Hydrogen bond mediated self‐assembly of two diblock copolymers

Two chemically dissimilar diblock copolymers, polybutadiene‐b‐poly(acrylic acid), PBd‐b‐PAA (Mw = 5.8–4 kg mol−1) and poly(styrene)‐b‐poly(ethylene oxide), PS‐b‐PEO (Mw = 9–5 kg mol−1) were blended in an effort to achieve morphologies typical of triblock copolymers. Blend compatibility was achieved by the hydrogen bond driven association of the PAA block of one diblock with the PEO block of the other. Small angle X‐ray scattering was used to determine the morphologies of the compositions, which were further investigated using transmission electron microscopy and selective staining techniques. The crystallinity of the PEO block was determined by differential scanning calorimetry. The hydrogen bond interactions between PEO and PAA yielded a complex triblock lamellar morphology of the form PS‐b‐(PEO/PAA)‐b‐PBd‐b‐(PEO/PAA). This morphology was stable when crystallization of PEO was suppressed by sufficient interaction with PAA. A complex lamellar morphology is observed in blends of two diblock copolymers, PS‐b‐PEO and PBd‐b‐PAA. The hydrogen bonding interaction between PAA and PEO suppresses PEO crystallinity and produces well‐ordered layered structures. The morphology of the blends was determined through SAXS and TEM coupled with differential staining, revealing a morphology with three different types of layers that repeats itself in a four‐layer pattern.