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Janus polytricyclononenes (PTCN) with rigid backbones and flexible n-alkyl (n = propyl, butyl, hexyl, octyl, decyl) are novel, innovative materials that show potential in separating hydrocarbons. These superglassy polymers were designed to show an enhanced and controllable gas permeability via flexible alkyl side chains that promote mass transport, as opposed to conventional microporous polymers, where permeability is a function of the free-volume entities.
PTCNs, investigated by small angle X-ray scattering (SAXS), show nanophase separation between the n-alkyl side chains and the backbones. The size of the nanodomains increases with the length of the n-alkyl side groups. In addition, for the alkyl chain-rich nanodomains a distinct α-relaxation was found by means of broadband dielectric spectroscopy (BDS) and temperature modulated DSC (TMDSC). The glass transition of the backbone-rich domains, which is beyond or near to the degradation of the materials, was evidenced by fast scanning calorimetry (FSC) by decoupling it from decomposition, employing high heating rates up to 104 K/s.
Further, Janus PTCNs were studied by quasielastic neutron scattering (QENS) employing the backscattering IN16B (ILL, Grenoble) and time of flight FOCUS (PSI, Villigen) instruments. For an overview of dynamic processes setting in at different temperatures inelastic (IFWS) and elastic fixed window scans (EFWS) were conducted. IFWS showed that the segmental motions of alkyl-rich nanodomains shift to higher temperatures with increasing alkyl chain length, which agrees with SAXS and BDS findings. For the lowest side chain lengths an additional low temperature relaxation process was found, assigned to methyl group rotations.