In this study, we report the curing of ESO with biobased dicarboxylic acids (DCAs) with different carbon chain-lengths to synthesize fully sustainable polymers. Both non-isothermal and isothermal curing processes analysis indicated that the curing rate and activation energy decreased with increasing chain-length of DCAs. The optimum-COOH/epoxy molar ratio is 0.7 for preparation of ESO/DCA cured product with maximum degree of crosslinking. Addition of 4-N, N-dimethylaminopyridine (DMAP) as a catalyst can efficiently accelerate the curing rate and reduce activation energy. We systemtically studied the effect of chain-length of DCAs on the physical properties of cured products, and found that with increase in chain-length of DCAs, the glass transition temperature of the cured ESO/DCA decreased, the tensile strength and Young's modulus increased while elongation at break decreased, due to the decreased crosslinking density resulted from the increased chain-length between crosslinking sites. All cured ESO/DCA showed excellent thermal stability with initial decomposition temperature of higher than 340 °C.

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Multiwalled carbon nanotubes (MWCNTs) were modified with a noncovalent functionalization method via ultrasonication in the presence of poly­(sodium 4-styrenesulfonate) (PSS) as a modifier. The PSS-functionalized MWCNTs dispersed well in PCL matrix and showed good interfacial adhesion with PCL after being incorporated by solution coagulation. The isothermal crystallization kinetics of neat PCL and PCL/MWCNT nanocomposites were comparatively investigated by DSC. It was found that the overall crystallization rate of PCL was enhanced significantly, while the crystallization mechanism was unchanged by incorporation of the functionalized MWCNTs. The addition of only 0.1 wt % MWCNT caused 23.4 times improvement in overall crystallization rates, ascribing to the efficient nucleating effect of well-dispersed PSS-functionalized MWCNTs toward crystallization of PCL in the nanocomposites. The spherulitic morphology observation by polarizing optical microscope confirmed the nucleating effect. X-ray diffraction investigation indicates that the crystal structure of PCL remained unchanged after incorporation of PSS-functionalized MWCNTs.