Introduction of hydrogen-bonding interaction into π-conjugated systems is a promising strategy, since the highly selective and directional hydrogen-bonding can increase the binding strength, provide enhanced stability to the assemblies, and position the π-conjugated molecules in a desired arrangement. The helical packing of the rigid melamine cores seems to play a dominating role in the subsequent formation of the peripheral helical PDA backbone. The polymerized Langmuir–Blodgett (LB) films exhibited reversible colorimetric and chiroptical changes during repeated heating–cooling cycles, which should be ascribed to the strong hydrogen-bonding interaction between the carboxylic acid and the melamine core. Further, the closely helical packing of the melamine cores could be destroyed upon exposure to HCl or NH₃ gas, whereas the peripheral helical polyaniline and polydiacetylene (PDA) backbone exhibited excellent stability. Although similar absorption changes could be observed for the films upon exposure to HCl or NH₃ gas, their distinct circular dichroism (CD) responses enabled us to distinguish the above two stimuli. Chirality 27:492-499, 2015. © 2015 Wiley Periodicals, Inc.

Herein, we synthesize a coumarin-substituted diacetylene monomer (CODA) and report the novel photo-controlled reversible assembly and disassembly behavior of the polymerized CODA (PCODA) vesicles. The photo-triggered dimerization and cleavage reactions of the coumarin groups within the surface of the adjacent PCODA vesicles can be utilized as the driving force to induce assembly and disassembly of PCODA vesicles. Moreover, the boundary of PCODA vesicles in the aggregates becomes more obscure when the irradiation time exceeds 30 min. Fusion occurs upon close docking of target membranes, driven by sufficient dimerization of the coumarin groups within the surface of PCODA vesicles.

Multimodal imaging and simultaneous therapy is highly desirable because it can provide complementary information from each imaging modality for accurate diagnosis and, at the same time, afford an imaging-guided focused tumor therapy. In this study, indocyanine green (ICG), a near-infrared (NIR) imaging agent and perfect NIR light absorber for laser-mediated photothermal therapy, was successfully incorporated into superparamagnetic Fe₃O₄@mSiO₂ core–shell nanoparticles to combine the merit of NIR/magnetic resonance (MR) bimodal imaging properties with NIR photothermal therapy. The resultant nanoparticles were homogenously coated with poly(allylamine hydrochloride) (PAH) to make the surface of the composite nanoparticles positively charged, which would enhance cellular uptake driven by electrostatic interactions between the positive surface of the nanoparticles and the negative surface of the cancer cell. A high biocompatibility of the achieved nanoparticles was demonstrated by using a cell cytotoxicity assay. Moreover, confocal laser scanning microscopy (CLSM) observations indicated excellent NIR fluorescent imaging properties of the ICG-loaded nanoparticles. The relatively high r₂ value (171.6 mM⁻¹ s⁻¹) of the nanoparticles implies its excellent capability as a contrast agent for MRI. More importantly, the ICG-loaded nanoparticles showed perfect NIR photothermal therapy properties, thus indicating their potential for simultaneous cancer diagnosis as highly effective NIR/MR bimodal imaging probes and for NIR photothermal therapy of cancerous cells.

Herein, we report a novel model that combines supramolecular chemistry and the LB technique for the chirality regulation of the PDA films. The helical packing of PCDA molecules and the chiroptical properties of the resulting PDA LB films can be easily modulated by different azobenzene derivatives. Moreover, the effect of the photo-isomerization of azobenzene chromophores on the helical formation of PCDA assemblies is investigated in detail.

Herein, we prepare three azobenzene-functionalized polydiacetylene (PDA) aggregates in 1,2-dichlorobenzene solution with reversible thermochromic and novel photo-induced chromatic behavior. The influence of chemical structural variation on the chromatic transition properties of the PDAs aggregates has been explored in detail by in situ FTIR spectroscopic analyses. The links between chromatic transitions and the molecular structure of PDA aggregates has been established. The results demonstrate that suitable head group interactions and alkyl side chain lengths are both essential for the sensitivity and reversibility of the thermochromic and photochromic properties of PDAs aggregates in solution.