Abstract

Due to their unusual physical properties, perfluorocarbon (PFC) solvents have found applications as immiscible reaction medium when unstable reagents are to be used. We became interested in using a fluorous biphasic system (FBS) for the metallocene-based polymerization of [alpha]-olefins. Here we present a study on its potential influences on the coordination polymerization mechanism and physical properties of the polymers synthesized in such conditions. The first step of our study consisted of the design and set-up of a new polymerization reactor. Using zirconocene and methylaluminoxane (MAO), as catalytic system, preliminary tests of ethylene polymerization were carried out in order to test the system and assess process stability through the evaluation of ethylene polymerization yields and catalyst efficiency parameters (e.g., activity, turn over number, turn over frequency). Catalyst efficiency parameters were all correlated, suggesting that the presence of a PFC in the reaction medium had a limited influence on the catalyst efficiency with little impact on the kinetics of the coordination polymerization process. When ethylene--1-hexene copolymerization reactions were performed in FBS, a negative comonomer effect was observed. Catalyst efficiency parameters calculated for FBS conditions were also affected by the presence of two monomers in the reaction medium. Differential scanning calorimetry (DSC) was used to evaluate the melting temperature and the crystallinity of the synthesized polymers. The copolymers obtained in FBS were characterized by a relative higher proportion of amorphous structure compared to those synthesized in toluene only. The relative proportion of comonomer incorporated in the copolymers synthesized in FBS increased with increasing the 1-hexene concentrations. Owing to their great potential, the study of FBS for Ü-olefin polymerization and copolymerization should be pursued until they find widespread application at the plant scale