Effects of fluorination on the electrochromic performance of benzothiadiazole-based donor-acceptor copolymersElectronic supplementary information (ESI) available: NMR spectra, TGA results, DSC and GPC plots, degradation profiles of electrochromic devices, and TD-DFT calculations. See DOI: 10.1039/c5tc00725a

A series of thiophene and benzothiadiazole-based copolymers ( PDAT-DTBT ) is synthesized through Stille coupling polymerization with two mono- and di-fluorinated benzothiadiazole analogues: PDAT-DTBT-F (1F) and PDAT-DTBT-2F (2F). The introduction of fluorine atoms onto the conjugated polymer backbone is found to have a pronounced effect on the optical, electrochemical and morphological properties, which in turn, influences the electrochromic performance of the fabricated absorption/transmission type devices greatly. All the polymers switch reversibly between the colored neutral states (green/blue) to transmissive oxidized states. Systematic enhancement in the reduction process to sub-second speeds (