Effects of compatibilizer on immiscible polymer blends near phase inversion

e consider the effects of adding a PIB-PDMS diblock copolymer as a compatibilizer in model lends composed of polyisobutylene PIB and polydimethylsiloxane PDMS . The ratio of PIB to DMS was varied from 20:80 to 80:20 and, hence, these blends are dubbed “concentrated” blends. ost experiments were conducted on blends containing 0.01 or 0.1 wt. % compatibilizer. All lends had a droplet-matrix morphology, with the minor phase being the drop phase; thus, phase nversion occured when PIB and PDMS were in a 50:50 ratio. Previously, we have studied effects f compatibilizer in “dilute” blends with PIB and PDMS in a 10:90 ratio. Much of the rheological ehavior of the concentrated blends studied here is found to be qualitatively similar to that of ilute blends: compatibilizer increases the terminal complex viscosity, the terminal relaxation time, teady shear viscosity, and the ultimate recovery upon cessation of shear. However, there are two oteworthy differences. The first is that in blends in which PIB forms the continuous phase, the ompatibilizer can suppress coalescence of the PDMS drops. Therefore, rheological properties that epend on drop size, e.g., relaxation time or ultimate recovery, are correspondingly affected. econd, the compatibilizer increases the viscosity, especially the terminal complex viscosity, of the oncentrated blends far more than it does in dilute blends. This can be interpreted in terms of a artial immobilization of drop surfaces by the compatibilizer. Indeed, in blends with PIB as the ontinuous phase, the viscosity is only slightly lower than of a suspension of rigid spheres, uggesting that the compatibilizer immobilizes the interface almost completely. © 2007 The ociety of Rheology. DOI: 10.1122/1.2742391