Strong Electron Acceptor Research Articles

Electron-acceptor density adjustments for preparation conjugated polymers with NIR-II absorption and brighter NIR-II fluorescence and 1064 nm active photothermal/gas therapy

Designing conjugated polymers (CPs) with both efficient second near-infrared wavelength (NIR-II) fluorescence and NIR-II photothermal therapy performance remains a huge challenge, as the introduction of excessively strong electron donor and acceptor units significantly increase non-radiative decay. Herein, we describe an “electron acceptor density adjustment” strategy to address this problem, since a lower electron acceptor density in the conjugated polymer backbone can enhance the radiative rate constant and improve NIR-II fluorescence brightness. We used quaterthiophene (4T) with four repeated thiophene chain units and bithiophene (2 TC) modified with long alkyl side chains to reduce the electron acceptor density in the conjugated polymer backbone. The resultant 1064 nm absorption polymer, TTQ-2TC-4T displayed approximately 7.30-folds enhancement in NIR-II emission intensity compared to that of undoped TTQ-1T at the same mass concentration in toluene solution. Furthermore nanoparticles (TTQ-MnCO NPs) based on TTQ-2TC-4T and CO donors (Mn2(CO)10) were developed to realize NIR-II FI-guided 1064 nm laser-triggered NIR-II PTT/Gas synergistic therapy. The TTQ-MnCO NPs nanoparticles exhibited high photothermal conversion efficiency (η) of 44.43% at 1064 nm and high specific NIR-II fluorescence imaging of the cerebral vasculature of live mice. The in vivo results demonstrate that TTQ-MnCO NPs nanoparticles have excellent PTT/Gas synergistic therapeutic effects in MCF-7 tumor-bearing mice under 1064 nm laser irradiation. This study provides a new approach for optimizing both NIR-II fluorescence and NIR-II photothermal performance of NIR-II absorption conjugated polymers.

Self-wetting triphase photocatalysis for effective and selective removal of hydrophilic volatile organic compounds in air

Photocatalytic air purification is widely regarded as a promising technology, but it calls for more efficient photocatalytic materials and systems. Here we report a strategy to introduce an in-situ water (self-wetting) layer on WO3 by coating hygroscopic periodic acid (PA) to dramatically enhance the photocatalytic removal of hydrophilic volatile organic compounds (VOCs) in air. In ambient air, water vapor is condensed on WO3 to make a unique tri-phasic (air/water/WO3) system. The in-situ formed water layer selectively concentrates hydrophilic VOCs. PA plays the multiple roles as a water-layer inducer, a surface-complexing ligand enhancing visible light absorption, and a strong electron acceptor. Under visible light, the photogenerated electrons are rapidly scavenged by periodate to produce more •OH. PA/WO3 exhibits excellent photocatalytic activity for acetaldehyde degradation with an apparent quantum efficiency of 64.3% at 460 nm, which is the highest value ever reported. Other hydrophilic VOCs like formaldehyde that are readily dissolved into the in-situ water layer on WO3 are also rapidly degraded, whereas hydrophobic VOCs remain intact during photocatalysis due to the “water barrier effect”. PA/WO3 successfully demonstrated an excellent capacity for degrading hydrophilic VOCs selectively in wide-range concentrations (0.5−700 ppmv).

Organic dyads and triads based on the triphenylene-rylenediimide couple: Molecular design, self-organization, and photo-physical properties

Liquid-crystalline D-A dyads and A-D-A triads, based on the chemical association of electron-donor (D) triphenylene discogens and electron-acceptor (A) perylene/benzoperylene diimides, have been synthesized by the Pd-catalyzed Sonogashira coupling/DBU-promoted cyclization reactions tandem. These molecular heterojunctions spontaneously self-organize into columnar hexagonal (Colhex) or/and rectangular (Colrec) mesophases, over broad temperature ranges including room temperature, with the antagonist moieties segregated into alternated homo-molecular (homolithic) stacks within mixed columns. Their intramolecular electron and energy transfers have been studied by UV/Vis absorption and fluorescence emission spectroscopies. Due to photo-induced electron transfer between donor and acceptor units, fluorescence quenching is systematically observed for all the dyads and triads. This study further reveals that perylenediimide is a stronger electron acceptor than the larger benzoperylenediimide building block. Density function theory calculations of their molecular structures and HOMO-LUMO energy levels and gaps support the experimental results and demonstrate that these donor-acceptor systems have potential applications in various optoelectronic devices.

