Polymer gels, method of preparation and uses thereof

Abstract

The invention relates to a method for the preparation of a polymer gel, comprising cross-linking a polymer by using a cyclic dianhydride of carboxylic acid as cross-linking agent and treating the polymer gel with bicarbonate. The invention further concerns the polymer gel obtainable by the method of the invention and the uses thereof in various applications.

1 . A method for preparing a polymer gel, the method comprising:
 (a0) adding a cyclic monoanhydride to a first solution comprising a first polymer comprising hydroxyl groups, in the presence of a first catalyst,
 wherein the polymer comprising hydroxyl groups is selected from the group consisting of polysaccharides and derivatives thereof, 
   (a) adding a cyclic dianhydride to a second solution comprising a second polymer comprising hydroxyl groups in the presence of a second catalyst,   (b) maintaining the solution of step (a) under conditions suitable for cross-linking of the second polymer comprising hydroxyl groups by the cyclic dianhydride; thereby forming a polymer gel, and   (c) treating the polymer gel with an aqueous solution of bicarbonate.   
     
     
         2 . The method according to  claim 1 , wherein the second solution is the solution resulting from step (a0). 
     
     
         3 . The method according to  claim 1 , wherein the first catalyst comprises the same chemical species as the second catalyst. 
     
     
         4 . The method according to  claim 1 ,
 wherein the second polymer comprising hydroxyl groups is selected from the group consisting of cellulose, hemicellulose, cellulose acetate (mono, di or tri or a mixture thereof), cellulose propionate (mono, di or tri or mixtures thereof), carboxymethylcellulose and mixtures thereof.   
     
     
         5 . The method according to  claim 1 ,
 wherein the cyclic dianhydride is selected from the group consisting of pyromellitic dianhydride (PMDA), ethylenediaminetetraacetic dianhydride (EDTA), diethylenetriaminepentaacetic dianhydride (DTPA), 3,3′,4,4′-bisphenyltetracarboxylic dianhydride (BPDA), pyromelitic diimide (PyDi), benzophenone-3,3′,4,4′-tetracarboxylicdianhydride and mixtures thereof.   
     
     
         6 . The method according to  claim 1 ,
 wherein the cyclic monoanhydride is selected from the group consisting of aliphatic anhydrides such as maleic and succinic anhydrides, or aromatic anhydrides such as phthalic anhydride and 1,2,4-benzenetricarboxylic anhydride and mixtures thereof.   
     
     
         7 . The method according to  claim 1 ,
 wherein the cyclic monoanhydride is phthalic anhydride.   
     
     
         8 . The method according to  claim 1 ,
 further comprising a step (d) of drying the polymer gel of step (c).   
     
     
         9 . The method according to  claim 1 ,
 wherein the molar ratio of dianhydride per hydroxyl group of the second polymer in the solution of step (a) is about from 0.1 to 2 mol/mol.   
     
     
         10 . The method according to  claim 1   wherein the molar ratio of monoanhydride per hydroxyl group of the first polymer in the solution of step (a0) is about from 0.1 to 1 mol/mol.   
     
     
         11 . A polymer gel produced by the method of  claim 1 . 
     
     
         12 . The polymer gel according to  claim 11 ,
 wherein said polymer gel is a hydrogel that has a swelling ratio according to ASTM JIS K 7223—tea bag method, of at least about 10,   
     
     
         13 . The polymer gel according to  claim 11 ,
 wherein said polymer gel is a hydrogel that has a swelling ratio according to ASTM JIS K 7223—tea bag method, of at least about 50.   
     
     
         14 . The polymer gel according to  claim 11 ,
 wherein said polymer gel is a hydrogel that has a swelling ratio according to ASTM JIS K 7223—tea bag method, of at least about 100.   
     
     
         15 . An article of manufacture comprising a polymer gel according to  claim 11 ,
 wherein said article of manufacture is selected from the group consisting of devices the controlled release of water, nutrients or phytochemicals in agriculture, devices for environmental remediation, absorbent products for personal and household hygiene, toys and devices adapted to altering their size when brought into contact with water or aqueous solutions.   
     
     
         16 . A polymer gel comprising a polymer matrix comprising polymeric chains wearing hydroxyl pending groups, a first portion of said hydroxyl pending groups being substituted by a divalent hydrocarbon group crosslinking the polymeric chains to one another, a second portion of said hydroxyl pending groups being substituted by a monovalent hydrocarbon group, said divalent hydrocarbon group wearing a polar function COOH or a salt thereof. 
     
     
         17 . A polymer gel according to  claim 16 ,
 wherein a second portion of the hydroxyl pending groups is substituted by a monovalent hydrocarbon group, said monovalent hydrocarbon group wearing a polar