This work details the phase behavior of a pseudoternary polymer blend system containing poly(ethylene oxide) (PEO) and polystyrene (PS) homopolymers, a PS−PEO block copolymer, and lithium bis(trifluoromethane)sulfonamide (LiTFSI). The phase behavior of the system is described along the volumetrically symmetric isopleth at a fixed LiTFSI concentration relative to the PEO component. The addition of LiTFSI dramatically increases the segregation strength of the blend, causing the otherwise globally disordered blends to exhibit a variety of microstructured morphologies typically found in salt-free ternary polymer blends, such as lamellae, a hexagonal phase, and a bicontinuous microemulsion. The breadth of morphologies and segregation strengths that can be accessed in this system by simply tuning blend composition establishes a new framework for the design of future ternary blend systems and, more broadly, polymeric materials where microstructured, wellsegregated domains with tunable ion transport properties are desirable.

Quaternized chitosan (QCh) was homogeneously synthesized by reacting chitosan with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) in alkali/urea aqueous solution for the first time. The structure and solution properties of QCh were characterized by using element analysis, FT-IR, 13 C NMR, SEC-LLS, rheology, viscometer, and ξ-potential measurements. Subsequently, polyelectrolyte complex (PEC) hydrogels were constructed by in situ polymerization of acrylic acid (AA) monomers in the concentrated QCh solution. The structure and mechanical behavior of the prepared hydrogels were systematic studied. Because of the high charge density and solubility of QCh, strong electrostatic interactions were formed in the hydrogels and endowed them tough with self-recovery properties. The mechanical behavior of the hydrogels was accurately tuned from stiff and viscoelastic to soft and elastic by changing the poly(acrylic acid) (PAA) content. The regulation mechanism relied on the remarkable difference in the chain segmental mobility between QCh and PAA. Moreover, the QCh/PAA PEC hydrogels displayed excellent solvent-induced shape-memory behavior due to the reversible properties of the ionic bonds. In summary, we offered a novel modification method for chitosan and opened up a new avenue to construct chitosan-based hydrogels with outstanding mechanical properties.

We present cloud point measurements on low molecular weight binary polymer blends doped with salts that exhibit unusual phase behavior. These blends include poly(ethylene-alt-propylene)/poly(ethylene oxide) (PEP/PEO) doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI), NaTFSI, KTFSI, LiClO 4 , and sodium iodide NaI. The addition of salt dramatically decreases the miscibility of the binary blends and results in an asymmetric cloud point profile. The phase behavior is found to be governed by the concentration of the salt, the size of the anion, and the composition of the polymer mixture. The experimental results are compared with a recent theory, which predicts the effect of ions on the polymer phase diagram by taking into account both ion-induced cross-linking and self-energy effects. Furthermore, the coexistence curve of salt-doped PEP/PEO blends is determined quantitatively by 1 H NMR spectroscopy when the volume fraction of PEO is maintained at 0.6. The coexistence curve does not coincide with the cloud point profile, which can be attributed to the effect of the redistribution of ions between the two coexisting phases. In the interest of generality, the cloud point profile of polystyrene/poly(ethylene oxide) (PS/PEO) doped with LiTFSI is also mapped out, in which similar phenomena are observed.

We have systematically examined the phase behavior of lithium salt-doped A/B/AB ternary polymer blends composed of low-molar-mass poly(ethylene oxide) (PEO) and polystyrene (PS) homopolymers, a symmetric PS-b-PEO block copolymer (SO), and lithium bis-(trifluoromethane) sulfonimide (LiTFSI) by a combination of small-angle neutron scattering and small-angle X-ray scattering, bolstered by ionic conductivity measurements. The salt partitions exclusively to the PEO and acts to increase the segregation strength of the blends, leading either to macroscopic or microscopic phase segregation. By constraining the volume fractions of the two homopolymers to be the same (ϕ PEO+LiTFSI /ϕ PS = 1), a two-dimensional phase diagram along the volumetrically symmetric isopleth of the phase prism has been mapped out, and a well-structured bicontinuous microemulsion (BμE) is found over a wider range of total homopolymer composition (ca. ϕ H ≈ 80−86%), compared to the neutral polymer case, where a 1−3% range in ϕ H is typical. The characteristics of the BμE are obtained via the Teubner−Strey structure factor and are tunable by ϕ H , temperature, and salt concentration. Moreover, the BμE possesses superior ionic transport properties, demonstrating higher conductivity compared to both microphase-separated (lamellar) and nonstructured disordered blends. This work offers a strategy to obtain well-defined microstructured ion-containing polymer systems with tunable co-continuous morphology and favorable conductivity properties, which could help optimize the design of polymer electrolytes.