Aggregation-Induced Fluorogens in Bio-Detection, Tumor Imaging, and Therapy: A Review

Aggregation-Induced Fluorogens in Bio-Detection, Tumor Imaging, and Therapy: A Review

Approaching Ohmic hole contact via a synergetic effect of a thin insulating layer and strong electron acceptors

有效的电荷注入是发展低电压、高效率有机发光二极管 (OLEDs)的关键. 然而, 目前应用最广泛的空穴注入材料(HATCN) 的注入效率仅约10%, 无法满足高清显示和照明的需要. 因此, 我们 基于薄绝缘层(特氟龙(Teflon))和强电子受体(HATCN)的协同效 应设计了一种高效、通用的空穴注入技术. 研究表明特氟龙诱导 形成的纳米岛状结构有助于增强界面电场局域化, 搭配HATCN可 以实现高效的电荷产生和空穴注入. 新型的注入层(Teflon/HATCN)可实现近似欧姆接触的高效空穴注入, 其注入效率高达 80%以上. 基于该方法制备的红色磷光OLED的启亮电压仅为2.4 V, 最大外量子效率高达33.1%. 本文关于薄绝缘层和强电子受体的协 同效应的研究为发展高性能电荷注入材料提供了新策略.

Effectively controlling the ESIPT behavior and fluorescence feature of 2-(2′-hydroxyphenyl)-4-chloromethylthiazole by changing its π-conjugation: A theoretical exploration

Based on density functional theory (DFT) and time-dependent DFT (TD-DFT), the effects of π-conjugation on the excited-state intramolecular proton transfer (ESIPT) process and photophysical properties of 2-(2′-hydroxyphenyl)-4-chloromethylthiazole (HCT) have been studied. The strong electron acceptor with π-conjugated structure (MN1, MN2) have been chosen to analyze the changes of intramolecular H-bond, the frontier molecular orbital, the absorption/fluorescence spectrum and the energy barrier of ESIPT process. Our results show that the strong electron-withdrawing groups (MN1, MN2) weaken the intramolecular H-bond in the S1 state. The substitution effect on the H-bond strength in the S0 state is opposite. For MN1-HCT and MN2-HCT, both the forward and backward ESIPT reactions can occur. The normal and tautomer form can exist simultaneously in the S1 state. The absorption and fluorescent peaks of MN1-HCT and MN2-HCT all red-shift more than 150 nm due to the extended π-conjugated chain.

Influence of Consistency and Composition of Growth Medium on Surface Physicochemical Properties of Streptomyces

Streptomyces are known for their ability to produce various secondary metabolites used in biotechnology, human medicine and agriculture. Understanding of surface properties is very interesting in the control of interfacial phenomena. The objective of this study was to investigate the effect of consistency and composition of growth medium on the physicochemical properties of the surface of Streptomyces strains. To achieve this objective, Six Streptomyces strains belonging to bioprocess and bio-interfaces laboratory are cultivated in two media Bennett (rich) and GBA (minimum). Both media are tested in solid (agar) and liquid (broth) mode. The wettability θw, electron donor character ˠ (-), electron acceptor character ˠ (+) and Surface free energy ΔGiwi are determined using contact angle measurements. On the two solid media Bennett and GBA, Streptomyces strains develop a hydrophobic surface (96.9° <θw<167.9°) with a weak electron donor character (0.3 mJm-2 < (ˠ (-)) <12.14 mJm-2) and a strong electron acceptor character (0.26 mJm-2 < ˠ (+) < 17.8 mJm-2) and a negative surface free energy ((- 11.8 mJm-2) < ΔGiwi < (-110 mJm-2)). Whereas on both Bennett and GBA liquid media, the surfaces of Streptomyces strains are generally hydrophilic (1.3° < θw < 9.33°) with a strong electron donor character (13.76 mJm-2 < ( ˠ (-)) < 70.06 mJm-2) and a positive surface free energy. By changing the composition of the culture medium, only a slight change in the degree of hydrophobicity and surface free energy of Streptomyces is observed. Regarding the effect of medium composition on the surface properties of Streptomyces, the degree of wettability and the values of surface free energy are no longer the same when the composition of the medium changes. These results could be applied in further studies interested in interfacial phenomena and microbial adhesion in biotechnological fields.

