On the Impact of Linear Siloxanated Side Chains on the Molecular Self‐Assembling and Charge Transport Properties of Conjugated Polymers

Abstract

Herein reported is the impact of the functionalization of four different semiconducting polymer structures by a linear siloxane‐terminated side‐chains. The latter is tetrasiloxane (Si4) or trisiloxane (Si3) chains, substituted at their extremity to a pentylene linker. The polymer structure is based on 5,6‐difluorobenzothiadiazole comonomer (PF2), a diketopyrrolopyrrole unit (PDPP‐TT), a naphtalediimide unit (PNDI‐T2), and a poly[bis(thiophen‐2‐yl)thieno[3,2,b]thiophene (PBTTT). The properties of these siloxane‐functionalized polymers are scrutinized and compared with the ones of their alkyl‐substituted polymer analogues. The impact of the alkyl‐to‐siloxane chain substitution clearly depends on the molecular section of the side chains. When a branched 2‐octyldodecyl chain (C20) is replaced by a Si4 chain of same molecular section, the greatest impact is the strong increase of the π‐stacking overlap of the polymer backbones. This effect leads to a significative enhancement of the charge mobility values of the polymers. As in‐plane and out‐of‐plane mobility are increased simultaneously, this π‐overlap enhancement effect happens to be preponderant over the polymer orientation variations. When a linear tetradecyl chain (C14) is replaced by a linear Si3 chain of twice larger molecular section, the polymer structure is profoundly affected. While PBTTT‐C14 is crystalline and purely edge‐on, PBTTT‐Si3 is mesomorphic and shows a mixed face‐on/edge‐on orientation.

Enhanced Performance of Cyclopentadithiophene-Based Donor-Acceptor-Type Semiconducting Copolymer Transistors Obtained by a Wire Bar-Coating Method

“…Furthermore, the intramolecular peaks were clearly red-shifted by 12, 6, and 6 nm for the films. As reported in [ 27 ], the emergence of those additional peaks and the red shifts was regarded to be attributed to the molecular aggregation. By stacking with the same adjacent polymer sub-units, the relevant energy states of the conjugated polymers (additional peaks) were formed, thereby resulting in decreases in the optical band gap of the polymeric films.…”

Functionalization of Biphenylcarbazole (CBP) with Siloxane-Hybrid Chains for Solvent-Free Liquid Materials

“…Recently, there is a growing interest for siloxane-functionalized materials for optoelectronic applications [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. This trend might be surprising because of the electrical insulating character of siloxanes.…”

Functionalization of Biphenylcarbazole (CBP) with Siloxane-hybrid Chains for Solvent-Free Liquid Materials

“…Recently, there is a growing interest for siloxane-functionalized materials for optoelectronic applications [4][5][6][7][8][9][10][11][12][13][14]. This trend might be surprising because of the electrical insulating character of siloxanes.…”

“…However, the incorporation of short siloxane segments into electro-active conjugated species enables a valuable improvement of the organization, thermal and mechanical properties of the materials. For instance, siloxane-hybrid sidechain conjugated polymers have been reported to exhibit lamellar mesomorphic organization with enhanced charge transport properties [11][12][13][14]. This effect was attributed to the singular fluid and segregating character of siloxane chains that impose a better facing of the polymers with improved -stacking overlap [14].…”

“…For instance, siloxane-hybrid sidechain conjugated polymers have been reported to exhibit lamellar mesomorphic organization with enhanced charge transport properties [11][12][13][14]. This effect was attributed to the singular fluid and segregating character of siloxane chains that impose a better facing of the polymers with improved -stacking overlap [14]. Multiple functionalization of conjugated molecular systems by short siloxane chains also led to preparation of molecular liquids with luminescent and/or semiconducting properties [4][5][6][7][8][9].…”