Strictly monofunctional methyl ethers of poly(ethylene glycol) and the related methacrylate macromonomers

Monomethyl ethers of poly(ethylene glycol) with M = 2000 and 5000 and free of PEG admixtures were prepared by the living anionic polymerization of eth ylene oxide under the action of alcoholate of methyl ether of triethylene g lycol. Their molecular characteristics and purity were studied by vapor-pre ssure osmometry, IR and H-1 NMR spectroscopy, and liquid chromatography und er critical conditions. With respect to the content of monomethyl ethers of PEG (according to NMR spectroscopy, this value is 96.8-99.4%), the resulti ng polymers are dose to the polymers prepared by the chromatographic purifi cation of their commercial analogs (97.1-99.9%), which contained up to 25% PEG before purification. Methacrylation of homogeneous methyl ethers of PEG yielded macromonomers with a functionality not exceeding 1.0. Preliminary experiments showed that polymerization of these macromonomers leads to solu ble polymers, whereas macromonomers prepared from the commercial methyl eth ers of PEG and containing branching dimethacrylate give rise to the crossli nked polymers. A preliminary characterization of the soluble products was p erformed. Their hydrodynamic parameters in an aqueous medium are consistent with a compact, presumably star-shaped structure of macromolecules, and th e number of arms for various samples ranges from 25 to 120. These estimates are close by an order of magnitude to the data derived from the study of t he elastic behavior of PEO hydrogels, in which similar star-shaped fragment s play the role of network junctions.