Synthesis, characterization, and application of monodisperse poly L-Dopa microspheres

Abstract

In this study, 3,4-dihydroxy-L-phenylalanine (L-Dopa) was solvothermally polymerized to monodispersemicrospheres 1 µm in diameter. Polymerization was carried out in dimethylformamide containing appropriate amountsof urea and L-Dopa at 120 ◦ C for 24 h. Synthesis of the polymer in basic aqueous solution under hydrothermal conditionsor via conventional heating resulted in the formation of bulky powders including irregularly shaped particles of thepolymer. The morphologies of the synthesized polymers were characterized by scanning electron microscopy (SEM).The microspheres synthesized by solvothermal method (with ∼1 µm average diameter) were clearly observable in SEMmicrographs. The thermal stability of the synthesized polymer was studied by thermogravimetry and differential scanningcalorimetry techniques. It was recognized that the polymer is thermally stable at more than 200 ◦ C. Applicability of thepolymer microspheres was investigated for catalyzing the reaction of one-pot multicomponent synthesis of dihydrofurans.Several dihydrofuran derivatives were successfully synthesized using poly L-Dopa as a novel, environmentally friendly,and efficient catalyst with efficiency of more than 90%. Poly L-Dopa is easily separated by filtration from the reactionmixture. It can be used several times without decreasing the catalyzing activity after washing by suitable solvents.