Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLE7 Nov 2022Intrinsically Viscoelastic Supramolecular Conjugated Polymer toward Suppressing Coffee-Ring Effect Yamin Han†, Lubing Bai†, Xiang An, Man Xu, Chuanxin Wei, Zongqiong Lin, Mengna Yu, Jinyi Lin, Lili Sun, Ning Sun, Changting Wei, Linghai Xie, Xuehua Ding, Qi Wei, Chengrong Yin, Chenghui Li, Wenming Su and Wei Huang Yamin Han† Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Lubing Bai† Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE), Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an 710072 , Xiang An Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Man Xu State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 , Chuanxin Wei State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 , Zongqiong Lin Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE), Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an 710072 , Mengna Yu State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 , Jinyi Lin *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Lili Sun Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Ning Sun Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Changting Wei Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 , Linghai Xie *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 , Xuehua Ding Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Qi Wei Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE), Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an 710072 , Chengrong Yin Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 , Chenghui Li State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 , Wenming Su Printable Electronics Research Center, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 and Wei Huang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Key Laboratory of Flexible Electronics (KLOFE), Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), Nanjing 211816 Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE), Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University (NPU), Xi'an 710072 State Key Laboratory of Organic Electronics and Information Displays, Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 https://doi.org/10.31635/ccschem.021.202101308 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The rational molecular design of light-emitting conjugated polymers that inherently suppress the ubiquitous coffee-ring effect (CRE) is a great challenge and the critical bottleneck for printing displays. Herein, we describe a supramolecular route to construct an intrinsically viscoelastic rigid conjugated polymer (RCP) (PHDPF-Cz) toward avoiding the CRE without sacrificing optoelectronic properties. The π–π stacking interactions derived from the pendant carbazole (Cz) units enable PHDPF-Cz to self-assemble into criss-cross nanofibers and endow its solution with great viscosity. Consequently, a high-quality and continuous PHDPF-Cz film was obtained by impeding the transport of aggregates to the droplet edge due to outward capillary flow during evaporation, in sharp contrast to the random aggregate migration and rapid precipitation generated from the controlled poly[4-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene]-co-[5-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene] and poly(9,9-dioctylfluorene) solutions. Finally, an efficient random laser is also achieved based on these cross-linked films with ultrastable single-chain excitonic behavior, confirming the effectiveness of our design strategy. Download figure Download PowerPoint Introduction Printed processing has become one of the most promising technologies for manufacturing high-quality optoelectronic devices, including printed displays,1–3 sensor arrays,4–6 and other devices,7–10 because of its convenience, low-cost, flexibility, and large area. However, the generation of ring-like patterns in evaporating droplets, known as the coffee-ring effect (CRE), has an adverse influence on the depositional morphology (Scheme 1a, left), and hence on the pattern resolution, device stability, and performance reproducibility.11–15 Research on suppressing the CRE to achieve a homogenous film deposition by manipulating outward capillary flows or controlling the three phase contact line (TCL) movement during droplet evaporation has been one of the most critical tasks in inkjet and screen printing optoelectronic devices.16–18 To date, many physical and engineering strategies have been implemented, such as doping surfactants in the solvent,19–21 adopting co-solvents or cross-network materials,2,22–24 changing the particle shape,25,26 and regulating the surface energy of the substrate.27,28 For the semiconductor polymers with rigid conjugated backbones, the inherent reason for generating undesirable "coffee rings" is that the inter-chain aggregates without attraction produce uneven deposition with