Molecular scale stretchable single ion polymer electrolyte
Stretchability functional polymer is of great significance for the preparation of a stretchable device. To date, the stretchable functional polymer synthesis methods are mainly functional polymer component and the flexible polymer adhered together by a physical component, due to the weak physical force but often it usually results in use many problems, such as a functional group and a separate stretchable base material results in failure. Further, with respect to the conventional polymer electrolyte having positive and negative ions simultaneously movable, the list polymer electrolyte (sodium ion and lithium ion conductivity close to 1) has unique advantages, such as higher ion conductivity can reduce the positive electrode pole of suppressing lithium dendrite growth and the like. Recently, Oak Ridge National Laboratory researcher Cao Pengfei and the University of Tennessee, a joint research team on \”macromolecules\” magazine published an article entitled \”Elastic Single-ion Conducting polymer Electrolytes: Towards a Versatile Approach for Intrinsically stretchable functional Polymers\” article, reported a molecular scale stretchability functional polymers. Single ion-conductive solid polymer electrolyte (SICPEs) thus prepared by the method shown considerable energy efficiency and battery life, there is a great potential in the field of a flexible battery / conductive material or the like. Mechanical properties of films made from such an electrolyte having a maximum of 88% to 252% elongation, and the film can be regulated by chemical means. In the constant current test, the film thus assembled cells exhibit a good cycle performance after 100 cycles, still 81.5% of capacity. Also demonstrated the preparation of other flexible functional polymer may by this method: a flexible material having semiconductor characteristics were prepared made using polyvinyl carbazole gas poly (vinyl-carbazole), and the use of polyethylene glycol poly (ethylene glycol) release film.
1. Preparation of functional polymer stretchable
The structure of the polymer is a schematic diagram shown in Figure 1A. By branched polydimethylsiloxanes (PThe DMS, FIG. 1B, I) chemical transformation, 60% of the side chain amino function is transformed into a chain (FIG. 1B, III) having a chain transfer group so as to the polymerization initiator reversible addition fragmentation chain transfer (RAFT). RAFT polymerization is for polymerizing a monomer having a single ion conductor: STF-Li +, or MPA-Li + and polyethylene glycol monomer: poly (ethylene glycol) methacrylate (PEGMA), after the completion of the polymerization, the compounds of structure (FIG. 1B, IV ) were confirmed by nuclear magnetic resonance spectra and infrared spectra. Terminal-modified PDMS isocyanate derivative as a crosslinking agent, a polymer network structure is formed by intramolecular or intermolecular chemical crosslinking. The advantage of this construction is that the chemical structure of a PDMS backbone may provide stronger mechanical properties and stretchability, a graft polymer side chains may be implemented in different functional groups selected functional requirements of the different components are connected by free.
2. The elastic properties of functional polymer
All single elastomeric polymer electrolyte ions exhibit good thermal stability at temperatures to 200 ° C . Effect of polyethylene glycol can be seen that the performance of the components of the sample from the parameter Tg, the sample is added PEGMA, Tg has significantly decreased, both at room temperature or below, the low Tg gives a higher elasticity of the polymer electrolyte chain single ion activity significantly improved ductility at room temperature. Mechanical properties, Figure 2 shows the tensile properties of the material data, by comparing samples 2 and 3, increasing the degree of polymerization of the side chains of the graft copolymer does not have a greater impact on the mechanical properties of the film; Comparative Sample 2 and sample 4, changing the terminal groups are alkyl PEGMA, i.e. elongation PEGMEMA, the sample will increase 1.4-fold, but the modulus drops to 23% of the original, this phenomenon is due to hydroxyl end groups can be provided PEGMA additional chemical cross-linking to enhance the degree of crosslinking will lead to increased modulus, decreased elongation. It also demonstrates the effect of varying amounts of PDMS crosslinker mechanical properties of the samples, increasing the content of the crosslinking agent, the sample will increase the modulus, elongation decreases. These findings help us understand how you can change the chemical compositionTo influence the mechanical properties of the sample film, there is significance for new structural design polymer.
investigated the electrical properties of the polymer electrolyte may be stretched by using a broadband dielectric spectroscopy (Broadband Dielectric Spectroscopy). Systematically studied the effects of different chemical structures SICPEs relaxation time, and a variety of relaxation time associated with the temperature, FIG. 3A shows the conductivity of the sample at different temperatures. The electrochemical characteristics of a battery prepared from SICPEs also be implemented via a variety of characterization methods were characterized 3B shows the specific capacity and coulombic efficiency of the sample cell, the battery after 100 cycles, the battery still remaining capacitance than 81.5%. Conductivity
In addition to the single application of the polymer electrolyte ions, the authors also demonstrated a stretchable material having a semiconductor function polyvinylcarbazole prepared using poly (vinyl-carbazole), and the use of polyethylene glycol poly (ethylene glycol ) gas separation membrane prepared. Polymer functional film produced has better mechanical properties. Notably, in the field of gas separation membrane, in this method under the guidance of a flexible synthetic gas separation membrane, to achieve a high separation efficiency CO2 / N2 = 36.5 ratio.
In summary, the authors show general method of polymer material for preparing a stretchable functional cross-linker based on the graft copolymer. This method successfully guided a series of single ion elastomeric polymer electrolyte was prepared. These electrolyte films have demonstrated good mechanical strength and ductility, the author implements effective regulation of the mechanical properties. The prepared polymer electrolyte battery exhibiting good electrochemical stability, is expected to be more widely used in electronic components and flexible battery or other flexible material. The full text link: https: //pubs.acs.org/doi/10.1021/acs.macromol.9b02683