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The blend miscibility of cellulose alkyl esters, mainly butyrate (CB) and acetate butyrate (CAB), with synthetic homo-and copolymers comprising N-vinyl pyrrolidone (VP) and/or vinyl acetate (VAc) units, i.e., PVP, PVAc, and P(VP-co-VAc), was examined by differential scanning calorimetry. A miscibility map for the CB/vinyl polymer systems was constructed as a function of the degree of substitution (DS) of CB and the VP fraction of the mixing component. CBs were immiscible with PVAc regardless of the DS used (2.11 -2.94), but miscible or immiscible with PVP depending on whether the butyryl DS was <2.5 or >2.5. The critical value of DS % 2.5 is lower than the corresponding one (DS % 2.8) evaluated formally for cellulose acetate (CA)/PVP blend series. This lowering is ascribable to an effect of steric hindrance of the bulky butyryl substituents, leading to suppression of the hydrogen-bonding interactions, as a driving factor for miscibility attainment, between residual hydroxyls of CB and carbonyl groups of PVP. The CB/vinyl copolymer system imparted a 'miscibility window' in which the VP/VAc composition participated; viz., CBs of DS = 2.54 -2.94 were miscible with some P(VP-co-VAc)s of 30 -70 mol% VP fractions, in spite of the immiscibility with both PVP and PVAc homopolymers. The result was interpreted in terms of another inter-component attraction derived from repulsion between the monomer ingredients constituting the vinyl copolymer component. For CAB/P(VP-co-VAc) blends, it was observed that the VP/VAc range forming such a miscibility window became further expanded, compared with the corresponding series of CB blends. Fourier transform infrared and solid-state 13 C NMR spectroscopy revealed not only the presence or absence of the intermolecular hydrogen-bonding formation, determined according to the lower or higher DS of the cellulose ester component in the blends considered, but also a difference in the mixing scale between the polymer pairs regarded as miscible by the thermal analysis.

Poly(N-vinylpyrrolidone) (PVP) is miscible with cellulose acetate (CA) with a degree of acetyl substitution (DS) of less than ca. 2.75, and a random copolymer of N-vinylpyrrolidone (VP) and methyl methacrylate (MMA) can also form completely miscible blends with CA, when the VP fraction in the copolymer is >30 mol % and the DS of CA is ≤2.5. The molecular orientation and optical anisotropy induced by uniaxial deformation of the miscible blends of the VP-containing vinyl polymers [P(VP-co-MMA)s] with CA were characterized by a fluorescence polarization method and birefringence quantification, respectively. Film samples of more than 10 pairs of CA/P(VP-co-MMA) were cast from mixed polymer solutions in N,N-dimethylformamide containing a slight amount of a stilbene derivative as a fluorescent probe, to assume different blend compositions for each individual polymer pair. Through analysis of polarized fluorescence intensity, it was found that all the drawn films gave a positive orientation function, but the orientation development became suppressed with increasing content of the vinyl polymer component. In comparison between different CA/PVP series, the drawn blends comprising a CA of comparatively lower DS and a PVP of higher molecular weight indicated a higher degree of orientation at any stage of elongation. The molecular orientation in CA/VP−MMA copolymer blends was affected by the DS of CA in a similar manner to that in the CA/PVP series, but the VP:MMA ratio in the copolymer was less effective. The optical birefringence of the drawn films, when compared at a given draw ratio for a series of blends, decreased drastically with an increase in the vinyl polymer content and changed from positive to negative values at a certain blend composition. This optical behavior is interpretable in terms of an effect of birefringence compensation due to the positive and negative contributions of oriented CA and vinyl polymer, respectively, to the overall birefringence. The critical binary composition where the blend remains a birefringence-free material shifted to the CA-rich composition side with increasing DS of the CA used as well as with increasing VP fraction in the P(VP-co-MMA) component. At vinyl polymer-rich compositions, the negative birefringence observed for the drawn blends was even greater in absolute value than that of the drawn, unblended vinyl polymer, suggesting that the two constituent polymers can orient cooperatively as a result of their high miscibility.

The miscibility of CA/P(VP‐co‐MMA) blends was examined as a function of DS of CA and the VP fraction in the copolymer composition, in an extension of the previous studies on cellulose ester blends using P(VP‐co‐VAc) as a counter component. It was observed by DSC thermal analysis that when CA of DS ≤ 2.5 and P(VP‐co‐MMA) of VP > 30 mol‐% were two blending components, most of the binary polymer systems were miscible, whereas the other combinations of DS and VP values led to an immiscible series of blends, a possible exception being the miscible pair of DS = 2.70 and VP = 100 mol‐%. Results of FT‐IR and solid‐state 13C CP/MAS NMR spectra measurements suggested the miscibility to be driven by the hydrogen‐bonding interaction between the residual hydroxyls of CA and the carbonyls of VP units in P(VP‐co‐MMA), as in the case of CA/P(VP‐co‐VAc) blends where the range of miscible pairing of acetyl DS and VP fraction was rather wide. From evaluations of proton spin‐lattice relaxation times in the NMR study, it was confirmed that the homogeneity of the miscible blends of CA/P(VP‐co‐MMA) was substantially on a scale within a few nanometers. To interpret the difference in the DS‐ and copolymer composition‐dependence of the miscibility behavior between three blend systems, CA/P(VP‐co‐MMA), CA/P(VP‐co‐VAc), and CB/P(VP‐co‐VAc), Krigbaum‐Wall intermolecular interaction parameters were estimated by solution viscometry for different polymer pairs pertinent to those blends. In particular, discussion took into consideration the effectiveness of an intramolecular repulsive action between the two units (VP and VAc, or VP and MMA) constituting the vinyl copolymers.magnified image

Binary blends and pseudo complexes of cellulose acetate (CA) with vinyl polymers containing N-vinyl pyrrolidone (VP) units, poly(N-vinyl pyrrolidone) (PVP) and poly(N-vinyl pyrrolidone-co-vinyl acetate) [P(VP-co-VAc)], were prepared, respectively, by casting from mixed polymer solutions in N,N-dimethylformamide as good solvent and by spontaneous co-precipitation from solutions in tetrahydrofuran as comparatively poor solvent. The scale of miscibility and intermolecular interaction were examined for the blends and complexes by solid-state 13 C-NMR spectroscopy. It was revealed that the formation of complexes was due to a higher frequency of hydrogen-bonding interactions between the residual hydroxyl groups of CA and the carbonyl groups of VP residues in the vinyl polymer component. From measurements of CP/MAS spectra and proton spin-lattice relaxation times (T 1q H ) in the NMR study, the existence of the hydrogen-bonding interaction was also confirmed for the miscible blends and the homogeneity of the mixing was estimated to be substantially on a scale within a few nanometers.

Transparent films of Fe-doped indium tin oxide (ITO) were grown at oxygen pressures of 5, 1, 10-1, 10-2, and 10-3 Pa on yttria-stabilized zirconia (001) substrates by a pulsed-laser deposition method. We observed X-ray diffraction peaks from (00h) planes of In2O3 crystalline phase for the films. The films grown at 5 and 1 Pa were paramagnetic and semiconducting, that at 10-1 Pa was ferromagnetic and semiconducting, and those at 10-2 and 10-3 Pa were ferromagnetic and metallic. The Fe-ITO films grown below 10-1 Pa exhibited room-temperature (RT) ferromagnetism. Nanoscale Fe clusters in the highest oxidation state such as γ-Fe2O3 resulted in the RT ferromagnetism.