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In this study, we report a strategy to control the localization of carbon nanotubes (CNTs) in immiscible polymer blends of polylactide (PLA) and vulcanized epoxidized soybean oil (VESO) through the gel fraction of sebacic acid (SA) cured epoxidized soybean oil (ESO) precursors (SEP). CNTs disperse in the VESO phase for the SEP with no gel or low gel fraction. With medium gel fraction, CNTs disperse in both PLA and VESO phases. For high gel fraction, CNTs tend to locate in PLA phase and at the interface. With different locations, the composites behave different electrical conductivities . This strategy can be extended to some other particles filled immiscible polymer blends to tailor filler localizations and the final properties of the corresponding composites.

The use of soybean oil or its derivatives to toughen polylactide (PLA) usually leads to limited toughening efficiency, due to the incompatibility between toughening agents and parent PLA. Herein, we report a dynamic vulcanization method to toughen PLA using sebacic acid cured epoxidized soybean oil (VESO), a fully sustainable and biodegradable component. A series of sebacic acid cured epoxidized soybean oil precursors (SEPs) were prepared with different carboxyl/epoxy equivalent ratio (R), which consequently dictates the chemical structure and the morphology of PLA/VESO blends after the dynamic vulcanization. We demonstrated that the chemical structure of VESO plays a critical role in the compatibility, morphology, and toughness of the PLA/VESO blends. By optimizing the R-value, supertoughened PLA blends can be obtained, as evidenced by the significant improvement in the tensile toughness (up to 150.6 MJ/m3) and the impact strength (up to 542.3 J/m). The results of the toughening mechanism from the morpho...

Dynamic vulcanization of polylactide (PLA) with castor oil (CO) and three different diisocyanates, namely 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), was performed to study the effect of diisocyanate type on the vulcanization process and on the morphology as well as mechanical properties of the PLA/CO-based polyurethane blends. The reactivity of the three diisocyanate followed the order of MDI > HDI > IPDI when reacting with castor oil. Interfacial compatibilization between PLA and the CO-based polyurethane occurred when the less reactive HDI and IPDI was used. Among all the blends, PLA/CO-IPDI showed the finest morphology and the best toughening efficiency. Incorporation of 20 wt% CO-IPDI increased the elongation at break and notched impact strength of PLA by 47.3 and 6.6 times, respectively. Cavitation induced matrix plastic deformation was observed as the toughening mechanism for the PLA blends with CO-based polyurethane. The effect of CO-IPDI content on the morphology and mechanical properties of PLA was studied in detail. The particle size of dispersed CO-IPDI and the elongation at break increased gradually, the tensile strength and Young's modulus decreased gradually, while the impact strength first increased and then decreased with increasing CO-IPDI content from 5 to 30 wt%. The maximum impact strength appeared for the blends with 20 wt% CO-IPDI.

Dicarboxylic acid (DA) cured expoxidized soybean oil (ESO) resins are nonprocessable and usually exhibit low mechanical performance, which significantly restrict the application of these sustainable materials. In this study, we report a facile and efficient way of endowing these thermosetting ESO resins with high performance and thermoplasticity via dynamic vulcanization of ESO with sebacic acid (SA) and poly(lactic acid) (PLA). A phase-separated morphology with vulcanized ESO resin (VESO) dispersed in PLA matrix was formed for the dynamically vulcanized blends even with the content of VESO as high as 80 wt %. Rheological analysis indicated that the obtained VESO/PLA blends showed good melt processability as evidenced by the low complex viscosity at high frequency range. The blend contained 80 wt % cross-linked VESO could also be injection molded. The tensile strength and Young’s modulus of VESO were improved by ∼11 and ∼16 times after incorporation of only 20 wt % PLA and could be further increased by ∼3...

Multi-walled carbon nanotubes (MWCNTs) were modified via a non-covalent functionalization technique with poly(sodium 4-styrenesulfonate) (PSS) as the modifier. A well dispersed and stable water dispersion of carbon nanotubes was prepared by ultrasonication of aqueous suspension of MWCNTs in the presence of PSS. Successful wrapping of MWCNTs by PSS was confirmed by High resolution transmission electron microscope (HRTEM). The dispersion was used to fabricate nanocomposites with poly(e-caprolactone) (PCL) through solution coagulation. Scanning electron microscope (SEM) and transmission electron microscope (TEM) indicate that PSS wrapped MWCNTs dispersed uniformly in PCL matrix without obvious aggregation even with MWCNT loading increased up to 1.0 wt%. Rheological investigation confirmed that rheological network existed in the PCL/MWCNT nanocomposites with the percolation threshold of only 0.3 wt%. The electrical conductivity of the composites was investigated and the results indicate that electrical percolation threshold was also 0.3 wt%. The mechanical properties of PCL were significantly reinforced as evidenced by the improvement in yielding strength, Young's modulus, and dynamic storage modulus with incorporation of PSS wrapped MWCNTs.

