Effect of amino group modification at allyl position of methacrylamides on polymerization and polymer pH-/thermo-responsiveness

With an interest in β-amino acid derivative polymers containing a carbon backbone, the polymerization of N-n-propyl α-(aminomethyl)acrylamide (4b) and N-isopropyl α-(aminomethyl)acrylamide (4b) were investigated. The synthesis of 4 was achieved within many fewer steps than reported by using selective acylation and subsequent conjugate substitution of α-(chloromethyl)acryloyl chloride. 4 hardly homopolymerized, but copolymerization with N-substituted acrylamides afforded polymers with various compositions. Surprisingly, substitution with amino groups increased the hydrophobicity of the polymers and lowered the cloud point (T_c). Nevertheless, polymers containing the amino monomers as major components exhibited significantly higher T_c in 1 M HCl aq than those in water. Thus, in order to give clear pH responsiveness, it is necessary to use 4 as a major monomer.