Single-shot measurement of solids and liquids T1 values by a small-angle flip-flop pulse sequence.

We propose the small-angle flip-flop (SAFF) pulse sequence as an alternative procedure for the rapid measurement of the 1 H spin-lattice relaxation time in the laboratory frame (T1 ) of solid and liquid substances, in a time-domain NMR experiment. Based on the original flip-flop pulse sequence, this technique allows the fast estimation of T1 values of samples that require minutes to hours of acquisition time if traditional pulse sequences are employed. We have applied SAFF to different substances, with T1 ranging from microseconds up to seconds, including natural clays, polymers, and organic and inorganic solvents. We also demonstrate the potential of the pulse sequence in the real-time monitoring of dynamic processes, such as the conformational changes of polymeric materials during heating. The results we obtained with SAFF are comparable with those acquired with the inversion-recovery pulse sequence, with the addition of several benefits. This pulse sequence obeys steady-state and magnetization-conserving principles, making it possible to dismiss the need for relaxation delay times of the order of 5T1 . SAFF has shown high sensitivity in the resolution of individual components of T1 in multiexponential systems and can be easily integrated to well-established pulse sequences, such as Magic Sandwich Echo and Carr-Purcell-Meiboom-Gill, for the single-shot determination of T1 and T2 or T2* .

Data on tensile tests and NMR measurements of poly(vinilidene fluoride) before and after stress relaxation.

Poly(vinilidene fluoride) was characterized before and after stress relaxation by tensile tests and time-domain nuclear magnetic resonance (TD-NMR). Tensile tests were performed to provide mechanical properties, focused on the data of elastic modulus for this matter. The TD-NMR technique was used to calculate the fraction of crystalline, constrained amorphous and free amorphous phase, and the transversal relaxation time of each of these phases.

Proton NMR relaxometry as probe of gelatinization, plasticization and montmorillonite-loading effects on starch-based materials.

The effects of granule disruption, the addition of glycerol and montmorillonite on the granule structure of corn starch were investigated by proton NMR relaxation, through the T2*, T1 and T1ρ relaxation times. Films containing 0%, 1%, 5% and 7%(w/w) of clay were prepared by solution casting and the relaxometry data were compared with those gleaned from WAXD, TGA and SEM techniques. Starch gelatinization without glycerol or clay results in an amorphous and rigid film having a dipole coupling higher than that observed for the granule. The plasticization reduces the chains rigid fraction by more than 20% and increases the adsorption of moisture in the region of greater molecular mobility. The addition of 1% of clay reduces the adsorption of moisture and, in concentrations of 5% and 7%, the agglomerates reduce the plasticization effect. These features studied were observed by the Tube-Reptation and Renormalized Rouse models applied at low frequencies.