NOVELTY - Making conjugated polymer having end group with selected function, comprises forming reaction mixture comprising monomer compound AA, where A comprises first moiety selected for its ability to form covalent bond in polymer chain, monomer compound B1B1, where B1 comprises second moiety selected for its ability to form covalent bond in polymer chain, and end capping compound and reactive group selected for its ability to react with monomer compound AA or B1B1 so that functional group is coupled to end of the polymer and allow end capping compound to react with monomer compound AA or B1B1.    USE - The method is useful for making conjugated polymer (comprising F1-(AA-B1B1)n or F1-(AA-B1B1)n-F1) which is useful in device comprising LED, FET or photovoltaic cell (all claimed).    ADVANTAGE - The method provides conjugated polymer: having tailored functional properties; that has ability to modulate optical or electrical properties comprising semiconductor charge transport; that is utilized in potentially low-cost, solution-processable devices for achieving sustainable energy generation.    DETAILED DESCRIPTION - Making a conjugated polymer having an end group with a selected function, comprises forming a reaction mixture comprising a monomer compound AA, where A comprises a first moiety selected for its ability to form a covalent bond in the polymer chain, a monomer compound B1B1, where B1 comprises a second moiety selected for its ability to form a covalent bond in the polymer chain, and an end capping compound, where the end capping compound comprises a functional group selected for its ability to modulate an optical or electrical property of the conjugated polymer and a reactive group selected for its ability to react with monomer compound AA or monomer compound B1B1 so that the functional group is coupled to an end of the polymer, where the monomer compound AA, the monomer compound B1B1 and the end capping compound are combined to allow the monomer compound AA and compound B1B1 to polymerize and form a polymer; and allow the end capping compound to react with monomer compound AA or monomer compound B1B1 so that the conjugated polymer having the end group with the selected function is made. INDEPENDENT CLAIMS are also included for:    (1) a conjugated polymer comprising F1-(AA-B1B1)n or F1-(AA-B1B1)n-F1, where F1 comprises an end capped functional group, and the polymer synthesized by the method;    (2) a device comprising conjugated polymer comprising endcap-(AA-B1B1)n or endcap-(AA-B1B1)n-endcap, where the polymer has an end capped functional group that provides charge transporting and/or light absorption properties and the polymer is synthesized by the method; and    (3) a polymerization system comprising: the monomer compound AA; the monomer compound B1B1; and the end capping compound; and the reactive group selected for its ability to react with A or B so that the functional group can be coupled to an end of the polymer, where the monomer compound AA, the monomer compound B1B1 and the end capping compound can be combined in reaction mixture that forms copolymer having the functionalized end group conjugated on it.