Oligomers glycol ethers

Many of the crown ether syntheses with which we are concerned in this book are one form or another of the Williamson ether synthesis. Although the simplest example of such a reaction would involve an co-haloethylene glycol oligomer which undergoes intramolecular cyclization, it is more common for two new bonds to be formed in crown syntheses. An early example of the formation of a crown by a double-Williamson can be found in Dale s synthesis of 18-crown-6. The rather obvious chemical steps are shown in Eq. (2.1). 

Kawakami, Suzuki and Yamashita showed that compound 7, among many others, could be polymerized to derivatives of the corresponding open-chained species by treatment with boron trifluoride ether complex. Yamashita and Kawakami formed these same sorts of materials by heating the glycols and paraformaldehyde in the presence of toluenesulfonic acid. This led to prepolymers which were then thermally depolymerized to afford the cyclic oligomers which were separated by fractional distillation. 

The phase behavior of several polybibenzoates with oxyalkylene spacers has been reported [11,14,15,20-27]. These spacers include the dimer of trimethylene glycol and different ethylene oxide oligomers. The most noticeable characteristic of these polybibenzoates with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Thus, Fig. 8 shows the DSC curves corresponding to a sample of poly[oxybis(trimethylene)p,p -bibenzoate], PDTMB, with a structure similar to that of P7MB but with the... 

In this way the unstable 1,3-dioxacycloalkanes and their oligomers would be converted into stable ethers. This has been proved experimentally, and the reaction offers some exciting synthetic possibilities [17, 18]. In particular, it provides a new route to a variety of new crown ethers, such as the l,4,7,10-tetraoxa-ll,ll-dimethylcyclotridecane (a 13-crown-[4]-ether) from isobutene and the formal of triethylene glycol but that is another story ... 

The mean-square optical anisotropies of four oligomers of polyoxyethylene glycol dimethyl ether are determined from measurements of depolarized Rayleight scattering. They are interpreted using the valence optical scheme and RIS theory. 

Esters and ethers based on poly(tetramethylene glycol) and propylene oxide or a combination of propylene and ethylene oxides commonly are used in reactive processing. The chemistry of leading to polyurethane formation, has been analyzed in many publications 15 7 however, the practical problems of processing real initial oligomers and molding compounds based on them into articles for different applications have received less attention. 

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