Functional Polymeric Nanoobjects by Cross-Linking Bulk Self-Assemblies of Poly(tert-butyl acrylate)-block-poly(glycidyl methacrylate)

We report the bulk self-assembly of diblock copolymer poly(tert-butyl acrylate)-block-poly(glycidyl methacrylate) (PtBA-b-PGMA) with the PGMA that bears many epoxy groups as a cross-linkable segment and the PtBA as a hydrolyzable segment. The PtBA-b-PGMA block copolymers of a different composition were synthesized by two-step atom transfer radical polymerization (ATRP). After bulk self-assembly, the morphologies of microphase separation of the block copolymers were studied with small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The results showed that with decrease of volume ratio of the PGMA segments the PtBA-b-PGMA self-assembled into lamellae, cylinders, and spheres with the dispersed PGMA domains. The epoxy groups in the PGMA domains were cross-linked by exposing the microphase-separated films into an atmosphere of either ethylenediamine (EDA) or propargylamine (PA). Then the bulk materials were dispersed into the good solvent of PtBA to generate the polymeric nanoobjects of plates, fibers, and spheres, of which the cross-linked PGMAs were the cores and the PtBAs were the coronas. After hydrolysis of the PtBA segments into the poly(acrylic acid)s (PAAs), the cross-linked nanoobjects could be dispersed in basic water and showed reversible pH responsibility. The pendant alkyne groups in the PA cross-linked nanoobjects were applied to anchor anthracenes by click reaction with 9-(azidomethyl)anthracene (9-AMA).