ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Chemoenzymatic polycondensation of para-benzylamino phenol

Pinar Yildirim, Ersen Gokturk, Ersen Turac, Haci O Demir, and Ertugrul Sahmetlioglu

^aDepartment of Chemistry, Nigde University, 51240 Nigde, Turkey

E-mail: sahmetlioglu@gmail.com

Abstract: para-Benzylamine substituted oligophenol was synthesized via enzymatic oxidative polycondensation of 4-(benzylamino)phenol (BAP). Polymerization involved only the phenolic moiety without oxidizing the sec-amine (benzylamine) group. Chemoselective polycondensation of BAP monomer using HRP enzyme yielded oligophenol with sec-amine functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polycondensation were studied. Optimum polymerization process with the highest yield (63 %) and molecular weight (M_n = 5000, degree of polymerization ≈ 25) was achieved using the EtOH/ buffer (pH 5.0; 1 : 1 vol. ratio) at 25 °C in 24 h under air. Characterization of the oligomer was accomplished by ¹H NMR and ¹³C NMR, Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), ultraviolet-visible spectroscopy (UV-Vis), cyclic voltammetry (CV) and thermogravimetric analysis (TGA). The polymerization process involved the elimination of hydrogen from BAP, and phenolic-OH end groups of the oligo(BAP), confirmed using ¹H NMR and FT-IR analyses. The oligomer backbone possessed phenylene and oxyphenylene repeat units, and the resulting oligomer was highly soluble in common organic solvents such as acetone, CHCl₃, 1,4-dioxane, N,N-dimethylformamide (DMF), tetrahydrofurane (THF) and dimethylsulfoxide (DMSO). Oligo(BAP) was thermally stable and exhibited 5 % and 50 % mass loss determined by thermogravimetric analysis at 247°C and 852°C, respectively.

Keywords: enzymatic oxidative polymerization – horseradish peroxidase enzyme – oligophenol – hydrogen peroxide

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0242

Chemical Papers 70 (5) 610–619 (2016)