Ring-Opening Metathesis Copolymerization Of Macrocyclic Olefin And Synthesis Of Cyclic Polymers

Ring-opening metathesis polymerization(ROMP) is a widespread tool to synthesize well-defined and highly functionalized polymers,which has attracted considerable research attention recently in the field of polymer chemistry.Degradable block copolymer was synthesized by one-pot ring-opening metathesis polymerization of functional cyclooctene and 23-membered macrocyclic olefin bearing the degradable Si-O bond,which was synthesized by ring-closing metathesis reaction of its corresponding long chain diene precursor.The copolymers were characterized by ~1H NMR and GPC measurements,and the reasults showed the prepared polymer has an expected multiblock structure,which could be degraded into telechelic functional polymer under the mild hydrolyzed conditions.Cyclic polymers with various chemical structure,composition,molecular characteristics,and architectures are paid steadily increasing attention,because cyclic polymers possess higher density,molecular weight-dependent melt viscosity,higher refractive index,and higher glass transition temperatures as compared to linear polymers.Up to now,only scarce examples of syntheses of cyclic polymers have been reported.In this paper cyclic poly(cyclooctene) bearing bromo-functionalized pendant(PCOE-Br) was synthesized via ROMP and ring-closing metathesis(RCM). But the cyclo-depolymerization(CDP) was also carried out,which leads to depolymerization of PCOE-Br.This paper also described the synthesis of cyclic poly(ε-caprolactone)(PCL) via ring-closing metathesis(RCM),ring closing enyne metathesis(RCEM),and"click"reaction of different difunctional linear PCL.Linear PCL precursors were prepared by ring-opening polymerization(ROP) of e-caprolactone in bulk,followed by reacting with corresponding acyl chloride containing vinyl or azido end group.The subsequent end-to-end intramolecular coupling reactions were performed under high dilution conditions.The successful transformation of linear PCL precursor to cyclic PCL was confirmed by gel permeation chromatography,~1H NMR,and Fourier transform infrared measurements.