Composition Fluctuation at Order-to-Disorder Transition: <i>χN</i> effects of Symmetric Diblock Copolymers

We report that the thermodynamic segregation power of cN where χ is the Flory-Huggins interaction parameter and N is the overall degree of polymerization will also be an important parameter for block copolymers (BCPs) to influence the composition fluctuation inhomogeneity at order-to-disorder transition (ODT). For this purpose, a series of symmetric BCPs of polystyrene-b-poly(2-vinlyprydine) (PS-b-P2VP), PS-b-poly(methyl methacrylate) (PS-b-PMMA), and PS-b-poly(n-hexyl methacrylate) (PS-b-PnHMA) with modest molecular weights were prepared to represent the (χN)_ODT sequence of . The latent heat (ΔH_ODT) at ODTs were estimated by differential scanning calorimetry (DSC) and Porod invariant (Q) at ODTs from the small angle x-ray scattering (SAXS), and the properties of local composition profiles at ODTs are described in terms of (χN)_ODT of BCPs.