期刊
CELLULOSE
卷 13, 期 3, 页码 245-259出版社
SPRINGER
DOI: 10.1007/s10570-005-9014-3
关键词
blends; cellulose acetate butyrate; cellulose butyrate; miscibility window; poly(N-vinyl pyrrolidone); poly(N-vinyl pyrrolidone-co-vinyl acetate)
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 C-13 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.
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