Surface-Confined Synthesis of One-Dimensional Schiff Base Polymers Investigated by Scanning Tunneling Microscopy

The surface-mediated synthesis of ordered linear or zigzag polymers on a highly oriented pyrolytic graphite surface was investigated either at a solid/liquid interface or with moderate heating under low vacuum. Scanning tunneling microscopy (STM) reveals the submolecular details of the structure and growth dynamics of surface-confined one-dimensional polymers. We discovered that the substituent and concentration of monomers have a significant effect on the assembling structure of the in-situ-synthesized one-dimensional polymer at the octanoic acid/graphite interface

From a Two-Dimensional Supramolecular Network to One-Dimensional Covalent Polymer at the Liquid/Solid Interface: Insight into the Role of the Stoichiometric Ratio of the Precursors

Co-condensation reaction between 2,6-diaminoanthraquinone and aromatic aldehyde at the octanoic acid/highly oriented pyrolitic graphite (HOPG) interface has been studied with scanning tunneling microscopy (STM). We found that the stoichiometric ratio of the precursors plays a vital role in the formation of the assembling structures. By controlling the molar ratio of the amine and aldehyde monomers, either an ordered, hydrogen-bond-stabilized two-dimensional supramolecular network or assembly of one-dimensional covalent polymers can be successfully constructed. The supramolecular network can also be transformed to covalent polymers by annealing the sample to 373 K

Surface- and Guest-Promoted Product Selection from a Dynamic Covalent Library: A Scanning Tunneling Microscopic Study

Surface-assisted reaction has gained much attention in the field of nanoscience and nanotechnology, due largely to its irreplaceability in the fabrication of one- and two-dimensional polymers on various substrates. In this work, surface- and guest-molecule-promoted product selection from a dynamic covalent library as well as transimination were investigated at the liquid/solid interface by virtue of scanning tunneling microscopy (STM). The significant role played by the substrate in the selection and redistribution of the products is highlighted, which arises from the self-assembling and competitive adsorption of the products. Furthermore, our result demonstrated that the surface-assisted redistribution of the products can be further promoted by addition of a proper guest, which, by forming supramolecular assemblies, enhances the selection toward specific products

Surface-Confined Crystalline Two-Dimensional Covalent Organic Frameworks <i>via</i> on-Surface Schiff-Base Coupling

We performed a co-condensation reaction between aromatic aldehyde and aromatic diamine monomers on a highly oriented pyrolytic graphite surface either at a solid/liquid interface at room temperature or in low vacuum with moderate heating. With this simple and moderate methodology, we have obtained surface-confined 2D covalent organic frameworks (COFs) with few defects and almost entire surface coverage. The single crystalline domain can extend to more than 1 μm². By varying the backbone length of aromatic diamines the pore size of 2D surface COFs is tunable from ∼1.7 to 3.5 nm. In addition, the nature of the surface COF can be modified by introducing functional groups into the aromatic amine precursor, which has been demonstrated by introducing methyl groups to the backbone of the diamine. Formation of small portions of bilayers was observed by both scanning tunneling microscopy (STM) and AFM, which clearly reveals an eclipsed stacking manner

Novel l‑Cysteine Incomplete Degradation Method for Preparation of Procyanidin B2-3′‑<i>O</i>‑Gallate and Exploration of its <i>in Vitro</i> Anti-inflammatory Activity and <i>in Vivo</i> Tissue Distribution

In this study, an effective method for preparation of bioactive galloylated procyanidin B2-3′-O-gallate (B2-3′-G) was first developed by incomplete depolymerization of grape seed polymeric procyanidins (PPCs) using l-cysteine (Cys) in the presence of citric acid. The structure–activity relationship of B2-3′-G was further evaluated in vitro through establishing lipopolysaccharide (LPS)-induced inflammation in RAW264.7 cells. The results suggested that the better protective effects of B2-3′-G against inflammation were attributed to its polymerization degree and the introduction of the galloyl group, compared to its four corresponding structural units. In vivo experiments demonstrated that the B2-3′-G prototype was distributed in plasma, small intestine, liver, lung, and brain. Remarkably, B2-3′-G was able to penetrate the blood–brain barrier and appeared to play an important role in improving brain health. Furthermore, a total of 18 metabolites were identified in tissues. Potential metabolic pathways, including reduction, methylation, hydration, desaturation, glucuronide conjugation, and sulfation, were suggested