the flow of the liquid, which restricts their practical applications in printing optoelectronic devices. The development of large-scale printed plastic devices is thus dependent on the ability to develop rigid conjugated polymers (RCPs) that can be manufactured into a large-area uniform film by solution-processed techniques.29 Abundant natural polymers, such as cellulose and chitosan, show an excellent process-independent sticky film-forming ability through hydrogen-bonded cross-linked networks.30 Compared to the nonconjugated polymers with effective inter-mainchain entanglement and reversible cross-linked framework, the RCP chains tend to be rod-like and then are easily transferred to the edge of printed ink drop under capillary force of low viscous solution,31,32 causing severe CRE in film deposition. Therefore, enhancing the solution viscosity of RCPs is an effective method for suppressing the detrimental CRE. Supramolecular functionalization, such as introducing hydrogen bonds33,34 and reversible metal–ligand interactions35–37 into the molecules, has been developed to facilitate the intrinsic viscoelasticity of RCPs through reversible bond cleavage and dynamic binding sites formation. Moreover, the use of pendent conjugated units to tune the aggregate structures has been employed in other organic optoelectronic materials such as photovoltaic donor and acceptor.38,39 Here, we creatively prepared an RCP by a facile and universal supramolecular strategy to enhance the inter-chain non-covalent interactions through incorporating carbazole (Cz) groups into the side chains of diarylfluorenes, named poly[4-(6-(9H-carbazol-9-yl)hexyloxy)-9,9-diphenylfluorene]-co-[5-(6-(9H-carbazol-9-yl)hexyloxy)-9,9-diphenylfluorene] (PHDPF-Cz, Scheme 1c), exploiting its intrinsic viscoelasticity to suppress the CRE in droplet evaporation. Through systematic comparison with poly(9,9-dioctylfluorene) (PFO) and the specially designed poly[4-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene]-co-[5-(6-(9H-diphenylaniline-9-yl)hexyloxy)-9,9-diphenylfluorene] (PHDPF-DPA) (Scheme 1c and Supporting Information Figure S1), we demonstrate that Cz-containing side chains act as dynamic bonding moieties and facilitate the unique rheological property of PHDPF-Cz in viscous toluene solution. Entangled polymer chains and cross-linked aggregates of PHDPF-Cz are carried to the air-solvent interface instead of the liquid-solid contact line driven by the outward capillary flow, in sharp contrast to the "coffee-ring" aggregate (precipitation) generated from PHDPF-DPA and PFO solutions. The detailed process is described as follows: Gelation occurs first at the edge of the film due to the higher evaporation rate. The liquid film keeps gelling from edge to center, and the liquid phase region keeps shrinking. With the development of the gel structure, gelation tends to accelerate. The gradually forming gel structure in the liquid region can improve the viscosity and inhibit migration of polymer chains to the droplet edge, thus weakening the CRE (Scheme 1a, right). Therefore, it is an effective method for RCPs to suppress the CRE in printing plastic optoelectronics by supramolecular functionalization strategy. Scheme 1 | Design principle of the supramolecular strategy toward suppressing CRE in intrinsically viscoelastic RCP. (a) Schematic diagram of the evaporation process. Drop-coating of the supramolecular conjugated polymer (PHDPF-Cz) yields a relatively homogeneous cross-linked framework which deposits evenly upon droplet drying, while the traditional RCPs (model as PFO and PHDPF-DPA) result in a series of CREs due to the outward capillary flow during solvent evaporation. (b) Photographic images of PHDPF-Cz, PHDPF-DPA, and PFO drop-coated films under UV 365 nm lamp. It is easily observed that relatively continuous and homogeneous film is obtained for PHDPF-Cz but several coffee rings formed for PHDPF-DPA and PFO, suggesting the effectiveness of our strategy for suppressing CRE. Scale of substrate is approximately 1.5 cm × 1.5 cm. (c) Chemical structure of PHDPF-Cz, together with the control polymer, PHDPF-DPA. (d) Structural model for the ordered self-assembly of PHDPF-Cz cross-linked superstructure in condensed state. Download figure Download PowerPoint Experimental Methods Time resolved photoluminescence measurement For femtosecond optical spectroscopy, the laser source was a Coherent Legend regenerative amplifier (150 fs, 1 kHz, 800 nm) seeded by a Coherent Vitesse Integrated Oscillator (100 fs, 80 MHz). The 800 nm wavelength laser pulses were generated from the regenerative amplifier's output, whereas the 400 nm wavelength laser pulses were generated with a β-BaB2O4 (BBO) doubling crystal. The pump source were 500 nm laser pulses with pulse width of ∼50 fs that were generated from an optical parametric amplifier (OPerA