MEAN-FIELD THEORY OF POLYMER MELTING

We study the Flory model for the melting of a semiflexible polymer chain on a lattice. Using a field theoretical representation of the partition function, we propose a new mean-field theory. Within this theory, the system undergoes a first-order transition at temperature T(c), between a liquid-like phase at temperature T > T(c) and an ordered (almost stretched) phase at T < T(c), in agreement with the original Flory idea. In addition, we find a disorder point T(D) (> T(c)), separating two liquid phases with different short-range correlations. For T > T(D), the short-range correlations are isotropic, whereas for T < T(D), one-dimensional short-range order sets in. This disorder point may be relevant to the glass transition.