Amine polyacrylamide

This section will cover blends of polymers, both exhibiting water solubihty. Many of the water soluble polymers have been noted in earher sections in this chapter to exhibit misci-bihty with non-water soluble polymers. These water soluble polymers include poly(ethylene oxide), poly(N-vinyl pyrollidone), poly(vinyl amine), polyacrylamide, poly(N,N-dimethyl acrylamide poly(acryhc acid), poly(methacrylic acid), poly(ethyl oxazohne), poly(styrene sulfonic acid), poly(vinyl pyridine), poly(vinyl alcohol), hydroxyl ethyl ceUulose, hydroxy propyl cellulose, carboxy methyl ceUulose, poly(itaconic acid) and poly(ethyleneimine) (several structures shown below). 

Mannich Reaction. Aminomethylation of polyacrylamide with formaldehyde [50-00-0] and a secondary amine to produce a Mannich polyacrjiamide has been extensively studied (40). 

Transamidation. Polyacrylamide reacts with primary amines such as hydrazine [302-01-2], N2H4, (54) and hydroxjlamine [7803-49-8]. NH O, (55—57) to form substituted amides with loss of ammonia. 

Hoffman Degradation. Polyacrylamide reacts with alkaline sodium hypochlorite [7681-52-9], NaOCl, or calcium hypochlorite [7778-54-3], Ca(OCl)2, to form a polymer with primary amine groups (58). Optimum conditions for the reaction include a slight molar excess of sodium hypochlorite, a large excess of sodium hydroxide, and low temperature (59). Cross-linking sometimes occurs if the polymer concentration is high. High temperatures can result in chain scission. 

Fig. 2. Functional groups on modified polyacrylamides (a) formed by reaction with dimethylamine and formaldehyde (Mannich reaction) (b), quatemized Mannich amine (c), carboxylate formed by acid or base-cataly2ed hydrolysis or copolymerization with sodium acrylate and (d), hydroxamate formed by...

A number of cationic muds have been developed and used. These ate formulated around quaternary amines or positively charged polymers (108,109). The polymer in some iastances may be a cationic polyacrylamide. Poly(dimethylarnine-fi9-epichloiohydrin) is another material that has been used successfiiUy for drilling shale formations (110,111). Some of these additives may requite a salt such as sodium or potassium chloride for best results. 

A Hofmann degradation of polyacrylamide by use of a very small excess of sodium hypochlorite and a large excess of sodium hydroxide at 0°C to 15°C for about 15 h polyvinylamine (95 mol% amine units) is obtainable ... 

The Mannich reaction of polyacrylamide with formaldehyde and an amine may be used for the obtaining product that contains N-methylol groups (or ethers or ethers thereoO-... 

The reaction rate increases when heated to temperatures up to 40°C. The amino derivatives can then be quaternized if desired. The N-methylol derivatives of polyacrylamide can be made cationic by heating with amines, or they can be made anionic by heating with aqueous bisulfite solution under basic conditions. 

Conversion of Graft Polyacrylamide to Amines via the Hofmann and Mannich Reactions... 

In a second step, the gel is fimctionahzed for NA attachment. Common methods for polyacrylamide gel fimctionahzation are based on the treatment of the polymerized support with reagents such as hydrazine or ethylenedi-amine. These treatments generate amine groups in the gel that can react with amine-modified ONDs via glutaraldehyde coupling, or directly with oxidized DNA probes (Fig. 15). Alternatively, the fimctional groups may be introduced by copolymerization reactions (e.g. co-polymerization with N-hydroxysuccinimide acryhc or oxirane acryhc derivatives) [59]. 

We chose to employ PEGA1900 and PEG (polyacrylamide backbone with PEG spacer and amine functionalization) because its higher polarity allows water or buffer as solvent and better enzyme permeation with respect to classical polystyrene-based resins [99-100], while it is still compatible with a wide range of organic transformations and solvents. 

The first task was to design a linker between the primary amine functionality on the resin and the hydrazine function that ultimately binds the macrocyclic aldehyde. As mentioned above, the employed resin (PEGA1900) features a primary amino group at the end of a PEG spacer connected to the polyacrylamide backbone. To assure monofunctionalization, the amino group was monobenzylated, thereby preventing possible proximity problems. Subsequently, the resulting secondary amine was provided with a handle for the introduction of the hydrazine functionality (see Scheme 29). 

In contrast, the use, in chromatography, of poly(trityl methacrylate) appears much more promising. Both the insoluble polymer and macroporous silica gel coated with a soluble polymer have been used. The latter system gives better results, especially with regard to elution time. The columns have proved quite efficient in resolution of a great variety of chiral organic compounds (365, 388). Other examples of usefiil chiral polymer supports are the substituted polyacrylamides (389). Earlier used adsorbents obtained by reacting optically active amines with polyacryloyl chloride have been superseded by new chiral phases prepared by direct polymerization of optically active acrylamides. 

As an illustrative example, the monomers used for the preparation of a typical polyacrylamide support (Pepsyn) and its schematic representation are sketched in Figure 2.6. The ester functionality, obtained by copolymerization with A-acryloylsarco-sine methyl ester, can be used as the attachment point for a suitable linker. This can be achieved by aminolysis with ethylenediamine, followed by acylation of the resulting primary amine with 3-(4-hydroxymethyl)phenylpropionic acid [163] or other linkers. Similar supports have been prepared by copolymerization of protected allylamine [37] or lV-(acryloyl)-l,3-diaminopropane [173] with V,lV-dimethylacrylamide and... 

Amidines and sulfonamides have also been used as linkers for primary or secondary aliphatic amines (Entries 4, 5, and 7, Table 3.23). These derivatives are stable under basic and acidic reaction conditions and can only be cleaved by strong nucleophiles. Phenylalanine amides can be hydrolyzed by treatment with certain enzymes (Entry 8, Table 3.23), and can therefore be used for linking amines to supports compatible with enzyme-mediated reactions (CPG, some polyacrylamides, macroporous polystyrene, etc.). 

Amines have been prepared on insoluble supports by Hofmann degradation of amides [222] followed by hydrolysis of the intermediate isocyanates (Figure 10.5). One reagent suitable for this purpose is [bis(trifluoroacetoxy)iodo]benzene, which can be used both on cross-linked polystyrene [223] and on more hydrophilic supports such as polyacrylamides (Figure 10.6). Support-bound carboxylic acids can also be degraded via the acyl azides (Curtius degradation [224,225]) to yield isocyanates. 

Most of these procedures are incompatible with common linkers, and are therefore unsuitable for the transformation of support-bound substrates into carboxylic acids. A more versatile approach for this purpose is the saponification of carboxylic esters. Saponifications with KOH or NaOH usually proceed smoothly on hydrophilic supports, such as Tentagel [19] or polyacrylamides, but not on cross-linked polystyrene. Esters linked to hydrophobic supports are more conveniently saponified with LiOH [45] or KOSiMe3 in THF or dioxane (Table 13.11). Alternatively, palladium(O)-mediated saponification of allyl esters [94] can be used to prepare acids on cross-linked polystyrene (Entries 9 and 10, Table 13.11). Fmoc-protected amines are not deprotected under these conditions [160],... 

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