Interaction and Scale of Mixing in Cellulose Acetate/Poly(N-vinyl Pyrrolidone-co-vinyl Acetate) Blends

Abstract

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.

Estimation of Miscibility and Interaction for Cellulose Acetate and Butyrate Blends with N‐Vinylpyrrolidone Copolymers

“…In order to remedy the drawback, the authors' attention has been paid to two potential methods; one is graft copolymerization of CA with biodegradable aliphatic polyesters, [5][6][7][8] and the other is compatibly blending CA with flexible polymers as a polymeric plasticizer. [9][10][11][12] Polymer/polymer blending is a well-established, useful method to improve the original physical properties of one or both of the components, or to design new polymeric materials exhibiting wide-ranging properties and/or synergistic functions without parallel in single polymers and in the gross mechanical mixture. [13] This should also hold for blending cellulosics as one component.…”

“…[13] This should also hold for blending cellulosics as one component. [1,14] In the preceding papers [10][11][12] of this series, we investigated the miscibility and intermolecular interaction for blends of cellulose alkyl esters, mainly CA [10,11] and cellulose butyrate (CB), [12] with synthetic homo-and random co-polymers comprising N-vinylpyrrolidone (VP) and/or vinyl acetate (VAc) units and, successfully, constructed a miscibility map for the respective blend systems as a function of the degree of ester substitution (DS) and the intramolecular copolymer composition (VP:VAc ratio). In conclusion, we inferred that the miscibility state in the cellulose ester/poly[(N-vinylpyrrolidone)-co-(vinyl acetate)] [P(VP-co-VAc)] systems would be determined by the balance of three factors: (1) attractive interaction based on the hydrogen bonding between the residual hydroxyls of the cellulosic component and the carbonyls of VP units in the vinyl polymer component; (2) steric hindrance of bulky acyl groups such as butyryl, resulting in suppression of the above interaction (1); and (3) indirect attraction of the two polymer components originating from a stronger repulsive action in the copolymer component.…”

“…The miscibility estimation for CA/PVP blends has already been completed; [10,11] viz., CA formed a miscible monophase with PVP unless the acetyl DS exceeded a value of ca. 2.8.…”

“…Moreover, a hydrogen-bonding interaction may be speculated to lie between the CA-hydroxyl and VP-carbonyl groups, possibly serving as a driving force for attainment of the blend miscibility, as in the situation of the previous CA/P(VP-co-VAc) system. [10,11] Spectroscopic Characterization of CA/P(VP-co-MMA) Blends…”

“…[13,14,26] Form NMR measurements of the 1 H spin-lattice relaxation time in the rotating frame (T H 1r ), it is possible to evaluate an upper limit in heterogeneity usually on a scale of a few nanometers. [27] The T H 1r quantification in solid-state 13 C NMR spectroscopy is well established and has often been used for investigating in detail the mixing state of cellulosic polymer/ synthetic polymer blends [11,12,24,28] and interpenetrating networks. [29,30] T H 1r values can be obtained practically by fitting the decaying carbon resonance intensity to the following single-exponential equation:…”