SYNTHESIS AND THERMAL PROPERTIES OF CARBON DIOXIDE-CYCLOHEXENE OXIDE COPOLYMERS

Abstract

Cyclohexene oxide copolymer (PCHC) with high molecular weight was synthesized using ternary rare earth metal coordinate catalyst (Y(Cl3COO)(3)-ZnEt2-glycerine) The catalytic activity reached 11. 8 kg polymer/mole Zn under optimal condition, the obtained PCHC showed number average molecular weight (M-n) of 7. 0 x 10(4), with carbonate unit over 95%. The glass transition temperature (T-g) of PCHC was between 110 degrees C and 120 degrees C, it increased with increasing M-n when M-n was below 8.5 x 10(4), and leveled between 119 degrees C and 120 degrees C when M-n was over 8.5 x 10(4). The highest T-g may be reached as 120 degrees C if the M-n of PCHC is high enough, and the characteristic free volume constant K is 1. 91 x 10(5). The influence of molecular weight on thermal stability of PCHC was investigated, raising molecular weight was beneficial for improving thermal stability of PCHC, and a 60 degrees C increase of the onset degradation temperature was observed when M-n increased from 39. 9 x 10(3) to 93. 1 x 10(3). Since the rare earth ternary catalyst changed to metal oxide (mainly ZnO) after polymerization and post-polymerization treatments, the influence of Zn content on thermal stability of PCHC was studied based on Kissinger method, PCHC with Zn content below 5 x 10(-6) showed surface activation energy for thermal decomposition of 199. 9 kJ/mol, whereas it decreased to 143. 9 kJ/mol for PCHC with Zn content of 4400 x 10(-6). Therefore, reducing Zn content could improve the thermal stability of PCHC.