Real Polymer Chains

Abstract Chapter 3 begins with a discussion of the effect of the repeat unit excluded volume on the distribution of a chain’s end-to-end distance. It points out that the degree of chain swelling is directly related to the chain’s packing parameter characterizing the relative importance of the chain’s rigidity and its repeat unit excluded volume. The discussion continues with the adaptation of the lattice model to describe chain swelling and collapse in the presence of solvent. The polymer/solvent affinity is quantified by introducing the Flory interaction parameter that controls solvent quality for the polymer backbone. The Flory approach is used to account for chain swelling and collapse. In the collapsed (globule) state, the effect of the globule’s surface energy on the coil–globule transition is discussed. This analysis highlights the conditions leading to a breakdown of the Flory approach to the coil–globule transition. The thermal blob concept is introduced to qualitatively describe conformations of polymer chains in both swollen and collapsed states. The section ends with a discussion of a real chain’s deformation by an external applied force, and chain confinement within a pore.