Synthesis and chracterization of amphiphilic block-copolymers low band gap rigid segment-block-P4VP

Two homologous series of rod-coil b[lock copolymers, composed by a low band gap rod moiety (poly[2,6-(4,4 bis-(2ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b' ]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) anda flexible poly(4-vinylpyrydine) (P4VP) based polar block, were synthesized by two different approaches. Step Grwoth-like procedure provided copolymers with longer coil, whilst copolymers with longer rod arise from Chain Growth-like process. Both the series were deeply investigated with different analytical tecniques (1H NMR, SEC-DV, and MALDI-TOF MS) in order to prove the coupling process and elucidate of the obatined materials. Chemical composition was evaluated by 1H NMR analysis. DSC heating traces of rod-coil copolymers synthesized by Step Growth-like route present two well resolved glass transition temperatures corresponding to the rod and coil blocks. The low band-gap rod-coil copolymers especially these with short coil can find application in hybrid solar cells. The length of the coil block is strongly limited by the low reactivity of the macroiniziator related two the rigid ity of the conjugated systems with respect to the poly( 3-hexyl thiophene) (P3HT). The shortness of a coil segmente (P4VP) allows to perform a proper MALDI-TOF MS characterization which is in agreement with 1H-NMR data. A series of rod-coil copolymers was prepared with predominance of the rod block (>86%w) stating from a fixed ro block and tuning the length of the rod moiety, by varying both the Macroiniziator/4VP ratio and the time of the nitroxide mediated radical polymerization (NMRP). The two series of obtained materials aggregate indifferent manners and show ditinct organizations in solid stat films depending of the respective length of the two blocks in the copolymers, from globular micelle-like to lamellar segregation as highlighted by AFM images with the increasing of the length of the coil segment.