Strong Electron Acceptor of a Fluorine-Containing Group Leads to High Performance of Perovskite Solar Cells.

Organic-inorganic hybrid perovskites have become one of the most promising thin-film solar cell materials owing to their remarkable photovoltaic properties. However, nonradiative recombination of carriers usually leads to inferior performance of perovskite (PVK) devices. Interface modification is one of the effective ways to improve separation of charges for perovskite solar cells (PSCs). Here, a small organic molecule of tetrafluorophthalonitrile (TFPN) is used to enhance the extraction and transportation of carriers at the PVK/hole transport layer (HTL) interface. The electron-rich C-F group effectively reduces the trap state density in the perovskite through chemical combination with the empty orbital of Pb2+ or other electron traps on the PVK surface, resulting in enhanced interface contact between the PVK and HTL. Meanwhile, the C≡N group in TFPN also inactivates the defects caused by Pb2+. The Fermi level of the perovskite shifts by 0.15 eV to its valence band due to the strong electron acceptor nature of the F atom, indicating that positive dipoles and p-type doping emerge, which validly suppress the recombination of carriers for the PVK film. Therefore, the optimized PSC shows the highest power conversion efficiency (PCE) of 22.82% compared to 19.40% for the control one. The champion FF reaches up to 81.2% (PCE 21.44%) due to the effectively enhanced carrier separation. In addition, the unencapsulated device shows enhanced stability under air conditions.

Intramolecular Photoinduced Charge Transfer and Recombination Dynamics in Vinylarene Terminated Organosilanes.

We report on charge-transfer dynamics of newly designed acceptor-donor-acceptor organosilanes, with a specific focus on how donor-acceptor combination and local chemical environment can be used to control the lifetime for intramolecular charge-separation between silane electron donors and organic acceptors. In this work linear oligosilanes were capped with arene-vinyl end groups of variable electron-accepting strength: weak (diester vinyl), intermediate (ester,cyano vinyl), and strong (dicyanovinyl). Ultrafast transient absorption spectroscopy was used to characterize their structure-dependent charge-transfer and recombination behaviors. All structures exhibit similar photoinduced ultrafast spectral dynamics that we ascribe to relaxation of the nascent charge-separated excited state followed by a return to the ground state via charge recombination. We find that relaxation of the nascent "hot" charge-separated excited state scales with the strength of dipole-dipole interactions between solvent molecules and the polar arene-vinyl acceptor. Furthermore, electron-accepting strength governs whether electronic coupling dictates charge recombination rate: weak acceptors produce charge-separated states that exhibit relatively large electronic coupling for back-electron transfer (approaching the adiabatic limit) that result in fast recombination, whereas the strong and moderate-strength acceptors support more stable charge-separated states with weaker coupling and longer lifetimes. We find that recombination rates increase substantially for structures with weak and moderate-strength acceptors in cyclohexane (i.e., negligible solvent reorganization energy), which we attribute to an increased electronic coupling in a nonpolar solvent environment where charge pairs are weakly screened. In contrast, for structures with strong electron acceptors, the very low reorganization energy of cyclohexane places back-electron transfer even further into the Marcus inverted regime, with a resultant increase in charge-separation lifetime. Together these results provide critical insights on how to tune photoinduced charge-transfer behavior in organic-inorganic hybrids that have potential material applications in molecular electronics and optoelectronics.

