Pseudoliving Ring-Opening Metathesis Polymerization with an Ill-Defined Catalyst System via Intermolecular Chain Transfer

Pseudoliving ring-opening metathesis polymerization (ROMP) was conducted using an industrial catalyst system WCl6/alkyl aluminum/alcohol via a semicontinuous strategy. The classical mechanism of living ROMP fails to fully account for the observed living characteristics in this polymerization. However, the incorporation of an intermolecular chain transfer successfully resolves these contradictions. As the chain transfer agent is consumed, active centers are able to randomly activate all polymer chains via intermolecular chain transfer and undergo propagation, thereby achieving pseudoliving polymerization. In sequential copolymerization, diffusion ordered spectroscopy demonstrated the transition from homopolymers to copolymers, proving the existence of intermolecular chain transfer. Additionally, 13C NMR spectra of copolymers produced by different polymerization strategies further revealed that sequential polymerization yielded copolymers with a multiblock structure. MATLAB simulations demonstrated that the dispersity of polymers being less than 2 was a result of the similar intermolecular chain transfer probabilities of dead polymers with different polymerization degrees.