Self-Assembled Monolayers as Platforms for Analyzing Molecular Interaction Mechanisms

Abstract

Understanding the mechanisms of intermolecular interactions is essential for designing and controlling the performance of biomaterials and functional polymers. In particular, adhesion and molecular behavior at interfaces directly influence biocompatibility, mechanical stability, and the properties of composite materials. Therefore, quantitatively elucidating interfacial interactions is indispensable for material design and applications. Self-assembled monolayers (SAMs) provide well- defined model surfaces that enable systematic investigation of interactions with specific functional groups. In this thesis, a Surface Forces Apparatus (SFA) was employed to quantitatively analyze the interactions between functionalized SAMs and polymers/biomolecules, with particular focus on the effects of pH, contact time, and salt concentration.

Chapter 1 introduces the fundamental concepts, structures, and preparation methods of SAMs, along with the importance and potential applications of mixed SAMs. Chapter 2 examines the adhesion behavior of high molecular weight chitosan with four functionalized SAMs (COOH, NH₂, CH₃, Phenyl) under different pH, contact time, and salt conditions, confirming hydrophobic interactions as the dominant mechanism. Chapter 3 investigates the interactions of chitosan with mixed NH₂/CH₃ SAMs, demonstrating that adhesion is maximized at a specific mixing ratio and revealing synergistic effects at mixed interfaces. Chapter 4 explores the interactions between a DSPHTELP peptide derived from M13 bacteriophage and functionalized SAMs under varying pH and contact time, identifying hydrophobic and cation–π interactions as governing specific binding behavior. Chapter 5 analyzes the adhesion mechanisms of polyurethanes (PUs) synthesized from XDI and H6XDI with different polyols, elucidating the relative contributions of hydrogen bonding and hydrophobic interactions, and clarifying structure–property relationships.

This thesis demonstrates the utility of SAM-based model interfaces in elucidating the interaction mechanisms of diverse polymers and biomolecules, including chitosan, polyurethanes, and peptides. The results highlight the possibility of precisely tuning intermolecular interactions under different environmental conditions, thereby providing fundamental insights and design strategies for advanced biomaterials and functional composites.