Entropy of disorientation

If X is large, the first term is negligible compared with the second, and the entropy of disorientation per segment reduces to... 

Each chain thus gains the entropy of disorientation... 

Hg. 2.15 Method to find the entropy of disorientation and the entropy of mixing in polymer solutions. 

Let us consider the free energy (6.2) of the dimer formation. The conformational free energy appears because the entropy of disorientation is reduced when two chains are combined. If we use the lattice-theoretical entropy of disorientation (2.90), we have... 

For the conformational free energy, we employ the lattice theoretical entropy of disorientation (2.90), and find... 

The formation of the polymer solution takes place in two separate steps. In the first the polymer molecules are disordered or disorientated, and subsequently this disordered or disoriented polymer is mixed with the solvent. The entropy of the first step, the disorientation process, is given by eq. (9.52) when we neglect the effect of having solute molecules present by setting NM =0, thus ... 

Although the disorientation process might be looked upon as a melting process, eq. (9.54) does not give a good estimate of the entropy of fusion of polymers. A more reasonable approach is to introduce the mean square displacement length of the actual chain in its unperturbed state [7], The number of such units would then replace r in eq. (9.54), but one still needs to determine the coordination number z in an independent manner. 

Here Nc, total number of copolymer molecules in system viy volume fraction of component i m, number of blocks per copolymer molecule nA, number of A units per copolymer molecule ASdis, disorientation entropy change gain on fusion per segment and AScryst, molar entropy of crystallization per A unit. 

Equation (2) contains contributions from two processes the disorientation of the perfectly ordered polymer molecules and the mixing of the disoriented polymer with solvent. In order to determine the configurational entropy of mixing an amorphous polymer with a solvent, AS, the disorientation entropy term, obtained from Eq, (2) by setting n 0, must be subtracted from AS, ... 

The formation of the solution may be conceived to occur in two steps disorientation of the polymer molecules and mixing of the disoriented polymer with solvent. The separate entropy changes are readily obtained as follows The first is given by Eq. (8) with ni = 0, i.e. 

The process of mixing can be considered to take place in two distinct steps first, disorientation of the polymer segments in the absence of solvent second, mixing of solvoit with the disoriented polymer. The entropy associated with the disorientation (d5 °) is obtained by setting i =0 in equation (3.8). This eliminates the mixing step whence... 

---