Self-assembly is the process during which discrete structures such as
molecules spontaneously and often reversibly organize themselves into
nanomaterials. The organization of these molecular building blocks is
driven by a combination of thermodynamic factors and kinetic factors,
many of which can be understood through examining the underlying
intermolecular interactions. The interactions may be covalent in nature,
leading to strong bonds between the molecules and resulting in an irreversibly self-assembled nanostructure. Covalent interactions—heavily
involved in much of what you learned in general chemistry—are mentioned throughout this chapter. Examples of specific self-assembled
materials are further discussed in Chapters 9 and 10. However, many selfassembly processes involve weaker noncovalent interactions, which can
have significant influence on the thermodynamics and kinetics of selfassembly due to being ubiquitous and varied in type and range of
interaction distances. It is important to appreciate that self-assembly can
be spontaneous and directed. We begin this chapter by reviewing some
important noncovalent intermolecular interactions that govern the formation of self-assembled nanomaterials.
Various forces are responsible for intermolecular interactions. Most of the
forces are electrostatic in origin, and we discuss them from a classical
perspective, although it should be noted that a quantum mechanical
approach to understanding intermolecular forces is perhaps more
correct.
Any interaction between two molecules can be thought of as a sum of a
variety of different forces. We will discuss many of these forces, including
ion–ion (Coulomb) forces, ion–dipole forces, dipole–dipole forces,
induced dipole forces, dispersion forces, and hydrogen bonds. Depending on the types of atoms or molecules interacting, one force or another
may predominate.
Scientists often express intermolecular interactions not as forces, but as
intermolecular potentials (or the potential energy of interaction). The
potential energy (U) and force (F) between two interacting molecules are
related by
F r
ð Þ = −
dU r
ð Þ
dr
(5.1)
where r is the distance between the two molecules. The intermolecular
distance, r, may be defined differently for different types of interacting
molecules. The negative sign on the derivative means that as the potential
CHAPTER 5: Intermolecular Interactions and Self-Assembly
134
molecules spontaneously and often reversibly organize themselves into
nanomaterials. The organization of these molecular building blocks is
driven by a combination of thermodynamic factors and kinetic factors,
many of which can be understood through examining the underlying
intermolecular interactions. The interactions may be covalent in nature,
leading to strong bonds between the molecules and resulting in an irreversibly self-assembled nanostructure. Covalent interactions—heavily
involved in much of what you learned in general chemistry—are mentioned throughout this chapter. Examples of specific self-assembled
materials are further discussed in Chapters 9 and 10. However, many selfassembly processes involve weaker noncovalent interactions, which can
have significant influence on the thermodynamics and kinetics of selfassembly due to being ubiquitous and varied in type and range of
interaction distances. It is important to appreciate that self-assembly can
be spontaneous and directed. We begin this chapter by reviewing some
important noncovalent intermolecular interactions that govern the formation of self-assembled nanomaterials.
Various forces are responsible for intermolecular interactions. Most of the
forces are electrostatic in origin, and we discuss them from a classical
perspective, although it should be noted that a quantum mechanical
approach to understanding intermolecular forces is perhaps more
correct.
Any interaction between two molecules can be thought of as a sum of a
variety of different forces. We will discuss many of these forces, including
ion–ion (Coulomb) forces, ion–dipole forces, dipole–dipole forces,
induced dipole forces, dispersion forces, and hydrogen bonds. Depending on the types of atoms or molecules interacting, one force or another
may predominate.
Scientists often express intermolecular interactions not as forces, but as
intermolecular potentials (or the potential energy of interaction). The
potential energy (U) and force (F) between two interacting molecules are
related by
F r
ð Þ = −
dU r
ð Þ
dr
(5.1)
where r is the distance between the two molecules. The intermolecular
distance, r, may be defined differently for different types of interacting
molecules. The negative sign on the derivative means that as the potential
CHAPTER 5: Intermolecular Interactions and Self-Assembly
134