Cross-Polarization/Magic Angle Spinning ¹³C-NMR Study

CP/MAS13C NMR analyses of hydrogen bonding and the chain conformation in the crystalline and noncrystalline regions for poly(vinyl alcohol) films

“…CP/MAS 13 C NMR measurements were performed at room temperature on a JEOL JNM‐GSX200 spectrometer operating at a static magnetic field of 4.7 T. 1 H and 13 C radio frequency field strengths γB 1 /2π were 69.4 kHz for both CP and dipolar decoupling processes. The CP contact time was 1 ms and the recycle time after the acquisition of a free induction decay (FID) was 10 s. Each sample was packed into a 7 mm cylinder‐type MAS rotor with an O‐ring seal9, 16, 17 and further dried at 50 °C for 15–24 h in vacuum, to prevent the absorption of moisture before and during NMR measurements. The MAS rate was about 3.5 kHz.…”

Structural investigation of amylose complexes with small ligands: inter- or intra-helical associations?

“…The other variations concern the C6 carbon with chemical shift at 61.3 ppm after rehydration instead of 60.7 in the WD sample and 60 ppm for the DW sample. Therefore, the carbon spectrum of the 'washed before being conditioned' menthone sample is characteristic of a V-6 hydrate packing of amylose [12][13][14][15][16]34] with the presence of a small quantity of the B-allomorph, which displays the typical doublet signal at 100.5 and 99.5 ppm (Fig. 6b).…”

“…Nevertheless, for some types of complex whose crystallographic structure has been completely resolved, the ligand can be included within helices [1,2]. The structure of amylose complexes formed with a wide range of small molecules has been investigated mainly by X-ray and electron diffractions [2][3][4][5][6][7], differential scanning calorimetry (DSC) [8][9][10][11] and solid-state nuclear magnetic resonance (NMR) [12][13][14][15][16]. The best-known and described complex is the V-6I amylose hydrate (V-h) which is obtained with linear alcohols [3,[17][18][19][20] and monoacyl lipids [8,9,21,22].…”

“…Solid-state NMR has been shown to be a non-invasive efficient method to complement X-ray diffraction for investigating the structure of native and complexed starch [12][13][14][15][16][36][37][38][39][40][41][42]. Use of the cross polarisation magic angle spinning (CPMAS) method allows detection of distributions of isotropic signals for each glycosidic carbon.…”

Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. IV. The relationships between the permselectivity of alginic acid membrane and its solid state structure

“…The upfield shift of C1 and C4 carbons in the 1,4-glycosidic linkage of the neutralized alginic acid will be caused by the different conformation of this linkage. Namely, the values of the tortion angles P and which are defined as shown in Figure 6 will affect the 13C chemical shift of C1 and C4 carbon, and a simple linear relationship exists mutually, as pointed out for cellulose by Horii et al 4 From the viewpoint of the "holes" conception, the effect of the size of alcohol molecules (methanol, ethanol, n -propanol, and i-propanol ) on the permeation rate and separation factor of sodium alginate membrane were investigated. The results are shown in Table 11, where the pervaporation experiment was carried out using 77.9 mol % alcohol mixture (in the case of ethanol, alcohol concentration corresponds to 90 wt ' ?6 ) .…”