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Photocontrolled Hydrogen Bonding in Main-Chain Azobenzene Polymers
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DOI：10.1021/acsmacrolett.6c00273.png)
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Abstract
En 中文
Incorporating azobenzene into polymer backbones enables reversible, light-driven modulation of macroscopic properties through trans–cis photoisomerization. Despite substantial work in this area, properties accessible at intermediate isomer populations remain underexplored, particularly in main-chain architectures. Here, structurally analogous azobenzene-containing polymers with and without urethane hydrogen-bonding motifs were synthesized. FTIR spectroscopy shows trans–cis isomerization disrupts hydrogen bonding in urethane groups, accompanied by suppressed crystallinity and a ≈30 °C decrease in Tg. This change is well-described by a modified Fox model, suggesting isomerization acts to tune local interactions in analogy to random copolymers. By contrast, the non-hydrogen-bonding analogue required higher cis enrichment for photoinduced melting and showed little change in Tg. Shear rheology reveals a change in dynamic moduli over ≈3 orders of magnitude as isomerization alters interchain associations, segmental mobility, and solidification. Collectively, these results establish targeted isomer populations and intermolecular interactions as a strategy for postpolymerization modulation of thermomechanical properties.
Journal
IF:
5.2
Papers:
336
Citations:
1.4W