Solo) coupled to a one-box integrated Ti-Sapphire amplifier (Coherent). The emission from the samples was collected at a back-scattering angle of 150° by a pair of lenses into an optical fiber that is coupled to a spectrometer (Acton, SP-2500i) to be detected by a charge coupled device (Princeton Instruments, Pixis 400B). Time-resolved photoluminescence (PL) was collected using an Optronis Optoscope streak camera system, which has an ultimate temporal resolution of ∼10 ps. Amplified spontaneous emission characterization The samples were optically pumped at 355 nm with the second harmonic of a femtosecond regenerative amplifier (Clark-MXR model CPA-1) delivering pulses of 150 fs duration at 1 kHz repetition rate. To optimize the measurements, the laser stripe was positioned on the sample parallel to the substrate edges. The PL arising from the edge of the waveguide was spectrally dispersed with a spectrometer (SP2500, Acton Research) equipped with a liquid nitrogen cooled back-illuminated deep depletion charge-coupled device (CCD) (Spec-10:400BR, Princeton Instruments). The pumping intensity was regulated with neutral density filters. Results and Discussion Physically cross-linked network of PHDPF-Cz In general, conventional conjugated polymers with rigid backbone have diverse π–π stacking and electrostatic interactions, and introducing flexible side chains with van der Waals forces and point-to-point non-covalent interaction is a universal strategy to optimize the post-processed film morphology.40–42 The inherent rigid feature of a conjugated backbone results in weak mainchain entanglement and extremely low solution viscosity, leading to rapid precipitation of aggregates upon solvent evaporation. In contrast to the rapid aggregate precipitation in supersaturated solutions, the cross-linked polymer network in precursor solution ensures film deposition evenly upon droplet drying. As shown in Scheme 1d, the π–π stacking interactions resulted from the pendant Cz units likely induced the formation of a cross-linked network in the PHDPF-Cz condensed structure. To confirm this, we also prepared the reference sample according to our previous method,43,44 named PHDPF-DPA, in which the pendent unit was replaced by diphenylamine (DPA) (Scheme 1c). The number-average molecular weight (Mn) of the reference polymer is 20 kDa, with a polydispersity index (PDI) of 2.6, which is similar to that of PHDPF-Cz in this work (Mn = 18 kDa, PDI = 2.1). The detailed synthetic procedure and molecular characterizations for the novel monomer and conjugated polymer are shown in Supporting Information Figures S1–S11. As shown by the single-crystal structures and packing patterns of PHDPF-Cz and PHDPF-DPA monomer displayed in Supporting Information Figure S12, pendant Cz has a rigid planar configuration, and the large torsion angle between the Cz and the alkyl chain is 114.52°. Remarkably, we observed a distinct π–π stacking structural arrangement with a plane-to-plane stacking distance of 2.803 Å, which indirectly demonstrated the possibility of intermolecular pendent Cz π–π stacking interactions in concentrated PHDPF-Cz. In contrast, a disordered packing pattern without a regular π–π stacking structure of DPA units is observed in the single-crystal structure of PHDPF-DPA monomer. The dihedral angle between the benzene rings of DPA is 71.96°, with a torsion angle of 119.64° between the linked bonds. Therefore, these π–π stacked Cz units possibly act as physical cross-links to induce the formation of the PHDPF-Cz multidimensional network and improve its gelation ability. As expected, the concentrated PHDPF-Cz toluene solution presented reversible aggregation-induced gelation upon aging for several minutes (>10 mg/mL, Supporting Information Figure S13), and no precipitation occurred at room temperature for months. However, the toluene solution of PHDPF-DPA maintained a relatively homogeneous state under the same conditions, and no gelation occurred even though the concentration increased up to 100 mg/mL ( Supporting Information Figure S14), indicating that the π–π stacking interactions derived from the pendant Cz units enable PHDPF-Cz chains to self-assemble into a physically cross-linked network, which is a prerequisite to suppress the CRE in evaporating droplets. To probe the chain self-organization behavior of PHDPF-Cz in this gelation process, dynamic light scattering (DLS) measurements were conducted on the aging solution of PHDPF-Cz (5 mg/mL) at 25 °C (Figure 1a). As the solution aged, the DLS curves gradually shifted to a longer relaxation time because of the formation of micrometer-sized aggregates, as manifested by the outermost DLS curve, similar to the chain rearrangement in printed ink droplet evaporation. For the pristine solution, the hydrodynamic radius (Rh) distribution displayed three modes, where the fast mode with