In this paper, the formation of nanostructured triblock terpolymer polystyrene--poly(4-vinylpyridine)--poly(solketal methacrylate) (PS--P4VP--PSMA), polystyrene--poly(4-vinylpyridine)--poly(glyceryl methacrylate) (PS--P4VP--PGMA) membranes via block copolymer self-assembly followed by non-solvent-induced phase separation (SNIPS) is demonstrated. An increase in the hydrophilicity was observed after treatment of non-charged isoporous membranes from PS--P4VP--PSMA, through acidic hydrolysis of the hydrophobic poly(solketal methacrylate) PSMA block into a hydrophilic poly(glyceryl methacrylate) PGMA block, which contains two neighbored hydroxyl (-OH) groups per repeating unit. For the first time, PS--P4VP--PSMA triblock terpolymers with varying compositions were successfully synthesized by sequential living anionic polymerization. Composite membranes of PS--P4VP--PSMA and PS--P4VP--PGMA triblock terpolymers with ordered hexagonally packed cylindrical pores were developed. The morphology of the membranes was studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM). PS--P4VP--PSMA triblock terpolymer membranes were further treated with acid (1 M HCl) to get polystyrene--poly(4-vinylpyridine)--poly(glyceryl methacrylate) (PS--P4VP--PGMA). Notably, the pristine porous membrane structure could be maintained even after acidic hydrolysis. It was found that membranes containing hydroxyl groups (PS--P4VP--PGMA) show a stable and higher water permeance than membranes without hydroxyl groups (PS--P4VP--PSMA), what is due to the increase in hydrophilicity. The membrane properties were analyzed further by contact angle, protein retention, and adsorption measurements.