Functionalized ordered nanoporous polymeric materials: From the synthesis of diblock copolymers to their nanostructuration and their selective degradation

Self-organized block copolymers can be effectively utilized as nanostructured precursors to functionalized ordered mesoporous polymeric materials. Novel nanoporous polystyrene frameworks with carboxylic acid (COOH)-coated pore walls were obtained from the selective degradation of the polyester block in polystyrene-block-poly(d,l-lactide) (PS-b-PLA) diblock copolymers. By resorting to an asymmetric difunctional initiator, an orthogonal atom transfer radical polymerization (ATRP)/ring-opening polymerization (ROP) tandem approach enabled the synthesis of such diblock copolymers with a carboxyl group at the junction point between both blocks. Upon the shear flow induced by a channel die processing, highly oriented copolymers were afforded as evidenced by small-angle X-ray scattering (SAXS). Under mild alkaline conditions, the quantitative hydrolysis of the PLA nanodomains yielded ordered mesoporous materials containing nanoscopic channels lined with chemically accessible and modifiable COOH functional groups. The PS-b-PLA precursors were carefully analyzed by size exclusion chromatography (SEC) and 1H NMR, while the resulting porous frameworks were investigated by scanning electron microscopy (SEM) and nitrogen sorption porosimetry.