Suppression of the dielectric secondary relaxation of poly(2-vinylpyridine) by strong intermolecular hydrogen bonding

The secondary relaxation of poly(2-vinylpyridine) (PVPy) in a complex and blends with poly(4-vinylphenol) (PVPh) was studied by broadband dielectric spectroscopy. The polymer complex can be obtained by mixing PVPh and PVPy in methyl ethyl ketone as a result of the very strong hydrogen bonding between two polymers, and it has a glass transition temperature higher than that of either component. The secondary relaxation of PVPy is clearly suppressed in the complex, and it is found that the reduction of its dielectric relaxation strength is approximately proportional to the intermolecular hydrogen bonding fraction. In addition, the relaxation time of unassociated PVPy side groups is also slowed down by about 1 decade compared to that of the neat PVPy. Homogeneous PVPh/PVPy blends can be achieved if the polymers are mixed in NN-dimethylformamide. However, the degree of intercomponent hydrogen bonding is much lower in the blends, and therefore the suppression of the PVPy secondary relaxation is not as significant as in the complex. Furthermore, by comparing with results reported earlier, it is concluded that the stronger the intermolecular hydrogen bonding, the more significantly it influences the secondary relaxation of the proton-accepting component.