Starburst-Shaped D-π-A Chromophores Possessing a Hexaethynylbenzene Core for Dye-Sensitized Solar Cells.

Two starburst-shaped organic chromophores, incorporating a hexaethynylbenzene core modified by five donor branches (D-branches) of (p-dioctylaminostyryl)benzene and one acceptor/anchoring branch (A-branch) of either carboxylic acid-terminated phenylethynylbenzene (SB-07) or cyanoacrylic acid-terminated diketopyrrolopyrrole (DPP)-thiophene (SB-08), were synthesized and applied to dye-sensitized solar cells (DSSCs). In these chromophores, the common donor moiety, five (p-dioctylaminostyryl)phenyl groups, exhibits excellent optical absorption in the visible region (molar absorption coefficient ε > 105 M-1 cm-1 below 500 nm). The A-branch of SB-07 does not possess strong electron-accepting properties; however, the A-branch of SB-08, the DPP-thiophene moiety, serves as a strong electron acceptor site. Furthermore, the intramolecular charge-transfer (ICT) transition between the thiophene and DPP moieties extends the optical absorption range to the near-infrared region (∼800 nm). Optimized DSSC devices using SB-08 with coadsorption of chenodeoxycholic acid, in conjunction with iodide/triiodide-based electrolytes, exhibited incident photon-to-current conversion efficiency (IPCE) exceeding 70% in the 370-700 nm range and over 20% even at 800 nm, with a short-circuit photocurrent density (Jsc) of 19.3 mA cm-2 and a power conversion efficiency (PCE) of 6.4% under AM 1.5G illumination (100 mW cm-2). These results are considerably better than those of SB-07 (Jsc = 7.0 mA cm-2, PCE = 3.3%). The starburst-shaped architecture presented here can be used as a novel structural motif for metal-free organic sensitizers because it enables flexible modification of the multiple D-branches that enhance light-harvesting ability and the A-branch that serves as an excited electron transport pathway.

Polyoxometalates-Based Semi-flexible Metal-Semiconductor Triboelectric Nanogenerators for Low Frequency and Small Amplitude Mechanical Energy Harvesting.

The development of high-performance and low-cost durable triboelectric nanogenerators (TENGs) is essential for converting mechanical energy into electrical energy. Many organic polymer friction materials used widely have thermal stability problems, which makes TENGs with semiconductors as friction materials stand out. Here, we report a semi-flexible TENG based on metal and TiO2 modified by polyoxometalates (POMs) as pure inorganic friction materials. Six different POMs are firstly selected to modify the friction materials of TENGs, and the output performance of TENGs with different POMs-modified semiconductors and different metals as friction materials are tested. Compared with the unmodified TENGs, the open-circuit voltage (VOC ) of the optimal Ag-K6 P2 Mo18 O62 (P2 Mo18 )/TiO2 TENG device is increased by more than 4 times, which is mainly attributed to the strong electron-accepting and storage capabilities of POMs. This study has demonstrated that TENGs modified by POMs have potential application prospects and provided a new method for increasing the electrical output of TENGs.

Tuning the Fluorescence and the Intramolecular Charge Transfer of Phenothiazine Dipolar and Quadrupolar Derivatives by Oxygen Functionalization.

A series of new naphthalimide and phenothiazine-based push–pull systems (NPI-PTZ1–5), in which we structurally modulate the oxidation state of the sulfur atom in the thiazine ring, i.e., S(II), S(IV), and S(VI), was designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction. The effect of the sulfur oxidation state on the spectral, photophysical, and electrochemical properties was investigated. The steady-state absorption and emission results show that oxygen functionalization greatly improves the optical (absorption coefficient and fluorescence efficiency) and nonlinear optical (hyperpolarizability) features. The cyclic voltammetry experiments and the quantum mechanical calculations suggest that phenothiazine is a stronger electron donor unit relative to phenothiazine-5-oxide and phenothiazine-5,5-dioxide, while the naphthalimide is a strong electron acceptor in all cases. The advanced ultrafast spectroscopic measurements, transient absorption, and broadband fluorescence up conversion give insight into the mechanism of photoinduced intramolecular charge transfer. A planar intramolecular charge transfer (PICT) and highly fluorescent excited state are populated for the oxygen-functionalized molecules NPI-PTZ2,3 and NPI-PTZ5; on the other hand, a twisted intramolecular charge transfer (TICT) state is produced upon photoexcitation of the oxygen-free derivatives NPI-PTZ1 and NPI-PTZ4, with the fluorescence being thus significantly quenched. These results prove oxygen functionalization as a new effective synthetic strategy to tailor the photophysics of phenothiazine-based organic materials for different optoelectronic applications. While oxygen-functionalized compounds are highly fluorescent and promising active materials for current-to-light conversion in organic light-emitting diode devices, oxygen-free systems show very efficient photoinduced ICT and may be employed for light-to-current conversion in organic photovoltaics.

