The development of stimuli-responsive materials with precise spatial control has attracted significant interest in advanced functional systems. In this study, a novel approach to photoinduced surface patterning is demonstrated using ion-pairing materials composed of anionic azobenzene and a cationic polymer complexed with a fluorescent π-electronic system. The key innovation lies in harnessing the difference in surface tension generated by photoisomerization to drive large-scale mass transport through Marangoni flow, enabling fluorescence patterning even with minimal photoisomerized species.
The system employs azobenzene carboxylate (Azb⁻) as the photosensitive unit paired with poly(4-vinyl-N-dodecylpyridinium) (P4VP⁺), forming Azb⁻-P4VP⁺ ion pairs. To enhance functionality, the anion-binding receptor dipyrrolyldiketone boron complex (PB) was introduced to form PB·Azb⁻-P4VP⁺, where PB acts as a pseudo-π-electronic anion via strong anion recognition. While the formation of this complex suppresses bulk photoisomerization due to restricted molecular motion and energy transfer from azobenzene to PB, it enables localized surface-level changes upon UV irradiation. Grazing-incidence small-angle X-ray scattering (GISAXS) revealed that Azb⁻-P4VP⁺ exhibits a well-ordered hexagonal columnar (Colh) structure, whereas PB·Azb⁻-P4VP⁺ shows amorphous ordering, confirming the disruption of long-range crystallinity.
Upon UV exposure at 140 °C, the surface tension of Azb⁻-P4VP⁺ decreased due to the transition from Colh to amorphous phase, reducing hydrophobic chain exposure at the film-air interface. In contrast, PB·Azb⁻-P4VP⁺ exhibited increased surface tension despite no detectable bulk structural or spectral changes, indicating trace photoisomerization occurring primarily at the surface. This subtle shift in polarity drives the Marangoni effect: material flows from regions of low surface tension (trans state) to high surface tension (cis state), resulting in macroscopic topographical changes.
Using photomasks, controlled UV irradiation induced trench-and-ridge patterns on Azb⁻-P4VP⁺ films, confirmed by white-light interferometric microscopy.YTHDF2 Antibody Autophagy Remarkably, similar patterning occurred in PB·Azb⁻-P4VP⁺, demonstrating that surface-driven Marangoni flow can be activated even without extensive photoisomerization. Stripe-patterned photomasks enabled the fabrication of periodic surface gratings with a pitch of 20 μm. Fluorescence microscopy revealed enhanced emission intensity in exposed regions, directly correlating with higher local concentration of the fluorescent PB·Azb⁻ complex, proving successful transfer of functional molecules via mass migration.SPRR4 Proteinsupplier
This work establishes a new paradigm for dynamic surface engineering in ionic materials.PMID:34952266 It demonstrates that even trace amounts of photoisomerization—insufficient for bulk response—can initiate significant material motion through surface tension gradients. The ability to pattern non-photoresponsive fluorophores via Marangoni flow opens avenues for applications in microfluidics, biosensing, and adaptive coatings. Importantly, this is the first report of surface relief grating in ionic systems driven by the Marangoni effect, expanding the scope of photoresponsive materials beyond traditional chromophore-rich polymers.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com