Understanding the Seeded Heteroepitaxial Growth of Crystallizable Polymers: The Role of Crystallization Thermodynamics.

Seeded heteroepitaxial growth is a "living" crystallization-driven self-assembly (CDSA) method that has emerged as a promising route to create uniform segmented nanoparticles with diverse core chemistries by using chemically distinct core-forming polymers. Our previous results have demonstrated that crystallization kinetics is a key factor that determines the occurrence of heteroepitaxial growth, but an in-depth understanding of controlling heteroepitaxy from the perspective of crystallization thermodynamics is yet unknown. Herein, we select crystallizable aliphatic polycarbonates (PxCs) with a different number of methylene groups (xCH2, x = 4, 6, 7, 12) in their repeating units as model polymers to explore the effect of lattice match and core compatibility on the seeded growth behavior. Seeded growth of PxCs-containing homopolymer/block copolymer blend unimers from poly(ε-caprolactone) (PCL) core-forming seed platelet micelles exhibits distinct crystal growth behavior at subambient temperatures, which is governed by the lattice match and core compatibility. A case of seeded growth with better core compatibility and a smaller lattice mismatch follows epitaxial growth, where the newly created crystal domain has the same structural orientation as the original platelet substrate. In contrast, a case of seeded growth with better core compatibility but a larger lattice mismatch shows nonepitaxial growth with less-defined crystal orientations in the platelet plane. Additionally, a case of seeded growth with poor core compatibility and larger lattice mismatch results in polydisperse platelet micelles, whereby crystal formation is not nucleated from the crystalline substrate. These findings reveal important factors that govern the specific crystal growth during a seeded growth approach by using compositionally distinct cores, which would further guide researchers in designing 2D segmented materials via polymer crystallization approaches.

Superionic Bifunctional Polymer Electrolytes for Solid-State Energy Storage and Conversion.

Achieving superionic conductivity from solid-state polymer electrolytes is an important task in the development of future energy storage and conversion technologies. Herein, a platform for innovative electrolyte technologies based on a bifunctional polymer, poly(3-hydroxy-4-sulfonated styrene) (PS-3H4S), is presented. By incorporating OH and SO3 H functional groups at adjacent positions in the styrene repeating unit, "intra-monomer" hydrogen bonds are formed to effectively weaken the electrostatic interactions of the SO3 - moieties in the polymer matrix with embedded ions, promoting rich structural and dynamic heterogeneity in the PS-3H4S electrolyte. Upon the incorporation of an ionic liquid, interconnected rod-like ion channels, which allow the decoupling of ion relaxation from polymer relaxation, are formed in the stiff motif of the polymeric domains passivated by interfacial ionic layers. This results in accelerated proton hopping through the glassy polymer matrix, and proton hopping becomes more pronounced at cryogenic temperatures down to -35 °C. The PS-3H4S/ionic liquid composite electrolytes exhibit a high ionic conductivity of 10-3 S cm-1 and high storage modulus of ≈100 MPa at 25 °C, and can be successfully applied in soft actuators and lithium-metal batteries.

All-Solid-State Lithium-Organic Batteries Comprising Single-Ion Polymer Nanoparticle Electrolytes.

Advances in lithium battery technologies necessitate improved energy densities, long cycle lives, fast charging, safe operation, and environmentally friendly components. This study concerns lithium-organic batteries comprising bioinspired poly(4-vinyl catechol) (P4VC) cathode materials and single-ion conducting polymer nanoparticle electrolytes. The controlled synthesis of P4VC results in a two-step redox reaction with voltage plateaus at around 3.1 and 3.5 V, as well as a high initial specific capacity of 352 mAh g-1 . The use of single-ion nanoparticle electrolytes enables high electrochemical stabilities up to 5.5 V, a high lithium transference number of 0.99, high ionic conductivities, ranging from 0.2×10-3 to 10-3  S cm-1 , and stable storage moduli of >10 MPa at 25-90 °C. Lithium cells can deliver 165 mAh g-1 at 39.7 mA g-1 for 100 cycles and stable specific capacities of >100 mAh g-1 at a high current density of 794 mA g-1 for 500 cycles. As the first successful demonstration of solid-state single-ion polymer electrolytes in environmentally benign and cost-effective lithium-organic batteries, this work establishes a future research avenue for advancing lithium battery technologies.

Simultaneous Improvement of Ionic Conductivity and Mechanical Strength in Block Copolymer Electrolytes with Double Conductive Nanophases.

The most daunting challenge of solid polymer electrolytes (SPEs) is the development of materials with simultaneously high ionic conductivity and mechanical strength. Herein, SPEs of lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI)-doped poly(propylene monothiocarbonate)-b-poly(ethylene oxide) (PPMTC-b-PEO) block copolymers (BCPs) with both blocks associating with Li+ ions are prepared. It is found that the PPMTC-b-PEO/LiTFSI electrolytes with double conductive phases exhibit much higher ionic conductivity (2 × 10-4 S cm-1 at r.t.) than the BCP electrolytes with a single conductive phase. Concurrently, the storage moduli of PPMTCn -b-PEO44 /LiTFSI electrolytes are ≈1-4 orders of magnitude higher than that of the neat PEO/LiTFSI electrolytes. Therefore, simultaneous improvement of ionic conductivity and mechanical properties is achieved by construction of a microphase-separated and disordered structure with double conductive phases.