The segmental and global dynamics in lamellar microphase-separated poly(styrene-b-isoprene) diblock copolymer studied by 1H NMR and dielectric spectroscopy

Glassy and Polymer Dynamics of Elastomers by 1H Field-Cycling NMR Relaxometry: Effects of Cross-Linking

“…Almost identical master curves were obtained for all the sulfur-cured IR rubbers, which differ from those of uncured IR only at very low frequency, where regime II of the TR model is observed for the latter sample (Figure a). The master curve obtained for uncured IR is quite similar to that reported in the literature for samples of linear high-molar mass polyisoprene. ,, The χ″(ωτ s ) curve of uncured BR results from the contribution of glassy dynamics and polymer dynamics in regimes I and II, in analogy to that reported in the literature for linear high-molar mass polybutadiene samples. ,,− On the other hand, the χ″(ωτ s ) curves of cross-linked BR-based rubbers show the contribution from glassy dynamics and regime I of polymer dynamics. A deviation from the slope of regime I is observed at the lowest ωτ s values for BR_S1_150 (Figure b), as already evidenced by the NMRD and susceptibility curves at the highest temperatures.…”

“…The master curve obtained for uncured IR is quite similar to that reported in the literature for samples of linear high-molar mass polyisoprene. 29,30,54 The χ″(ωτ s ) curve of uncured BR results from the contribution of glassy dynamics and polymer dynamics in regimes I and II, in analogy to that reported in the literature for linear high-molar mass polybutadiene samples. 25,27,29−31 On the other hand, the χ″(ωτ s ) curves of cross-linked BR-based rubbers show the contribution from glassy dynamics and regime I of polymer dynamics.…”

Dynamics of poly(vinyl butyral) studied using dielectric spectroscopy and 1H NMR relaxometry

“…In the motional narrowing regime, A Ã ¼ 1 3 g 2 DM 2 , with g representing the proton gyromagnetic ratio and DM 2 the reduction of the second moment caused by the motion. 50,51 We considered conformational and segmental reorientation dynamics of proton pairs on the same segment, disregarding contributions arising from interactions between different segments on the same macromolecule, which are of lower magnitude, 52 and used the HN function, J HN (n) (eqn (3)), to express the associated spectral density. 37 For PVB, 1 H longitudinal relaxation is mainly determined by the reorientations of the inter-proton CH 2 vector and, assuming isotropic motion, A* = 2.5 Â 10 9 s À2 .…”

Effects of Asymmetric Molecular Architecture on Chain Stretching and Dynamics in Miktoarm Star Copolymers

“…These master curves confirm that the PI chain and α-relaxations are well separated in the time domain ( cf . eq ) and the spectral shapes of each relaxation are constant with temperature . The master curve spectra in Figure S8 were fit for each polymer using two empirical Havriliak–Negami functions to reveal the spectral shapes of individual relaxations at each temperature, as detailed in Part B of the Supporting Information.…”

“…eq 2) and the spectral shapes of each relaxation are constant with temperature. 54 The master curve spectra in Figure S8 were fit for each polymer using two empirical Havriliak−Negami functions to reveal the spectral shapes of individual relaxations at each temperature, as detailed in Part B of the Supporting Information. For all of the polymers studied, the temperaturedependent frequency of maximum loss (ω α,max = 2πf α,max ) and the spectral shapes of the α-relaxation are displayed in Figure S12.…”