Reactions of Acrylic, Methacrylic, and Related Polymers

The functional groups of polymers from acrylic and methacrylic esters can undergo all the typical reactions of such groups. There are, therefore, numerous reports in the literature on such reactions. 

Perhaps the most reported reactions of these polymers are reductions of the functional groups. Among them is the reaction with lithium aluminum hydride to reduce the ester groups. The success, however, depends upon the reaction medium. Poly(methyl methacrylate) can be reduced to poly(methaUyl alcohol) in ether solvents [236]  

The results, however, are inconclusive, because combustion analyses fail to match the theoretical composition for poly(methallyl alcohol). It is impossible to tell to what extent the reduction takes place [236]. Inconclusive results are also obtained in similar reductions of polyfmethyl acrylate) in mixtures of tetrahydrofuran and benzene. The product of such reduction is acetylated with acetic anhydride in pyridine [237] as follows  

Hydrolysis in water of the product of acetylation, followed by treatment with hot w-cresol, and subsequent extraction with hydrochloric acid to remove the suspended inorganic matter [237], yields a material that is still only soluble in pyridine and w-cresol. 

Somewhat similar results are obtained in reductions of high molecular weight poly(methyl acrylate) with lithium aluminum hydride [238] in tetrahydrofuran. The reaction yields a product that is only soluble in mixtures of hydrochloric acid with either methyl alcohol, dioxane, or tetrahydrofuran. The problem is apparently due to some residual aluminum that is hard to remove [239]. If, however, the reduction is carried out in a W-methylmorpholine solution, followed by addition of potassium tartrate, a pure product can be isolated [240]. W-methylmorpholine is a good solvent for reductions of various macromolecules with metal hydrides [236]. In addition, the solvent permits use of strong NaOH solutions to hydrolyze the addition complexes that form. Other polymers that can be reduced in it are those bearing nitrile, amide, imide, lactam, and oxime pendant groups. Reduction of polymethacrylonitrile, however, yields a product with only 70% of primary amine groups [241]. 

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