In this Thesis we discuss, from a statistical mechanical perspective, how excluded
volume effects influence the mechanical and dynamical behaviours of
biopolymers. It has long been recognized that steric constraints can affect
dramatically the physical properties of polymers in thermal equilibrium [1, 2].
Though the presence of steric hindrance in polymer models typically makes
them intractable by exact analytical means, the theoretical progress made in
the past three decades turned polymer thermodynamics in a very mature and
well-established research field. In recent years completely new avenues for
polymer physics and chemistry were provided by a variety of experimental
advancements capable of probing the mechanical and kinetic behaviours of
single polymeric molecules. This stimulated the development of new models
capable of accounting, in a quantitative manner, for the experimental
observations.
In particular, the models that we have introduced and discussed in this
thesis address two major topics stimulated by the latest single-molecule and
micromanipulation techniques. The first one is related to the elastic behaviour
of linear polymers that are stretched by pulling at both ends. The
second one, instead, is focused on the kinetics and thermodynamics of loop
formation in polymers. Though both problems have been computationally
and theoretically tackled before, the models used lacked almost invariably,
the treatment of the steric effects. We explicitly consider and model such
effects and discuss the qualitatively new emerging behaviour.
In the rest of the introduction we shall provide a phenomenological background
for both problems and motivations for the approach by means of .
which we have investigated the two problems.
