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NMR Investigations of Self-healing Processes in Supramolecular Elastomers Kay Saalwächter

Observables/Methods. motion of/within supramolecular links (high-res. MAS NMR) phase composition, domains (low-resolution 1 H NMR) monomer-scale detection of chain motion ( 1 H MQ-NMR) macroscopic mechanical and self-healing behavior (rheology).

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NMR Investigations of Self-healing Processes in Supramolecular Elastomers Kay Saalwächter

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  1. Observables/Methods • motion of/within supramolecular links (high-res. MAS NMR) • phase composition, domains (low-resolution 1H NMR) • monomer-scale detection of chain motion (1H MQ-NMR) • macroscopic mechanical and self-healing behavior (rheology) NMR Investigations of Self-healing Processes in Supramolecular Elastomers Kay Saalwächter Structures relevant for self-healing elastomers [entangled melt] [permanent network] supramolecular network (homogeneous) supramolecular network (nanophase-separated) hybrid network SPP 1568: “Design and Generic Principles of Self-healing Materials” new proposal

  2. 1H high-resolution MAS NMR 7 10 permanent elastic plateau 6 10 H-bonds 5 10 cool G’, G'' at 1 rad/s (Pa) heat 4 10 G’ self-healing rubber 3 10 G’’ 2 10 0 20 40 60 80 100 120 140 160 °C NMR experiments on stretched rubbers 28mm local stretching by MQ NMR 8mm 2.0 unstretched R 1.5 a stretched l=2 1.0 probabilty classical affine model 0.5 phantom model 0.0 stretching/com-pression device 0 1 2 3 4 5 Dres/Dres,l=1 R. Pérez-Aparicio et al., Macromolecules46, 5549 (2013) Relevant previous work ageing in Leibler’s self-healing rubber R. Zhang et al., Macromolecules46, 1841 (2013)

  3. reference direction time-dependent orientation autocorrelation function Ca(t) = < P2(cos a0)P2(cos at)>t,n,N fast segmental motions (ns-ms) a(t) log Ca reptation, cooperative processes (ms-s) ~1% network: S2 plateau log time • residual average orientation • ~ semilocal backbone order parameter • dependent on N-1 (~ ne/c ~ 1/Me/c ) • NMR-observable dipolar coupling Dres ~ line width ~ 1/T2 ! Orientation correlations in polymers polymer melt far above Tg: n entangled/x-linked chains, Nsegments each

  4. 7 10 permanent elastic plateau 6 10 5 10 cool • implement analytical theory • use in fits to various materials • determine bond life-time tb G’, G'' at 1 rad/s (Pa) heat 4 10 G’ C(t) for supramolecular rubber: self-healing rubber 3 10 G’’ tb(T) elastic plateau 2 10 0 20 40 60 80 100 120 140 160 °C Sb2 ~ 1/Nb2 permanent crosslinks vs. flow correlate tR(M) td(M) Segmental orientation correlation function MQ NMR probes fast and slow chain dynamics 10 0 0 10-1 10-2 I 10-3 C(t/te) experimental (linear PB): 10-4 FFC NMR (3 kDa, 11 kDa) MQ NMR (87 kDa) constructed (linear PB): 10-5 2000 kDa II III-IV 87 kDa 10-6 35 kDa ts te 10-7 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 108 109 t/te F. Vaca-Chavez, KS, Phys. Rev. Lett. 104, 198305 (2010); Macromolecules44, 1549 & 1560 (2011)

  5. Collaborations within the SPP 1568 Samples from other projects • W. Binder: H-bonded supramolecular thermoplastic elastomers and ionomers based upon PIB • F. Böhme/G. Heinrich:self-healing ionic liquidsbased upon PIB) • A. M. Schmidt: ionomeric elastomers based upon PBA and hydrogenated NBR Complementary methods • W. Pyckhout-Hinten: neutron scattering, rheology • W. Paul (new): theory support • C. M. Papadakis/B. Rieger (new): X-ray scattering, rheology

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