Shrestha Amit, Sumiya Yosuke, Okazawa Kazuki, Tsuji Yuta, Yoshizawa Kazunari
Center for Polymer Interface and Molecular Adhesion Science, Kyushu University 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Department of Applied Chemistry, Yamaguchi University, Tokiwadai 2-16-1, Ube 755-8611, Japan.
Langmuir. 2024 Oct 15;40(41):21573-21586. doi: 10.1021/acs.langmuir.4c02473. Epub 2024 Oct 3.
The molecular mechanism of adhesion of two epoxy resins based on diglycidylether of bisphenol A (DGEBA) cured with 4,4'-diaminodiphenyl sulfone (DDS) and 4,4'-diaminodiphenylmethane (DDM) to the carbon fiber (CF) surface is investigated by employing density functional theory (DFT) calculations. The CF surface was modeled by the armchair-edge structure of graphite functionalized with carboxyl (COOH) groups. Two adhesion interfaces were constructed using the CF surface: one with the DGEBA-DDS molecule (CF/DGEBA-DDS interface) and the other with the DGEBA-DDM molecule (CF/DGEBA-DDM interface). The interfacial properties were analyzed by calculating the maximum adhesion stress () at the interface. The adhesion stress-displacement curve revealed that is 1160.37 MPa, higher for the CF/DGEBA-DDS interface compared to the CF/DGEBA-DDM interface, which is 1060.48 MPa. The energy decomposition analysis showed a similar DFT contribution to adhesion stress for both interfaces, but the dispersion contribution is more significant at the CF/DGEBA-DDS interface. The crystal orbital Hamilton population (COHP) analysis revealed distinct interfacial interactions despite similar DFT contributions. Hydrogen bonding (H-bonding) between the functional groups at both interfaces including feeble OH-π interactions between the benzene rings of epoxy resins and COOH groups on the CF surface were observed. The orbital interaction energies calculated from integrated COHP, i.e., IpCOHP, revealed that the CF/DGEBA-DDS interface has six H-bonding interactions with large absolute IpCOHP values (>1 eV), whereas the CF/DGEBA-DDM interface has five. The interaction between the amine group of the DGEBA-DDM molecule and the CF surface has a large IpCOHP value among all interactions. The sulfone group being at the center of the DDS molecule and its strong surface interaction positioned the DGEBA-DDS molecule closer to the CF surface than the DGEBA-DDM molecule, enhancing dispersion interaction at the CF/DGEBA-DDS interface. Hence, the CF surface exhibits a stronger affinity toward the DGEBA-DDS molecule than the DGEBA-DDM molecule through dispersion interaction.
采用密度泛函理论（DFT）计算方法，研究了两种基于双酚A二缩水甘油醚（DGEBA）的环氧树脂，分别用4,4'-二氨基二苯砜（DDS）和4,4'-二氨基二苯甲烷（DDM）固化后，与碳纤维（CF）表面的粘附分子机制。CF表面采用羧基（COOH）官能化的石墨扶手椅边缘结构进行建模。利用CF表面构建了两个粘附界面：一个与DGEBA-DDS分子（CF/DGEBA-DDS界面），另一个与DGEBA-DDM分子（CF/DGEBA-DDM界面）。通过计算界面处的最大粘附应力（）来分析界面性质。粘附应力-位移曲线表明，CF/DGEBA-DDS界面的为1160.37MPa，高于CF/DGEBA-DDM界面的1060.48MPa。能量分解分析表明，两个界面的DFT对粘附应力的贡献相似，但在CF/DGEBA-DDS界面，色散贡献更为显著。晶体轨道哈密顿布居（COHP）分析表明，尽管DFT贡献相似，但界面相互作用明显不同。观察到两个界面上官能团之间的氢键（H键），包括环氧树脂苯环与CF表面COOH基团之间微弱的OH-π相互作用。从积分COHP计算得到的轨道相互作用能，即IpCOHP，表明CF/DGEBA-DDS界面有六个H键相互作用，其绝对IpCOHP值较大（>1eV），而CF/DGEBA-DDM界面有五个。在所有相互作用中，DGEBA-DDM分子的胺基与CF表面之间的相互作用具有较大的IpCOHP值。DDS分子中心的砜基及其较强的表面相互作用使DGEBA-DDS分子比DGEBA-DDM分子更靠近CF表面，增强了CF/DGEBA-DDS界面的色散相互作用。因此，通过色散相互作用，CF表面对DGEBA-DDS分子的亲和力比对DGEBA-DDM分子更强。
