Curable Polyphosphazene Copolymers and Terpolymers

This invention is further illustrated by reference to the following examples which are not intended to limit the scope of the invention.

An alkoxide mixture was prepared by the reaction of CF.sub.3 CH.sub.2 OH (18.0 g, 0.18 mole), n-C.sub.3 F.sub.7 CH.sub.2 OH (36.0 g, 0.18 mole) and CH.sub.3 CH(0H)C.sub.2 H.sub.4 CH (16.2 g, 0.18 mole) with sodium (10.1 g, 0.44 mole) in 400 ml of dry tetrahydrofuran. The alkoxide mixture was stirred overnight at room temperature and refluxed for 3 hours. The [Cl.sub.2 PN].sub.n polymer (23.2 g, 0.2 mole) in benzene was added to the alkoxide solution at reflux in about 1.5 hours. After the addition was complete the reaction mixture was stirred for 0.5 hour and allowed to cool to room temperature. The liquid was decanted and the solid portion was washed with water. The solid product was dissolved in 600 ml of the azeotrope of CC1.sub.2 FCCIF.sub.2 and acetone and washed with water until the aqueous layer was free of chloride ion. Upon precipitation into benzene, an opaque white rubbery solid (26 g) was obtained. The terpolymer had an intrinsic viscosity of 0.83 dl/g in CCl.sub.2 FCCIF.sub.2 /acetone at 28.degree.C. By titration, the CH.sub.3 CH(OH)C.sub.2 H.sub.4 O-- concentration of the title terpolymer was found to be about 11 mole percent. Anal. Calcd. for the title terpolymer which contains 10 mole percent of CH.sub.3 CH(OH)CH.sub.2 CH.sub.2 O- :C; 22.5; H, 1.6; N, 4.2; Cl, 0.0. Found: C, 22.7; H, 1.7; N, 4.6; Cl, 0.2. The title terpolymer was also prepared with the amount of --OH functionality varying from 0.5 to 35 mole percent by using initial quantities of 0.01 to 0.15 mole, respectively, of CH.sub.3 CH(OH)C.sub.2 H.sub.4 ONa and decreasing the amounts of sodium fluoroalkoxides accordingly.

Separate curing studies with an aliphatic diisocyanate DDI and 2,4-toluene diisocyanate (TDI) were carried out. A 10 percent solution of the above polymer ([n]=0.83) was prepared in the azeotrope of CCl.sub.2 FCCIF.sub.2 and acetone, crosslinking agents were added, and the mixture was observed at room temperature. The curing data are summarized in Table 1. In a similar manner the terpolymers of this example were also crosslinked by polymethylene polyphenylisocyanate (PAPI, trademark of Upjohn Co.)

The polymer of Example 1 was also cured with 3,3', 4,4'-benzophenone/tetracarboxylic dianhydride by heating at 150.degree.C. The polymer was also cured with 2,4-toluene diisocyanate (TDI) and dibutyltin diacetate catalyst as a coating as follows: a glass sheet was coated with a solution of the polymer and solvent was allowed to evaporate. When the film was slightly tacky, a small amount of a solution of TDI (15% by weight on polymer) and dibutyltin diacetate (0.5% by weight on polymer) was sprayed over it. Further drying led to a crosslinked coating.

Following the procedure of Example 1, using the indicated amounts of the alcohols and the indicated reaction conditions, the corresponding coand terpolymers of Examples 2-12 were prepared. When reaction temperatures in excess of 70.degree.C were employed, bis(2-methoxyethyl)ether and chlorobenzene were used as solvents for the alkoxides and [Cl.sub.2 PN].sub.n polymer, respectively. The polymers were found to be curable with toluene diisocyanate or the other curing agents listed above.

A solution of the sodium salt of 1,3-butanediol was prepared from 1.8 g 1,3-butanediol (0.02 mole) and 0.12 g sodium (0.005 mole) in 20 ml dry tetrahydrofuran. The sodium hydroxybutoxide was added to a solution of 3.43 g [(CF.sub.3 CH.sub.2 O).sub.2 PN-(n-C.sub.3 F.sub.7 CH.sub.2 O).sub.2 PN].sub.n (1:1) copolymer (0.01 mole) in 70 ml of (F[CF(CF.sub.3)CF.sub.2 C].sub.2 CHFCF.sub.3)/dioxane (5v/2v). The reaction was stirred overnight at room temperature and then heated 3 hours at 70.degree.C. Polymer was precipitated upon addition of methanol and was isolated as described in Example 1. The product (3.2 g) was a yellowish, weak rubbery solid which had an intrinsic viscosity of 0.80 dl/g in Freon TA at 28.degree.C. The initial copolymer had an intrinsic viscosity of 0.83 dl/g. Analysis of product was essentially the same as that described in Example 1. Crosslinking was effected with 2,4-toluene diisocyanate.

Similarly a terpolymer with an intrinsic viscosity of 0.21 dl/g was prepared. This material was mixed with TDI and dibutyltin diacetate catalyst and poured into an open mold. Upon standing a crosslinked elastomeric mass was produced. This same mixture also served as a sealant material upon crosslinking.

Following the procedure of Example 13, but using the homopolymers and copolymers indicated below, the corresponding hydroxyl containing copolymers and terpolymers, respectively, were obtained. All the products could be crosslinked by reaction with 2,4-toluene diisocyanate.

A solution prepared from sodium (0.069 g, 0.003 mole) and 100 ml ethylene glycol was added to a refluxing solution (70.degree.C) of [(CF.sub.3 CH.sub.2 O).sub.2 PN-(H(CF.sub.2).sub.4 CH.sub.2 O).sub.2 PN].sub.n (1:1) copolymer (11.3 g, 0.03 equiv.) in 300 ml tetrahydrofuran. The reaction was refluxed 4-1/2 hours, cooled and polymer was precipitated. The title terpolymer (6.0 g) was obtained after water washing and drying. A solution of terpolymer in tetrahydrofuran crosslinked upon standing at room temperature in the presence of 2,4-toluene diisocyanate and dibutyltin diacetate catalyst.

Following the procedure of Example 18, using the indicated poly(fluoroalkoxyphosphazene) and glycol, the corresponding curable polymers of examples 19-21 were prepared.