Controlled Formation of Carboxylic Acid Groups at Polyphosphazene Surfaces:  Oxidative and Hydrolytic Routes

Abstract

Two methods have been developed for the controlled formation of carboxylic acid units at the surfaces of aryloxyphosphazene high polymers. The first involves a permanganateinduced oxidation of p-methylphenoxy side groups, with the surface density of carboxylic acid units being controlled by the ratio of p-methylphenoxy to phenoxy groups along the polymer chains. The second approach involves a base-induced hydrolysis of carboxylate ester functions at the para-positions of surface aryloxy side groups. In this method the surface density of carboxyl units is controlled by the reaction conditions, especially by the temperature and the solvent for the base. The same ester functions were converted to alcohol moieties by surface reductions using lithium aluminum hydride in diethyl ether. The surface structures before and after these reactions were studied by a combination of contact angle measurements, X-ray photoelectron spectroscopy, scanning electron microscopy with X-ray microanalysis, and ATR-IR spectroscopy.

Phosphazenes and Surfaces

“…Surface oxidation [79,80] of 4-methylphenoxy substituents in PMPP and in phosphazene copolymers containing variable percentages of the same substituent, or hydrolysis reactions of propyl-4-carboxylatophenoxy moieties [80] in poly[bis(4-carboxylatophenoxy propylester)phosphazene], PCPP, are also useful reactions to introduce free carboxylic groups on the surface of poly(organophosphazene) films. The general procedure adopted for these reactions is reported in Scheme 11.…”

“…The general procedure adopted for these reactions is reported in Scheme 11. Moreover, the structure of the final oxidized films could be tuned either by carefully controlling oxidation conditions (i.e., reaction times and temperatures) or by tuning the chemical composition of the starting 4-methylphenoxy/phenoxy copolymers [80]. Moreover, the structure of the final oxidized films could be tuned either by carefully controlling oxidation conditions (i.e., reaction times and temperatures) or by tuning the chemical composition of the starting 4-methylphenoxy/phenoxy copolymers [80].…”

Expanding Options in Polyphosphazene Biomedical Research

“…3. Linkage of bioactive molecules to polyphosphazene surfaces [86][87][88][89]. Proteins have been immobilized on polyphosphazene surfaces via reactions with -CH 2 Br units on phenoxy side groups.…”

Synthesis and characterization of oxime‐bearing hexakis(2‐formylphenoxy)‐phosphazene and its derivatives

“…Phosphazenes, which are the best known and most intensively studied phosphorusnitrogen compounds [1][2][3][4][5], possess a number of characteristics such as biomedical properties and applications due to their strong antitumor activity [6][7][8][9][10][11]. Their antimicrobial and biological activities on bacterial and yeast cells have been studied [12][13][14].…”