Block copolymers exhibiting a high Flory–Huggins interaction parameter (high χ) have attracted considerable attention because of their potential in forming microphase-separated domains with very small feature sizes (<10 nm) useful for next-generation lithography. Here, we report the synthesis, characterization, and self-assembly of poly(styrene)-block-poly(2-vinylpyridine N-oxide) (PS-b-P2VPNO) and poly(styrene)-block-poly(4-vinylpyridine N-oxide) (PS-b-P4VPNO) block copolymers. These PS-b-PVPNOs were obtained from the oxidations of their precursors, poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) and poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP), respectively. The PS-b-PVPNOs exhibit enhanced block incompatibility as revealed by ordered cylindrical and lamellar structures in the sub-10 nm scale from copolymers with low molecular weight. For several samples, the respective non-oxidized precursor copolymers remained disordered. This highlights how the facile oxidation and respective increase in the dipole-moment of the vinylpyridine N-oxide segments lead to an increased immiscibility with polystyrene. The morphologies and periodicities of the ordered structures were determined by small-angle X-ray scattering, while atomic-force microscopy was used to image the self-assembly in thin films. Our results demonstrate that PVPNO-based block copolymers are versatile candidates for nanopatterned structures with small feature sizes critical for the future microelectronics industry and beyond.

Kunlun Hong

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