This report describes a simple strategy to produce copolymers of tetrahydrofuran (THF) and glycidyl phenyl ether (GPE) by using B(C6F5)(3) as a catalyst. The control of the synthesis conditions, such as reaction time, catalyst concentration, and monomer concentration, allows the formation of copolymers with molecular weights in the range of 15-330 kg/mol. MALDI-TOF mass spectrometry revealed that with a low THF content in the feed cyclic copolymers are the major reaction products, whereas with a high THF content, linear copolymers are the main products. To explain these results, a zwitterionic ring-opening copolymerization mechanism was postulated based on DFT calculations and experimental results. Physical properties of the resulting copolymers demonstrated that by changing the relative amounts of monomers copolymers with tailored glass transition temperatures in a broad range of temperatures from -84 to -4 degrees C can be obtained and that crystallization of THF fragments can be suppressed. Rheological measurements showed that by controlling the degree of crystallization, copolymers with rubber-like behavior can be obtained in a broad temperature range below room temperature.