EFFECT OF CROSS-LINKS ON THE MISCIBILITY OF A DEUTERATED POLYBUTADIENE AND PROTONATED POLYBUTADIENE BLEND

The effect of peroxide cross-linking on the phase diagram and the scattering function for a critical mixture of perdeuterated polybutadiene (DPB) and protonated polybutadiene (HPB) hm been examined by small-angle neutron scattering as a function of temperature. The scattering curves for the cross-linked blends were essentially temperature independent. It was found that even at temperature (T) below the critical temperature (T(c)) of the un-cross-linked (linear) blend (e.g., T = 0-degrees-C; T(c) = 99.2-degrees-C), the cross-linked blends remained single phase and did not undergo microphase separation. The calculation of the reduced temperature, epsilon, for the cross-linked blends also implied that the cross-linking greatly increased the single-phase region of the phase diagram. A comparison of the scattering for the cross-linked blend with that of the linear blend at the cross-linking temperature (150-degrees-C) allowed a suppression in the scattering due to the presence of the cross-links. However, it was experimentally found that the concentration fluctuations present at the temperature of cross-linking dominate the scattering, which made it rather difficult to verify the prediction on the scattering function made by de Gennes.