An enormous number of investigations conducted over the past half-century have focused on development and implementation of methods to probe macro-
molecular features such as chain dimensions, chain dynamics, molecular weight,
and molecular shape. The intense interest in this area has been fueled by the
recognition that the unique and versatile properties of polymers are a direct
consequence of their being endowed with an extreme range of accessible confor-
mations. From a practical standpoint, this means that bulk mechanical and
thermal properties, morphology, and processing behavior reflect both the aver-
age equilibrium chain dimensions and the chain flexibility or ease with which
changes in size and shape can occur. Thus, the development of an understanding
of how polymer structure affects chain flexibility has been a major focus of
polymer science since its inception. Much progress has been made in this area on
both theoretical and experimental fronts. Flory [1] reviewed developments in
this area up to 1969 in a classic monograph. Establishing correlations between
polymer conformation and mechanical and thermal properties has proved more
difficult. Recently, however, much progress has been made in terms of correlat-
ing the plateau modulus and other rheological parameters [2-9] with para-
meters of chain flexibility.