Morphological and impedance studies on electropolymerized 3,4-(2,2-dibenzylpropylenedioxy)thiophene nanostructures on micron sized single carbon fiber

Micron sized single carbon fibers were cyclovoltammetrically coated with poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] resulting in a nanofiber network at the surface. The method provides conjugated polymer nanostructures covalently and uniformly bound to micron sized substrates. When the electropolymerization is carried out with different electrolytes in acetonitrile the dopant influences the structure of the coating layer what is proved by electrochemical impedance spectroscopy and electron microscopy. Electrodes based on poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] on single carbon fiber microelectrodes (SCFMEs) prepared in Bu₄NPF₆/ACN show the best capacitance performance due to their higher surface area. The improvement is attributed to the formed nanofiber network structure which results in a more efficient charge transport and collection.Impedance spectra show the typical form of Z_IM vs. Z_RE curves for transmission-line at a frequency of 10 Hz, with transition to almost pure capacitive behavior up to 10 MHz. Equivalent circuit modeling was simulated for the electrolyte/polymer film/SCFME system. A good agreement was achieved for the calculated capacitances in comparison with the experimental EIS measurement results.     

An electrochromic diquat-quaterthiophene alternating copolymer: A polythiophene with a viologen-like moiety in the main chain

A bis-bithiophenyl derivative of diquat, 3,10-bis(2,2′-bithiophene-5-yl)-6,7-dihydropyrido[1,2-a:2′,1′-c]pyrazinodiynium hexafluorophosphate (bt2dq), was synthesized by quaternization of 5,5″-bis(2,2′-bithiophene-5-yl)-2,2′-bipyridine with 1,2-dibromoethane. Its UV–vis absorption spectrum is explained by TD-DFT calculations. It shows the electrochemical properties characteristic for bipyridinium salts (viologens and diquats) and can be electropolymerized to form a conjugated polymer composed of alternating quaterthiophene and diquat blocks. The polymer has been characterised by cyclic voltammetry and UV–vis spectroelectrochemistry: it can be reversibly oxidized, with spectral signs of p-doping of the oligothiophene blocks, and reversibly reduced, with formation of viologen-like cation radicals, which dimerize or form π-stacks.     

Extraction Equilibria of Trimellitic and [ 1,1′-Biphenyl]-2,2′-dicarboxylic Acid with 1-Octanol, 50%TBP,and 10%TRPO in Kerosene

To explore the feasibility of extracting aromatic acid products from oxidizing coal, two aromatic acids, trimellitic and [1,1′-biphenyl]-2,2′-dicarboxylic acid, were selected as the solutes, and the extraction equilibrium of the acids were studied with 1-octanol, 50% tributyl phosphate （TBP） in kerosene, and 10% trialkylphosphine oxide （TRPO） in kerosene. The results showed that the degree of extraction of [1,1′-biphenyl]-2,2′-dicarboxylic acid was larger than that of trimellitic acid for all of the solvent, and the extraction capacity with TRPO is more effective than the one with TBP. The extraction behavior of aromatic polyacid is different from that of carboxylic acid, and the reactive extraction function of aromatic acids with TBP and TRPO is not as effective as that of carboxylic acid. 1-octanol could be used to remove [1,1′-biphenyl]-2,2′-dicarboxylic acid from the mixture of trimellitic acid and [1,1′-biphenyl]-2,2′-dicarboxylic acid. Because the weak hydrogen bond association exists between -OH in 1-octanol and -COOH in aromatic acid, the extractive selectivity of [ 1, 1′-biphenyl]-2,2′-dicarboxylic to trimellitic acid depends on the stoichiometric ratio.     

Efficiency of ligands in atom transfer radical polymerization of lauryl methacrylate and block copolymerization with methyl methacrylate

Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 °C. The ligands used were 2,2′-bipyridyl,4,4′-dimethyl-2,2′-bipyridyl, N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) and N-(n-propyl)-2-pyridylmethanimine (PPMI). Controlled polymerization was observed with PMDETA and PPMI ligands and poly(LMA)s with narrow molecular weight distribution (MWD) (M_w/M_n≤1.2) were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order time-conversion plot with a small induction period (∼10 min) was observed in the presence of PPMI ligand. Di-block copolymers of LMA and methylmethacrylate with controlled molecular weight and narrow MWDs were synthesized via sequential monomer addition.     

