Synthesis and organic field effect transistor properties of isoindigo/DPP-based polymers containing a thermolabile group

Abstract

(E)-6,6'-Dibromo-1,1-bis(2-octyldodecyl)-(3,3'-biindolinylid-ene)-2,2'-dione and/or 2,5-bis(2-octyldodecyl)3,6- di(5-bromothien-2-yl) pyrrolo[3,4-c] pyrrole-1,4-(2H, 5H)-dione and their tBoc-counterparts were propagated with 2,5-bis(tributylstannyl) thiophene in a molar ratio of 0.8 : 0.2 : 1.0 to release P(ODIDT-BID), P(ODIDT. BDPP), P(ODDPPT. BID) and P(ODDPPT. BDPP) as a new series of random conjugated polymers (RCPs) bearing a large number of octyldodecyl chains to ensure solubility and a small number of thermocleavable tBoc function to cast H-bonding upon heating up to 220 degrees C. All new polymers were synthesised via Pd catalysed Stille cross-coupling methodology in high yields and reasonable average molecular weights. The cast polymer films exhibited considerable red-shifted UV-vis absorption spectra and a further red-shift was also obtained in the thermal annealed films (at 220 degrees C for 30 min), which reflected the increasing of crystalline structure. The formation of H-bonding in these polymers was investigated using X-ray diffractometry (XRD) measurements. The field-effect mobilities of these polymers were investigated in the configuration of bottom-gate and bottom-contact (BGBC) field-effect transistors (FETs). The results from FETs indicated that the crystalline structure of RCPs exhibited reasonable FET mobilities with 1.17 x 10(-3) cm(2) V (-1) s (-1) for P(ODDPPT. BID) and 1.41 x 10(-3) cm(2) V (-1) s(- 1) for P(ODDPPT. BDPP).