Poly acrylic compounds

In another study, oscillating rheometry was used to examine the effect of adding various simple metal salts to glass-ionomer cements (Crisp, Merson Wilson, 1980). It was found that cement formation for certain glasses which react only slowly with poly(acrylic acid) could be accelerated significantly by certain metal salts, mainly fluorides such as stannous fluoride and zinc fluoride. Some non-reactive glasses could be induced to set by the addition of such compounds. 

The conventional techniques for the purification of low-molecular-weight compounds, such as distillation, sublimation, and crystallization, are not applicable to polymers. In some cases, it is possible to remove the impurities by cold or hot extraction of the finely powdered polymer with suitable solvents or by steam distillation. Separation of low-molecular-weight components from water-soluble polymers [e.g., poly(acrylic acid),poly(vinyl alcohol), poly(acryl amide)]... 

Association Complexes. The unshared electron pairs of the ether oxygens, which give the polymer strong hydrogen bonding affinity, can also take part in association reactions with a variety of monomeric and polymeric electron acceptors (40,41). These include poly(acrylic acid), poly(methacrylic acid), copolymers of maleic and acrylic acids, tannic acid, naphtholic and phenolic compounds, as well as urea and thiourea (42—47). 

Analysis for Poly(Ethylene Oxide). Another special analytical method takes advantage of the fact that poly (ethylene oxide) forms a water-insoluble association compound with poly (acrylic acid). This reaction can be used in the analysis of the concentration of poly(ethylene oxide) in a dilute aqueous solution. Freshly prepared poly (acrylic acid) is added to a solution of unknown poly(ethylene oxide) concentration. A precipitate forms, and its concentration can be measured turbidimetrically. Using appropriate calibration standards, the precipitate concentration can then be converted to concentration of poly(ethylene oxide). The optimum resin concentration in the unknown sample is 0.2—0.4 ppm. Therefore, it is necessary to dilute more concentrated solutions to this range before analysis (97). Low concentrations of poly(ethylene oxide) in water may also be determined by viscometry (98) or by complexation with KI3 and then titration with Na2S203 (99). 

A large number of optically active poly-acryl-derivatives, mainly esters or amides, have been described in literature, although no series of homologous compounds has been systematically investigated. 

A comparison between the optical activity of some poly-acrylic or poly-methacrylic esters and of some model compounds, having approximately the same optical purity, shows that in general the optical activity is in both cases of the same order of magnitude (Table 19). 

The drag is distributed throughout a polymer matrix. Such a system can be relatively easy to manufacture, the simplest case being when the drag is dispersed directly in a blend composed of, for example, a mixture of poly(acrylic acid) and elastomeric compounds such as poly(isobutylene) and poly(isoprene). 

Poly(vinyl alcohol) is utilized as a component of starch-based adhesives.11121114 Other patents report the use of partially oxidized starch,1115 dextrins,1116 dextrins and urea,1117 borax,1118 boric acid,1119 and vinyl methyl ether-maleic acid copolymers.1120 Other patents indicate the use of poly (vinyl alcohol) with partially hydrolyzed poly(vinyl acetate),1121 nonhy-drolyzed poly(vinyl acetate),1122 and poly(vinyl chloride).1123 A few patents have reported such poly acrylic additives as poly (acrylic acid)1124 and its salts,1125 poly(acrylamide),1126 1127 A-methylacrylamide or poly(A-acryl-amide),1128 and polyethyleneimine.1129 Polystyrene has also been used,1130 as well as more complex copolymers such as a maleic acid monobutyl ester-methyl vinyl ether copolymer, together with dextrin and polyacrylamide),1131 carboxylated ethyl acrylate-styrene zinc salt copolymer,1132 ethylene-methyl acrylate-vinyl acetate copolymer,1133 vinyl acetate-vinyl pyr-rolidone copolymer,1134 and ethylene-vinyl acetate copolymer.1135 Some adhesives are compounded with SBR latex1136 1138 and phenol-formaldehyde resins.1139... 