Alternating copolymers of oligoarylenes and naphthalene bisimides as low band gap semiconductors: Synthesis, electrochemical and spectroelectrochemical behavior

Three novel electroactive copolymers, consisting of alternating naphthalene bisimide and oligoarylene segments have been synthesized and studied by cyclic voltammetry and UV–vis-NIR spectroelectrochemistry. These studies show that the conjugation between both copolymer segments is very weak and the reduction of the bisimide part is essentially uninfluenced by the oligoarylene segment. The oxidation of the oligoarylene segment strongly depends on its length but is not affected by the presence of the bisimide part. The HOMO levels, determined electrochemically are systematically below −5.0 eV with respect to the vacuum level, changing from −5.45 eV for poly[1,4-phenylene-(4,3′(4′),3″-trioctyl-2,2′,5′,2″-terthiophene-5,5″-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (6) to −5.50 eV in poly[1,4-phenylene-(4,4′-dioctyl-2,2′-bithiophene-5,5′-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (5) and −5.84 eV for poly[1,4-phenylene-(3,4-dioctylthiophene-2,5-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (4). The LUMO levels in all three cases are close to −4.0 eV. The obtained results clearly indicate that 5 and 6 are good candidates for the fabrication of ambipolar transistors operating in air whereas 4 can be considered as an active component of n-channels FETs.     

Fine tuning of frontier orbital energy levels in dithieno[3,2-b:2′,3′-d]silole-based copolymers based on the substituent effect of phenyl pendants

A series of dithieno[3,2-b:2′,3′-d]silole-based π-conjugated copolymers containing thieno[3,4-c]pyrrole-4,6-dione or thieno[3,4-b]thiophene units bearing 4-substituted phenyl pendants were synthesized and their thermal stability, optical properties and frontier orbital energy levels were systematically investigated. The introduction of electron-withdrawing substituents on the phenyl rings lowered their frontier orbital energy levels without deteriorating their thermal and optical properties. By replacing an electron-donating methoxy group with an electron-withdrawing trifluoromethyl group, both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital energy levels of the polymers were deepened by more than 0.3 eV. A relatively linear relationship was observed between the HOMO energy levels and the Hammett substituent constants.     

Morphological and impedance studies on electropolymerized 3,4-(2,2-dibenzylpropylenedioxy)thiophene nanostructures on micron sized single carbon fiber

Micron sized single carbon fibers were cyclovoltammetrically coated with poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] resulting in a nanofiber network at the surface. The method provides conjugated polymer nanostructures covalently and uniformly bound to micron sized substrates. When the electropolymerization is carried out with different electrolytes in acetonitrile the dopant influences the structure of the coating layer what is proved by electrochemical impedance spectroscopy and electron microscopy. Electrodes based on poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] on single carbon fiber microelectrodes (SCFMEs) prepared in Bu₄NPF₆/ACN show the best capacitance performance due to their higher surface area. The improvement is attributed to the formed nanofiber network structure which results in a more efficient charge transport and collection.     

