Phase behavior, polymers

In this review, we focus on the effect of anisotropic interactions, in particular parallel attractions, and demonstrate that the inclusion of such interactions in a model leads to a great richness in possible polymer phase behavior. From a practical point of view, the model that we describe has the advantage that it is computationally very cheap—although this advantage comes at the price of sacrificing the greater realism of an off-lattice model. 

Bates FS (1991) Polymer-polymer phase behavior. Science 251 898-905... 

For PIPAAm hydrogels, a large temperature increase originating below the polymer transition temperature of 32°C induces an outside-in shrinking response in the gel thermal transfer and polymer mass transfer kinetics compete for the determining of the polymer phase behavior. For this condition, the result is the formation of a dense shrunken collapsed polymer layer at the gel-water interface (a skin layer). These dehydrated polymer skin layers on the surface of shrunken PIPAAm hydrogels prevent even water molecules from... 

F.S. Bates, Polymer-Polymer phase behavior. Science, 251, 898-905 (1991). 

SEI Seiler, M., Hyperbranched polymers Phase behavior and new applications in the field of chemical engineering. Fluid Phase Equil., 241, 155, 2006. 

Kleintjens, L. (1998) Polymer phase behavior Today s achievements and tomorrow s needs. Presented at the NATO Advanced Study Institute on Supercritical Fluids, Kemer, Turkey, July 12-24, 1998. [Manuscript is included in this volume]. 

POLYMER PHASE BEHAVIOR Todays Achievements and Tomorrows Needs... 

Polymer phase behavior Todays achievements and tomorrows needs L.A.L. Kleintjens... 

Recent studies have shown that structural differences among components, eg differences in tacticity, affect phase behavior (33-35). The inability of the Flory-Huggins theory to account for these experimental observations is mainly a result of neglecting the particular molecular structure of the pol3rmer chains. Extensive studies have been imdertaken in order to be able to link polymer phase behavior to molecular structure (36). The polymer reference interaction site model (PRISM) represents one of the successful approaches in imderstanding the relationship between molecular structin-e, local packing and thermodynamics. 

K. R. Sharma, Phase Computer to Predict Polymer Phase Behavior, ASEE North Central Regional Meeting, Erie, PA, April 1999. 

Bates [3] discussed the role of molecular architecture in polymer-polymer phase behavior. There are a number of molecular configurations available to a pair of chenucally distinct polymer species. Star polymers with a specific arm number with predeternuned molecular weights and with narrow molecular weight distribution can be synthesized using anionic polymerization. Diblock and multiblock arrangements are possible. Different polymers can be combined into a single material in several different ways that can lead to a variety of phase behaviors. Four factors control the phase behavior of polymer-polymer systems [3]. These are... 

Bates [3] discussed the role of molecular architecture in polymer-polymer phase behavior. 

A. Macrophase separation into two layers, which commonly arises when two homopolymers are mixed. B. Microphase segregation can arise with diblock copolymers. Here, striated layers appear. C. Mixing homopolymers with the corresponding diblock copolymer gives intermediate-scale phase separation. A surfactant-like mixture occurs. Figure modified from Bates, F. S. "Polymer-Polymer Phase Behavior." Science, 251, 898 (1991). 

Bates, F. S. "Polymer-Polymer Phase Behavior." Science, 251,898 (1991). 

Before leaving this section it is worthwhile to explicitly offer two other observations concerning SCF-polymer phase behavior. The first observation is that the impact of polymer molecular weight falls off dramatically once the molecular weight increases above 100,000. The second observation is that polymer solubility drops to near zero at temperatures less than the solidification (melting) temperature of the polymer. Both of these observations are also found with liquid solvents. 

It is more appropriate to describe the impact of SCF solvent quality and polymer architecture on solution behavior with a select number of examples rather than presenting a large number of phase behavior studies. The reader is directed to a comprehensive review of SCF-polymer phase behavior available in the... 

Shaw [52] noted that an improved procedure for utilizing the solubility parameter method to predict polymer phase behavior involved matching the polar and dispersive contributions to the solubility parameter Spot and S ) to achieve a better potential for miscibility. Other approaches utilizing multidimensional solubility parameter matching includes Hansen [94,... 

Additional Methods of Predicting Polymer Phase Behavior... 

---