Side Chain Dynamics of poly(norbornene)-g-Poly(propylene oxide) Bottlebrush Polymers

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The segmental dynamics of the side chains of poly(norbornene)-g-poly(propylene oxide) (PNB-g-PPO) bottlebrush polymer in comparison to PPO is studied by quasi-elastic neutron scattering. Having experimental time and length scale information simultaneously allows to extract spatial information in addition to relaxation time. Tethering one end of the PPO side chain onto a stiff PNB backbone slows down the segmental relaxation, over the length and time scales investigated. The power law dependence of the relaxation time on the momentum transfer, Q, indicates a more heterogeneous relaxation pattern for the bottlebrush polymer, whereas the linear PPO has less deviations from a homogenous relaxation. Similar conclusions can be drawn from the time dependent mean square displacement, 〈r (t)〉, and the non-Gaussian parameter, α (t). Here the bottlebrush polymer shows a more restricted dynamics, whereas the linear PPO reaches 〈r (t)〉∝t at the highest temperature. The deviations from Gaussian behavior are evident at the α (t). Both samples show a decaying α (t). The non-Gaussian parameter supports the results from the power law dependence of the relaxation times, with lower α (t) values for PPO compared to those for PNB-g-PPO, pointing to less deviations from Gaussian behavior. This article is protected by copyright. All rights reserved.

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Macromolecular rapid communications

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