Temperature blob model

Now consider the weak coupling region / < 1. Prom Eq. (13.33 ii) we find that q2 —v g2, z fixed, implies,/ — 0. From Eqs. (13,24), (14.16) we then find the trivial limiting behavior Ja(q) 1/q2, in accord with the temperature blob model. For a system close to the excluded volume limit for large q we first may find some region described by the law (14.17), the trivial behavior developing only for extreme values of the momentum (see Fig. 14.2),... 

Monomers on a polymer chain in a solvent interact with each other through the effective long-range force. The temperature blob model predicts a crossover from a random coil to a compact globule. On the basis of the mean-field free energy, this section studies the possibility of a sharp CG transition [16,20]. 

Temperature blobs have been introduced in [DJ78]. They have been exploited to model the internal structure of a chain for instance in [WC79]. 

In cases of intermediate degrees of chain swelling, the temperature blob approach [21] has been useful in modeling excluded volume effects. It consists in defining a blob comprising a number nt of monomers that obey ideal chain statistics while the blobs themselves show excluded volume effects ... 

Fig. 1.7 Thermal blob model describing the conformational change of a polymer chain with the temperature. The vertical axis is the dimensionless reduced temperature t with the theta temperature as the reference temperature.

Vd = 0.5. At higher temperatures excluded volume behavior is exhibited, Vj>=0.6. Figure 2 shows the variation of between these two values based on the thermal blob model... 

---