Synthesis of stretchable polyetherimides containing multiple alkyl side chains

Two series of diamine monomers, i.e., 4-[3,4,5-tris(n-alkan-1-yloxy)benzyl]-3,5-diaminobenzoate and 2,2′-bis{4-[3,4,5-tris(n-alkan-1-yloxy)benzoate]}-4,4′-biphenyldiamines containing multiple alkyl side chains, were synthesized in which the length of the alkyl side chains was varied from 5 to 18 ethylene units. Polyetherimides (PEIs) were prepared from these two diamines and bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydrides (BisADA) using a one-step method in 1-chloronaphthalene. All the polymers possessed good solubility in chlorinated solvents. The high-molecular weight PEIs could be solution cast into transparent, tough films. The polymers containing the side chains which were at least 16 methylene units could be crystallized. The melting points of the crystals increased as the length of the side chains increased. The glass transition temperatures (T_gs) of the PEIs decreased as the length of the side chains increased due to an internal plasticizing effect of the alkyl side chains. The PEIs containing multiple alkyl side chains showed excellent drawability with much higher elongations but lower tensile strengths and moduli compared with the commercial PEI, Ultem^® 1000. The film's in-plane refractive index parallel to the drawing direction (n_//) increased and its in-plane refractive index perpendicular to the drawing direction (n_⊥) decreased during drawing mainly due to the orientation of main chains in the drawing direction. The film's in-plane birefringence increased with the drawing ratios.     

Synthesis, characterization and fluorescence adjustment of well-defined polymethacrylates with pendant π-conjugated benzothiazole via atom transfer radical polymerization (ATRP)

Two compounds containing the benzothiazole moiety, 4-(2-benzothiazole-2-yl-vinyl)-phenyl methacrylate (BVMA) and 2-bromo-2-methyl-propionic acid 4-(2-benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) were synthesized. Atom transfer radical polymerization (ATRP) of BVMA was conducted at 60 °C using BPBVE and CuBr/2,2′-bipyridine (BPY) as initiator and catalyst, respectively. Chain extension with 4-methacryloxy-hexyloxy-4′-nitrostilbene (MHNS) was conducted using PBVMA as the macroinitiator. The homopolymer PBVMA in DMF solution emitted blue fluorescence, and the copolymer PBVMA-b-PMHNS emitted orange fluorescence at about 610 nm due to the intramolecular energy transfer. ATRP of BVMA was also conducted using 2-bromo-2-methyl-propionic acid 4-nitrostilbene-hexyloxy ester (BPNHE) as an initiator. The obtained polymer was characterized via ¹H NMR and the fluorescence intensity was found to change with increasing number average molecular weight (M_n). The polymer with M_n = 15900 emitted white fluorescence in DMF solution.     

Synthesis and properties of cyclopentadithiophene-based poly(silarylenesiloxane) derivatives

Poly(silarylenesiloxane) derivatives with 4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene moiety, bearing dimethyl- (P1), methylphenyl- (P2) and diphenyl- (P3) substituents on silyl moieties, were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,6-bis(dimethylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M1), 2,6-bis(methylphenylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M2), and 2,6-bis(diphenylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M3), respectively. P1-P3 exhibited the good solubility in common organic solvents, such as benzene, toluene, chloroform, dichloromethane, THF, and so on. The glass transition temperatures (T_gs) of P1, P2 and P3 were determined by differential scanning calorimetry to be 56, 97 and 137 °C, respectively, depending on the substituent on the silyl moieties. No melting temperatures (T_ms) of P1, P2 and P3 were observed, suggesting the obtained P1-P3 are amorphous polymers. The temperatures at 5% weight loss (T_d5s) of P1, P2 and P3 were 460, 459 and 479 °C, respectively, indicating that the larger number of phenyl group on the silyl moieties resulted in the better thermostability. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing silyl substituents onto 4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene moiety. In addition, the bathochromic shift of the maximum absorption (λ_abs) and the increase in the fluorescence quantum yield (Φ_F) were observed by the introduction of phenyl group onto the silyl moieties.     

Theoretical studies on the electronic and optical properties of two thiophene-fluorene based π-conjugated copolymers

