Copolymerization of carbon monoxide and norbornene derivatives with ester groups by palladium catalyst

Abstract

In this article we will discuss the synthesis of the new copolymers of norbornene derivatives with an ester group and carbon monoxide, using Pd(CH 3 CN) 4 (BF 4 ) 2 as a catalyst and 2,2'-bipyridine as a ligand in nitromethane/methanol at 60°C. Elementary analysis, infrared spectra, and NMR spectra indicated that copolymers contain ketone, ester, and bicyclic structures. Methanol functions as the coinitiator and chain transfer agent in copolymerization. A decrease in the molar ratio of [CH 3 OH]/[Pd] caused an increase in molecular weight and a decrease in yield of the copolymer. The number-average molecular weight of copolymers (M n ) ranged from 3800 to 5300, and the glass transition temperature (T g ) ranged from -32 to 117°C. Thermal analysis revealed that both T d10% and T dmax exceeded 180 and 230°C, respectively. Linear long-chain substituents such as n-C 11 H 23 C(O)-O-CH 2 - drastically reduced T g to a value of-32°C. In general, copolymers having a longer linear side-chain substituents of ester on norbornene have a more desirable solubility. Moreover, X-ray diffraction demonstrated that the degree of crystallinity decreases with an increasing length of side chain substituents.