Amphiphilic Graft Copolymer Electrolytes for Lithium-Ion Polymer Batteries. - Preparation and Characterisation

In the present work amphiphilic graft copolymers were prepared by free radical copolymerization of macromonomers in solution. The graft copolymers consisted of methacrylate backbones bearing ethylene oxide (EO)n side chains of varying length as ionophilic groups, and fluorocarbon (CF2)6 side chains or hydrocarbon groups as ionophobic groups. Homogenous polymer gel electrolytes were prepared by adding an electrolyte solution consisting of a solvent and a lithium salt, where the anion was fluorinated, to the copolymers. The gel electrolytes based on the amphiphilic copolymers bearing (CF2)6 side chains were found to have significantly higher ion conductivity than corresponding gels based on amphiphilic copolymers containing hydrocarbon groups. The lithium ions in the gels were found to coordinate cooperatively to the (EO)9 units in competition with the solvent. For copolymers bearing (EO)1, (EO)2 and (EO)4 side chains the coordination to the polymer was weaker. However, the ion conductivity was influenced only slightly by the varying strength of coordination of lithium ions by the different (EO)n side chains, in competition with the solvent. It was concluded that the ionophobic-ionophilic balance of the amphiphilic graft copolymers had to be controlled for achieving high ion conductivities in the gel electrolytes. From diffusion measurements it was concluded that the (CF2)6 side chains of the amphiphilic graft copolymer associated to form ionophobic microdomains in the gels. The (EO)n side chains seemed to stabilize the microdomains, and a high ionophobic content in combination with an appropriate EO content and (EO)n side chain length resulted in high ion conductivities. Moreover, the data suggested that the aggregating behaviour of the semi-fluorinated amphiphilic graft copolymers had a more intramolecular than intermolecular character at high concentrations of electrolyte solution. The self-diffusion coefficients of the lithium ions were significantly higher for the semi-fluorinated amphiphilic graft copolymer gels than for the gels based on a non-amphiphilic homopolymer. Furthermore, the lithium transference numbers were also higher, by almost a factor three. This effect was partly due to a higher EO content in the non-amphiphilic homopolymer, resulting in cooperative coordination of lithium ions by ether oxygens in competition with the oxygens in the solvent molecules. From 19F NMR data it was observed that the fluorinated anions in the semi-fluorinated amphiphilic copolymer gels were most probably present both in a solvent-rich environment, and an environment dominated by the ionophobic microdomains formed by the associating (CF2)6 side chains. If the TFSI anions associated to the microdomains formed in the semi-fluorinated amphiphilic copolymer gels, or were “captured” by the microdomains, the lithium salt dissociation might increase, leading to improved lithium mobility in the gel electrolytes

Beaded and cross-linked poly(aminoalkylene) matrix and uses thereof

The present invention relates to the synthesis of a beaded and cross-linked, high loading capacity polymer for solid phase synthesis, purification of reaction mixtures, chromatographic separation procedures, and the like. The invention can thus be used for the isolation of molecular entities having an affinity for the polymer beads or a chemical entity attached thereto. The beaded polymer matrix can be formed by cross-linking an optionally substituted poly(aminoalkylene), under inverse suspension or inverse emulsion polymerisation conditions, with a cross-linking unit of functionality =2

Amphiphilic polymer gel electrolytes. I. Preparation of gels based on poly(ethylene oxide) graft copolymers containing different ionophobic groups

Amphiphilic graft copolymers were prepared via the radical copolymerization of poly(ethylene oxide) (PEO) macromonomers with fluorocarbon or hydrocarbon acrylates in toluene with 2,2 ' -azobisisobutyronitrile (AIBN) as an initiator. H-1 NMR spectroscopy confirmed that the composition of the graft copolymers corresponded well to the monomer feed. For gel electrolytes prepared from the amphiphilic copolymers, the nature of the ionophobic parts of the amphiphilic graft copolymers had a great influence on the ion conductivity. Gel electrolytes based on graft copolymers containing fluorocarbon side chains showed significantly higher ion conductivity than electrolytes based on graft copolymers containing hydrocarbon groups. The ambient-temperature ion conductivity was about 2.6 mS/cm at 20 degreesC for a gel electrolyte based on an amphiphilic graft copolymer consisting of an acrylate backbone carrying PEO and fluorocarbon side chains. Corresponding gels based on graft copolymers with PEO side chains and hydrocarbon groups showed an ambient-temperature ion conductivity of about 1.2 mS/cm. The gel electrolytes contained 30 wt % copolymer and 70 wt % 1 M LiPF6 in an ethylene carbonate/gamma -butyrolactone (2/1 w/w) mixture

Amphiphilic solid polymer electrolytes

Amphiphilic graft copolymers consisting of methacrylate backbones carrying approximately 48 wt.% of ethylene oxide [(EO)(9) or (EO)(23)] side chains as ionophilic groups and fluorocarbon or hydrocarbon side chains as ionophobic groups were prepared. Solid polymer electrolytes based on the copolymers and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were characterized by DSC and the impedance spectroscopy. A maximum ion conductivity of 8 x 10(-5) S cm(-1) at 60 degreesC was found for a polymer electrolyte based on a copolymer having hydrocarbon side chains and (EO)(23) side chains, despite an EO content of only 50 wt.%. No (EO)(n) side chain crystallinity in the electrolytes was detected by calorimetry. The hydrocarbon side chains, on the other hand, were found to form a crystalline phase in the electrolytes. The melting of this phase was not reflected in the shape of the Arrhenius conductivity plot. This indicated that the segmental mobility in the ion conducting phase did not decrease as a result of the presence of the crystalline hydrocarbon phase