71092-60-9Relevant articles and documents
Synthesis and preliminary characterization of some polyester rotaxanes
Gibson, Harry W.,Liu, Shu,Lecavalier, Pierre,Wu, Charles,Shen, Ya Xi
, p. 852 - 872 (2007/10/02)
A series of polyester rotaxanes containing polysebacate backbones [decamethylene, tri(ethyleneoxy), and 1,4-butylene] and ethylene oxide-based crown ethers [30-crown-10,42-crown-14, 60-crown-20, and bis(p-phenylene)-34-crown-10] was synthesized via step growth polymerizations using diacid chloride-diol and transesterification reactions. The polyrotaxanes were purified by multiple reprecipitations in good solvents for the crown ethers, and the physical linkage of the crown ether to the polymeric backbone was confirmed by a variety of experiments, including hydrolysis, NMR, GPC, and VPO. Up to 55 wt % macrocycle was incorporated, depending on the size and shape of the macrocycle and the feed ratios employed. In all cases, the solubilities of the polyrotaxanes were strongly influenced by the cyclic component; enhanced solubilities in polar solvents were observed relative to the simple parent polysebacates. Mark-Houwink K and a values were also strongly affected by rotaxane formation; in the case most thoroughly investigated, K decreased by almost 2 orders of magnitude and a doubled. Interpretation of this observation is complicated by the changes in solubility. Thermal behavior was also affected. In the tri-(ethyleneoxy) system, Tg is lowered in the rotaxanes; in the 60-crown-20 system, the macrocycle crystallized! The poly(butylene sebacate) 60-crown-20 and 42-crown-14 systems also possessed two crystalline phases, a crown ether phase and a poly(butylene sebacate) phase. These exciting result demonstrate the mobility of the macrocycle along the polyester backbone in melt and solution states, allowing aggregation and crystallization without dethreading.
Synthesis and Characterization of Large (30-60-Membered) Aliphatic Crown Ethers
Gibson, Harry W.,Bheda, Mukesh C.,Engen, Paul,Shen, Ya Xi,Sze, Jean,et al.
, p. 2186 - 2196 (2007/10/02)
We report a new synthetic approach to large (30-72 membered) crown ethers based on isolation of the small and large cyclic polyethers made by combination of 1 mol or 2 mol each, respectively, of oligo(ethylene glycol)s and oligo(ethylene glycol) ditosylates.The advantages of this approach are the use of readily available glycols as starting materials and the ability to optimize the procedure for selective production of either macrocycle, producing yields superior or comparable to previous methods.At higher reaction temperatures the large crown ether is preferentially formed.This approach has been used to produce the crown ethers on 100-g scales.Purification was achieved by a combination of filtration through silica gel, treatment with a polymeric acid chloride, and recrystallization techniques, avoiding standard column chromatography.The pure crown ethers, 60-crown-20, 48-crown-16, 42-crown-14, 36-crown-12, and 30-crown-10, were characterized by melting points, 1H- and 13C-NMR, elemental analysis, and/or MS, GC-MS, and TGA-MS.Melting points were as much as 26 deg C higher than previously reported for these crown ethers.All the aliphatic crown ethers larger than 18-crown-6 decompose upon heating in air at ca. 200 deg C.
TEMPLATE EFFECTS. 7. LARGE UNSUBSTITUTED CROWN ETHERS FROM POLYETHYLENE GLYCOLS: FORMATION, ANALYSIS, AND PURIFICATION
Vitali, Chiara Antonini,Masci, Bernardo
, p. 2201 - 2212 (2007/10/02)
Through the reaction of polyethylene glycols with tosyl chloride and heterogeneous KOH in dioxane not only coronands from crown-4 to crown-8 can be obtained but also larger homologues.A systematic investigation has shown that: i) crown-9 and crown-10 can be formed from nona- and deca-ethylene glycol, respectively, and isolated in pure form; ii) the whole series of polyethylene glycols from tri- to deca-ethylene glycol yields not only the corresponding crown ethers but also higher cyclooligomers that can be analyzed up to about crown-20 by glc: in particular crown-12 and crown-16 were obtained from tetraethylene glycol and purified by column chromatography on cellulose; iii) the reaction, as applied to commercial mixtures of polyethylene glycols (from PEG 200 to PEG 1000), gives fairly high yields of crown ethers also in the region of large ring sizes.The contribution of the template effect of K(+) ion and the cyclooligomerization reactions for the various ring sizes are discussed.
