NOVELTY - Polar group-substituted S,S-dioxodibenzothiophene monomers (I) are new.    USE - (I) are useful in preparing polar group-substituted S,S-dioxodibenzothiophene unit-containing water/alcohol soluble polymers for light emitting diode and solar cells.    ADVANTAGE - The polymer produces from (I): has lower highest occupied molecular orbital (HOMO) energy level when compared to existing cathode interface layer polymer poly((9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene) (PFN); exhibits electron injection and hole blocking effect at the same time; can be dissolved in methanol, N,N-dimethylformamide, dimethyl sulfoxide, water and other polar solvent; and avoids interface mixing between electronic transmission layer and active layer of multilayered devices.    DETAILED DESCRIPTION - Polar group-substituted S,S-dioxodibenzothiophene monomers of formula (I) are new. INDEPENDENT CLAIMS are also included for:    (1) preparation of (I);    (2) polar group-substituted S,S-dioxodibenzothiophene unit-containing water/alcohol soluble polymers (II), which are linear polymer of formula (IIa) and hyper-branched polymers of formulae (IIb) and (IIc); and    (3) use of (II) as cathode interface material in light emitting diode and solar cells, where a layer of the polymer film is inserted between light-emitting layer and high work-function metal electrode of multilayer structured light-emitting diode, and a layer of the polymer film is inserted between photovoltaic active layer and high work-function metal electrode of bulk heterojunction solar cell device.    R = H, or -(CH2)nX;    n = 1-30;    X = dimethylamino, diethylamino, amphoteric ionic group e.g. (-N+((C2H5)2)-(CH2)3-SO3-), bis(2-hydroxyethyl)amino, trimethylammonio or phosphonate group e.g. (-P(=O)(OC2H5)-O-C2H5) and (-P(=O)(O- Na+)-O- Na+);    x = 0-0.7;    y = 0.3-1;    x+y = 1;    m = 1-300;    a = 0-0.65;    b = 0.3-0.95;    x+y = 0.95;    p, q, r, s = 1-300;    A = substituted fluoren-2,7-diyl group of formula (III), substituted fluoren-3,6-diyl group of formula (IV), spirobi(fluorene)-2,7-diyl group of formula (V), silafluoren-2,7-diyl group of formula (VI), carbazol-2,7-diyl group of formula (VII), carbazol-3,6-diyl group of formula (VIII), 5,11-dihydroindolo(3,2-b)carbazol-3,9-diyl group of formula (IX), 5,11-dihydroindolo(3,2-b)carbazol-2,8-diyl group of formula (X), 6,12-dihydroindeno(1,2-b)fluoren-3,9-diyl group of formula (XI), 6,12-dihydroindeno(1,2-b)fluoren-2,8-diyl group of formula (XII), benzen-1,4-diyl group of formula (XIII), spirobi(fluorene)-2,2'-diyl or indol-2-one-3,3-diyl group of formula (XIV);    R1 = 1-16C alkyl;    B1 = triphenylamin-4,4',4''-triyl, triphenyltriazin-4',4'',4'''-triyl, benzen-1,3,5-triyl, N-phenylcarbazol-3,6,4'-triyl or 3,4,5-triphenyl-1,2,4-triazol-4',4'',4'''-triyl; and    B2 = 4,7-di(diphenylamino)-2,1,3-benzothiadiazol-4',4'',4''',4''''-tetrayl, 4,7-di(4-(diphenylamino)phenyl)-2,1,3-benzothiadiazol-4''',4'''',4''''',4''''''-tetrayl, S,S-dioxo-3,7-di(diphenylamino)dibenzothiophen-4',4'',4''',4''''-tetrayl or S,S-dioxo-3,7-di(4-(diphenylamino)phenyl)dibenzothiophen-4',4'',4''',4''''-tetrayl.    Provided that when x is 0 and y is 1, (II) is a homopolymer of formula (IIa1).