A study of the molecular weights of tetrahydrofuran–propylene oxide copolymers by gel permeation chromatography and other methods

The cationic copolymerization of tetrahydrofuran and propylene oxide was studied in a batch system. Boron fluoride ethyl ether and 1,2-propanediol were used as catalyst—co—catalyst system. Number-average molecular weights M?_n of various copolymers were determined by vapor-pressure osmometry (VPO) and hydroxyl endgroup analysis (OH). The VPO and OH molecular weights differed considerably. To explain the differences, several copolymers were analyzed by gel permeation chromatography (GPC). The chromatograms obtained showed for each copolymer analyzed two peaks, one located in the high molecular weight region, the other in the low molecular weight region. An attempt is made to correlate the results and to show the usefulness of GPC in the characterization of THF—PO copolymers.