Correlations between the Effects of Pressure and Molecular Weight on Polymer Blend Miscibility

Abstract

We examine the effects of pressure on polymer blend miscibility for two polyolefin blends as well as for blends of polystyrene (PS) and polybutadiene (PB). Each of the blends studied exhibits an upper critical solution temperature (UCST), and for the PS/PB blend we report experimental results on the pressure dependence of the UCST for different molecular weight combinations. We make use of the Born-Green-Yvon integral equation theory to exploit the connection between the pressure dependence of the UCST and the sign of the volume change on mixing, leading us to predict that through judicious choice of polymer molecular weights the response of the UCST to pressure may be controlled.

Calculation of the effect of macromolecular architecture on structure and thermodynamic properties of linear–tri-arm polyethylene blends from Monte Carlo simulation

“…For all compositions, blend density is higher compared to either of the two pure polymers indicating that the blends examined assume negative excess volume values. Such behavior agrees with lattice model predictions for poly(ethylene-alt-propylene) e head-to-head polypropylene blends [27] and with Monte Carlo simulations on model polyethylene blends [64]. As a result, one may conclude that pressure is expected to have a substantial effect on the mixing properties of this blend.…”

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

“…Although Equation 9 still holds for UCST/UDOT systems, DV mix can be either positive or negative. [90] Since the UCST/UDOT systems are characterized by endothermic mixing (DH mix > 0), a negative DV mix shifts the UCST/UDOT to a lower temperature, whereas a positive DV mix serves to increase the UCST/UDOT, with increasing P. [90] Both pressure-induced increases [84,[90][91][92][93] and decreases [90,94] in UCST/UDOT have been experimentally observed. Complex P-T relationships wherein the temperature initially decreases and then increases upon pressurization have likewise been reported for UCST/UDOT [95,96] and LCST/LDOT systems.…”

Effect of Pressure on the Phase Behavior and Segmental Dynamics in Blends of Polystyrene with Poly(methylphenyl siloxane)

“…[11][12][13][14][15][16] These observations have motivated numerous studies of the thermodynamics and dynamics of polymer blends. Although the effect of pressure, with its relevance in polymer blend processing, is much less investigated, there are some recent experimental [17][18][19][20][21][22][23][24][25][26] and theoretical 27,28 efforts that focus on the effects of pressure on the dynamic heterogeneity and phase behavior. With respect to the issue of dynamic heterogeneity, there have been two studies in athermal polymer blends/copolymers: polyisoprene-b-poly(vinyl ethylene) (PI-b-PVE) (ΔT g ≈ 60 K) 17 and poly(methyl methacrylate)/poly(ethylene oxide) (PM-MA/PEO) (ΔT g ≈ 180 K).…”

“…Pressure dependence of T g (defined at τ ≈ 1 s) for the "fast" (filled triangles) the "slow" (filled rhombus) processes in the PS28 / PMPS 17 blend and of the PMPS (open triangles, ref 36) and PS (open circles, T g -scaled data from ref 38) homopolymers. Notice the proximity of the two T g values at all pressures investigated.…”

“…Predicted phase diagram for PS28 /PMPS 17 at atmospheric pressure. Given are the binodal (solid) and spinodal (dashed) curves.…”