Amino-functionalized monomers have versatile applications in the field of medicine. Their current applications include enhanced nucleic-acid based drug delivery as well as the formation of polyplexes for non-viral gene delivery. The cationic amino group in these monomers conjugates with negatively charged amino acids and DNA. One of the most common amino-functionalized monomers is 2-aminoethyl methacrylamide (AEMA). To synthesize the methacrylamide, ethylene diamine is reacted with methacrylic anhydride (or methacryloyl chloride) via nucleophilic acyl substitution. The most prevalent synthesis involves the use of a tert-butyloxycarbonyl (Boc) protection group to ensure that only one of the amino groups is functionalized. This synthesis is expensive, involves numerous steps, and has led to a moderate overall yields. The purpose of this study is to synthesize AEMA using an alternative approach that is more cost-effective and efficient. Rather than using a protecting group, ethylene diamine is directly reacted with methacrylic anhydride. Low temperatures, slow addition, and partial protonation of the diamine help to favor mono-addition over di-addition. Both mono and dimethacryalmide products are formed in about a 3:1 ratio and can be further purified to yield the pure AEMA monomer in good yields. Another alternative is to synthesize 2-aminoethyl methacrylate, another amino-functionalized monomer. The reagent for this synthesis, 2-aminoethanol, undergoes protonation of its amino group at low pH. The non-protonated hydroxyl group can then selectively react with the methacryloyl chloride to form the monomer. Though these are structurally similar monomers, the presence of different carbonyl functional groups results in different properties in terms of their application. The use of these alternative methods can be effective routes in synthesizing amino-functionalized monomers.

Synthesis of amino-functionalized methacrylamide and methacrylate monomers

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