Preparation of novel and highly active magnetic ternary structures (metal-organic framework/cobalt ferrite/graphene oxide) for effective visible-light-driven photocatalytic and photo-Fenton-like degradation of organic contaminants

Herein, MIL-101(Fe), CoFe2O4, novel binary (MIL-101(Fe)/CoFe2O4, MIL-101(Fe)/GO and CoFe2O4/GO), and ternary (MIL-101(Fe)/CoFe2O4/(3%)GO and MIL-101(Fe)/CoFe2O4/(7%)GO) magnetic composites based upon the MIL-101(Fe) were synthesized. The XRD, FESEM, TEM, EDX, BET-BJH, FTIR, VSM, DRS, PL, EIS and other electrochemical analyses were applied to characterize samples. The MIL/CoFe2O4/(3%)GO demonstrated the best performance compared to other samples for visible light photocatalytic and photo-Fenton-like degradation of Direct Red 23 (DtR-23), Reactive Red 198 (ReR-198) dyes as well as Tetracycline Hydrochloride (TC-H) antibiotic. Degradation of dyes using the ternary composite after 70 min of visible light irradiation was greater than that of 99%. The presence of the optimum GO as a strong electron acceptor in MIL/CoFe2O4/(3%)GO not only led to the effective separation of charge carriers and thus reduction of their recombination but also increased the absorption of visible light. The composite possessed good durability in terms of stability and reusability. The PL, EIS and electrochemical analyses indicated that the MIL/CoFe2O4/(3%)GO improved the optical properties and photocatalytic performance.

Electrochemical properties and optical response of cadmium selenide quantum dot film electrodes

Electrochemical charge/discharge mechanisms in the electrophoretically deposited CdSe quantum dot (QD)film electrodes in NBu4PF6 acetonitrile solution have been investigated. The films were deposited from CdSe colloidal solution in nitrobenzene at variable QD size (diameter) from 3.4 to 6.3 nm onto transparent conducting glass substrates. Electrochemical behavior and optical response were characterized by cyclic voltammetry (CV) and in situ absorption spectroscopy. Electrochemical charging under an inert gas atmosphere results in a reversible color change (electrochromism), due to the bleach of exciton absorption with 0.3 optical density changes. The mechanism of electrochemical charging comprises electron transfer from conducting substrate to QD, interparticle transfer and also electron capturing by acceptors in solution. The introduction of a strong electron acceptor (O2) into the solution results in a suppression of electrochromism. The influence of oxygen is rather reversible which is observed from recovered electrochromic behavior after electrolyte resaturation with argon.

Electronic Characterization of a Charge-Transfer Complex Monolayer on Graphene.

Organic charge-transfer complexes (CTCs) formed by strong electron acceptor and strong electron donor molecules are known to exhibit exotic effects such as superconductivity and charge density waves. We present a low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) study of a two-dimensional (2D) monolayer CTC of tetrathiafulvalene (TTF) and fluorinated tetracyanoquinodimethane (F4TCNQ), self-assembled on the surface of oxygen-intercalated epitaxial graphene on Ir(111) (G/O/Ir(111)). We confirm the formation of the charge-transfer complex by dI/dV spectroscopy and direct imaging of the singly occupied molecular orbitals. High-resolution spectroscopy reveals a gap at zero bias, suggesting the formation of a correlated ground state at low temperatures. These results point to the possibility to realize and study correlated ground states in charge-transfer complex monolayers on weakly interacting surfaces.

