This article discussed the root causes of the interesting differences between rac-Et(Ind) 2 ZrCl 2 and dimethyl (pyridyl-amido)hafnium in catalyzing the propylene/x-halo-a-alkene copolymerization. Confirmed by density functional theory (DFT) calculations, the larger spacial opening around the active center of rac-Et(Ind) 2 ZrCl 2 contributes to the coordination and insertion of the monomers, resulting in the higher catalytic activity, while the narrow spacial opening around the Hf center retards the chain transfer reaction, leading to the much higher molecular weights (M w s) of the copolymers. The superior tolerability of Zr catalyst toward halogen groups might be attributed to that the dormant species generated from halogen coordination could be promptly reactivated. DFT calculations indicated the higher probability for the x-halo-a-alkene vinyl to coordinate with the Hf catalyst leading to the better ability to incorporate halogenated monomers. The high M w s and the outstanding isotacticity achieved by the Hf catalyst determined the higher melting temperature values of the copolymers with a certain amount of halogen groups. In addition, the chain transfer schemes were employed to analyze why the presence of halogenated monomers greatly decreased the M w s of the copolymers when rac-Et(Ind) 2 ZrCl 2 was used, while had no or little effect upon the M w s in the copolymerization by the Hf catalyst.

We report here a series of novel spontaneously healable thermoplastic elastomers (TPEs) with a combination of improved mechanical and good autonomic self-healing performances. Hard-soft diblock and hard-soft-hard triblock copolymers with poly[exo-1,4,4a,9,9a,10-hexahydro-9,10(1',2')-benzeno-l,4-methanoanthracene] (PHBM) as the hard block and secondary amide group containing norbornene derivative polymer as the soft block were synthesized via living ring-opening metathesis copolymerization by use of Grubbs third-generation catalyst through sequential monomer addition. The microstructure, mechanical, self-healing, and surface morphologies of the block copolymers were thoroughly studied. Both excellent mechanical performance and self-healing capability were achieved for the block copolymers because of the interplayed physical cross-link of hard block and dynamic interaction formed by soft block in the self-assembled network. Under an optimized hard block (PHBM) weight ratio of 5%, a significant recovery of tensile strength (up to 100%) and strain at break (ca. 85%) was achieved at ambient temperature without any treatment even after complete rupture. Moreover, the simple reaction operations and well-designed monomers offer versatility in tuning the architectures and properties of the resulting block copolymers.