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Complexes of amic acids with polar aprotic solvents

IX. Interpolymer complexes of a polyamic acid with polybases

Journal of Thermal Analysis and Calorimetry
Authors: L. A. Shibaev, N. G. Stepanov, T. A. Kostereva, A. V. Novoselova, T. N. Spirina, and Yu. N. Sazanov

The polymer-polymer interactions of a polyamic acid (PAA) with polybases (polyvinylpyrrolidone, polyacrylonitrile and polyvinylpyridine) were studied by means of massspectrometric thermal analysis (MTA), TG, DTA and IR-spectroscopic methods in solution and in the solid state. The polybases were shown to substitute the solvent from its complex with PAA, forming H-bonds or salt-type polycomplexes with PAA. The MTA method proved to be very informative for the investigation of interpolymer interactions in the solid state.

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The miscibility of poly(N-isopropylacrylamide) (PNIPA) with poly(vinyl pyrrolidone) (PVP) and a cross-linked poly(acrylic acid) (Carbopol 971P) was evaluated from the rheological data of aqueous dispersions and the temperature of glass transitions of films made of binary mixtures. PNIPA has a low critical solubility temperature (LCST) of about 33C, below which 1% dispersion behaves as a viscous system. At temperatures above LCST, the hydrophobic interactions among the isopropyl groups initially provide transient networks of greater elasticity. The LCST of PNIPA as well as its T g (144C, estimated by DSC and MTDSC of films) were not modified by the presence of PVP. The immiscibility of PNIPA and PVP was confirmed by the absence of interaction between both polymers as shown by FTIR analysis of the films. In contrast, PNIPA and carbopol were miscible and the behaviour of their mixtures differed significantly from that of the parent polymers; i.e. a strong synergistic effect on the viscoelasticity of the dispersions was observed below the LCST. As temperature increased, the blends showed a decrease in the loss and storage moduli, especially those with greater PNIPA proportions. The fall was smoother as the PNIPA proportion decreased. This behaviour may be explained as the result of the balance between PNIPA/carbopol hydrogen bonding interactions (as shown in the shift of C=O stretch in FTIR spectra) and PNIPA/PNIPA hydrophobic interactions. The T g values of the films of the blends showed a positive deviation from the additivity rule; the mixtures containing more than 1:1 amide:carboxylic acid groups have a notably high Tg (up to 181C). This increase is related to the stiffness induced in the films by the PNIPA/carbopol interactions.

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.052 ± 0.004 for the given range of composition of CdS, respectively. All three terms of interaction in the empirical relation are defined below: (1) Main interaction is between the molecules of polymer, also called polymer–polymer interaction, and is

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.1016/0014-3057(87)90046-2 . 4. Lin , JL , Roe , RJ . Relationship among polymer–polymer interaction energy densities and the deuterium isotope effect . Macromolecules . 1987 ; 20 : 2168 – 2173 . 10.1021/ma00175a021

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is the universal gas constant, Δ Η 0 is the heat of fusion of the perfectly crystallizable polymer, m is the degree of polymerization, is the volume fraction of the component in the blend, and χ 12 is the polymer–polymer interaction parameter

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