We examine the relationship between structure and ionic conductivity in salt-containing ternary polymer blends that exhibit various microstructured morphologies, including lamellae, a hexagonal phase, and a bicontinuous microemulsion, as well as the disordered phase. These blends consist of polystyrene (PS, M n ≈ 600 g/mol) and poly(ethylene oxide) (PEO, M n ≈ 400 g/ mol) homopolymers, a nearly symmetric PS−PEO block copolymer (M n ≈ 4700 g/ mol), and lithium bis(trifluoromethane)sulfonamide (LiTFSI). These pseudoternary blends exhibit phase behavior that parallels that of well-studied ternary polymer blends consisting of A and B homopolymers compatibilized by an AB diblock copolymer. The utility of this framework is that all blends have nominally the same number of ethylene oxide, styrene, Li + , and TFSI − units, yet can exhibit a variety of microstructures depending on the relative ratio of the homopolymers to the block copolymer. For the systems studied, the ratio r = [Li + ]/[EO] is maintained at 0.06, and the volume fraction of PS homopolymer is kept equal to that of PEO homopolymer plus salt. The total volume fraction of homopolymer is varied from 0 to 0.70. When heated through the order−disorder transition, all blends exhibit an abrupt increase in conductivity. However, analysis of small-angle X-ray scattering data indicates significant structure even in the disordered state for several blend compositions. By comparing the nature and structure of the disordered states with their corresponding ordered states, we find that this increase in conductivity through the order−disorder transition is most likely due to the elimination of grain boundaries. In either disordered or ordered states, the conductivity decreases as the total amount of homopolymer is increased, an unanticipated observation. This trend with increasing homopolymer loading is hypothesized to result from an increased density of "dead ends" in the conducting channel due to poor continuity across grain boundaries in the ordered state and the formation of concave interfaces in the disordered state. The results demonstrate that disordered, microphase-separated morphologies provide better transport properties than compositionally equivalent polycrystalline systems with long-range order, an important criterion when optimizing the design of polymer electrolytes.

Direct precipitation of salbutamol sulfate (SS) by antisolvent crystallization in the presence of surfactants and polymeric additives was investigated to obtain micrometer-sized SS for use in inhaled drug delivery. Among the additives studied -hydroxypropyl methyl cellulose (HPMC), polyvinylpyrrolidone (PVP K25), lecithin (from soybean), and Span 85 -PVP K25 showed the strongest effect on crystal growth inhibition. By adding 2.5 mg/mL PVP K25 into the SS solution, the habit of SS crystallized was modified from a needle-like shape to a block-like shape with a lower aspect ratio, and the crystal size was reduced to less than 10 μm. On the basis of the predicted morphology of SS and the possible intermolecular interaction of the additives with a developing SS crystal in solution, we propose that PVP has a higher propensity to form hydrogen bonds with the functional groups that are exposed at the crystal surface. Further supporting evidence based on the effects of PVP concentration and molecular weight on SS crystallization, together with the trends of dispersive surface energy of crystallized SS particles as determined by inverse gas chromatography, strongly suggest that PVP adsorbs on the SS crystals and thereafter inhibits growth.

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Polymer electrolytes with high Li + -ion conductivity provide a route toward improved safety and performance of Li + -ion batteries. However, most polymer electrolytes suffer from low ionic conduction and an even lower Li + -ion contribution to the conductivity (the transport number, t + ), with the anion typically transporting over 80% of the charge. Here, we show that subtle and potentially undetected associations within a polymer electrolyte can entrain both the anion and the cation. When removed, the conductivity performance of the electrolyte can be improved by almost 2 orders of magnitude. Importantly, while some of this improvement can be attributed to a decreased glass transition temperature, T g , the removal of the amide functional group reduces interactions between the polymer and the Li + cations, doubling the Li + t + to 0.43, as measured using pulsed-field-gradient NMR. This work highlights the importance of strategic synthetic design and emphasizes the dual role of T g and ion binding for the development of polymer electrolytes with increased total ionic conductivity and the Li + ion contribution to it.