NOVELTY - A fluorescent polymer comprises pyrene-containing repeating unit(s) (I).    USE - Fluorescent polymer is used for electroluminescent material, electronic device, polymer light emitting diode, organic light emitting diode, organic integrated circuit, organic field effect transistor, organic light-emitting field effect transistor, organic thin film transistor, organic solar cell, thermoelectric device, electrochromic device and organic laser diode (all claimed).    ADVANTAGE - The fluorescent polymer has high chemical stability, and provides electroluminescent material having excellent morphological stability, brightness and color purity.    DETAILED DESCRIPTION - A fluorescent polymer comprises pyrene-containing repeating unit(s) of formula (I).    R1-R8=H, F, SiR100R101R102 or organic substituent;    or R6+R7, R3+R4, R1+R2, R2+R3=aromatic or heteroaromatic ring or optionally substituted ring;    n1,n2=0, 1, or 2;    R100-R102=1-18C alkyl or optionally substituted 6-18C aryl;and    Ar1,Ar2=optionally substituted arylene or heteroarylene.    INDEPENDENT CLAIMS are included for the following:    (1) method for alkylating pyrene rings in 2- and/or 7-position, which involves preparing pyrene-2-boronate or pyrene-2,7-bis(boronate) compound, and reacting the prepared compound with copper(II) bromide, to obtain bromopyrene derivative which is brominated in 2- and/or 7-position, reacting the prepared compound with magnesium chloride-R (MgCl-R, where R is tert-butyl) or zinc bromide-R (ZnBr-R) in presence of palladium catalyst, to obtain mono- or dialkylated pyrene, or reacting the prepared compound with R-bromide (R-Br) in one-step Suzuki coupling reaction, to form a mono- or dialkylated pyrene; and    (2) preparation of poly-7-alkyl-l,3-pyrenylene, which involves mono-alkylating pyrene to provide 2-alkylpyrene, reacting 2-alkylpyrene with bromine or N-bromosuccinimide as brominating agent, to provide 1,3-dibromo-7-alkylpyrene monomer, and polymerizing the monomer in a Yamamoto coupling reaction in presence of catalyst e.g. nickel oxide catalyst.