We have investigated transition behavior for block copolymer (BCP) mixtures composed of a lamella-forming polystyrene-block-poly(2-vinylpyridine) (PS-b-P2V P) and phenylacetamide derivatives, where the hydroxyl functionality it phenylacetamide unit is available only for 4-hydroxyphenylacetamide (H PA) and not for phenylacetamide (PA) Unlike a similar transition temperature for BCP mixtures with PA, measured by in situ small-angle X-ray scattering (SAXS) and depolarized light scattering (1)PLS), an annealing temperature dependence for BCP mixtures with HPA indicates that only the complex by H-bonding mediation between the nitrogen units of P2VP block and hydroxyl group in the HPA enhances nonfavorable segmental interactions between two block components, leading to a significant increase in d-spacing, for BCP mixtures with HPA. This result illustrates the importance of the availability for H-bonding mediation to control over tiansition behavior for BCP mixtures with the functional molecules