Shiyan Chen, Lixia Peng, Yanan Liu, Xiang Gao, Ying Zhang, Chun Tang, Zhenghao Zhai, Liulin Yang, Weitai Wu, Xumin He, Liu Leo Liu, Feng He and Haiping Xia*
Conjugated polymers usually require strategies to expand the range of wavelengths absorbed and increase solubility. Developing effective strategies to enhance both properties remains challenging. Herein, we report syntheses of conjugated polymers based on a family of metalla-aromatic building blocks via a polymerization method involving consecutive carbyne shuttling processes. The involvement of metal d orbitals in aromatic systems efficiently reduces band gaps and enriches the electron transition pathways of the chromogenic repeat unit. These enable metalla-aromatic conjugated polymers to exhibit broad and strong ultraviolet–visible (UV–Vis) absorption bands. Bulky ligands on the metal suppress π–π stacking of polymer chains and thus increase solubility. These conjugated polymers show robust stability toward light, heat, water, and air. Kinetic studies using NMR experiments and UV–Vis spectroscopy, coupled with the isolation of well-defined model oligomers, revealed the polymerization mechanism.
Kinetic control over structures and functions of complex assembly systems has aroused widespread interest. Understanding the complex pathway and transient intermediates is helpful to decipher how multiple components evolve into complex assemblies. However, for supramolecular polymerizations, thorough and quantitative kinetic analysis is often overlooked. Challenges remain in collecting the information of structure and content of transient intermediates in situ with high temporal and spatial resolution. Here, the unsolved evolution mechanism of a classical self-sorting supramolecular copolymerization system was addressed by employing multidimensional NMR techniques coupled with a microfluidic technique. Unexpected complex pathways were revealed and quantitatively analyzed. A counterintuitive pathway involving polymerization through the ‘error-correction’ of non-polymerizable transient intermediates was identified. Moreover, a ‘non-classical’ step-growth polymerization process controlled by the self-sorting mechanism was unraveled based on the kinetic study. Realizing the existence of transient intermediates during self-sorting can encourage the exploitation of this strategy to construct kinetic steady state assembly systems. Moreover, the strategy of coupling a microfluidic technique with various characterization techniques can provide a kinetic analysis toolkit for versatile assembly systems. The combined approach of coupling thermodynamic and kinetic analyses is indispensable for understanding the assembly mechanisms, the rules of emergence, and the engineering of complex assembly systems.
Conventional shape memory polymers (SMPs) are restricted to predetermined permanent shapes and therefore cannot be reconfigured arbitrarily to adapt to variant application scenarios. Meanwhile, shape memory behaviour is mostly thermally active and is often induced by direct heating and lacks spatial or remote control. Herein, we report a novel SMP with a reconfigurable network containing a semi-crystalline polymer chain, radically exchangeable covalent bond and photothermoresponsive carbolong complex moiety. The photothermal effect of the carbolong complex and the thermal responsiveness of the semi-crystalline polymer chain and radically exchangeable covalent bond lead to shape memory behaviour and network topological rearrangement using near-infrared light irradiation. Such a strategy offers an opportunity for building reconfigurable shape memory polymers that can be manipulated by either direct heating or remote light irradiation.
Photo-generation of a proton gradient over a lipid bilayer is of interest due to its essential role in photosynthetic bacteria. Membrane asymmetry is key to the proton gradient generation via directional proton transport. Here, we report a light-driven proton pump based on two-dimensional, porphyrin-based Janus metal-organic layers (Janus-MOLs). The Janus-MOL, functionalized with carboxyquinone on one side and Acitretin on the other via a microemulsion-based method, was attached to liposome surface. Upon photoexcitation, the porphyrins initiate electron and hole transfers to carboxyquinone and Acitretin, respectively, which undergo redox reactions with freely diffusing quinone (Q)/hydrosemiquinone (HQ·) in the lipid bilayer to produce a concentration gradient of quinone-based species. Owing to different pKa values of HQ+and HQ·, these redox reactions trigger proton transport across the membrane to create a pH gradient, which drives ATP production by CFoF1-ATP synthase in a similar fashion as photosynthetic bacteria.