Cyano-functional polyether copolymers based on THF were prepared via cationic ring-opening copolymerization of THF with cyano ethylene oxide (CEO). The CEO content of poly(tetrahydrofuran) (polyTHF) based copolymers varied from 3.3 to 29.3%, and molecular weights ranged from 5100 to 31900 g.mol(-1) with M-w/M-n in the range of 1.31 to 1.74 (SEC in THF, PS standards). The polymerization was conducted with methyl trifluoromethanesulfonate (MeOTf) as an initiator. Kinetic studies concerning incorporation of both monomers were performed via NMR spectroscopy. The cyano groups at the poly(THF-co-CEO) copolymers enable direct access to amino (polyTHF-NH2) and carboxyl groups (polyTHF COOH) in facile one-step procedures, respectively. The modified copolymers were characterized via NMR, MALDI-ToF mass, and FT-IR spectroscopy. Thermal properties of the materials were studied via differential scanning calorimetry (DSC), demonstrating a gradual decrease of the melting points with increasing amount of CEO in the copolymers (from 30 degrees C for 3.3% CEO to 21 degrees C for 8.4% CEO). After postmodification to carboxylic acid groups the melting points decrease from 26 to 18 degrees C in the series of copolymers. Contact angles of water on thin films of the polymers can be tuned in a wide range from 72.7 degrees to 17.8 degrees by varying the CEO fraction as well as by postmodification. Crystallization studies of CaCO3 with water-soluble polyTHF COOH revealed the composition-dependent inhibition of calcite growth, with crystallite size in the mineralization process being controlled by the amount of carboxylic acid groups at the poly(THF) copolymers.