Blends of Polybutadiene with Different Vinyl Contents and Polystyrene Studied with Small-Angle Neutron Scattering in Varying Temperature and Pressure Fields

Abstract

Blends of polybutadiene with three different vinyl contents and polystyrene were studied by small-angle neutron scattering as a function of temperature and pressure. The data were analyzed with a crossover function combining the universality classes of the 3D-Ising and the mean field behavior and thus yield the spinodal temperature T S, the Ginzburg number Gi, and the critical amplitude CMF. From these parameters the mean field Flory-Huggins interaction parameter is calculated in terms of entropic and enthalpic contributions. The application of the theory of random copolymers delivers large enthalpic and entropic contributions of the intramolecular interaction between the 1,2-and 1,4-butadiene units. These numbers could not be confirmed from measurements of the corresponding intermolecular interaction contributions in an h-PB(1,2)/d-PB(1,4) blend, which thus leads to speculations about the equivalence of inter-and intramolecular interactions in random copolymers. The Ginzburg number proved to be specific to the vinyl content and thus deviated from the universal behavior Gi ∝ V -1 predicted by deGennes. By our pressure experiments we find that the Clausius-Clapeyron equation suggests the phase boundary to be influenced by the Flory-Huggins parameter and the Ginzburg number.

Phase Behavior and Flory−Huggins Interaction Parameter of Binary Polybutadiene Copolymer Mixtures with Different Vinyl Content and Molar Volume

“…8 It appears that the differences between the PS and PB monomers are too strong in order to properly include them into a theoretical description as the LC theory. 12 For a systematic comparison between experiment and theory, a series of studies on systems with increasing complexity seem desirable.…”

“…The polymers were synthesized by anionic polymerization using high vacuum and break seal techniques as has been described in more detail in ref 8. sec-Butyllithium was used as initiator for all polymerizations.…”

“…8 In these experiments, strong discrepancies were observed for the interaction energy between PB (1,4) and (1,2) monomers depending on whether the interaction energy was determined from the PB(1,2)/PB (1,4) or PS/PB blend as an intermolecular or intramolecular interaction energy, respectively. This discrepancy would not have been visible from the phase boundaries alone as the critical temperature of the blend with the copolymer PB (1,2;1,4) is well between those with PB(1,4) and PB(1,2) (see Figure 7 in ref 8). The reason using the phase boundary alone is insufficient is because the full Flory-Huggins (FH) parameter is the noncombinatorial part of a free energy of mixing consisting of an enthalpic and entropic term which cannot be determined from the phase boundary alone.…”

Small angle neutron scattering studies of a polybutadiene/polystyrene blend with small additions of ortho-dichloro-benzene for varying temperatures and pressures. I. Mean field to 3D-Ising crossover behavior

“…͑11͒. 3,6,7,24,[30][31][32][33] All data are lying between the two dashed lines representing a power law with the exponents of Ϫ1 and Ϫ2. The N Ϫ1 power behavior is consistent with the Ginzburg criterion in Eq.…”

Influence of high pressure on higher-order structures of poly(oxyethylene) in its blend with poly(d,l-lactide)

“…Most experiments under pressure have been performed to elucidate the effect of pressure on miscibility of polymer blends [10][11][12][13][14][15]. Almost no researches had been done on the details of nano-structures of PLA/PEG blends under pressure.…”