Repairable Macroscopic Monodomain Arrays from Block Copolymers Enabled by Photoplastic and Photodielectric Effects.
basic_science · Level V
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- Record sourced from PubMed, PMID 37067380.
- Also identified by DOI 10.1021/acsnano.2c12800.
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Abstract
Upon exposure to UV light (120 mW/cm<sup>2</sup>, λ = 365 nm), a <i>trans</i>-<i>cis</i> isomerization occurs in a cylinder-forming, azobenzene-containing block copolymer of polydimethylsiloxane-<i>b</i>-poly((4(phenyldiazenyl)phenoxy)hexyl acrylate) (PDMS-<i>b</i>-PPHA) that enables the generation of monodomains of healable, long-range ordered arrays of nanoscopic domains over macroscopic distances. The <i>trans</i>-<i>cis</i> isomerization gives rise to a significant increase in the dielectric constant (from 6.52 to 19.8 at 100 Hz, photodielectric behavior) and a dramatic decrease in the <i>T</i><sub>g</sub> (from 54 to 1 °C, photoplastic behavior) of the PPHA block. By combining these characteristics with an <i>in-plane</i> electric field, macroscopic monodomains of near-perfectly aligned cylindrical microdomains are achieved at low temperatures, and a damage repair is clearly uncovered, where the 300 nm wide scratches can be completely healed at 40 °C, leaving a smooth, uniformly thick film where the continuity and orientation of the aligned microdomains are restored. Subsequent exposure to visible light causes a <i>cis-trans</i> isomerization, increasing the matrix <i>T</i><sub>g</sub> to 54 °C, producing highly oriented and aligned PDMS cylindrical microdomains in a PPHA matrix.