Synthesis and characterization of thermochromic thiophene copolymers containing pyrene groups

[Display omitted] •New polythiophene copolymers containing pyrene units were successfully synthesized.•Pyrene units incorporation in the P3DT chains generated different optical behavior.•Absorbance range, PL, conjugation length, and stability were increased in copolymers.•Pyrene incorporation in P3DT caused a change of optical transmittance with temperature. Two thiophene-derived copolymers containing pyrene groups were synthesized using FeCl3 as oxidizing agent. The 3-methyl-4-(4-(pyren-1-yl)butoxy)thiophene/3-dodecylthiophene (PyT/3DT) molar ratio was varied: P(PyT1-co-3DT25) (1/25) and P(PyT1-co-3DT40) (1/40). The polymers were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), ultraviolet–visible spectroscopy (UV–vis), electric conductivity, cyclic voltammetry, and photoluminescence analysis (PL). P(PyT1-co-3DT25) and P(PyT1-co-3DT40) exhibited good thermal stability with T10 (10 wt% loss temperature) values at 428 and 415 °C, and Tg values of 62 and 64 °C, respectively. The incorporation of pyrene-labeled thiophene units in poly(3-dodecylthiophene) (P3DT) generated a new absorption band at a lower wavelength than the absorption band corresponding to P3DT. The thermal effect was studied in the transmittance spectra, and compared with their analog P3DT. The transmittance spectra of the polymers showed a temperature dependence. For P(PyT1-co-3DT25), with a temperature change of 55 °C (from 25 to 80 °C), the maximum displacement of the transmittance spectrum was around 95 nm. P(PyT1-co-3DT25) showed a polydispersity (Mw/Mn) of 2.8, similar to P3DT.