Understanding of Face-On Crystallites Transitioning to Edge-On Crystallites in Thiophene-Based Conjugated Polymers

Son, Sung Yun; Park, Jin Young; You, Wei

doi:10.1021/acs.chemmater.1c00946

Cited by 51 publications

(55 citation statements)

References 54 publications

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“…It should be noted that there are a few exceptional cases for which a conversion from face-on to edge-on can complete without reaching a melting state. 40 Overall, our observation regarding the occurrence of form I and form II and orientation evolution indicates that it is possible to transform from form I to form II while maintaining a majority face-on texture with thermal annealing, and that the constantly reported co-occurrence of form I (form II) and faceon (edge-on) are not correlated in nature. 15−17 Discussion.…”

Section: ■ Results and Discussionmentioning

confidence: 70%

Capturing the Phase Transformation and Thermal Behavior of P(NDI2OD-T2) with In Situ Grazing Incidence WAXS

Tang

McNeill

2022

Macromolecules

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The thermal behavior of the well-known electron transporting polymer P(NDI2OD-T2) is investigated using in situ temperature-dependent grazing incidence wide-angle X-ray scattering (GIWAXS). Careful study of the evolution of lattice parameters, peak widths, and scattering patterns enables us to observe the phase transition from form I to form II, with these two polymorphs exhibiting distinct thermal expansion and crystal growth behavior. Over the range of 30−230 °C, form I is observed to be dominant, characterized by thermal expansion in both lamellar and π−π stacking directions with comparable thermal expansion coefficients of 2 × 10 −4 K −1 . Form II is observed with heating from 230 °C to 320 °C (and persists with subsequent cooling) and is characterized by negative thermal expansion in the lamellar stacking direction and accelerated thermal expansion (5-fold increase in thermal expansion coefficient) in the π−π stacking direction. For both forms, no noticeable lattice expansion or contraction is found in the backbone direction. The growth of P(NDI2OD-T2) crystals with annealing is also found to be anisotropic. In particular, the size of crystallites in the lamellar stacking direction increases throughout the heating process from room temperature to 320 °C with a faster rate of growth in form II than in form I. In the backbone direction, crystallite size increases in form I but decreases in form II; in the π−π direction no systematic change in coherence length is observed. With regard to texture, the face-on orientation is found to remain dominant throughout the heating and cooling cycle, with a minority edge-on population found to slightly increase with heating to 320 °C and subsequent cooling. This work provides new insights into the thermal behavior and polymorphism of P(NDI2OD-T2) and the understanding of the structure−property relationship.

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Section: ■ Results and Discussionmentioning

confidence: 70%

Capturing the Phase Transformation and Thermal Behavior of P(NDI2OD-T2) with In Situ Grazing Incidence WAXS

Tang

McNeill

2022

Macromolecules

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“…The geometrically corrected pole figures were constructed according to procedures discussed in previous works (Supplementary Fig. 5 ) 21 , 22 . The total integrated areas for RP–T50–COOH is ~1.95 times larger than that for P3ET–COOH, suggesting the degree of π–π stacking in the RP–T50–COOH film is significantly higher.…”

Section: Resultsmentioning

confidence: 99%

Integrating charge mobility, stability and stretchability within conjugated polymer films for stretchable multifunctional sensors

et al. 2022

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Conjugated polymers (CPs) are promising semiconductors for intrinsically stretchable electronic devices. Ideally, such CPs should exhibit high charge mobility, excellent stability, and high stretchability. However, converging all these desirable properties in CPs has not been achieved via molecular design and/or device engineering. This work details the design, synthesis and characterization of a random polythiophene (RP-T50) containing ~50 mol% of thiophene units with a thermocleavable tertiary ester side chain and ~50 mol% of unsubstituted thiophene units, which, upon thermocleavage of alkyl chains, shows significant improvement of charge mobility and stability. Thermal annealing a RP-T50 film coated on a stretchable polydimethylsiloxane substrate spontaneously generates wrinkling in the polymer film, which effectively enhances the stretchability of the polymer film. The wrinkled RP-T50-based stretchable sensors can effectively detect humidity, ethanol, temperature and light even under 50% uniaxial and 30% biaxial strains. Our discoveries offer new design rationale of strategically applying CPs to intrinsically stretchable electronic systems.

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“…PII-2T has two fused aromatic (isoindigo) units next to each other and a relatively lower density of alkyl side chains, both of which should have a lower barrier for nucleating π−π interaction between the backbone of PII-2T chains, ultimately resulting in an edge-on orientation. 89 In the case of DPP-BTz, the fused aromatic rings, diketopyrrolopyrrole and benzotriazole units, are separated by thiophene units and the alkyl side-chain density is also greater. These aspects of the molecular structure potentially hinder the π−π interaction between the polymer chains and force them to adopt a face-on orientation even on graphene substrates.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…We postulate that the difference in molecular orientation between PII-2T and DPP-BTz on the same substrates and under similar processing conditions is due to the difference in their molecular structure. PII-2T has two fused aromatic (isoindigo) units next to each other and a relatively lower density of alkyl side chains, both of which should have a lower barrier for nucleating π–π interaction between the backbone of PII-2T chains, ultimately resulting in an edge-on orientation . In the case of DPP-BTz, the fused aromatic rings, diketopyrrolopyrrole and benzotriazole units, are separated by thiophene units and the alkyl side-chain density is also greater.…”

Section: Results and Discussionmentioning

confidence: 99%

Role of Interfacial Interactions in the Graphene-Directed Assembly of Monolayer Conjugated Polymers

et al. 2022

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Development of graphene−organic hybrid electronics is one of the most promising directions for next-generation electronic materials. However, it remains challenging to understand the graphene− organic semiconductor interactions right at the interface, which is key to designing hybrid electronics. Herein, we study the influence of graphene on the multiscale morphology of solution-processed monolayers of conjugated polymers (PII-2T, DPP-BTz, DPP2T-TT, and DPP-T-TMS). The strong interaction between graphene and PII-2T was manifested in the high fiber density and high film coverage of monolayer films deposited on graphene compared to plasma SiO 2 substrates. The monolayer films on graphene also exhibited a higher relative degree of crystallinity and dichroic ratio or polymer alignment, i.e., higher degree of order. Raman spectroscopy revealed the increased backbone planarity of the conjugated polymers upon deposition on graphene as well as the existence of electronic interaction across the interface. This speculation was further substantiated by the results of photoelectron spectroscopy (XPS and UPS) of PII-2T, which showed a decrease in binding energy of several atomic energy levels, movement of the Fermi level toward HOMO, and an increase in work function, all of which indicate p-doping of the polymer. Our results provide a new level of understanding on graphene−polymer interactions at nanoscopic interfaces and the consequent impact on multiscale morphology, which will aid in the design of efficient graphene−organic hybrid electronics.

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Understanding of Face-On Crystallites Transitioning to Edge-On Crystallites in Thiophene-Based Conjugated Polymers

Cited by 51 publications

References 54 publications

Capturing the Phase Transformation and Thermal Behavior of P(NDI2OD-T2) with In Situ Grazing Incidence WAXS

Capturing the Phase Transformation and Thermal Behavior of P(NDI2OD-T2) with In Situ Grazing Incidence WAXS

Integrating charge mobility, stability and stretchability within conjugated polymer films for stretchable multifunctional sensors

Role of Interfacial Interactions in the Graphene-Directed Assembly of Monolayer Conjugated Polymers

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