Low Elastic Modulus and High Charge Mobility of Low-Crystallinity Indacenodithiophene-Based Semiconducting Polymers for Potential Applications in Stretchable Electronics

Abstract

A series of alkyl-substituted indacenodithiophene (alkyl-IDT) semiconducting donor–acceptor polymers were designed by DFT to have varying degrees of backbone planarity and synthesized via direct arylation polymerization (DArP). These polymers exhibit weak intermolecular interactions, a glass transition temperature (T g) below room temperature, and low degrees of crystallinity from XRD measurements. Despite this, the field-effect mobilities (μ) of these polymers are relatively high (0.06–0.20 cm2 V–1 s–1) with mobility increasing with increasing backbone planarity. Because of the weak intermolecular interactions, the polymers exhibit low elastic moduli (E f) of less than 450 MPa. The polymer with the most twisted backbone exhibits high ductility with a crack-onset strain (CoS) over 100%. These structure–property relationship studies provide useful guidelines for designing semiconducting polymers with high mobility, low stiffness, and high ductility enabling applications in stretchable electronics.

Glass Transition Phenomenon for Conjugated Polymers

“…This is attributed to the long and branched alkyl sidechain increasing the degree of freedom and the configurational entropy of the polymer chain. Additionally, these polymers exhibit weak intermolecular interactions and low degree of crystallinity from X‐ray diffraction (XRD) measurements . The charge transport mobilities ( µ ) of these polymers remain relatively high (0.06–0.20 cm 2 V −1 s −1 ) and increase with backbone planarity …”

“…Instead of using a static picture to describe the transport of charges, what happened to the conjugated polymer above (high local chain dynamics) and below glass transition (in vitrified state) would be allow one to study the effect of the dynamic disorder on the charge transport. Interestingly, several high mobility conjugated polymers show glass transition near or below the room temperature, such as some DPP, isoindigo, and IDT polymers (see Tables 4 and 5 above). It is worthwhile to explore the difference for the charge transport at the glassy state, at the viscoelastic state, in liquid crystalline state, and in melt state.…”

WITHDRAWN: Near 14 cm2 V-1 s-1 Charge Carrier Mobility Enabled by Amorphous Indacenodithiophene-based Polymers with Controlled Regioregularity

“…Interestingly, polymers based on the extended fused-ring IDT core display high FET mobilities with high backbone coplanarity despite the lack of long-range crystalline order in the solid state. 2,3,[25][26][27][28] This intriguing feature considerably differs from the abovementioned theory and provides a new molecular-design guideline for achieving high mobilities in near-amorphous polymers, thus facilitating the development of intrinsically stretchable semiconducting polymers toward next-generation electronics. Driven by their unique, yet different properties, many polymers based on CDT and IDT units have been incorporated into high-performance FETs and continue to be studied (see Fig.…”

“…1 and Table S1). 2,14,16,23,26,[28][29][30][31][32][33][34][35][36] However, there is no systematic comparison study between CDT and IDT polymer systems with backbone regioregularity in terms of optoelectronic and morphological properties.…”

Indacenodithiophene Homopolymers via Direct Arylation: Direct Polycondensation versus Polymer Analogous Reaction Pathways

“…To date, few IDT monomers have been used in DAP protocols. 8,25,35 However, IDT monomer synthesis still involves Stille or Negishi cross couplings. Furthermore, side reactions such as homocouplings are possible for IDT monomers used in DAP-based copolymerization.…”