Synthesis of a Smart Conductive Block Copolymer Responsive to Heat and Near Infrared Light

S. BONGIOVANNI ABEL; M.A. MOLINA; C.R. RIVAROLA; K. RIBERI; C.A. BARBERO

Polymers

MDPI

Año: 2019 vol. 11 p. 1 - 13

2073-4360

A method for the synthesis of a linear block copolymer (PNIPAM-b-PANI), containing a 16 thermoresponsive block (poly(N-isopropylacrylamide), PNIPAM) and a Near Infrared (NIR) light17 absorbing block (polyaniline, PANI), is reported. The synthetic approach involves two-step 18 successive polymerization reaction. First, the radical polymerization of NIPAM using 4-19 aminothiophenol as a chain transfer agent for the obtention of thermosensitive block terminated20 with an aniline (ANI) moiety. Second, the oxidative polymerization of ANI initiated in ANI moiety of thermosensitive block to grow the second conductive PANI block. 21 1H NMR and FT-IR 22 spectroscopy shows the characteristics peaks of both polymeric blocks revealing the successful 23 copolymerization process. SLS and UV-Visible combined measurements allowed the determination of the Mw for PNIPAM-b-PANI macromolecule: 5.5 × 105 g mol−1 24 . The resulting copolymer is soluble in water (8.3 g L−1 25 ) and in non-aqueous solvents such as ethanol, formic acid, acetonitrile, and others. 26 Both polymer blocks chains show the properties of the polymer chains. The block copolymer shows27 a lower critical solution temperature (LCST) at the same temperature (32-34 °C) than PNIPAM, 28 while the copolymer show pH dependent UV-vis-NIR absorption similar to PANI. The PNIPAM 29 block suffer a coil to globule transition upon NIR light irradiation (785 nm, 100 mW), as shown by 30 turbidimetry and AFM, due to local heating (more than 9°C in 12 minutes) induced by the NIR 31 absorption at the PANI block. Furthermore, the electrical conductivity of PNIPAM-b-PANI thin films was demonstrate (resistivity of 5.3 × 10−4 Ω−1 cm−1 32 ), indicating that the PANI block is present 33 in its conductive form.