A review of wastewater bacterial bio oxidation: mechanisms, reactions, and behaviors

The most overlooked biological process is the oxidation process, due to the poor technical understanding of bioremediation and the many unexplained biological mechanisms. As a matter of fact, wastewater companies favor the physical and chemical approaches over the biological means to ensure process performance. Biological oxidation provides environmentally friendly treatment with limited operational requirements. It has a tremendous ability to metabolize ammonia, H2S, phosphate, and ferrous iron under the right conditions. Bacterial communities attack these wastewater components through using oxygen as a strong electron acceptor, resulting in simplified forms of wastewater components (e.g., ammonia to nitrogen gas). This manuscript reviews in details the mechanisms of wastewater bacteria against various pollutants, with the possible reactions and behaviors. It also presents the benefits of utilizing wastewater microorganisms against different pollutants.

Difluorodithieno[3,2-a:2′,3′-c]phenazine as a strong acceptor for materials displaying thermally activated delayed fluorescence or room temperature phosphorescence

A novel strong electron-acceptor unit, 9,10-difluorodithieno[3,2-a:2′,3′-c]phenazine (DTPz), is synthesized and applied in the design of two donor-acceptor type emitters displaying long-lived delayed emission. Using either 9,9-dimethyl-9,10-dihydroacridine (DMAC) or triisopropyl-substituted benzo[1,2-b:4,5-b']dithiophene (BDT-TIPS) as the donor component, push-pull type chromophores exhibiting charge-transfer emission are obtained and found to afford either thermally activated delayed fluorescence (TADF) for DMAC or room temperature phosphorescence (RTP) for BDT-TIPS.

Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push–pull electronic systems: Experimental and quantum chemical study

Electronic interactions in donor-π-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push–pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and 13C NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push–pull character of barbituric acid derivatives was performed by the 13CNMR chemical shift differences, Mayer π bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push–pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor.

Controlling Energy Gaps of π-Conjugated Polymers by Multi-Fluorinated Boron-Fused Azobenzene Acceptors for Highly Efficient Near-Infrared Emission.

We demonstrate that multi-fluorinated boron-fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor-acceptor (D-A) type π-conjugated polymers. Position-dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near-infrared (NIR) emission (λPL =758-847 nm) with high absolute photoluminescence quantum yield (ΦPL =7-23%) originating from low-lying LUMO energy levels of the BAz moieties (-3.94 to -4.25 eV). Owing to inherent solid-state emissive properties of the BAz units, deeper NIR emission (λPL =852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D-A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron-accepting unit through fine-tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials.

The Influences of Sulfoxide Electron Traps in Transparent Polyimides with Low Retardation, Yellow Index, and CTE

AbstractDue to the development of dynamic flexible organic light‐emitting diode displays, colorless polyimides (CPI) as the supporting or protecting optical films, are facing significant challenges due to the requirements of optical, mechanical, thermal, and chemical properties. Typical CPIs are derived from TFDB (2,2‐bis(trifluoro‐methyl)‐4,4′‐diaminobiphenyl)/6FDA (4,4′‐(hexafluoroisopropylidene)diphthalic anhydride), which still need to be improved in both dimensional stability and optical performance. In this communication, a strong electron acceptor group, the sulfoxide bond, is first introduced into the TFDB block of CPI chains. Based on this introduction, the distribution of the electron cloud in the polymer chain is reconstructed under the strongly pulling electron effect, and the spatial conformation of the polymer chain is also affected by the rigid and twisted sulfoxide group. The influences on CPI's optical properties, especially the refractive index and the retardation, are studied and discussed in detail by experimental results and theoretical calculations. It is shown that the CPI with the sulfoxide group exhibits higher optical transparency, lower yellow index, phase retardation and coefficient of thermal expansion, which is an ideal material for CPI optical films.