The low PL quantum efficiency, typically 1-3%, in solid film, limits the application of polythiophene and derivatives (PTs) in PLEDs. The six-member aromatic rings polyfluorenes (PFs) with higher PL efficiencies have been introduced into the backbone of PTs, in an effort to develop highly efficient, desirable charge carrier transporting and low energy gap thiophene-fluorene based light-emitting polymers. In this contribution, quantum-chemical techniques are employed to study two fluorene-thiophene incorporated π-conjugated polymers, namely, poly((5,5-E-α-(2-thienyl)methylene)-2-thiopheneacetonitrile)-alt-2,7-(9,9-dimethylfluorene) (PFTCNVT) and poly((5,5″-(3′,4′-dimethyl-2,2′;5′,2″-terthiophene1′,1′-dioxide))-alt-2,7-(9,9-dimethylfluorene)) (PFTORT). Density functional theory (DFT) and time-dependent DFT approaches are employed to study the neutral molecules, positive and negative ions, the IPs and EAs, HOMO-LUMO gaps (Δ_H-L), as well as the lowest excitation energies (E_gs). It is interesting to note that the two copolymers PFTCNVT and PFTORT are superior to the properties of pristine polyfluorene (PF) and polythiophene (PT). In addition to the improved PL efficiency, they still presented lower energy-gap comparable to PTs. Furthermore, the LUMO energies lower about 1.4 eV and thus the EAs increase around 1.4 eV in PFTCNVT and PFTORT compared with PFs, suggesting the significant improved electron-accepting and transporting abilities in the two copolymers. These properties can be explained by the presence of more electron-accepting thiophene units in the repeated unit of the copolymers and the more planar conformations in the two copolymers under study.     

TiO2 films prepared by micro-plasma oxidation method for dye-sensitized solar cell

Nanocrystalline TiO₂ films are widely investigated as the electrodes of dye-sensitized solar cell(s) with different preparation methods. In this paper, thin titanium dioxide films have been prepared on titanium plates by the micro-plasma oxidation method in the sulfuric acid solution. The thin TiO₂ films were sensitized with a cis-RuL₂(SCN)₂·2H₂O (L = cis-2,2′-bipyridine-4,4′-dicarboxylic acid) ruthenium complex and implemented into a dye-sensitized solar cell configuration. The influence of reaction current density (10, 15, 20, 25 and 30 A dm⁻²) on the structural and the surface morphology of the films was investigated by X-ray diffraction, scanning electron microscopy, atom force microscopy and X-ray photoelectricity spectroscopy. Impedance analysis for dye-sensitized solar cells was carried out by electrochemical impedance spectroscopy. The results show that the rise of current density leads to the increase in the amount of rutile and the thickness of the TiO₂ film, which makes the TiO₂ films have different photovoltages and photocurrents. The relatively higher photoelectricity properties were obtained in the TiO₂ films prepared at a current density of 20 A dm⁻². The open-circuit voltage and the short-circuit current are 605 mV and 165 μA cm⁻², respectively.     

Dispersion polymerization of N-vinylcarbazole using siloxane-based and fluorine-based surfactants in compressed liquid dimethyl ether

Spherical poly(N-vinylcarbazole) (PVK) was synthesized by dispersion polymerization of N-vinylcarbazole (NVCA) in compressed liquid dimethyl ether (DME) using siloxane-based (PDMS-g-pyrrolidone carboxylic acid) (Monasil PCA™) and fluorine-based (poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate)) (poly(HDFDMA)) polymers as surfactants and 2,2′-azobisisobutyronitrile (AIBN) as the initiator. Spherical and relatively uniform PVK particles can be produced even at 20 bar.     

A stability comparison of redox-active layers produced by chemical coupling of an osmium redox complex to pre-functionalized gold and carbon electrodes

The production of stable redox active layers on electrode surfaces is a key factor for the development of practical electronic and electrochemical devices. Here, we report on a comparison of the stability of redox layers formed by covalently coupling an osmium redox complex to pre-functionalized gold and graphite electrode surfaces. Pre-treatment of gold and graphite electrodes to provide surface carboxylic acid groups is achieved via classical thiolate self-assembled monolayer formation on gold surfaces and the electro-reduction of an in situ generated aryldiazonium salt from 4-aminobenzoic acid on gold, glassy carbon and graphite surfaces. These surfaces have been characterized by AFM and electrochemical blocking studies. The surface carboxylate is then used to tether an osmium complex, [Os(2,2′-bipyridyl)₂(4-aminomethylpyridine)Cl]PF₆, to provide a covalently bound redox active layer, E^0′ of 0.29 V (vs. Ag/AgCl in phosphate buffer, pH 7.4), on the pre-treated electrodes. The aryldiazonium salt-treated carbon-based surfaces showed the greatest stability, represented by a decrease of <5% in the peak current for the Os(II/III) redox transition of the immobilized complex over a 3-day period, compared to a decrease of 19% and 14% for the aryldiazonium salt treated and thiolate treated gold surfaces, respectively, over the same period.     

