This lecture describes the synthesis of a series of poly(isoindigo-dithiophene) based conjugated polymers with varying amounts of low molecular weight polystyrene (PS) side-chains via random copolymerization.The PS side-chain-decorated copolymers demonstrated better thin film processability,without compromising the electronic and optical properties when the molar content of the PS-containing repeating units were ＜10 ％.