Supporting Information I. Polymer synthesis

Materials. All chemicals were purchased from commercial sources (Sigma-Aldrich or Acros) and used without further purification unless otherwise stated. 4,8-Bis(alkoxy)benzo[1,2-b:4,5-b’]dithiophene (1a and 1b) and 4,6dibromothieno[3,4-b]thiophene-2-carboxylic acid (3) were synthesized according to the reported procedure[35]. Characterization. 1H and 13C NMR spectra were recorded with on a Bruker Advance III HD 500MHz NMR spectrometer using CDCl3 with TMS as the internal standard. Molecular weights and molecular weight distributions of polymers were obtained using SEC with THF as an eluent at 35 oC and a flow rate = 1.00 mL min-1. The SEC was equipped with Polymer Standards Services (PSS) columns (guard, 105, 103, and 102 Å SDV columns) and connected with a differential refractive index (RI) detector (Waters, 2410) using PSS WinGPC 7.5 software. The apparent molecular weights were calculated based on linear polystyrene (PS) standards. High Resolution Mass Spectra (HRMS) were recorded on a Bruker micrOTOF II Mass Spectrometer operating in positive ESI(+) mode. Differential scanning calorimetry (DSC) was performed using a DSC-1 (Mettler Toledo), scans were performed under N2 from -60 to +280 oC with heating and cooling at 10 °C/min and repeated 3 times.