In some cases of the titration of one polymer with another one (polymers are complementary, i.e. they contain groups, which are capable to interact specifically, e.g. poly(acrylic add) and the copolymer of N-vinylpyrrolktone and acrylic add) no inflection point on the titration curves were observed. Therefore, the titrations do not indicate the interaction in PAA-VP/AA system, in contrast to systems composed of poly(methacrylic acid) and the copolymer N-vi nylpyrrolidone and acrylic add221 (Fig. 2). Apparently, subtle differences in the chemical structure of components predetermine the possibility or impossibility of complex formation, which is an evidence for a high selectivity of the polymer-polymer interactions. Even when one of the components is a low molecular compound (Fig. 1, curve 1), complex formation is not observed. Interpolymer complexes can be divided into several types, due to the kind of the dominating interaction ... 

Reactions of the cyclic compounds with different kinds of organic reagents at room temperature readily give a seri of pyrimidine derivatives without using any cata-lyst One of the typical reactions involves esterification with acetic add in bulk to afford the corresponding acetate. When the reaction is applied to polymeric adds, e.g. poly(acrylic acid) and poly(methacrylic add), polyacrylate and polymethacrylate having pendant uracil and thymine units are obtained in high yield (Schemes 6 and 1) ... 

The nature of the solvent plays an important role in the reactions between carboxy-containing compounds and diazoalkanes. Protic solvents of the R-OH type can react with diazoalkanes in the presence of carboxylic acids to form the corresponding ethers Hence, in reactions with polymers dissolved in alcohols or alcohol-containing mixtures (poly(acrylic and methacrylic acids) etc.) the yield of the main reaction can decrease to 30—50% (with respect to ADM) 1 Consequently, when polymers soluble in aprotic solvents undergo anthryhnethylation, the reaction should be carried out in such solvents as benzene or toluene. 

Finally, it should be noted that during the last decade both weakly crosslinked poly(acrylic acid) derivatives and chitosan derivatives were described as safe penetration enhancers for hydrophilic compounds especially as they can trigger mechanisms of tight junction opening of mucosal tissues and did not show acute toxicity. Poly(acrylic acid) derivatives were shown to have excellent mucoadhesive properties and can inhibit the activity of gut enzymes, such as trypsin, chymo-trypsin, and carboxypepsidases. Chitosan salts and Ni-trimethylchitosan chloride revealed to be potential absorption enhancers for nasal absorption of calcitonin and insulin and for the intestinal absorption of buserilin.f ... 

Interactions between macromolecules can occur in formulations, for example when preparations are mixed. They can be put to good advantage in the synthesis of novel compounds. Polyethyleneimine and poly(acrylic acid) form a polyelectrolyte complex with saltlike bonds as shown in (V). If the complex is heated as a film, interchain amide bonds are formed between the groups which formed electrostatic links. The nonionised -COOH and -NH groups in the chain are the points of structural defects in the film. 

Table 6.7.2 (continued). Compounds identified in the pyrogram of poly(acrylic acid) = 1,000,000 shown in Figure 6.7.2. 

The presence of the double bonds in the polymer backbone and its further thermal decomposition may explain the formation of certain aromatic compounds in poly(acrylic acid) pyrolysate. 

A number of substances from the pyrolysate in the presence of TMAH are methylated compounds corresponding to nonmethylated molecules in the pyrolysate of pure (with no TMAH) poly(acrylic acid). (The pyrogram of poly(acrylic acid) is shown in Figure 6.7.2.). The list of compounds that were methylated includes acetic acid, propanoic acid, 2-propenoic acid, 2-methy -2-propenoic acid, and 2-methylenebutanoic acid. 

Some other compounds are identifiable as methyl esters although they were not seen in the pyrogram of poly(acryiic acid) because they are not eluted as free acids from the Carbowax column. One additional observation is that the pyrogram after methylation shown in Figure 6.7.4 and that of poly(methyl acrylate) given in Figure 6.7.7 show high similarity. This indicates that pyrolysis mechanisms of poly(acrylic acid) and of poly(methyl acrylate) are very similar. 

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