고분자 네트워크의 형태제어를 통한 생체모방 기능성 젤 개발

Abstract

In living organisms, network frameworks are established through a hierarchical self-assembly process, ensuring the formation of defect-free interconnections among biopolymers like actin, collagen, and mucin. Primary role of this network is to provide the organism with its structural shape and the ability to withstand mechanical deformation. Additionally, biopolymers undergo self-assembly to create intricate network structures that exhibit unique and diverse functions. For instance, F-actin, a microfilament integral to the intracellular cytoskeleton, forms a complex and dynamic network that supports essential biological functions such as cell migration and contractile dynamics. Collagen, the most prevalent microfiber within the extracellular matrix, contributes to a broad spectrum of stiffness and elasticity, from supple skin to rigid bone tissues. Mucins assemble into branched networks and create mucus hydrogels, which play a critical role in molecular transport and as a physical barrier against infections. Attempts have been made to mimic the functions of biomolecules through synthetic supramolecular hydrogels but have not been implemented due to insufficient knowledge about molecular engineering and self- assembly. Therefore, we sought to create an ideal network that mimics an organismal network through sophisticated self-assembly of block copolymers and to express and analyze its function. This paper summarizes the possibilities of block copolymers by designing from cationic and anionic polyelectrolytes to hydrogels in two chapters. In the first chapter, we closely analyzed the impact of improving mechanical properties by suppressing loop formation, a topological defect created by micelle-based networks, and increasing the fraction of elastically effective bridges. In the second chapter, a mucus-mimicking organogel was synthesized through the self-assembly of polyelectrolytes to reveal the absorption and retention mechanism of gas molecules depending on the viscosity of the organogel, and a method to simultaneously absorb and retain gas as much as possible by applying the sol-gel transition was demonstrated. In chapter 2, we have demonstrated a straightforward approach to creating tough hydrogels with high water content by enabling the self-assembly of oppositely charged multiblock polyelectrolytes. The majority of ABA triblock copolymer-based physical hydrogels typically establish three-dimensional networks by arranging micelles, where the formation of polymer loops creates a structural flaw leading to reduced hydrogel elasticity. To address this issue, it is crucial to maximize the presence of elastically effective bridges within the hydrogel network. In our study, we present hydrogels crafted from the interaction of oppositely charged multiblock copolymers specifically designed with sequence patterns that enhance the entropic and enthalpic penalties associated with micellization. These copolymers undergo self-assembly to form branched and bridge-rich network structures known as netmers, rather than sparsely interconnected micelles. Our findings revealed that the storage modulus of the netmer-based hydrogel was 11.5 times higher than that of the micelle-based hydrogel. Moreover, as netmer compositions can incorporate diverse physical interactions such as hydrophobic interactions, hydrogen bonding, and metal-ligand coordination, we anticipate significant progress in developing robust and physically fortified hydrogels in the future. In Chapter 3, inspired by the properties of nasal mucus, we designed polymer sol and gel and created a matrix that efficiently absorbed VOCs with high retention. The function of nasal mucus in the sense of smell involves absorbing and carrying chemicals to olfactory receptors. Drawing inspiration from the physical characteristics of mucus, which enable it to transport molecules despite its high viscosity, we engineered a polymeric organogel with a similar viscosity and examined its overall performance. Our qualitative and quantitative assessments confirmed that the viscosity of the matrix primarily impacts the absorption and retention of volatile organic compounds (VOCs) rather than their diffusion within the matrix. Furthermore, we observed that the vapor pressure of VOCs directly influences the absorption and retention efficiencies of the matrix. By leveraging a comprehensive understanding of mucus properties and employing the sol-gel transition, we successfully developed an effective agent for absorbing and retaining VOCs. This approach has enabled the creation of an efficient VOC absorbent and retention agent inspired by the properties of mucus.