crosslinked hy diisocyanates or hy cyclic anhydrides. 

For this use, the preferred powders are based on acrylic, epoxy or polyester and epoxy resins. For best colour, epoxy resins are crosslinked with anhydrides of dicarboxylic acids in the straight epoxy coatings, or with saturated polyesters of high acid content in the epoxy-polyester type. Acrylics contain epoxide rings via, for example, glycidyl methacrylate (CH2=C(CH3) —CO—O—CHj—CH —CH2), and these groups crosslink... 

It was concluded that the crosslinking reaction proceeded through initial alkylation of N-7 of adenine by the aziridine ring, followed by guanine N-7 alkylation by the epoxide (Figure 11.12). This seems inconsistent with Armstrong s earlier conclusions, but the very short oligonucleotides used by Saito et al. may influence the DNA alkylation chemistry. 

Very recently, the Shipman group have made a further step towards a comprehensive structure/activity profile for noncovalent interactions between azinomycin B and DNA [152]. They synthesized simplified azinomycin analogues 69 and 96-98 (Scheme 11.13), retaining both the epoxide and aziridine alkylating functionalities, with systematically altered substitution on the naphthoate fragment, and analyzed their DNA crosslinking by gel electrophoresis. They found that cross-... 

Void-free phenolic networks can be prepared by crosslinking novolacs with epoxies instead of HMTA. A variety of difunctional and multifunctional epoxy reagents can be used to generate networks with excellent dielectric properties.2 One example of epoxy reagents used in diis manner is the epoxidized novolac (Fig. 7.34) derived from the reaction of novolac oligomers with an excess of epichlorohydrin. 

The final resin product is obtained by reacting (curing or crosslinking) the above di-epoxide with acid anhydrides or polyamines. The curing agents (sometimes incorrectly called catalysts) react with the three-membered epoxide rings to produce a highly crosslinked polymer. 

By analogy to simple olefins, we propose that 0(3P) initially adds to the 1,4 or 1,2 double bonds in polybutadienes at ambient temperature. Since the rate constants for 0(3P) addition to cis-2-butene and 1-butene (as models for 1,4 and 1,2 double bonds, respectively) are in the ratio 4.2 1 at 298 K ( 6), preferential addition to the 1,4 double bonds is assumed to persist to very high vinyl contents (-8011). The biradical adducts then rearrange to epoxides and carbonyl compounds or give rise to chain rupture and/or crosslinking as a consequence of PIF, according to the scheme ... 

In addition to the use of peroxides for crosslinking, metal oxide, polyfunctional alcohols, amines and epoxide resin cure systems can be used with CSM rubbers. In the metal oxide based cure systems it is usual to add a weak acid, such as stearic acid, and accelerators, such as MBT, MBTS or TMTD magnesium or lead oxides are generally used. 

Canali et al.17 reported the use a linear poly(tartrate) ligand in the asymmetric epoxidation of allylic alcohols. Moderate results were obtained. They also reported the use of branched/crosslinked poly(tartrate), which gave moderate to good results in the asymmetric epoxidation of allylic alcohols. As shown in Scheme 4-9, when L-(+)-tartaric acid and 1,8-octanediol are heated... 

Hargreaves has suggested that the insolubilization of some closely related polymers is due to photolytic homolysis of the endoperoxide 0-0 bond and subsequent generation of carbon-centered radicals from the O radicals (19). There are several facts that make this an extremely unlikely explanation for the data described here these include the quantitative insufficiency of the maximum amount of endoperoxide reaction obtainable with a few hundred mJ/cm2 dose (homolysis quantum yield <0.5 (46), and extinction coefficient 1 (M cm)-1 (47)), and the synthetic utility of such homolysis reactions in related molecules in the presence of good hydrogen atom donors (implying facile epoxide formation) (48). Clearly the crosslinking observed under N2 is not accounted for by this mechanism. 

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