NOVELTY - A block copolymer of polyalkyl thiophene and polyoxyethylene, having number average molecular weight of 6000-120000 is new. The number average molecular weight of the polythiophene block is 3000-20000 and the molecular weight of the polyethylene glycol block is 3000-100000.    USE - As block copolymer of polyalkyl thiophene and polyoxyethylene (claimed) used in the solar energy battery, photo-electric sensor and biomedicine fields.    ADVANTAGE - The compound uses conjugated macromolecule poly thiophene and flexible hydrophilic high molecular polyethylene which is prepares water-soluble conjugated block copolymer, improves the solubility and adjustability of conjugated macromolecule by clicking method. The product has one end being rigid and the other end being flexible; and therefore, has self-characteristics such as water solubility, multiple self-assembled nanometer structures and low temperature processing, based on maintaining the polymer component.    DETAILED DESCRIPTION - A block copolymer of polyalkyl thiophene and polyoxyethylene of formula (I) having number average molecular weight of 6000-120000 is new. The number average molecular weight of the polythiophene block is 3000-20000 and the molecular weight of the polyethylene glycol block is 3000-100000.    R=alkane with the length longer than propyl.    An INDEPENDENT CLAIM is included for synthesizing the block copolymer (I) involving: (1) preparing the polyethylene glycol using a normal method to prepare polyethylene glycol with different molecular weights and single methoxy terminated; (2) dissolving the polyethylene glycol prepared in the step 1) in organic solvent, adding triethylamine, stirring and reacting for 30 minutes to 24 hours to obtain white polymer; (3) dissolving the white polymer obtained in the step 2) in N,N-dimethyl formamide at 34-30 degrees C, decompressing and distilling to remove the solvent, concentrating to obtain white compound; (4) preparing 2-bromine-5-iodine-3-methyl thiophene by using a conventional method; (5) under the protection of inert gases, dissolving 2-bromine-5-iodine-3-methyl thiophene into anhydrous tetrahydrofuran, adding isopropyl magnesium chloride solution, ethinyl magnesium bromide, filtering, to obtain the compound e; and (6) under the protection of inert gases, adding molar weight of cuprous bromide being the polymer (1-50%), and with methyl bromide, ethylene triamine, reacting for 1-24 hours, separating semi-permeable membrane to obtain the block target block copolymer.