비평형 상태의 자기조립 시스템: 비평형 상태의 지속적 유지와 시공간적 조절에 관한 연구

Abstract

The present thesis describes the studies on the development of complex supramolecular self-assembling systems with emergent properties that reside in an out-of-equilibrium state and deals with some of the present challenges in the field of systems chemistry, such as (1) maintaining long-lived non-equilibrium steady states and (2) spatiotemporal control over the self-assembling process. The general introduction to each research topic is presented in Chapter 1. Current research efforts in the field of systems chemistry are devoted to exploring continuously dissipative long-lived non-equilibrium steady states to achieve more life-like behavior. In general, a set of chemical reactions is operated in a closed system and therefore chemical wastes produced in repeated cycles keep accumulating within the system causing a decrease in the efficiency of the emergent properties of the transient self-assembling structures. Chapter 2 describes the chemical fuel-driven transient crystallization of a cucurbit[8]uril-based host-guest complex, which maintains long-lived non-equilibrium steady states. Base-catalyzed thermal decarboxylation of trichloroacetic acid that chemically fuels the crystallization process dissolves the crystals and produces volatile chemical wastes that are spontaneously removed from the system. Such a self-clearance process prevented the significant accumulation of waste products and the damping in the formation of the transient crystals even after refuelled cycles. The morphology and structural integrity of the crystals were also maintained in the subsequent cycles. After establishing our approach to the formation of energy-dissipative crystalline materials in long-lived non-equilibrium steady states, we utilized a gaseous fuel mixture to drive transient out-of-equilibrium self-assembly of methyl orange (MO) and aggregation of perylene tetracarboxylic acid (PTCA): these results are discussed in Chapter 3. The combination of an active gaseous chemical fuel (CO2) and an inert gas (argon) or compressed air, which assisted in the degassing of the gaseous fuel from the solution, operated the CO2-sensitive self-assembling systems. The gaseous nature of the fuel as well as the exhaust helped in their easy removal and thereby minimized the accumulation of chemical wastes within the system, maintaining the efficiency of the transient self-assembly and aggregation processes. The strategy was executed with a rather simple experimental setup and operated at ambient temperatures as analogous to a naturally occurring self-assembling system. One of the grand challenges in the field of systems chemistry, namely the production of synthetic life, is to control the self-assembly process in a spatiotemporal manner. Living systems owe their function from spatiotemporal control over biochemical distribution through the sensing of external signals, which are then processed using binary Boolean logic or more complicated computational models. Inspired by such a behavior, Chapter 4 delineates the spatiotemporal control over out-of-equilibrium chemical systems with multiple input signals and programs them using basic Boolean logic for the execution of functions such as spatiotemporally controlled chemical gradients and patterns, programmable cargo movements and transporting cargo through a maze. The spatiotemporal control with the use of light, sound and chemical inputs in out-of-equilibrium chemical logic systems, which ultimately leads to obtaining smart functions, mimics the complexity of biological processes and their programmability. Our approach to the development of supramolecular systems in long-lived non-equilibrium steady states and spatiotemporal control over the out-of-equilibrium systems to execute transient functions may help to increase the complexity of out-of-equilibrium chemical systems and expand the realms of systems chemistry and related research.