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Chorngshyan Chern - One of the best experts on this subject based on the ideXlab platform.

  • mechanisms and kinetics of non isothermal polymerization of n n bismaleimide 4 4 diphenylmethane with Barbituric Acid in dimethyl sulfoxide
    Thermochimica Acta, 2019
    Co-Authors: Quocthai Pham, Yuxuan Zhan, Fuming Wang, Chorngshyan Chern
    Abstract:

    Abstract Mechanisms and kinetics of non-isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) with Barbituric Acid (BTA) in dimethyl sulfoxide (DMSO) were investigated. The polymerization of BMI with BTA in DMSO was characterized by using differential scanning calorimeter (DSC), electron spin resonance (ESR) and 1H-NMR techniques. The polymerization was primarily governed by the Michael addition reaction and aza- Michael addition reaction mechanisms. By contrast, free radical polymerization mechanism of BMI/BTA could be ruled out in DMSO medium. Model-free (isoconversional) method in combination with model-fitting method were used to determine triplet kinetic parameters for the polymerization of BMI with BTA in DMSO. Average activation energy (Eα) and pre-exponential factor (Aα) were ca. 51 kJ  mol−1 and 1.33 × 106 min−1 in the fractional conversion (α) range 0.1–0.9, respectively. The polymerization of BMI with BTA was primarily reaction-controlled [f(α) = (1 − α)].

  • effect of solvent proton affinity on the kinetics of michael addition polymerization of n n bismaleimide 4 4 diphenylmethane with Barbituric Acid
    Polymer Engineering and Science, 2014
    Co-Authors: Jungmu Hsu, Jingpin Pan, Tsunghsiung Wang, Yuching Chiang, Winnie Lin, Jyhchiang Jiang, Chorngshyan Chern
    Abstract:

    The effect of solvent proton affinity on the kinetics of the Michael addition polymerizations of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) and Barbituric Acid (BTA) in different solvents [N-methyl-2-pyrrolidone (NMP), N,N′-dimethylacetamide (DMAC), and N,N′-dimethylformamide (DMF)] were investigated. This was achieved by the complete suppression of the competitive free radical polymerization via the addition of a sufficient amount of hydroquinone (HQ). A mechanistic model was developed to adequately predict the polymerization kinetics before a critical conversion, at which point the diffusion-controlled polymerization become the predominant factor during the latter stage of polymerization, was achieved. The activation energy (Ea) of the Michael addition polymerization of BMI with BTA in the presence of HQ in increasing order was: NMP DMAC > DMF). By contrast, the frequency factor (A) in increasing order is: NMP < DMAC < DMF. As a result of the compensation effect between Ea and A, at constant temperature, the Michael addition rate constant decreased with increasing solvent proton affinity. POLYM. ENG. SCI., 54:559–568, 2014. © 2013 Society of Plastics Engineers

  • kinetics of michael addition polymerizations of n n bismaleimide 4 4 diphenylmethane with Barbituric Acid
    Polymer Engineering and Science, 2013
    Co-Authors: Jungmu Hsu, Jingpin Pan, Tsunghsiung Wang, Chorngshyan Chern
    Abstract:

    With the addition of sufficient hydroquinone to completely suppress the free radical polymerization, the kinetics of Michael addition polymerizations of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) and Barbituric Acid (BTA) with BMI/BTA = 2/1 (mol/mol) in 1-methyl-2-pyrrolidone was investigated independently. A mechanistic model was developed to adequately predict the polymerization kinetics before a critical conversion (ca. 60%), at which point the diffusion-controlled polymer reactions started to predominate in the latter stage of polymerization. The Michael addition polymerization rate constants and activation energy in the temperature range 383–423 K were determined accordingly. Beyond the critical conversion, a relatively stationary limiting conversion (ca. 69%) independent of the reaction temperature was achieved. A diffusion-controlled polymerization model taken from the literature satisfactorily predicted the limiting conversion data. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

  • synthesis and characterization of phenylsiloxane modified bismaleimide Barbituric Acid based polymers with 3 aminopropyltriethoxysilane as the coupling agent
    Polymer International, 2012
    Co-Authors: Quocthai Pham, Jungmu Hsu, Jingpin Pan, Tsunghsiung Wang, Chorngshyan Chern
    Abstract:

    The preparation and characterization of phenylsiloxane (PhSLX)-modified N,N � -bismaleimide-4,4 � -diphenylmethane (BMI)/Barbituric Acid (BTA) (10/1 mol/mol) oligomers are described. 3-Aminopropyltriethoxysilane (APTES) was used as the coupling agent. The resultant hybrid BMI/BTA-APTES-PhSLX polymers were characterized primarily using thermogravimetric analysis in combination with differential scanning calorimetry and Fourier transform infrared measurements. The thermal stability of the BMI/BTA oligomer was improved significantly by incorporation of a small amount (20‐30 wt%) of the copolymer of PhSLX and APTES (PASi). After adequate post-curing reactions, the PASi-modified BMI/BTA oligomers (HYBRID20 and HYBRID30 containing 20 and 30 wt% PASi, respectively) exhibited greatly reduced thermal degradation rates in the temperature range 300‐800 ◦ C and an increased level of residues at 800 ◦ C as compared to the native BMI/BTA oligomer. This was further confirmed by thermal degradation kinetic studies, in which the activation energies for the thermal degradation reactions of the cured PASi-modified BMI/BTA oligomers were shown to be higher than that of the pristine BMI/BTA oligomer. c � 2012 Society of Chemical Industry

