Anthracene‐Substituted Polynorbornenes as Highly Permeable Gas Separation Membranes: The Impact of Introducing Methyl Groups on Gas Transport Properties

ABSTRACT The incorporation of polycyclic moieties and methyl groups into the structure of rigid‐chain glassy polymers are two known approaches to improve their gas transport properties. In this study, the combination of these approaches is reported for polynorbornenes. More specifically, the gas transport characteristics of glassy microporous polynorbornenes containing methylated 9,10‐dihydroanthracene pendant substituents were systematically studied. These membranes exhibit a combination of relatively high permeability (maximum CO 2 permeability is 1600 Barrer) and good separation parameters (α[CO 2 /N 2 ] up to 41, α[O 2 /N 2 ] up to 4.8) and noticeably better gas separation characteristics compared to analogous polymers without Me‐groups. The results obtained indicate that methyl groups positively influence the gas separation performance of glassy polynorbornenes when they are rigidly bonded to the main polymer chains, even through polycyclic moieties. This effect appears to strengthen as the number of methyl groups per substituent increases.