Process for the preparation of poly(oxyalkylene) terpolymer by h

Details Process for the preparation of poly(oxyalkylene) terpolymer by h Process for the preparation of poly(oxyalkylene) terpolymer by h

1995-09-22

1997-12-23

Clark, W. Robinson H.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525404, 528266, C08L 7102

Patent

active

057008809

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a process for the preparation of copolymers exhibiting solvating properties, useful for the production of ionically conductive materials.
It is known to employ solvating polymers for the production of ionically conductive materials. Ethylene oxide and dioxolane polymers are polymers which solvate cations, in particular alkali metal cations such as, for example, the Li.sup.+ ion present in the rechargable electrochemical generators of the lithium battery type with a polymer electrolyte. However, these polymers are semicrystalline, the degree of crystallinity changing as a function of the molecular mass of the polymer. This semicrystalline nature of the polymers has the consequence of decreasing the conductivity of the materials which contain it.
Solvating polymers which are amorphous throughout the range of temperatures of use, for example poly(propylene oxide) (PPO), have also been employed for the production of ionically conductive materials. The ionic conductivity at ambient temperature of the PPO/LiClO.sub.4 or PPO/CF.sub.3 SO.sub.3 Li complexes is markedly higher than that of their polyethylene oxide (PEO) homologues; however, at higher temperatures, salt precipitations appear in the PPO/LiClO.sub.4 or PPO/CF.sub.3 SO.sub.3 Li complexes, and this makes their conductivity lower than that of the PEO/LiClO.sub.4 or PEO/CF.sub.3 SO.sub.3 Li complexes at these elevated temperatures.
It was then found that it was possible to decrease the crystallinity of semicrystalline polymers, without affecting their solvating properties and their electrochemical stability, by introducing irregularities into the macromolecular chain, if possible at a regular interval. Examples which may be mentioned are the copolymers obtained from a substituted oxirane and from a cyclic ether containing more than 3 carbon atoms (U.S. Pat. No. 4,758,483, M. Armand, D. Muller et al.) or the copolymers of oxirane and of dioxolane (French Patent Application filed under No. 92.08716, G. Goulart et al.).
However, it was found that the introduction of units creating irregularities into a semicrystalline polymer such as, for example, a PEO of high mass, that is to say the replacement of the semicrystalline polymer with a copolymer or a polycondensate, was frequently accompanied by a decrease in the mechanical properties, especially at high temperature. Attempts were made to overcome this disadvantage by introducing into the polymer, units which make it possible to form three-dimensional networks by crosslinking the copolymer before or after it is shaped. Because of the constraints imposed by the electrochemical stability requirements, the units permitting crosslinking which are particularly preferred are chosen from carbon-carbon unsaturations such as the allyl or vinyl functional groups. It then appeared that when a sufficiently large quantity of units were introduced into the polymer in order to reduce the crystallinity to the desired degree, the copolymer contained a very large number of crosslinking nodes. The electrolyte which contained such a copolymer then had a very high glass transition temperature, and this decreased its ionic conductivity, its elastomeric nature and the adhesion between the electrolyte and the electrodes. On the other hand, when the quantity of crosslinkable monomer was maintained at a sufficiently low level for the elastomeric properties to be preserved, the chain sequences of solvating units were long and, as a result, the crystallinity was maintained at a high level.
To overcome these disadvantages, copolymers were then employed which simultaneously contained solvating units, units capable of decreasing the crystallinity and containing no carbon-carbon unsaturations, and units capable of decreasing the crystallinity and containing carbon-carbon unsaturations. Various processes of preparation were developed for this purpose. However, the copolymerization or the condensation of three different monomers is generally more complicated and more burdensome than

REFERENCES:
patent: 4758483 (1988-07-01), Armand et al.
patent: 5021308 (1991-06-01), Armand et al.
patent: 5072040 (1991-12-01), Armand
patent: 5136097 (1992-08-01), Armand
patent: 5162177 (1992-11-01), Armand et al.
patent: 5260145 (1993-11-01), Armand et al.
patent: 5350646 (1994-09-01), Armand et al.
patent: 5393847 (1995-02-01), Alloin et al.
patent: 5414117 (1995-05-01), Armand et al.
patent: 5459228 (1995-10-01), Armand et al.

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