Rational Polymer Design of Stretchable Poly(ionic liquid) Membranes for Dual Applications

Abstract

Many functional polymeric materials are inherently fragile at ambient conditions. Making them elastic and flexible is a challenging task, and such achievement is especially meaningful in a wide range of applications including separation membranes and stretchable devices. Poly­(ionic liquids) (PILs), such as vinyl-imidazolium-based polymers, are known to be “brittle” functional polymers due to their “glassy” nature at ambient temperature. We herein developed a viable approach to enable glassy PILs with high flexibility and good elasticity via a rational molecular design of chemical composition and polymer architectures. The reversible addition/fragmentation chain transfer agents (RAFT-CTAs) were attached to the flexible poly­(dimethylsiloxane) (PDMS) backbones. The polymerization of functional ionic liquid monomers from RAFT-CTAs provided grafted copolymers with the functional side chains, which were further cross-linked by di-functional PDMS. Poly­(ethylene glycol) methacrylate is copolymerized with ionic liquid monomers to reduce the glass transition temperature (T g), providing higher chain mobility and elasticity at ambient temperature. The synthesized elastic PIL-based membranes (E-PILs) have dramatically improved stretchability, reaching 122–422%. In addition to significantly improved extensibility, the synthesized E-PILs also exhibit higher ionic conductivity, critical for potential applications in solid-state batteries. Moreover, in comparison to glassy solid PIL membranes, the E-PILs also exhibited enhanced flexibility and excellent gas-separation performance.

Critical Role of the Interfacial Layer in Associating Polymers with Microphase Separation

“…Currently, polymers with dynamic bonds attract significant attention due to their easy recyclability, unique viscoelastic properties, and potential use in many applications ranging from super-stretchable and self-healing materials to shape memory materials . These materials also exhibit extreme toughness and extensibility due to efficient energy dissipation by the dynamic bonds and their rearrangements. , …”

“…14 These materials also exhibit extreme toughness and extensibility due to efficient energy dissipation by the dynamic bonds and their rearrangements. 15,16 The simplest mode of association is binary interaction, in which two complementary functional groups associate together and the dynamics of the polymer is controlled by the lifetime of the associating bond. However, recent studies 17−19 revealed a deviation between the bond lifetime and the macroscopic network relaxation timescale, and this discrepancy can be reasonably well explained by the bond lifetime renormalization model.…”

Self-Healable, Highly Stretchable, Ionic Conducting Polymers as Efficient Protecting Layers for Stable Lithium-Metal Electrodes

“…After soaking in the ether-based electrolyte, the polymer exhibits even better extensibility (Figure S9) and a higher Li-ion conductivity of 1.21 × 10 –3 S cm –1 (Figure S10). On the contrary, after the same electrochemical process, the bare Cu electrode (Figure d) displays a loose morphology, which is explained by the severe side reactions between the electrolyte and the Li-metal electrode that leads to accumulation of “dead” Li.…”

Highly Stretchable, Ultratough, and Multifunctional Poly(vinyl chloride)-Based Plastics via a Green, Star-Shaped Macromolecular Additive

“…Developing elastomers with improved mechanical performance, low cost, high stability, and preferred functionalities is highly demanded for current industrial applications such as in sealants, medical devices, automotives, and other emerging areas including flexible strain sensors, stretchable batteries, roll-up displays and communication devices. − Currently, most of the elastomers are derived from polymers with low glass transition temperature ( T g ) far below the ambient temperature, such as poly­(isoprene), and poly­(butyl acrylate), poly­(dimethylsiloxane), and poly­(butadiene) . With liquid-like behavior and weak mechanical performance for these intrinsic elastic polymers, chemical/physical cross-linking or copolymerization with another type of glassy polymer ( T g > ambient temperature) is usually applied to achieve elastomers with improved modulus and high toughness. − Mays and co-workers have reviewed different types of living polymerization techniques, including anionic polymerization, that have been utilized for the synthesis of hard blocks and soft blocks containing copolymeric elastomers with different architectures, such as triblock linear polymers, star copolymers, and bottlebrush copolymers . However, with a relatively complicated process, most of the fabricated elastomers still suffer from chemical instability and unsatisfied mechanical performance.…”

“…However, with a relatively complicated process, most of the fabricated elastomers still suffer from chemical instability and unsatisfied mechanical performance. As an alternative approach, lowering the T g of traditional glassy polymers with excellent physical properties has been less investigated, although it will bring further opportunities to achieve cost-efficient, high-performance elastomers. ,− …”