We report the first in-depth ESR study of plasma-induced polycarbohydrate radicals in powdered cellulose and amylose. On the basis of the ESR kinetics coupled with the systematic computer simulations, it was found that plasma irradiation produced preferentially the alkoxylalkyl radical at CI of the glucose units in both polycarbohydrates. However, the observed ESR spectra are largely different in pattern between the two anomeric polymers: The triplet spectrum with ca. 3.0 mT of HSC was present only in celullose, which is assignable to the hydroxylalkyl radical at CZ and/or C3 of the glucose units of cellulose. Presumably, the hydroxylalkyl radical at C3 of the glucose units of amylose which should likewise exhibit a triplet was not formed due to the suppression of hydrogen abstraction at C3 in the helical tertiary structure of amylose.However, the acylalkyl radicals which are formed by dehydration of the hydroxylalkyl radicals were observed in both polycarbohydrates. This anomaly in amylose was rationalized in terms of spontaneous dehydration of the hydroxylalkyl radical formed at C2 of the glucose units due to a special rehybridization-induced effect of the carbon-radical center on such dehydration reactions valid only in a solid state. It was also shown that the polycarbohydrate radicals were rapidly reacted with oxygen in air, unlike monocarbohydrate radicals which are stable even after prolonged standing in air at room temperature. This difference could be ascribed to the difference in the polymorphic forms between polycarbohydrates and monocarbohydrates.
Blends of nylon 6 (Ny6) with poly(acrylic acid) (PAA) were prepared in film form from solutions in a mixture of formic acid and water by evaporating the solvent. The miscibility and phase constitution of the binary blends obtained over a wide composition range (5/95–95/5) were examined by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical measurements. A Ny6 homopolymer film and Ny6/PAA blends with PAA concentrations ≥ 50 wt% exhibited a WAXD profile stemmed from the coexistence of two different crystalline modifications of Ny6, i.e. the α and γ forms. Above 50 wt% PAA content, the solution‐cast blends showed no definite crystallinity. It was found by DSC thermal analysis that the polymer pair is substantially miscible in the non‐crystalline state, since a single glass transition temperature (Tg) was situated between the Tgs of the two homopolymers at every composition; however, the Tg versus composition plots did not follow a monotonic function but yielded a peak maximum at a PAA concentration of c. 25 wt%. In order to interpret this phenomenon, attention was given to the following point revealed by dynamic mechanical measurements: at the compositions of Ny6/PAA = 100/0–50/50, a phase of low regularity such as a nematic structure is formed in the cast films.
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