Spin diffusion and spin-lattice relaxation in multiphase polymers

Abstract

Reuse of AIP Publishing content is subject to the terms: https://publishing.aip.org/authors/rights-and-permissions. A model which treats spin diffusion and spin-lattice relaxation in multiphase polymers on the same footing is proposed. This new approach allows for more accurate determination of domain sizes and interfacial thickness in the probed polymers. In a poly͑styrene-b-isoprene͒ copolymer example a significant improvement in the agreement between the NMR measurements and the simulated results can be obtained with the incorporation of a spin-lattice relaxation term into the spin diffusion process. The obtained microphase structural parameters are similar to the small angle X-ray scattering results. In addition, the spin-lattice relaxation times ͑T 1 ) in different domains can be predicted reasonably well based on T 1 s of the component homopolymers and on the microphase structure in the present model.

Measurement of Spin Diffusion Coefficients in Glassy Polymers: Failure of a Simple Scaling Law

“…No non-volatile organometallic paramagnetic complex of Mn 2þ soluble in PS with a more suitable T el has been found, up to now. The value derived from the spin diffusion experiments on block copolymers, [4,5] D PS % 800 nm 2 Á s À1 , is reasonably close to the value we have obtained with our method on Mn 2þ -doped poly(4-vinyl pyridine) of very comparable structure, D P4VP ¼ 500 nm 2 Á s À1 . [21] These difficulties are removed in PSd 5 , both because the natural T 1r is much longer at room temperature, and the Measurement of Spin Diffusion Coefficients in Glassy Polymers: Failure of a Simple Scaling Law Table 2.…”

“…i) The considerable reduction of the spin diffusion in PSd 5 compared to PS, due to the lack of protons in the side chain. ii) The good agreement for D of PVAc with our previous measurement.…”

“…Solid-state NMR spectroscopy offers ways to recognize the existence of two phases [2,3] and to characterize the size of the domains using the phenomenon of spin diffusion. [4,5] At a mesoscopic scale, spin diffusion, resulting from energy conserving flip-flops of the nuclear spins, controls the return to a uniform equilibrium ''spin temperature'' from a situation where it is initially different in the two phases. There are several experimental ways to put the spins out of equilibrium and follow the recovery of the phases' magnetizations.…”

Miscibility and morphology of chiral semicrystalline poly‐(R)‐(3‐hydroxybutyrate)/chitosan and poly‐(R)‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/chitosan blends studied with DSC, 1H T1 and T1ρ CRAMPS

“…We have not attempted to model our complicated multiphase blends like other previously published works. 16,17 The single exponential T 1 values of chitosan at 3.7 ppm, and ␤-hydrogen of PHB or P(HB-co-HV) at 5.4 ppm are not exactly the same but the differences are only 20 -30%, which may be accounted for by the complex morphology in semicrystalline blends. The trends in the T 1 values of chitosan, and ␤-hydrogen are clearly the same as shown in Figures 11 and 12.…”

Molecular Conformation and Mobility of Polyamines Adsorbed on Silica Studied by Spin Labeling

“…The samples are (s) Nu100 -P 4 VP5%, (OE) Nu1000 -P 4 VP5%, (}) Nu100 -P 4 VP0.5%, and (v) Nu1000 -P 4 VP0.5%. domains has already been discussed, and the model includes spin diffusion as well as spin-lattice relaxation (30), which suggests at least that many different correlation times should indeed be used.…”