Poly methacrylic acid

The primary step in the photodegradation of poly(methacrylic acid) (3.34) is the cleavage of a carboxyl group from the main chain [201, 1085, 1086]. 

The ) -scission process causes degradation of the polymer alkyl radical 

In the presence of air (oxygen) polymer peroxy radicals (PO ) are formed, which abstract hydrogen from the same or a neighbouring macromolecule giving polymer hydroperoxides  

Photodecomposition of polymer hydroperoxides yields polymer oxy radicals (PO ), and finally carbonyl and hydroxide groups  

The UV irradiation of poly(methyl methacrylate) can also cause the formation of a radical at a methyl group  

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Polylacrylic Acid) and Poly(methacrylic Acid). Glacial acrylic acid and glacial meth-acrylic acid can be polymerized to produce water-soluble polymers having the following structures ... 

Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

Ladenheim and Morawetz [23] also showed that the reactivity of the carboxylate units in partially ionized poly(methacrylic acid) (PMA) toward BrCH2COO in the bromine displacement reaction was greatly diminished, while the reaction proceeded at an appreciable rate with uncharged p-bromoacetamide [23]. This inhibition of the reaction of the polyanion with a small anionic reagent can be attributed to the electrostatic repulsion between the polymer and the reagent. 

This potential reflects itself in the titration curves of weak polyacids such as poly(acrylic acid) and poly(methacrylic acid) [32]. Apparent dissociation constants of such polyacids change with the dissociation degree of the polyacid because the work to remove a proton from the acid site into the bulk water phase depends on the surface potential of the polyelectrolyte. 

Webber et al. [60, 78] also studied the fluorescence quenching of diphenylan-thracene (DPA) covalently bound to poly(methacrylic acid), PMAvDPA (23) [60], and to sodium poly(styrenesulfonate), PSSvDPA (24 )[78]. The fluorescence quenching of the excited DPA moiety by MV2+ and Cu2+ was also highly efficient. For example, with PMAvDPA of 0.073 mol% DPA content, the kq values at pH... 

The experimental results on poly(methacrylic acid) containing a small mole fraction of either 3-vinylperylene (PMAvPER, (30)) or lV-[12-(4-aminonaphthali-mide)]-2-methylacrylamide (PMAANI, (31)) show charge separation which is efficient for PMAvPER but not much for PMAANI. The quantum yields of charge separation for various chromophores covalently bound to PMA at pH 2.8 are summarized in Table 7. 

Table 7. Quantum yields of charge separation, (pcs, for poly(methacrylic acid)-bound chromophores at pH 2.8 [77]...

The salt effect is very strong in polyconjugated polyelectrolytes. Figure 15 is a graph of the proton dissociation energy vs. the dissociation degree of PPA of different structures. Also, the graphs for poly(methacrylic acid) and a copolymer... 

Table 8.3 Effect of Amines on Tacticity of Poly(methacrylic acid) at 60 DC90...

Some tailor-made homopolymers can serve as starting points for chemical modifications to yield new species. Poly(hydroxyethyl methacrylate) and poly(glyceryl methacrylate) 16), already mentioned, are obtained upon hydrolysis of the OH-protecting groups that allow the anionic polymerization to proceed. Another example is the acid hydrolysis of poly(t-butyl methacrylate), a reaction which proceeds easily to completion, yielding poly(methacrylic acid) of known degree of polymerization and narrow molecular weight distribution 44 45). 

The preparation by dispersion polymerization of the microsphere sample employed in this study was previously described [8]. The microsphere sample utilized in this study has a monomodal diameter distribution with mean diameter value d= 3.09 pm and standard deviation dsdev= 0-74 pm. The microsphere surface is covered by a poly(methacrylic acid-co-ethylacrylate) whose percent by weight is 1.1... 

The endopolygalacturonase obtained from a Kluyveromyces marxianus culture broth was purified through the addition of specifically designed core-shell microspheres consisting of an inner polystyrene core and an outer shell constituted by a poly(methacrylic acid-co-ethylacrylate) statistical copolymer. These microspheres were previously found very effective in purifying the pectinlyase within a commercial pectinase sample [15]. 

Poly-(methacrylic acid) was prepared in 1880 by Fittig and Engel-horn. Mjoen separated the polymer by precipitation and attempted to determine its molecular weight by cryoscopic and ebullioscopic methods. He decided that his product, which he regarded as a colloid, was an octamer but reached no conclusions as to its constitution other than that it was an octabasic acid of the formula C24H4o(COOH)8. 

Approximate results obtained by Katchalsky, Lifson, and Eisen-berg o swelling in water of poly-(methacrylic acid) gels cross-... 

Fig. 137.—Equilibrium swelling ratio qm of poly-(methacrylic acid) gels prepared by copolymerizing methacrylic acid with 1, 2, and 4 percent (upper, middle, and lower curves, respectively) of divinylbenzene plotted against degree of neutralization i with sodium hydroxide. (Katchalsky, Lifson, and Eisenberg. )...

Mandel Leyte (1964) found a similar order for the complexes of poly(methacrylic acid) ... 

Mandel, M. Leyte, J. C. (1964). Interactions of poly(methacrylic acid) and bivalent counterions. Journal of Polymer Science, A2, 2883-99. 

Rymden, R. Stilbs, P. (1985a). Counterion self-diffusion in aqueous solutions of poly(acrylic acid) and poly(methacrylic acid). Journal of Physical Chemistry, 89, 2425-8. 

A second project [10] was based on the production of Pd nanocluster inside poly-methacrylic acid (8%mol)-A,iV-di-methylacrylamide (88 % mol)-A, A -methylenebisacrylamide (4% mol). ISEC (Inverse Size Exclusion Chromatography) analysis of the resin in water in terms of cylindrical pores [7]... 

Figure 4. Carbonyl region of polytt-butyl styrene)-b-poly(methacrylic acid) after 90 min. of acid hydrolysis.

In an attempt to hydrolyze PSPDM completely to head-to-head poly(methacrylic acid), higher temperature, and more strongly basic conditions were employed. PSPDM was heated at 125 C for four days in 5M NaOH. Like the 0.1M NaOH experiments, the imide was hydrolyzed to the amic acid and no further. The amide of the ring opened imide (V) is extremely resistant to basic hydrolysis. 

Five-membered ring imides in cyclopolymers of N-substituted dimethacrylamides such as PSPDM can be hydrolyzed to amic acids under moderately basic conditions. The resulting N-substituted amide is extremely resistant to basic hydrolysis. Consequently, this basic hydrolysis approach can still not be employed for the preparation of head-to-head poly(methacrylic acid). 

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10).20 The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11).21 Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing water content.22... 

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