Synthesis and Hydrogenation of Poly(norbornadiene-co-cyclohexadiene) Block Copolymers with Enhanced Thermomechanical Performance

A novel di-block copolymer, poly(norbornadiene-co-cyclohexadiene) was synthesized via sequential ring-opening metathesis copolymerization (ROMCP) using Grubbs' third-generation catalyst. To overcome the intrinsic brittleness and limited thermal performance of cyclic olefin copolymers, the material was further modified through catalytic hydrogenation using a palladium supported on porous nickel decorated with carbon nanotubes (Pd@PN-CNT). The post-polymerization (catalytic hydrogenation) significantly enhanced the thermomechanical properties: the glass transition temperature increased from 127 ℃ to 139 ℃, and the degradation temperature rose from 438 ℃ to 519 ℃. Mechanical testing revealed improvements in tensile strength (from 14.58 MPa to 28.93 MPa), elongation at break (from 16.44 % to 32.34 %), and elastic modulus (from 28.61 MPa to 39.87 MPa). These improvements are attributed to the saturation of unsaturated bonds, reduction in chain defects, and enhanced phase separation. The high hydrogenation efficiency of the Pd@PN-CNT catalyst also demonstrated excellent reusability. This work presents a viable route for tailoring the thermal and mechanical performance of block copolymers, positioning hydrogenated poly(NBD-co-CHD) as a promising candidate for advanced applications in elastomers and high-performance engineering materials.