CATIONIC POLYMERIZATION OF 2,3-DIHYDROFURAN - STUDY ON THE RELATIONSHIP BETWEEN GLASS-TRANSITION TEMPERATURE AND TACTICITY OF THE POLYMER

The cationic polymerization behavior of 2,3-dihydrofuran (DHF) was inv estigated. Polymerization of DHF was carried out in the presence of bo ron trifluoride (BA) or ethylaluminum dichloride (EADC). The glass tra nsition temperature (T-g) of the polymer depended upon the polymerizat ion conditions. The T-g of the polymer obtained in the polymerization with BF3 at -78 degrees C was 150 degrees C. On the other hand, the T- g of the polymer obtained in the polymerization above -60 degrees C wa s ca. 130 degrees C. In the polymerization with EADC, addition of ethy l acetate increased the molecular weight of the polymer compared to th at of polymerization in toluene only. In the C-13-NMR spectra of the p olymer, splits of signals of main chain carbon atoms which corresponde d to erythro and three isomers were observed. A linear relationship be tween the ratio of isomers and T-g was confirmed. The all-trans confor mer of the threo-diisotactic isomer was concluded to be the most stabl e one from MM2' calculation. C-13-NMR and molecular mechanics studies suggested that the difference in T-g of the polymers was derived from the difference in tacticity of the polymers.