TY  - JOUR
A1  - Szymoniak, Paulina
A1  - Kolmangadi, Mohamed A.
A1  - Böhning, Martin
A1  - De Souza, N. R.
A1  - Juranyi, F.
A1  - Zorn, R.
A1  - Schönhals, Andreas
T1  - Inelastic and Quasielastic Neutron Scattering on Polynorbornenes with Bulky Carbocyclic Side groups
JF  - Polymer
N2  - This study investigates the molecular mobility and vibrational properties of polynorbornenes with bulky carbocyclic side groups using inelastic and quasielastic neutron scattering techniques. The polymers, synthesized via metathesis and addition polymerization, exhibit varying degrees of microporosity, which ignificantly influences their gas separation performance. By inelastic neutron scattering experiments, it could be shown that all considered polymers have excess contributions to the low frequency vibrational density of states known as the Boson peak. The maximum frequency of the Boson peak correlates to the microporosity of the polymers. 
This correlation supports the sound wave interpretation of the Boson peak, suggesting that the microporous structure enhances the compressibility of the material at a microscopic length scale. The molecular mobility, particularly the methyl group rotation, was characterized using elastic scans and quasielastic neutron scattering. The study revealed a temperature dependent relaxation process, with the onset of molecular fluctuations observed around 200 K for the polymer containing methyl groups. For the polymer having no methyl groups only elastic scattering is observed. The methyl group rotation was analyzed in terms of a jump diffusion in a threefold potential with three equivalent energy minima. This leads to an almost correct description of the q dependence of the elastic incoherent scattering function when the number of hydrogen nuclei undergoing the methyl group rotation is considered. It was further evidenced that the fraction of methyl undergoing the methyl group rotation increases with increasing temperature.
KW  - Polymers of Intrinsic Microporosity
KW  - Neutron scattering
PY  - 2025
UR  - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630297
DO  - https://doi.org/10.1016/j.polymer.2025.128358
SN  - 1873-2291
VL  - 328
SP  - 241
PB  - Elsevier Ltd.
AN  - OPUS4-63029
LA  - eng
AD  - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER  -