Synthesis, Characterization, and Modification of Poly(Organophosphazenes), that Bear Both 2,2,2-Trifluoroethoxy and Phenoxy Groups PDF Download

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 51

Get Book Here

Book Description
High molecular weight polyphosphazenes that bear varying ratios of phenoxy and 2,2,2trifluoroethoxy groups have been synthesized by the reactions of (NPC12)n with sodium phenoxide, PhO- Ne, and sodium 2,2,2-trifluoroethoxide, CF3CH20- Na+, using either competitive or sequential exposure to the two nucleophiles. The relative amounts of NP(OCH2CF3)2, NP(OCH2CF3)(OPh) and NP(OPh) 2 units in the polymer are dependent on both the synthesis method and the amounts of CF3CH20- Na+ and PhO- Na+ used for the synthesis. The sequential reaction of poly(dichlorophosphazene), (NPC12)n, with CF3CH20-Na+ followed by PhO- Na+ yields mixtures of polymers that have very different compositions depending on the presence or absence of tetra-n-butyl ammonium bromide or 15- crown-5 ether. The reactions are complicated by the fact that phenoxy groups in NP(OCH2CF3)(OPh) units are replaced by 2,2,2-trifluoroethoxy groups at elevated temperatures or at 25 deg C in the presence of either 15-crown-5 ether or tetra- n-butyl ammonium bromide. The sodium salt of 3-hydroxypropanol replaces both 2, 2,2-trifluoroethoxy and phenoxy groups in these polymers at room temperature in the presence of either tetra-n-butyl ammonium bromide or 15-crown-5 ether. These side group exchange reactions are affected by steric effects. The mechanisms of these reactions are interpreted from the perspective that the reaction of CF3CH20- Na+ alone with the small molecule model compound, (NPCl2)3, yields significant amounts of geminally substituted products in the presence of either tetra-n-butyl ammonium bromide or 15-crown-5 ether.