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Functionalization and cross-linking of the polyallyamine by boronate esters
The aim of this thesis is to develop smart gels from a simple water-soluble polymer, the polyallylamine. We have chosen to use the reversible reaction between boronic acids and diols as cross-linking system (formation of boronic esters).
The formation of those boronic esters has been studied for two model systems: 4-carboxyphenylboronic acid and cyclopentanediol or glucose. The functionalization of the polyallylamine has been done by two methods: the phenylboronic acid functions by an amidification reaction via a coupling carbodiimide agent. The diol functions by a reaction of cycle opening of the gluconolactone. This second grafting reaction may be reversible at high pH.
The mixing of both those polymer gives reversible gels on a wide range of pH (pH>6). This efficacy in gelation, even at neutral pH, is attributed to a stabilizing effect of the amines of the polymer on the boronic esters. It is shown as well that the gluconamide grafted polymers can easily form gels with borax.
The reaction between a polyamine and the gluconolactone is a simple and effective method to confer to this type of polymer an important rheo thickening power when it is combined with derivatives that bear boric or boronic acids.