We examined the composition and molecular weight dependence of the glass transition temperature in detail for two types of hydrogen bonding miscible blends: poly (2-vinyl pyridine)/poly (vinyl phenol) (2VPy/VPh) and poly (4-vinyl pyridine)/poly (vinyl phenol) (4VPy/VPh). Regarding the functional form of the glass transition temperature, Tg, as a function of the weight fraction, we found a weak deviation from the Kwei equation for 2VPy/VPh blends. In contrast, such a deviation was not observed for the 4VPy/VPh blend. By relating the difference in the functional forms of Tg between the two blend systems to the difference in hydrogen bonding ability, we proposed a modified version of the Kwei equation. As for the interaction parameter, q in the Kwei equation, clear molecular weight dependence was observed for 2VPy/VPh blends: the lower the VPh molecular weight in the oligomer level, the higher the q values, suggesting the higher hydrogen bonding formability near the polymer chain ends than the middle part of a polymer chain.
Polyvinylphenol (PVPh) and Poly-2-vinylpyridine (P2VP) are known to form polymer complex through the hydrogen bonding interaction between the nitrogen of P2VP and hydroxyl group of PVPh. We conducted differential scanning calorimetry for this particular blend in the wide range of blend composition and examined the effect of H-bonding interaction on the glass transition behavior.
We examined thermal and rheological behaviors for miscible polymer blends, poly(2-vinyl pyridine) / poly(4-vinyl phenol) (2VPy/VPh), in which intermolecular hydrogen bonds play an important role. The molecular weights of the 2VPy and VPh components are higher and lower than the critical sizes of the entanglement, respectively. In the mixture of these two polymers, only the 2VPy chains entangle each other, and the low molecular weight VPh is expected to act as a diluent. We found that the time-temperature superposition principle approximately held. The Williams-Landel-Ferry equation with a single parameter set (C 1 and C 2 ) could represent their shift factors by setting the reference temperatures to be T g + 64 ºC. From the comparison of the composite curves, we found that the intermolecular hydrogen bonds did not affect the entanglement densities but made the zero shear viscosities larger and the relaxation times longer.
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