Hierarchical microphase separation in bicontinuous ternary polymer blends

Bicontinuous Microemulsions in Partially Charged Ternary Polymer Blends

“…Furthermore, the characteristic length scale d also shows only a modest decrease with increasing temperature, while ξ values display a relatively significant decrease, indicating that while the average domain size of the BμE state is less sensitive to temperature variation the correlation between interfaces is reduced upon increasing temperature. Another striking point is that the BμE channel runs over the entire temperature range studied, without any evidence of other ordered phases at low temperature, as has been seen in some neutral blend systems. ,, It is also possible that the system is far from conditions where the multiphase and lamellar regions approach each other as a function of homopolymer concentration. As ϕ H increases further to 0.88, f a values increase compared to those with ϕ H = 0.85, which range from −0.64 to −0.42 over the entire temperature range (see Figure d), indicating a transition from a well-defined to a less structured microemulsion state as the homopolymer content further increases.…”

“…Another striking point is that the BμE channel runs over the entire temperature range studied, without any evidence of other ordered phases at low temperature, as has been seen in some neutral blend systems. 23,24,27 It is also possible that the system is far from conditions where the multiphase and lamellar regions approach each other as a function of homopolymer concentration. As ϕ H increases further to 0.88, f a values increase compared to those with ϕ H = 0.85, which range from −0.64 to −0.42 over the entire temperature range (see Figure 4d), indicating a transition from a well-defined to a less structured microemulsion state as the homopolymer content further increases.…”

“…The polymeric BμE phase was first discovered in moderately high molecular weight poly­(ethylene)–poly­(ethylene- alt -propylene) (PE–PEP)/PE/PEP ternary blends . Mean-field theory anticipates the existence of a Lifshitz multicritical point, where the line of ordered lamellar–disorder transitions meets the critical Scott line of macrophase separation and is also coincident with the terminus of the line of unbinding transitions, which separates the lamellar and macrophase-separated regimes. , However, experiments and theoretical considerations have shown that the mean-field Lifshitz point and unbinding transition are destroyed by fluctuation effects and are preempted by the formation of the BμE phase. ,, Channels of BμE have been reported in the vicinity of the predicted mean-field Lifshitz composition in a host of neutral uncharged ternary polymer blends, − suggesting that this disordered yet uniformly structured state is a universal feature of such systems. However, in all cases the molecular weights were adjusted such that a fully disordered ternary blend was accessible at higher temperatures, raising the question of whether a relatively weakly segregated blend system is essential to form a BμE.…”

Phase Behavior of Diblock Copolymer–Homopolymer Ternary Blends with a Compositionally Asymmetric Diblock Copolymer

“…Phase separation of binary homopolymer blends exhibits Ising-like critical behavior, instead of mean-field behavior, when close to the critical temperature. − As the diblock copolymer is added to the homopolymer mixture, a crossover occurs from Ising critical behavior to isotropic Lifshitz critical behavior as the composition moves along the Scott line of critical points, which terminates in the vicinity of the nominal LP. − The most dramatic effect induced by fluctuations is the formation of a region (previously referred to as a channel) of a thermodynamically stable BμE near the location of the mean-field-predicted LP. This intriguing state of nanoscale bicontinuity has been reported in ternary polymer blends with a variety of molecular weights and chemical structures − and in salt-doped and ionic ternary polymer blends. − These results, in concert with theoretical studies, ,, have led to the generally accepted conclusion that the LP is destroyed in any non-mean-field system due to fluctuation effects.…”

“…Ternary polymer blends of an AB diblock copolymer and the corresponding A and B homopolymers, which are high molecular weight analogues of water/oil/surfactant mixtures, show strikingly similar phase behavior. A BμE forms between the ordered lamellar phase (LAM) and multiphase coexistence regions in the vicinity of the order–disorder transition that separates the LAM and DIS states. − This polymeric BμE has been used as a template to create a host of functional materials, for example, for membrane applications. − Ternary polymer mixtures have unique advantages in designing bicontinuous structures due to the ability to precisely control component molecular weight, dispersity, and diblock copolymer composition. Moreover, in many systems, the intermolecular interactions are governed by simple van der Waals forces, and the overall phase behavior can be anticipated by mean-field theory.…”