Investigation on Viscoelasticity of Waterborne Polyurethane with Azobenzene-containing Pendant Groups under Ultraviolet and Visible-light Irradiation

• Published in: Chinese journal of polymer science Vol. 37; no. 12; pp. 1267 - 1272
• Main Authors: Liu, Yi-Jun, Liu, Dong, Li, Si-Han, Liang, Hua-Qing, Zhu, Fang-Ming
• Format: Journal Article
• Language: English
• Published: Beijing Chinese Chemical Society and Institute of Chemistry, CAS 01.12.2019; Springer Nature B.V
• Subjects: Adhesion; Atomic beam spectroscopy; Atomic force microscopes; Atomic force microscopy; Azo compounds; Butyric acid; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Diisocyanates; Industrial Chemistry/Chemical Engineering; Light; Light irradiation; Microscopes; Modulus of elasticity; Polycaprolactone; Polymer Sciences; Polyurethane resins; Single crystals; Thermomechanical analysis; Triethylamine; Ultraviolet radiation; Viscoelasticity; Viscoelasticity; Waterborne polyurethane; Photoisomerization; Azobenzene
• ISSN: 0256-7679; 1439-6203
• DOI: 10.1007/s10118-019-2289-x

In this study, a novel waterborne polyurethane (WPU) with azobenzene-containing (azo-containing) pendant groups was synthesized by isophorone diisocyanate, long-chain diol of polycaprolactone, 2-ethyl-2-methyl-butanoic acid (2,2-dimethylolpropionic acid), 10-(4-(phenyldiazenyl)phenoxy)decyl-3-hydroxy-2-(hydroxymethyl)-2-methylpropanoate, and N,N -diethyl-ethanamine (triethylamine). Moreover, the influence of ultraviolet and visible (UV-Vis) light irradiation on the viscoelasticity of azo-containing WPU film in terms of the reversible trans-cis photoisomerization of azo-containing pendant groups was investigated by UV-Vis light spectroscopy, atomic force microscopy, and dynamic thermomechanical analysis. The results revealed that the adhesion of azo-containing WPU with single crystal silicon atomic force microscope probe was about 13 nN when irradiated by 450 nm Vis light for 60 s at 25 °C. Subsequently, the adhesion increased to 82 nN after irradiation with 365 nm UV light for 60 s at 25 °C. In addition, the azo-containing WPU presented a photo-induced reversible transition of tensile modulus and tan δ in the range from about 2 MPa to 22 MPa and 6000 to 0.35 with UV-Vis light cyclic irradiation for 120 s at 25 °C, respectively.