The miscibility behavior in blends containing poly(4-vinyl pyridine) (P4VPy) and poly(2-vinyl pyridine) (P2VPy) as polymer components and the dihydric phenols 4,4'-thiodiphenol (TDP) and 4,4'-methylendiphenol (MDP) as low molecular weight compounds (LMWC), was studied by Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectrophotometry (FTIR) as main analytical techniques. The glass transition of P4VPy and the melting of TDP and MDP, were found to be significantly affected when the compounds were blended. This result was attributed to the miscibility between them, as a direct consequence of the specific interactions between the blend components. FTIR was used to investigate these interactions. The formation of intermolecular hydrogen bonds between the pyridine nitrogen atoms and the hydroxyl groups of TDP and MDP were discovered. When P2VPy was the macromolecular component, a difference was observed in the DSC behavior, which was attributed to a steric hindrance effect. Thermogravimetric and viscometry analysis were also used as additional techniques to complement the FTIR and DSC measurements performed.
Binary blends with poly(4-vinyl pyridine) (P4VPy) 160,000 g/mol and poly(2-vinyl pyridine) (P2VPy) 159,000 g/mol as polymer components and 4,4´-thiodiphenol (TDP), 4,4´-methylendiphenol (MDP), 2,2´-biphenol (22BP) and 4,4´-biphenol (44BP) as low molecular weight compounds (LMWCs), were prepared. Miscibility between the components was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM) were also used as complementary techniques. Hydrogen bonding formation was detected by FTIR due to the increasing of the wave number corresponding to the deformation absorption of pyridine groups in P4VPy and P2VPy. A decreasing of melting points and fusion heats of the LMWCs is observed by DSC, which shows a lower crystallinity level as the blends are richer in the polymer component as a consequence of the intermolecular interaction. A plasticizing effect is also observed by DSC when P4VPy is blended with TDP and MDP; the higher steric hindrance prevents this effect when P2VPy is blended with 22BP and 44BP. Miscible blends were obtained with a moderate trend to a higher interaction degree in blends containing P4VPy. This report is the fifth part of a series of works including polymer-LMWC blends. Variables such as molecular weight increase in P4VPy and steric hindrance in P2VPy have been comparatively analyzed with blends previously reported.
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