Surface Condensation Of One-dimensional Schiff Base Polymers On Hopg Investigated By Scanning Tunneling Microscopy

STM, as an atomic-scale resolution microscopy, is ideally suited to real-timeobservation of the surface defects, reconstruction, surface morphology and location ofadsorbed molecules, etc. The above features make STM particularly suitable forstudying structural properties of surface-confined zero-dimensional (0D),one-dimensional (1D), and two dimensional (2D) polymer arrangements in real space.In this thesis, we chose terephthaldicarboxaldehyde (TPA),isophthaldicarboxaldehyde (IPA), p-phenylenediamine, benzidine, and4,4’’-diamino-p-terphenyl as precursors in order to study the Schiff base reactionbetween the aromatic diamine and dialdehyde on HOPG surface. Our experimentsshow that TPA reacted at the octanoic acid/HOPG or gas/HOPG interfaces with threearomatic diamines with different chemical structures, they can form highly orderedadlayers of one-dimensional polymers.In addition, we also studied the structural properties of one-dimensional polymerarrangement at the octanoic acid/HOPG interfaces by combination of differentconcentrations of TPA and4,4’’-diamino-p-terphenyl. With the decreasingconcentration of monomers, crystalline structure gradually disappears, and results insparse linear structure of polymer. In order to study the mechanism of Schiff basereaction at the octanoic acid/HOPG interface, we have studied the growth dynamicsof one-dimensional polymer which constructed by TPA with4,4’’-diamino-p-terphenyl.Utilizing on-surface condensation via mild heating under low vacuum approach,extended and ordered domains of zigzag polymer arrays covering the HOPG surfacecan be observed for combination of the building block molecules IPA andp-phenylenediamine，benzidine，4,4’’-diamino-p-terphenyl, respectively. The zigzagpolymer aligned along three equivalent surface directions.We have prepared some surface COFs which were synthesised by either mixingbenzene-1,3,5-tricarbaldehyde with diamine（p-phenylenediamine，benzidine，4,4’’-diamino-p-terphenyl） in octanoic acid and allowing them to polymerize at theoctanoic acid/HOPG interface at room temperature or mixing them indimethylsulfoxide (DMSO) and polymerized on the surface with moderate heating.These nanopores have been used as reaction vessels and solutions containing TPA andp-phenylenediamine mixtures were added on the surface COFs. Our results show thatTPA and p-phenylenediamine can form one-dimensional polymer in defect areas of the surface COFS which constructed by benzene-1,3,5-tricarbaldehyde and4,4’’-diamino-p-terphenyl, while forming oligomers inside the pores of surface COF.