an average Rh of ca. 15 nm is ascribed to the translational diffusion of individual PHDPF-Cz chains. The slow modes Rh = 100 nm and 1 μm are attributed to the loose entanglement and compact aggregation of the PHDPF-Cz mainchains, respectively. With prolonged aging, the modes with Rh values of 15 nm, 100 nm, and 1 μm disappeared entirely, and another slow relaxation mode with a larger Rh appeared. This phenomenon effectively revealed that the formation of a three-dimensional (3D) physical network results from π–π stacked Cz links. Subsequently, we conducted small-angle X-ray scattering (SAXS) measurements on the PHDPF-DPA and PHDPF-Cz solutions after aging for the same amount of time to obtain deep insights into the chain arrangement in semi-diluted solutions, as shown in Figure 1b. The power-law dependence of the SAXS intensity changed from q−0.8 in the PHDPF-DPA solution to q−3.6 in the PHDPF-Cz gel, indicating the formation of a 3D cross-linked network. To further examine the formation of the cross-linked network upon solvent evaporation (similar to printed processing), we investigated PHDPF-Cz xerogel morphology by scanning electron microscopy (SEM), typical images are shown in Figure 1c. Interestingly, we observed criss-cross oriented nanofibers in the enlarged area, whose width was approximately 20–30 nm. These results convinced us of the formation of a cross-linked network induced by pendant Cz π–π stacking interactions. In addition, we compared the X-ray diffraction (XRD) patterns of PHDPF-Cz and PHDPF-DPA drop-coated films, as shown in Supporting Information Figure S15. The PHDPF-Cz drop-coated film presented a well-defined diffraction at 2θ of 5.72° compared to the amorphous feature of the PHDPF-DPA film, and the interchain distance was approximately 15.4 Å according to Bragg's law (d = nλ/2sinθ), indicating that the Cz π–π stacking interactions favored the formation of a structurally ordered cross-linked network. Further proof was provided by wide-angle X-ray scattering (WAXS) (Figure 1d): the PHDPF-Cz xerogel exhibited more pronounced Bragg diffraction peaks than the PHDPF-DPA drop-coated film at scattering vectors (q) of 13.9 and 3.6 nm−1, revealing that the Cz functionalized polymer chains (PHDPF-Cz) tended to self-assemble into ordered and oriented nanowires. The π–π stacking distance between mainchains was 0.45 nm, and the lamellar packing distance (interchain distance) was approximately 1.7 nm, which is consistent with the value of 15.4 Å calculated from the XRD peak at 2θ of 5.72°. The distance at the diffraction peak q value of 8.8 nm−1 was 0.71 nm, corresponding to the length of a single fluorene (0.887 nm). Figure 1e shows the configuration of this ordered packing structure, where the polymer backbones present edge-on packing orientation on the substrate as well as π–π interacting Cz units (as cross-links) among the lamellar structures. According to traditional polymer physics, these nanoscale-oriented superstructures are beneficial in improving the toughness of materials. These results demonstrate that the pendant Cz groups facilitated the self-assembly behavior of PHDPF-Cz chains to obtain a relatively homogeneous cross-linked network in supersaturated solutions upon solvent evaporation. Figure 1 | Formation of supramolecular cross-linked network induced by the π–π stacking interactions of pendent Cz units upon solvent evaporation. (a) Normalized intensity correlation function, g2(t)-1, and the hydrodynamic radius (Rh) distribution of PHDPF-Cz toluene solution (5 mg/mL) as a function of aging at 25 °C. (b) The SAXS profile of PHDPF-Cz gelation solution and PHDPF-DPA dilute solution (10 mg/mL). In comparison with the PHDPF-DPA, ordered cross-linked nanostructures are obtained in PHDPF-Cz concentrated solution. (c) SEM images of PHDPF-Cz xerogel from toluene solution. Large-scale uniform cross-linked superstructures are obtained with solvent molecules evaporation, equivalent to droplet evaporation. (d) WAXS data for PHDPF-Cz xerogel and PHDPF-DPA drop-coated film. (e) The schematic representation of the macromolecular cross-linked structure in the oriented region. Download figure Download PowerPoint Rheological behavior of RCPs Viscosity is a crucial factor in evaluating the performance of ink in printed processing. Optimizing the solution viscosity can effectively inhibit capillary flow during solvent evaporation and further suppress the CRE in inkjet printing.45,46 The self-assembled criss-cross networks can be expected to positively affect the rheological behavior of PHDPF-Cz, in contrast to conventional RCPs. Here, we measured the intrinsic viscosity of PHDPF-Cz and PHDPF-DPA solutions under different conditions by rotational rheometry (Figures 2a and 2c). For the PHDPF-Cz solution, the viscosity first showed a gradual increase below a concentration of 15 mg/mL, which is