Tailoring thermoresponsiveness of biocompatible polyethers: copolymers of linear glycerol and ethyl glycidyl ether.

Abstract

Linear polyglycerol is known as a highly hydrophilic and biocompatible polymer that is currently considered for numerous medical applications. Derived from this well-known structure, the synthesis of highly biocompatible, thermoresponsive polyether copolymers via statistical anionic ring-opening copolymerization of ethyl glycidyl ether (EGE) and ethoxy ethyl glycidyl ether (EEGE) is described. Subsequent deprotection of the acetal groups of EEGE yields copolymers of linear glycerol (linG) and EGE, P(linG-co-EGE). These copolymers showed monomodal and narrow molecular weight distributions with dispersities Đ ≤ 1.07. The microstructure was investigated via in situ1H NMR kinetics experiments, revealing reactivity ratios of rEEGE = 1.787 ± 0.007 and rEGE = 0.560 ± 0.002, showing a slightly favored incorporation of EEGE over EGE. Due to the deliberate incorporation of rather hydrophobic EGE units into the water soluble linPG, tunable thermoresponsive behavior is achieved with cloud point temperatures Tcp between 9.0-71.4 °C. Besides the commonly utilized method turbidimetry, temperature-dependent 1H NMR measurements were used for more accurate and reproducible results. The change of the hydrodynamic radii rH of the copolymers and their aggregates upon reaching Tcp was investigated via DOSY NMR spectroscopy. To explore possible biomedical applications, as an example, the cell viability and immunology of an exemplary P(linG-co-EGE) copolymer sample was investigated. Since both, cell viability and immunology are comparable to the gold standard PEG, the herein presented copolymers show high potential as biocompatible and thermoresponsive alternatives to PEG for biomedical applications.