Polythiophene-g-poly(methacrylic acid) and perylene diimide appended peptide conjugates with tuneable photoluminescence, OMEIC, and photo-switching properties

A water-soluble polymer-peptide conjugate, composed of poly(thiophene methacrylate) (PTMA) and cationic peptide appended perylene diimide (PBI-NH3+), was fabricated. The dipolar interaction between PTMA and PBI-NH3+ helped to uncoil the polythiophene backbone, resulting in an increase of the conjugation length, which was thoroughly studied by UV-Vis, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) spectra. The morphology of PTMA changes from vesicular to a highly entangled fibrillar network in the hybrid as evident from the HR-TEM study. Fluorescence spectroscopic study and time-correlated single-photon counting (TCSPC) studies were made to understand the effect of interaction on the photoluminescence (PL) properties of the hybrid. The current-voltage (I-V) plots of hybrid materials showed synergistic enhancement of current with voltage, showing an interesting organic mixed ionic and electronic conductivity (OMIEC) property, which was further supported through current-time (I-t) and Nyquist plot results. This conjugate material shows an enhancement of photo-switching behaviour with the highest photocurrent gain of 9. 8 (I-on/I-off) for the composite with 27 wt% PBI-NH3+. The increase in photoswitching property is attributed to efficient charge (electron-hole) separation and holds a future promise for fabricating new types of macromolecular OMIEC systems along with excellent photocurrent switching efficiency.