Correlation in SANS $\chi$ upon heating and pressurization for a diblock copolymer

The response of phase behavior to pressure for an A-$b$-B diblock copolymer in the disordered state has been studied by small-angle neutron scattering (SANS). Deuterated polystyrene-$b$-poly(n-propyl methacrylate) (dPS-$b$-PPrMA) copolymer, which possesses ordering transition upon heating and baroplasticity (suppressed demixing by pressurization), was taken as our model system. It was shown that effective Flory-Huggins parameter $\chi _F$ from scattering intensity profiles upon heating and pressurization forms a characteristic curve that is a function of pressure increment $\Delta P$ ($\equiv P-P_0$) divided by temperature dependent bulk modulus $B_0 $ at a reference pressure $P_0$. Each isotherm of $\chi _F$ is superposed into the curve by a scale factor $\tau$ determined by $B_0 $. The scattering intensity maxima $I_{max}$, which is governed by $\chi _F$, were also shown to reveal a similar superposition.