Polar Side Chains Enhance Selection of Semiconducting Single-Walled Carbon Nanotubes by Polymer Wrapping

Abstract

This paper describes the effectiveness of donor− acceptor (D-A) conjugated polymers to disperse and select for semiconducting single-walled carbon nanotubes (s-SWCNTs) when enhanced by the inclusion of polar oligoethylene glycolbased side chains, without altering the D−A backbone. We designed and synthesized two sets of naphthalenediimide(NDI)alt-bithiophene(T2)-based conjugated polymers with one of two alkyl side chains (decyl and dodecyl chains) of different lengths and with or without polar triethylene glycol side chains. The resulting low-band-gap copolymers all effectively disperse and select for s-SWCNT, but the inclusion of polar side chains enhances the interactions between the polymer backbone and the walls of the s-SWCNTs relative to the polymers with only alkyl side chains. As a result, the wrapping and selection efficiency of the polymer-SWCNT systems with polar side chains are both significantly enhanced. We further optimized the binding energy and surface coverage by combining glycol ether and dodecyl side chains to maximize wrapping efficiency, leading to a field-effect mobility of 2.82 cm 2 V −1 s −1 and on/off current ratios of ∼2 × 10 7 in polymer-wrapped SWCNTs. Our results provide insight into the role of the side-chain interactions in the polymer wrapping and dispersion technique, and, because we focus on manipulating side chains, they can be generalized for other conjugated polymer backbones.

Efficient Selective Sorting of Semiconducting Carbon Nanotubes Using Ultra-Narrow-Band-Gap Polymers

“…The synthesis routes and chemical structures of the two new conjugated polymers that were used to study the dispersion and discrimination of semiconducting carbon nanotubes are shown in Figure . The synthesis of PNDITEG-AH was carried out according to literature procedures . The monomers were synthesized and purified according to published procedures with slight modifications (see the Supporting Information for details). − Both polymers were synthesized by a typical palladium-catalyzed Stille polycondensation of symmetrical dibromo naphthalene diimide and distannyl thienylennevinylene monomers.…”

“…Comparison of electrical characteristics for the polymer wrapped s-SWCNT inks. (a–c) FET output characteristics for the examined inks for (a) a device fabricated from HiPCO: PNDITEG-AH (Adapted from our previous work), (b) HiPCO: PNDITEG-TVT , and (c) HiPCO: PNDIC8TEG-TVT . The arrows represent an increase in gate bias from 0 to ±50 V in steps of 10 V. (d) FET transfer characteristics for HiPCO: PNDITEG-AH (black), HiPCO: PNDITEG-TVT (red), and HiPCO: PNDIC8TEG-TVT (turquoise).…”

“…Chemical structures of (a) representative wide- or mid-band-gap conjugated polymers for selecting and sorting SWCNTs reported in the literature and (b) narrow-band-gap conjugated polymers for selecting and sorting SWCNTs reported so far. The mentioned mobilities are for s-SWCNT FETs (c) naphthalene diimide based low-band-gap conjugated polymers presented in this work. ,,,− , …”

“…Very recently, we addressed the weak interaction between D–A conjugated polymers and SWCNTs by introducing polar triethylene glycol side chains on the D–A conjugated polymer backbone. We demonstrated the wrapping ability of the mid-band-gap, D-A conjugated polymer ( PNDITEG-AH ), comprising NDI and head-to-head bithiophene, which is significantly improved by including polar triethylene glycol side chains as compared to alkyl side chains . For this work, we partly make use of the same data set regarding this specific polymer ( PNDITEG-AH ) and thereon-based devices.…”

“…We demonstrated the wrapping ability of the midband-gap, D-A conjugated polymer (PNDITEG-AH), comprising NDI and head-to-head bithiophene, which is significantly improved by including polar triethylene glycol side chains as compared to alkyl side chains. 41 For this work, we partly make use of the same data set regarding this specific polymer (PNDITEG-AH) and thereon-based devices.…”