NOVELTY - Conjugated phenylene polymer is new.    USE - Conjugated phenylene polymer for use in polymer blend or formulation useful as charge transport, semiconducting, electrically conducting, photoconducting, or light emitting material in optical, electrooptical, electronic, electroluminescent, or photoluminescent components or devices selected from organic field effect transistors, thin film transistors, integrated circuits, logic circuits, capacitors, radio frequency identification tags, devices or components, organic LED, organic light emitting transistors, flat panel displays, backlights of displays, organic photovoltaic devices (OPV), solar cells, laser diodes, photoconductors, photodetectors, electrophotographic devices, electrophotographic recording devices, organic memory devices, sensor devices, charge injection layers, charge transport layers or interlayers in polymer LEDs, Schottky diodes, planarizing layers, antistatic films, polymer electrolyte membranes, conducting substrates, conducting patterns, electrode materials in batteries, alignment layers, biosensors, biochips, security markings, security devices, or components or devices for detecting and discriminating DNA sequences (preferably bulk heterojunction (BHJ) OPV device) (all claimed). Uses include but are not limited to banknotes, credit cards, identification (ID) cards, national ID documents, licenses, stamps, tickets, shares, checks, and condensers.    ADVANTAGE - The conjugated phenylene polymer is easy to synthesize and exhibits low bandgap, high charge carrier mobility, high solubility in organic solvents, good processability for the device manufacture process, high oxidative stability, and long lifetime in electronic devices. The benzo(1",2":4,5;4",5":4',5')bis(silolo(3,2-b:3',2'-b')thiophene) unit exhibits a co-planar structure in the solid state, and thus individual polymer chains of the homopolymer, poly(benzo(1",2":4,5;4",5":4',5')bis(silolo(3,2-b:3',2'-b')thiophene)) also adopt a highly co-planar structure in the solid-state, which is beneficial for charge transport. The inclusion of two silicon bridging atoms in the benzo(1",2":4,5;4",5":4',5')bis(silolo(3,2-b:3',2'-b')thiophene) unit results in polymers with a lower lying lowest unoccupied molecular orbital energy level that yields a low bandgap, which is desirable for improved light harvesting and higher efficiencies in BHJ devices without any change in the highest occupied molecular orbital energy level in the device. Additional solubility can be introduced into the polymer by adding at the silyl group, longer alkyl chains, branched alkyl chains, or polyalkoxy ethers or comonomers containing multiple solubilizing groups.    DETAILED DESCRIPTION - Conjugated phenylene polymer comprising repeating unit(s) of formula (I) is new.    A1, A2=one of which is a single bond and the other of which is SiR1R2;    A3, A4=one of which is a single bond and the other of which is SiR3R4;    U1, U2=one of which is -CH= or =CH- and the other of which is -X-;    U3, U4=one of which is -CH= or =CH- and the other of which is -X-;    X=-S- or -Se-;    R1-R4=H, halo, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C(=O)NR0R00, -C(=O)X0, -C(=O)R0, -NH2, -NR0R00, -SH, -SR0, -SO3H, -SO2R0, -OH, -NO2, -CF3, -SF5, P'-Sp-, optionally substituted silyl, or carbyl or hydrocarbyl with 1-40C atoms that is optionally substituted and optionally comprises heteroatom(s);    Sp=spacer group or a single bond;    X0=halo;    R0, R00=H or optionally substituted carbyl or hydrocarbyl optionally comprising heteroatom(s);    Ar1, Ar2=optionally substituted aryl or heteroaryl, -CY1=CY2- or -CC-;    Y1, Y2=H, F, Cl, or CN;and    m1, m2=0 or 1, 2, 3, or 4.    INDEPENDENT CLAIMS are included for:    (1) a monomer of formula (II);    (2) polymer blend comprising conjugated phenylene polymer(s) and polymer(s), preferably selected from polymers having semiconducting, charge transport, hole/electron transport, hole/electron blocking, electrically conducting, photoconducting, or light emitting properties;    (3) formulation comprising conjugated phenylene polymer(s) or polymer blends and solvent(s), preferably selected from organic solvents; and    (4) process of preparing conjugated phenylene polymer.    R7, R8=halo, -CH2Cl, -CHO, -CH=CH2, -SiR'R"R"', -SnR'R"R"', -BR'R", -B(OR')(OR"), -B(OH)2, leaving group, or P'-Sp;and    R', R", R"'=R0 or halo, where R' and R" may also form a ring together with the heteroatom to which they are attached.