Multiple linear regression analysis was also performed on the physical mixtures (Figure ) to highlight differences post heat treatment. Adequate fitting with reasonable R 2 values (Table ) were obtained and a peak at r ~ 3.25 Å is evident in all three residuals. However, these peaks are weaker than those in the blend residuals (Figure ), qualitatively suggesting more interfacial interactions post heating. This difference is clearer when comparing the average blend residual (potential interface peak: r = 3.24 Å) with the average physical mixture residual (potential interface peak: r = 3.26 Å) and in the fact that the linear combination of the starting materials' PDFs fit the PDFs from the mixtures better (Figure ). This is evident in a plot of R 2 values against composition, in which R 2 values of the blends deviate more from an ideal fit (R 2 = 1) than those of the physical mixtures