Properties of the Polycomplex of Apple Pectin with Benzimidazolyl-2-methylcarbamate Hydrochloride after Micronization

X-ray diffraction, microscopic, and sorption studies of benzimidazolyl-2-methylcarbamate hydrochloride (BMCHC) with various types of pectin showed that the structure of the mixtures depends on the composition, grinding conditions, and pectin type.     

Mechanochemical Modification of Deoxypeganine Hydrochloride by Polyampholite

The solubility and dialysis of deoxypeganine hydrochloride and natural polyampholite were studied by IR spectra and x-ray diffraction analysis. Inclusion complexes form during mechanical treatment of a 1:1 mixture of deoxypeganine hydrochloride and natural polyampholite     

Structure and molecular conformation of tussah silk fibroin films treated with water–methanol solutions: Dynamic mechanical and thermomechanical behavior

The thermal response of tussah (Antheraea pernyi) silk fibroin films treated with different water–methanol solutions at 20°C was studied by means of dynamic mechanical (DMA) and thermomechanical (TMA) analyses as a function of methanol concentration and treatment time. The DMA curves of α-helix films (treated with ≥80% v/v methanol for 2 min and 100% methanol for 30 min) showed the sharp fall of storage modulus at about 190°C, and the loss peak in the range 207–213°C. The TMA curves were characterized by a thermal shrinkage at 209–211°C, immediately followed by an abrupt extension leading to film failure. Both storage and loss modulus curves significantly shifted upwards for β-sheet films, obtained by treatment with ≤60% methanol for 30 min. The loss peak exhibited a maximum at 236°C. Accordingly, the TMA shrinkage at above 200°C disappeared. The films broke beyond 330°C, failure being preceded by a broad contraction step. Intermediate DMA and TMA patterns were observed for the other solvent-treated films. The loss peak shifted to higher temperature (219–220°C), and a minor loss modulus component appeared at about 230°C. This coincided with the onset of a plateau region in the storage modulus curve. The TMA extension–contraction events in the range 200–300°C weakened, and the samples displayed a final broad contraction (peak temperature 326–338°C) before breaking. The DMA and TMA response of these films was attributed to partial annealing by solvent treatment, which resulted in the formation of nuclei of β-sheet crystallization within the film matrix. The increased thermal stability was probably due to the small β-sheet crystals formed, which acted as high-strength junctions between adjacent random coil and α-helix domains. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2717–2724, 1998     

Structure and molecular conformation of tussah silk fibroin films: Effect of heat treatment

Structural changes of tussah (Antheraea pernyi) silk fibroin films induced by heat treatment were studied as a function of the treatment temperature in the range 200–250°C. The DSC curve of tussah films with α-helix molecular conformation displayed characteristic endo and exo peaks at 216 and 226°C, respectively. These peaks first weakened and then completely disappeared after heating at 230°C. Accordingly, the TMA thermal shrinkage at 206°C disappeared when the films were heated at 230°C. The onset of weight loss was monitored at 210°C by means of TG measurements. X-ray diffraction profiles gradually changed from α-helix to β-sheet crystalline structure as the treatment temperature increased from 200 to 250°C. On raising the heating temperature above 200°C, the intensity of IR and Raman bands characteristic of β-sheet conformation increased in the whole ranges of amide and skeletal modes. The sample treated at 200°C showed a spectral pattern intermediate between α-helix and β-sheet molecular conformation. The IR marker band for random coil structure, still detectable at 200°C, disappeared at higher treatment temperatures. Spectral changes attributable to the onset of thermal degradation appeared at 230°C. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 841–847, 1997     

Reaction of perfluoro-2-methylpent-2-en-3-yl isothiocyanate with ethyl and isopropyl alcohols

Perfluoro-2-methylpent-2-en-3-yl isothiocyanate reacts with ethyl or isopropyl alcohols in the presence of NEt₃ to give derivatives of 4,5-dihydrothiazole and ethoxy(ethylthio)methylene-(1,1,1,4,4,5,5,5-octafluoro-2-trifluoromethylpent-2-en-3-yl)amine and isopropoxy(isopropylthio)methylene-(1,1,1,4,4,5,5,5-octafluoro-2-trifluoromethylpent-2-en-3-yl)amine, respectively. Heating of ethyl or isopropylN-(perfluoro-2-methyl-2H-pentylidene-3-amino)thiocarbamate with potassium carbonate in DMF yields the same products plus 3-tetrafluoroethylidene-5,5-bis(trifluoromethyl)thiazolidin-2-one. The structure of the latter was confirmed by X-ray diffraction analysis. The IR spectroscopy data for this compound in solution (CCl₄) and in the solid state (KBr) suggest the formation of the intermolecular NH...O=C hydrogen bond between the NH group and the oxygen atom of the heterocycle. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2021–2026, October, 1998.