a feature of non-interacting assemblies of constant size, mainly resulting from the intertwining polymer chains with weaker interchain interactions. Then, above this critical concentration (15 mg/mL), an apparent increase in the shear viscosity occurred, whereas that of the PHDPF-DPA solution exhibited a slight increase in the range of 1–30 mg/mL. From the logarithmic plots of the shear viscosity versus concentration at a shear rate of 25 s−1 (Figure 2b), we observed an abrupt slope increase in the fit curve of PHDPF-Cz. The critical association (gel) concentration (c*) was approximately 13 mg/mL, while no abrupt viscosity transition was observed for PHDPF-DPA. Because of the destruction of the π–π stacking interactions of Cz units under external shear force, the viscosity of PHDPF-Cz showed a more obvious shear thinning phenomenon, suggesting the characteristic behavior of a non-Newtonian fluid (Figure 2a). These differences effectively confirmed the formation of an interchain cross-linked supramolecular network instead of an individual chain in the PHDPF-Cz solution, in contrast to the weaker interchain secondary interactions among PHDPF-DPA chains. These can also reasonably explain the rapid aggregate precipitation and CRE of PHDPF-DPA in the supersaturated solution during droplet evaporation. Furthermore, the shear viscosity of PHDPF-Cz was clearly enhanced with prolonged aging, changing from 10−4 to 10−1 Pa•s after aging for whereas the viscosity of PHDPF-DPA showed a (Figures and This continuous of PHDPF-Cz ink viscosity in such a range is for controlling the outward capillary flow in solution processing In contrast, the viscosity range of PHDPF-DPA solution also a relatively movement of molecular chains and aggregates without attraction interactions or entanglement in the solution state. Therefore, the individual aggregates were to the drop contact line under the outward capillary force, resulting in a ring-like in the PHDPF-DPA, which is a phenomenon in conventional RCPs. With the solvent evaporation of an inkjet printing the concentration of the ink drop from the to the surface can be and this can also induce outward capillary flow and polymer chains to the this, the viscosity at the surface is for effectively suppressing the of polymer chains and aggregates to the contact From the cross-linked nanofibers at the air-solvent interface shown in the SEM images (Figure 1c), we that the π–π stacking interactions from the pendant Cz units are beneficial to uniform deposition of molecules and hence suppress the CRE during solvent evaporation. In addition, we measured the of the conjugated polymer solutions mg/mL) with different at room temperature ( Supporting Information Figure PHDPF-Cz and PHDPF-DPA showed a of The of the PHDPF-Cz solution increased with whereas that of PHDPF-DPA was indicating the energy in PHDPF-Cz cross-linked This was consistent with their shear viscosity, as displayed in Figure suggesting that the PHDPF-Cz solution displayed behavior than the PHDPF-DPA solution after attributed this to the gradual interaction of PHDPF-Cz driven by the supramolecular π–π stacking interaction of the Cz Figure | Rheological and viscosity property of PHDPF-Cz, together with the control PHDPF-DPA. (a) The shear viscosity of PHDPF-Cz and PHDPF-DPA in toluene solution at equivalent to the concentration in ink droplet evaporation. (b) The viscosity at the shear rate of 25 s−1 as function of the polymer concentration (c) The shear viscosity of PHDPF-Cz and PHDPF-DPA toluene solution mg/mL) at (d) The viscosity at shear rate of 25 s−1 for their toluene solution as a function of aging, and versus curves for the films of PHDPF-Cz and PHDPF-DPA on nm). of the and was conducted at three nm nm and nm respectively. The values of and with the of nm. Download figure Download PowerPoint Moreover, we the intrinsic of these conjugated polymer films with curves are shown in Figures and Compared to the control sample of PHDPF-DPA, the PHDPF-Cz film at the same and presented after the was Moreover, the curves of PHDPF-Cz presented The average and of PHDPF-Cz were and than of PHDPF-DPA = = (Figure Compared to the PHDPF-DPA PHDPF-Cz film presented higher ability and energy indicating its excellent Therefore, these results confirmed that the PHDPF-Cz film and due to pendent Cz π–π stacking interactions, thus this more to and This property of PHDPF-Cz film its self-assembled superstructure with physical upon external with the viscosity behavior in solution which is beneficial for the CRE. of the CRE of an individual or aggregate or particle to the contact line of a droplet is the prerequisite for the CRE during solvent evaporation. As by the above the criss-cross nanofibers in PHDPF-Cz drop-coated film leading to a distinct of ink viscosity, which can inhibit

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