monomers consecutively occupying 2D lattice sites in athermal concentrated
solutions (De Gennes 1979 ). The bond of the solute molecules should have four
orientations in vacuum. One orientation is lost when it is the neighbor of a single
solvent site. Therefore, around one solvent site, the loss is integrated into four
orientations, as demonstrated in the left-hand side of Fig.4.6. Around two individ-
ual solvent sites, the total loss of bond orientations is thus eight. If these two solvent
sites are neighboring with each other, the total loss of bond orientations becomes
six, as shown in the right-hand side of Fig.4.6. This implies that the orientation
entropy of solute molecules will drive the neighboring of two solvent sites, foster-
ing an effective attraction between them. Now, by replacing the solvent sites with
two neighboring chain units that most likely belong to the same chain, we obtain an
effective attraction between these chain units due to the anisotropic aspect of
volume exclusions of polymer chains. This effective attraction will compensate
the isotropic aspect of volume exclusions of chain units within each chain when
their distances are beyond a certain characteristic lengthx. Therefore, beyond this
screening lengthx, the spatial distribution of single-chain units behaves like an
ideal single chain, as demonstrated in Fig.4.7.
Fig. 4.5 Illustration of the radial distribution of fluorescent ends of other chains, demonstrating
the correlation hole
Fig. 4.6Illustration of the isolated (left) and the neighboring (right) situations for the solvent site
(solid dot) surrounded by the ends of single bonds representing solute molecules (hollow dots)
52 4 Scaling Analysis of Real-Chain Conformations