Synthesis and electrochemical characterization of bis(3,4-ethylene-dioxythiophene)-(4,4′-dinonyl-2,2′-bithiazole) comonomer

The synthesis and characterization of a novel donor acceptor donor type bis(3,4-ethylene-dioxythiophene)-(4,4′-dinonyl-2,2′-bithiazole) comonomer and its electrochemically prepared polymer on carbon fiber, Pt button and ITO plate is reported in this paper. Cyclic voltammetry of the polymer in 0.1 M Et₄NBF₄/CH₂Cl₂ exhibits a very well defined and reversible redox processes and this co-monomer can be either p-doped or n-doped. The half-wave oxidation potentials of the polymer (E_1/2) were observed at 0.303 and 0.814 V versus Ag/AgCl. The polymer is electrochromic; the onset for the π-π^* transition (E_g) of 1.75 eV with a λ_max at 2.15 eV and the homogeneous and high quality film of the polymer is stable of its optical properties offering fast switching time which is less than 0.25 s. The morphological studies reveal that the polymer was deposited as a continuous and very well adhering film to surface of the carbon fiber microelectrode. All these properties make this polymer favorable for use in electronic devices.     

Adsorption of camphor and 2,2′-bipyridine on Bi(1 1 1) electrode surface

Impedance spectroscopy and in situ STM methods have been used for investigation of the camphor and 2,2′-bipyridine (2,2′-BP) adsorption at the electrochemically polished Bi(1 1 1) electrode from weakly acidified Na₂SO₄ supporting electrolyte solution. The influence of electrode potential on the adsorption kinetics of camphor and 2,2′-BP on Bi(1 1 1) has been demonstrated. In the region of maximal adsorption, i.e. capacitance pit in the differential capacitance versus electrode potential curve, the heterogeneous adsorption and diffusion steps are the rate determining stages for camphor and 2,2′-BP adsorption at the Bi(1 1 1) electrode. It was found that for camphor | Bi(1 1 1) interface the stable adsorbate adlayer detectable by using the in situ STM method has been observed only at the positively charged electrode surface, where the weak co-adsorption of SO₄²⁻ anions and camphor molecules is possible. At the weakly negatively charged Bi(1 1 1) electrode surface there are only physically adsorbed camphor molecules forming the compact adsorption layer. The in situ STM data in a good agreement with impedance data indicate that a very well detectable 2,2′-BP adsorption layer is formed at Bi(1 1 1) electrode in the wide region of charge densities around the zero charge potential.     

An effective multipurpose building block for 3D electropolymerisation: 2,2′-Bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene

Novel thiophene-based oligomer, 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene (TX), was designed and synthesized, and its electrochemical and spectral properties characterised. TX was readily polymerised electrochemically to form well organized conducting homopolymer films on various solid electrode substrates. Moreover, it was successfully used for deposition by electropolymerisation of electrochemically active thin films of co-polymers with three different monomers of functionalised bis(2,2′-bithienyl)methane derivatives. It appeared that TX was an effective crosslinker and 3D promoter in these electropolymerisations involving co-monomers intrinsically showing limited aptitude for the electropolymerisation or forming polymer films of low conductivity. This attractive TX ability stems from combination of its (i) high conjugation efficiency in each of the two planar moieties, (ii) intrinsic 3D structure on account of the presence of the central node, and (iii) intrinsic regioselectivity in electropolymerisation on account of the positions of the two available free α-thiophene sites.     

