NOVELTY - End-capping a semiconducting polymer comprises replacing the end group of greater than or equal to 1 terminus of the polymer with an end-capping compound, which is not charge transporting and comprises greater than or equal to 2 rings.    USE - The process is for end-capping a semiconducting polymer used for a film or electronic device i.e. FETs, photovoltaic device, or preferably LED (claimed). It is used to obtain end-capped electroluminescent polymer.    ADVANTAGE - The use of an end-capping compound, which comprises greater than or equal to 2 rings and is not charge transporting, produces a more consistent charge balance in a semiconducting polymer and provides an increase in both the efficiency and the lifetime of the polymer. The greater than or equal to 2 rings of the end-capping moiety ensure that electron-rich monomers are spaced further away from the termini of the polymers and/or the termini of the side-chains of the polymer; and because the end-capping moiety is not charge transporting, a more favorable delocalization of the electrons of the electron-rich groups is achieved. By providing end-capping groups, stability of the polymer is increased because the long end-capping groups space the electron rich groups further from the polymer termini than a conventional phenyl end-capping group.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a process of forming a polymer comprising the polymerization of monomers, greater than or equal to 1 of which is one or both of a charge transporting unit and hydrocarbon monomer, where greater than or equal to 1C atom has been substituted by an atom or group with a greater quantity of unshared valence electrons than the carbon atom it has been substituted for, and greater than or equal to 1 of the monomers comprises an end-capping compound at one end of the monomer, where end-capping compound prevents polymerization at the end; and    (2) semiconducting polymer comprising polymerized monomers, where the end group of greater than or equal to 1 terminus of the polymer is an end-capping compound.