Realizing Sub-3 nm Vertical Lamellar Features in Thin Films by In-Situ Hydrolysis of PSM-b-P4VBP

We synthesized linear diblock copolymers of poly(solketal methacrylate-b-4‑vinyl biphenyl) (PSM‑b-P4VBP) that can form vertical sub-3 nm lamellar domains in thin films after in-situ acid catalyzed hydrolysis, among the smallest reported for synthetic block copolymers. Acid hydrolysis with trifluoracetic acid (TFA) vapor converts the hydrophobic PSM block into hydrophilic poly(glycerol monomethacrylate) (PGM), increasing immiscibility with P4VBP and driving microphase separation in the resulting PGM‑b-P4VBP. In the bulk state, small-angle X-ray scattering (SAXS) confirms lamellas with a 5.7 nm full-pitch, while thin films exhibit vertically aligned lamellae with a 5.4 nm full-pitch as verified by grazing-incidence SAXS (GISAXS) and atomic force microscopy (AFM). The interaction parameter 𝜒 for both PSM‑b-P4VBP and PGM‑b-P4VBP are determined by temperature-dependent SAXS.