Synthesis of poly(1,4-naphthylene) bearing crown ether side chain by asymmetric oxidative coupling polymerization

The oxidative coupling polymerization of racemic-, (R)-, and (S)-2,2′,3,3′-tetrahydroxy-1,1′-binaphthyl derivatives bearing a crown ether moiety was carried out in the presence of a Cu(I) or Cu(II) catalyst with various ligands, such as N,N,N′,N′-tetramethylethylenediamine, (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine, (−)-sparteine [(−)Sp], and (S)-(−)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline). Methanol-insoluble poly(binaphthyl crown ether) with a molecular weight up to M_n=4.1×10³ was synthesized in moderate yields. Polymerization using (−)Sp proceeded in an S-selective manner; the polymer with the highest negative specific rotation was obtained with the (S)-monomer. The obtained polymers exhibited characteristic abilities for chiral recognition toward amino acids, such as 2-phenylglycine hydrochloride and 2-phenylglycine methyl ester hydrochloride.     

Electrochromic performance and ion sensitivity of a terthienyl based fluorescent polymer

A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents directly attached to the 3,4-positions of the central thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(3,4-ethylenedioxythiophen-2-yl)thiophene-3,4-dicarboxylate. The corresponding polymer was characterized by cyclic voltammetry, FT-IR and UV–vis spectroscopy. The polymer has a well-defined redox process (E_p,1/2 = 0.74 V) and demonstrates a reversible electrochromic behavior; lilac in the neutral state and transparent sky blue in the oxidized state. Also, the polymer had low band gap (E_g = 1.82 eV) and high redox stability (retaining 94.0% of its electro-activity after 500th switch). Moreover, the sensitivity of both the monomer and its polymer towards metal cations was investigated by monitoring the change in the fluorescence intensity. Among various common ions both the monomer and its polymer were found to be selective towards Cu²⁺ and Cu⁺ ions by quenching the fluorescence efficiency with a Stern–Volmer constant (K_sv) of (1.4–1.6 × 10³ M^?1) and (1.5–1.8 × 10² M^?1) for monomer and polymer solutions, respectively.     

Fluorinated phenylethynyl-terminated imide oligomers with reduced melt viscosity and enhanced melt stability

Two novel fluorinated phenyethynyl-contained endcapping agents, 4-(3-trifluoromethyl-1-phenylethynyl)phthalic anhydride (3F-PEPA) and 4-(3,5-bistrifluoromethyl-1-phenylethynyl)phthalic anhydride (6F-PEPA) were synthesized, which were employed to synthesize two fluorinated model compounds, N-phenyl-4(3-trifluoromethyl)-phenylethynylphthalimide (3F-M) and N-phenyl-4(3,5-bitrifluoromethyl)-phenylethynyl phthalimide (6F-M). The thermal cure kinetics of 3F-M and 6F-M were analyzed using DSC and compared to the unfluorinated derivative, N-phenyl-4-phenylethynylphthalimide (PEPA-M). The thermal cure temperatures of 3F-M and 6F-M were 399 and 412 °C, which were 22 and 35 °C higher than that of PEPA-M, respectively. The thermal cure kinetics of 3F-M and 6F-M best fit a first-order rate law, although 3F-M and 6F-M reacted slower than PEPA-M. However, the exothermic enthalpy of 3F-M and 6F-M were only half of PEPA-M. Based on the model compounds study, a series of fluorinated phenylethynyl-terminated imide oligomers (F-PETIs) with different calculated molecular weights (Calc'd M_n) were synthesized by thermal polycondensation of 2,3,3′,4′-biphenyltetracarboxylic acid dianhydride (a-BPDA) and 3,4′-oxydianiline (3,4′-ODA) using 3F-PEPA or 6F-PEPA as the endcapping agent. The substituent effects of the trifluoromethyl (−CF₃) groups on the thermal cure behavior and melt processability of F-PETIs were systematically investigated. Experimental results reveal that the melt processability of F-PETI was apparently improved by the reduced resin melt viscosities and the enhanced melt stability due to the incorporation of the −CF₃ groups in the imide backbone. All of those F-PETIs exhibit outstanding thermal and mechanical properties.