  • kinetic and structural studies of the polymerization of n n bismaleimide 4 4 diphenylmethane with Barbituric Acid
    Polymer Engineering and Science, 2011
    Co-Authors: Jungmu Hsu, Jingpin Pan, Tsunghsiung Wang, Chorngshyan Chern
    Abstract:

    Both the isothermal and non-isothermal polymerizations of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) with Barbituric Acid (BTA) were investigated by the differential scanning calorimeter. The experimental results showed that the polymerizations of BMI with BTA were governed by the competitive Michael addition reaction and free radical polymerization mechanisms. Furthermore, the contribution of free radical polymerization becomes more important when the mole fraction of BTA decreases. 1H NMR and 13C NMR measurements further support the coexistence of the Michael addition reaction and free radical polymerization mechanisms. A preliminary kinetic model that took into account the competitive Michael addition reaction and free radical polymerization mechanisms was developed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Shahram Lotfi - One of the best experts on this subject based on the ideXlab platform.

Hojat Veisi - One of the best experts on this subject based on the ideXlab platform.

Junming Liu - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of Barbituric Acid doped carbon nitride for efficient solar driven photocatalytic degradation of aniline
    Applied Surface Science, 2018
    Co-Authors: Qingguo Meng, Lingling Shui, Yongguang Zhang, Zhang Zhang, Zhihong Chen, Mingzhe Yuan, Richard Notzel, Xin Wang, Junming Liu
    Abstract:

    Abstract A series of Barbituric Acid doped carbon nitride (CN-BA) photocatalysts were successfully prepared by copolymerizing dicyandiamide with Barbituric Acid (BA). Under AM1.5 simulated sunlight, CN-BA photocatalysts exhibit enhanced photocatalytic activity compared to pure carbon nitride for the degradation of aniline. The highest activity is obtained with 2% doped CN-BA photocatalyst. Results on the photodegradation of aniline indicate that for the optimized CN-BA photocatalyst, the concentration of aniline solution was reduced gradually from 16 mg/L to 1.354 mg/L in 2 h. This corresponds to a 6 times higher photodegradation efficiency than pure carbon nitride samples. The enhanced photocatalytic activity of CN-BA relies on the enhanced surface area, the higher light absorption and the reduced recombination of the photo-generated electron-hole pairs. This interpretation results from multiple characterizations with EPR, BET, N2 adsorption, Solid-state 13C NMR, UV–vis DRS, FESEM, and TEM. Under simulated sunlight irradiation, CN-BA is excited and generates electron-hole pairs. The photo-generated electrons in the CN-BA conduction band react with the molecular oxygen to form O2−. Part of the O2− transforms into OH, which further oxides aniline. Meanwhile, photo-generated holes in the valence band of CN-BA can benefit to the formation of OH or directly oxide aniline.

Zhihong Chen - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of Barbituric Acid doped carbon nitride for efficient solar driven photocatalytic degradation of aniline
    Applied Surface Science, 2018
    Co-Authors: Qingguo Meng, Lingling Shui, Yongguang Zhang, Zhang Zhang, Zhihong Chen, Mingzhe Yuan, Richard Notzel, Xin Wang, Junming Liu
    Abstract:

    Abstract A series of Barbituric Acid doped carbon nitride (CN-BA) photocatalysts were successfully prepared by copolymerizing dicyandiamide with Barbituric Acid (BA). Under AM1.5 simulated sunlight, CN-BA photocatalysts exhibit enhanced photocatalytic activity compared to pure carbon nitride for the degradation of aniline. The highest activity is obtained with 2% doped CN-BA photocatalyst. Results on the photodegradation of aniline indicate that for the optimized CN-BA photocatalyst, the concentration of aniline solution was reduced gradually from 16 mg/L to 1.354 mg/L in 2 h. This corresponds to a 6 times higher photodegradation efficiency than pure carbon nitride samples. The enhanced photocatalytic activity of CN-BA relies on the enhanced surface area, the higher light absorption and the reduced recombination of the photo-generated electron-hole pairs. This interpretation results from multiple characterizations with EPR, BET, N2 adsorption, Solid-state 13C NMR, UV–vis DRS, FESEM, and TEM. Under simulated sunlight irradiation, CN-BA is excited and generates electron-hole pairs. The photo-generated electrons in the CN-BA conduction band react with the molecular oxygen to form O2−. Part of the O2− transforms into OH, which further oxides aniline. Meanwhile, photo-generated holes in the valence band of CN-BA can benefit to the formation of OH or directly oxide aniline.