Chelating polymers, crosslinked

Partially hydrolyzed polyacrylamides, carboxymethylcellulose, polysaccharides, and acrylamido methylpropane sulfonate have been screened to investigate the performance of aluminum citrate as a chelate-type crosslinker. An overview of the performance of 18 different polymers has been presented in the literature [1646]. The performance of the colloidal dispersion gels depends strongly on the type and the quality of the polymer used. The gels were mixed with the polymers at two polymer concentrations, at three polymer-to-aluminum ratios, and in different concentrations of potassium chloride. The gels were quantitatively tested 1,7, 14, and 28 days after preparation. 

Polymerizable indazole derivatives have received some attention with respect to the preparation of redox polymers and metal ion chelating polymers (73MI11102). Monomers such as 3-vinyl-4,7-dihydro-1//-4,7-indazoledione (63) are readily prepared by 1,3-dipolar cycloaddition of vinyldiazomethane to 1,4-benzoquinones. Crosslinked, low swelling, recyclable redox polymers have been prepared from these monomers. 

Kosyanchuk, L. E, Babkina, N. V., Yarovaya, N. V, Kozak, N. V, and Lipatov, Y. S., 2008. Phase separation in semi-interpenetrating polymer networks based on crosslinked poly(urethane) and linear p>oly(methyl methacrylate) containing iron, copper, and chromium chelates. Polymer Science Series A 50(4) 434-433. 

In addition, molecular imprinting technique is also used in anion recognition. Ozkutuk et al. reported the preparation and adsorption ability of the phosphate-imprinted chitosan-succinate beads [34]. Chitosan was modified with succinic anhydrides firstly. Second the mixture of chitosan-succinate and Fe (III) ions stirred continuously at room temperature. And Na3P04 was added to Fe (III)-chitosan-succinate mixture. This mixture was slowly dropped into NaOH solution to form beads. Afterwards, beads were crosslinked with epichlorohydrin and the template (phosphate ions) was removed using IM KOH solution. Selective cavity for the phosphate ion was obtained in the phosphate imprinted metal-chelate polymer. The phosphate-imprinted metal-chelate polymer was used in the adsorption-desorption process. The adsorption process was fast and equilibrium was reached around 30 min. The adsorption behaviour of this system was described approximately by the Langmuir equation. 

Metal chelates have also been used in photografting and crosslinking of different types of polymers [61,65-67]. 

Gregor et al66 reported the Cu-complex formation of poly(methacrylic acid) (PMA) resins crosslinked with 1% or 9% divinylbenzene. The formation constants of the Cu complexes with the resins were smaller than that of noncrosslinked PMA. The stepwise formation constants decreased from Ki to KA in the resin system, which was the opposite of the noncrosslinked PMA system. The rigidity of the polymer-ligand chain was considered to hinder chelate formation. Formation constants of the PMA resin were also reported by Gustafson era/.67. The formation constant of the noncrosslinked PMA decreased for various metal ions ... 

We used partially crosslinked poly(4-vinyipyridine)(DBQP) as the polymer ligand. PVP was crosslinked by alkylation of the pyridine groups in PVP with 1,4-dibromobutane to yield insoluble DBQP resins. The free and unquaternized pyridine groups in DBQP could be used to form the polymer chelate, as represented in 33. 

The expansion and contraction of the polymer chain which accompanies the redox of Cu ions can also be visually confirmed by means of the mechanochemical system proposed by Kuhn161), as illustrated in Fig. 31. A film is prepared with a poly(vinylalcohol)-Cu(II) complex and is suspended with a sinker in water. The film is extended by about 20% on the reduction of Cu(II) to Cu(I) and shrinks back to its original length on the oxidation of Cu(I). The poly(vinylalcohol) chain is densely crosslinked by the extremely stable Cu(II) chelate, but is loosened when Cu ion forms the unstable Cu(I) chelate. This change is reversible as may be observed. 

Crosslinked polymers of vinyl-substituted imidazolecarboxylic acids have been studied as chelating resins for heavy metal ions (78MI11101). For example, polymer (75) displays stabilities and capacities in the order Cu2+ > Ni2+ > Cd2+ > Zn2+ > Mg2+ which is similar to that observed with other amino acid chelating resins. The unusual feature of the polymer, however, is that exceptionally strong complexing abilities are maintained even in strongly acidic media. Polymer (75) also displayed potential utility for the removal of mercury(II) ions from aqueous media. 

Polymer network solutions can also be formed from aqueous chemical systems. Aqueous metal chelates that have at least one additional carboxyl group as a reaction site can undergo polyesterification with a polyhydroxyl alcohol to form a network [39,40]. Aqueous metal ions can also react with polyaaylic acid and be precipitated as a crosslinked polymer [41]. The poljnnerization mechanism and its rate are important factors in determining the molecular weight of the pol5maers and the density distribution of the microstructure formed. 

Functionalization of crosslinked polymers by Mannich reaction" includes mainly polystyrenes and polyacrylics such as styrene/divinyl benzene copolymers 537-539114-117 gpjj acrylic ester/divinyl benzene copolymers 540, respectively." These materials are involved in the reaction as substrate (539)" or, more frequently, as amine reagent (sec also Fig. 163, Chap. Ill) when the crosslinked product, containing amino groups, is allowed to react with phosphorous acids (537,538, and 540). Thus, chelating properties are assumed by the resins. 

A soft contact lens comprises a water-swollen gel of a polymer prepared by polymerising one or more hydrophilic monomers, such as 2-hydroxyethyl methacrylate, one or more crosslinking monomers and a monomer, which contains metal-chelating functionality, such as an aminopolycarboxylic acid containing a polymerisable olefinic group. 

The process is initiated at terminal hydroxy groups and favoured by the spiral-like structure of polysiloxanes. Replacement of the hydroxy groups by methyl, or blocking them by chelation to copper, iron or zirconium acetylacetonates, considerably decreases the rate of decomposition of the polymer and increases its thermal stability (Table 9). However, pronounced crosslinking even at moderate temperatures was observed in the polymer stabilized by transition metal compounds. The effect of the metal additives during thermal ageing is associated with reactions leading... 

---