Ginzburg Number and Critical Amplitudes

The effect of solvent on the Ginzburg number is shown in Fig. 18 for the two dPB/PS blends that differ in the vinyl content of the PB component (Sample 2 and 3 in Table 2). Gi is plotted versus the total polymer concentration on a double logarithmic scale. A strong increase of Gi with solvent content is observed at 80% polymer concentration a 5 to 10 times larger Gi is observed and over this concentration range the Ginzburg number approximately fol- 

The mean field critical amplitudes of the correlation length of both blends are the same within experimental uncertainty and increase by about 10% for a 80% polymer content. The Ising amplitudes are smaller than their mean field numbers, and, instead, they decrease with polymer content by about 20%. In addition, the amplitudes are different in both blends PB(1,4)/PS shows slightly more than 10% larger values than PB(1,2 1,4)/PS. The mean field amplitude is proportional to the polymer radius of gyration and the square root of (1 + pr /rc) (Eq. 29) the polymer parameters are very similar, (Table 2) so the result of equal amplitudes is not surprising. On the other hand, the Ising critical amplitudes seem to depend more sensitively 

In Fig. 20 the FH parameters of the blend-solvent systems have been depicted versus the solvent content. In the upper figure the enthalpic /], of both blends are presented for ambient pressme, while in the two lower figures the entropic r is depicted at ambient and 200 MPa pressure fields. At ambient conditions one observes for the PB(1,4) blend a linear increase of about 50% for Th and 71,while for the (1,2 1,4) copolymer blends yield an oscillatory behavior with relative maximum and minimum values at about 3 and 12% solvent concentration, respectively. The difference of 71, at the two pressme fields may give information about the free volume. One can reasonably assume that practically no free voliune is siuwiving at 200 MPa. We proceed with this analysis by applying a simplified ansatz 71, = 7 + s/ s + l vl v with i2i and respectively, the molar volume and volume fraction of the solvent molecules and the imits of free volume [36]. The straight fine for 71, at 200 MPa describes the fimction 71, = -f is the contribution from 

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