PEG-based Multifunctional Polyethers with Highly Reactive Vinyl-Ether Side Chains for Click-Type Functionalization

Abstract

Introduction of highly reactive vinyl ether moieties along a poly(ethylene glycol) (PEG) backbone has been realized by copolymerization of the novel epoxide monomer ethoxy vinyl glycidyl ether (EVGE) with ethylene oxide (EO). A series of copolymers with varying structure (block and random) as well as EVGE comonomer content (5À100%) with molecular weights in the range of 3,900À13,200 g/mol and narrow molecular weight distributions (M w /M n = 1.06À1.20) has been synthesized and characterized with respect to their microstructure and thermal properties. The facile transformation of the vinyl ether side chains in click type reactions was verified by two different post polymerization modification reactions: (i) thiolÀene addition and (ii) acetal formation, employing various model compounds. Both strategies are very efficient, resulting in quantitative conversion. The rapid and complete acetal formation with alcohols results in an acid-labile bond and is thus highly interesting with respect to biomedical applications that require slow or controlled release of a drug, while the thiolÀene addition to a vinyl ether prevents cross-linking efficiently compared to other double bonds.

Reactivity Ratios and Mechanistic Insight for Anionic Ring-Opening Copolymerization of Epoxides

“…[31] The comonomer sequence of this actually results in a pseudo-block copolymer of poly[(ethylene glycol vinyl glycidyl ether)- grad -(ethylene oxide)]- b -poly(ethylene oxide) with a long stretch of pure EO repeat units of ca. 150 repeat units near the terminus.…”

“…[6, 8, 13, 17-27] In addition to AGE, ethylene glycol vinyl glycidyl ether (EGVGE)[29,30] has been recently copolymerized with EO and provides a versatile vinyl ether moiety, which may form hydrolytically cleavable acetal linkage as well as undergo thiol-ene click reactions to form permanent covalent linkages as in the case of AGE. [31] For copolymerizations of AGE and EGVGE with ethylene oxide, the distribution of comonomer sequences was characterized as random based on a qualitative 13 C NMR spectroscopy analysis of triad resonances. [8, 31]…”

“…[31] For copolymerizations of AGE and EGVGE with ethylene oxide, the distribution of comonomer sequences was characterized as random based on a qualitative 13 C NMR spectroscopy analysis of triad resonances. [8, 31]…”

Oxidation-Responsive and “Clickable” Poly(ethylene glycol) via Copolymerization of 2-(Methylthio)ethyl Glycidyl Ether

“…This trend is most distinct for the random PEG-ran-PMTEGE copolymers and is frequently observed for multi-functional PEGs. [27][28][29] EO/MTEGE ratios were also calculated from 1 H NMR spectra comparing the signal of the methyl group (-SCH 3 ) at 2.15 ppm to the polyether backbone signal at 3.4-3.8 ppm (Figure 2 and S7). Overall, ratios were varied from 3-24 mol%, yielding water-soluble polymers while preserving PEG's outstanding properties, and increasing its functionality ( Table 1).…”

Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks

“…Vinyl ether terminated urethane prepolymers [9,14] with cationic curing ability were synthesized but they still require blending with multifunctional reactive diluents to obtain higher crosslinking densities and a more distinct mechanical modulus increase upon polymerization. Recently, the first polymer systems bearing vinyl ether moieties along the backbone were reported, prepared as biocompatible polyether [15] and polyphosphorester [16] templates for post-polymerization modification through thiol-ene "click" reactions. In these reports, neither UV-initiated crosslinking nor mechanical material property variations were discussed.…”