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A series ternary composites of poly(ethylene oxide)/ionic liquid 30/70 (P30) with uniformly dispersed halloysite nanotubes (HNTs) are investigated in the homogeneous and two‐phase regions. For P30/HNTs composites, a relatively lower percolation threshold about 3 wt% of HNTs loading is observed in the single‐phase region of P30. Beyond the percolation threshold, the steady shear flow exhibits two shear‐thinning regions due to the coupled relaxation of HNTs network and polymer entanglement. In the two‐phase region of P30, the mobility of ionic liquids (ILs) can be impeded accounting for the filler network forming. Not only the phase recovery during cyclic heating–cooling treatment near the phase boundary is accelerated, but also the phase separation kinetics is significantly retarded owing to HNTs dispersed in the PEO‐rich phase impeding the escaping of ILs from PEO phase. The lower storage modulus G′ for P30/HNTs‐4wt% compared to P30/HNTs‐3wt% in a two‐phase region is connected with the competition between the filler contribution and additional elasticity induced by phase separation. [ABSTRACT FROM AUTHOR]

The combination of polymers with ionic liquids (ILs) is of significant interest for a variety of possible applications e.g., polymer electrolytes, nanoencapsulations and actuators. Knowledge of phase separation, crystallization and their interplay in polymer/IL mixtures is of crucial importance for realizing these applications. In this work, the effect of phase separation on crystallization behavior for poly(ethylene oxide)/1-ethyl-3-methylimidazolium tetrofluoroborate (PEO/[EMIM][BF 4 ]) mixtures with a lower critical solution temperature (LCST) was investigated for the first time. It is demonstrated that the crystallization of PEO/ILs mixtures could be highly accelerated by phase separation as the blended samples are quenched from two-phase region compared to those quenched from homogenous state. This phenomenon can be on one hand ascribed to the disruption of hydrogen bonds between PEO and IL molecules as evidenced by FTIR results, which causes an increase of chain mobility and diffusivity for developing a spherulite embryo, and on the other hand due to fluctuation concentration where local PEO-rich domains with higher crystallizable PEO concentration will exist, even though the interfacial area has disappeared upon quenching to the crystallization. The facilitating effect of phase separation on crystallization becomes more prominent as driven by spinodal decomposition (50 wt% PEO) than that driven by nucleation & growth (70 wt% PEO). This work will provide a new possibility to optimize the performance of polymer electrolytes by regulating the phase morphologies of polymer/IL blends. Image 1 • Largely facilitated crystallization rate and spherulite growth by phase separation. • More prominent acceleration of P50 driven by SD than P70 dominated by NG. • The coupling effect of phase separation kinetics and disrupted hydrogen bonds. [ABSTRACT FROM AUTHOR]

The irreversible and reversible phase transition behaviors during phase separation-recovery (heating-cooling) cycles for poly(ethylene oxide)/1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (PEO/[EMIM][BF4]) mixtures with a lower critical solution temperature phase diagram are reported for the first time. The evident differential scanning calorimetry endothermic and exothermic peaks are observed during the heating-cooling scan cycles near the phase boundary, in which the large heat loss for samples below the critical composition (60 wt% PEO) and obvious downward shift of phase transition temperature for all the compositions between the first and second cycles are particularly attractive. After the first recovery process, a reversible behavior during the next cycles is expected. These interesting phenomena are further confirmed by optical microscopy and Fourier-transform infrared measurements. It is demonstrated that the disruption and partial recovery of the hydrogen bonds, combined with the conformational change of PEO chains, can contribute to this irreversible behavior as well as a conversion to reversible phase transition behavior. [ABSTRACT FROM AUTHOR]