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Self assembly and Polymerization of Functional Macrocyclic Diacetylenes

Self assembly and Polymerization of Functional Macrocyclic Diacetylenes
Other Titles
기능성 거대고리 다이아세틸렌 단량체의 자가조립과 중합
Alternative Author(s)
Issue Date
2021. 2
Polydiacetylenes (PDAs) are conjugated polymers and display unique structural and optical properties. Owing to the extensively conjugated ene-yne backbones, PDAs absorbs visible light and often show an intense blue color with absorption maximum at around 650 nm. PDAs are easily obtained by topochemical polymerization (typically using 254 nm UV light) of self-assembled diacetylene (DA) monomers. It has been well known that various physical (temperature, mechanical stress, pressure, etc) and chemical (solvent, molecular recognition, pH, etc) stimuli causes distortion of the polymer backbone, resulting in a color transition from blue to red. Due to the colorimetric response, PDAs have been widely used as stimulus-responsive colorimetric sensors. Conventional tubular materials including carbon nanotubes (CNTs), organic and inorganic nanotubes have been extensively investigated in a variety of fields. Despite the wide applications, conventional nanotubes suffer from limitations including difficulty of diameter control (CNT and inorganic nanotubes) and chemical stability (organic nanotubes). In order to avoid these limitations, covalently connected nanotubular structures have emerged as potential alternatives. Among these, self-assembly of polymerizable macrocyclic diacetylenes (MCDAs) have received special attention since it allows both structural rigidity and chromogenic function to the nanotubes. In this dissertation research, three types of MCDA monomers were synthesized and characterized. Firstly, a naphthalene-containing macrocyclic diacetylene (MCDA-Naph) was synthesized to access covalently linked organic nanotubes (ONTs) through topochemical polymerization. Single crystal X-ray analysis revealed that MCDA-Naph adopts the desired tubular array with favorable molecular orientation. UV irradiation of the molecularly stacked MCDA-Naph resulted in 1,4-addition polymerization and the generation of conjugated ene-yne chromophores. Density functional theory (DFT) provided evidence for tubular polydiacetylene nanotubes. Secondly, the synthesis of the linearly connected, trimeric macrocyclic diacetylene (MCDA) (tri-MCDA) is described. The ultimate step in the sequence involves a coupling of an amine-functionalized MCDA with a dicarboxylic acid-containing MCDA. Evaporation of a THF solution of tri-MCDA produces a material that has a fibrous structure. As evidenced by Raman spectroscopic analysis, UV irradiation of the self-assembled fibrous tri-MCDA results in generation of a polydiacetylene (PDA). Lastly, we describe a colorimetric polydiacetylene (PDA) that is generated by polymerization of the aldehyde-functionalized macrocyclic diacetylene, MCDA-CHO. UV irradiation of self-assembled MCDA-CHO generates a blue-color PDA, which undergoes a sequential blue-purple-brown-orange color change upon heating. Interestingly, the PDA displays a remarkably high temperature reversible thermochromism between 30 (blue) and 180 oC (reddish-brown). In addition to displaying reversible thermochromism, polymerized MCDA-CHO can be employed for colorimetric differentiation between aromatic and aliphatic primary amines. Accordingly, a blue-to-reddish brown color change takes place when the PDA is exposed to primary aniline derivatives while no color change occurs in the presence of aliphatic primary amines. Infrared spectroscopic analysis confirms that this colorimetric selectivity is a consequence of the facile formation of imine groups through reactions of the aldehyde moieties in the PDA with anilines.
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