Bonding mechanism on TGDDM/CF and the influences of functional groups and interfacial water: An MD and DFT investigation

Abstract

Bonding mechanism between tetraglycidyl diamino diphenyl methane (TGDDM) epoxy resin and carbon fiber (CF) is investigated by employing MD and DFT methods. Edge sites of CF surface (CF(100) and (110)) are focused due to they are chemically active than the inert basal planes. Two kinds functional groups (OH and COOH) are anchored on these sites, and the impacts of interfacial water are examined. The most negative adsorption energy (Ead) goes to the model of TGDDM absorbed onto COOH-functionalized CF(110) (noted as CF(110)COOH). Mulliken population analysis implies that O-H hydrogen bonds have formed across the interface. More bonds tend to form with CF(110) surface and COOH groups. The energy per each hydrogen bond is around 25.95–31.07 kJ/mol, and bond length ranges around 1.81–2.49 Å, which are consistent with previous reports. For the interfacial bonds associated with OH-functionalizaion, TGDDM and OH groups are hydrogen acceptors and donors, respectively. While for the cases with COOH groups, both the TGDDM and COOH groups can act as either acceptors, or donors. Caused by interfacial water, the interfacial hydrogen bonds will be detached, and the interaction energy (Eint) between TGDDM-CF(110) decreases 84.04%. Meanwhile, new hydrogen bonds will form between H2O-TGDDM (and H2O-CF).