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 investig...

Dynamic vulcanization of biomass-derived castor oil in the presence of 4,4′-diphenylmethane diisocyanate (MDI) in a polylactide (PLA) matrix was performed with the aim of toughening PLA sustainably. Crosslinking of castor oil with MDI took place rapidly under dynamic vulcanization conditions, leading to the formation of a tough blend, which showed a phase-separated morphology with castor oil derived polyurethane (COP) as a dispersed phase and PLA as a continuous phase. The content of COP in the blends played an important role not only in the size of dispersed COP particles but also in the mechanical properties, rheological and crystallization behaviors of the formed PLA/COP blends. The size of dispersed COP, melt viscosity, and storage modulus of the blends increased significantly with COP content. The crystallization rate of PLA was enhanced by incorporation of COP due to the increased nucleation effect arising from interfacial nucleation of the phase-separated blends. The thermal stability of the blends was slightly reduced compared to neat PLA. The elongation at break of PLA was considerably increased by 45 times to 338%, compared to 7.5% of neat PLA, with the addition of only 5 wt% COP; meanwhile, the mechanical strength and modulus were largely retained. Cavitation, arising from dispersed phase debonding from the matrix, induced matrix plastic deformation was the toughening mechanism for the present PLA/COP blends.

A homogeneous and stable water dispersion of graphene nanosheets (GNS) was prepared through a non-covalent functionalization technique by ultrasonic processing of GNS in the presence of poly(sodium 4-styrenesulfonate) (PSS) as the modifier. The dispersion was then used to compound with poly(e-caprolactone) (PCL) through solution coagulation to fabricate PCL/GNS nanocomposites. Scanning and transmission electron microscope observations indicated that PSS modified GNS dispersed uniformly in and showed strong interfacial adhesion with the PCL matrix when the loading of GNS was not more than 0.5 wt%. While when the loading of GNS increased to 1.0 wt%, aggregation morphology of the GNS in the PCL matrix was detected. The crystallization temperature of PCL, as investigated using a differential scanning calorimeter, increased apparently by incorporation of PSS modified GNS. Investigation on isothermal crystallization kinetics of neat PCL and its composites indicated that the crystallization of PCL was accelerated considerably. Addition of only 0.05 wt% GNS caused a 5.8 times improvement in crystallization rate compared to neat PCL. The crystallization mechanism almost remained unchanged. The improvement in crystallization rate was ascribed to the enhanced nucleation density by incorporation of PSS modified GNS, as evidenced using a polarizing optical microscope (POM). Tensile tests showed that both the tensile strength and the Young's modulus of PCL were reinforced and increased gradually with increasing GNS loading within 0.5 wt%, meanwhile the elongation at break did not reduce but increased slightly. While when the loading of GNS increased to 1.0 wt%, the tensile strength and elongation at break reduced considerably due to the aggregation of GNS with increasing loading. Dynamic mechanical analysis indicated that the storage modulus of PCL was reinforced in the full temperature range by incorporation of PSS modified GNS.

With a large number of disordered proteins and their important functions discovered, it is highly desired to develop effective methods to computationally predict protein disordered regions. In this study, based on Random Forest (RF), Maximum Relevancy Minimum Redundancy (mRMR), and Incremental Feature Selection (IFS), we developed a new method to predict disordered regions in proteins. The mRMR criterion was used to rank the importance of all candidate features. Finally, top 128 features were selected from the ranked feature list to build the optimal model, including 92 Position Specific Scoring Matrix (PSSM) conservation score features and 36 secondary structure features. As a result, Matthews correlation coefficient (MCC) of 0.3895 was achieved on the training set by 10-fold cross-validation. On the basis of predicting results for each query sequence by using the method, we used the scanning and modification strategy to improve the performance. The accuracy (ACC) and MCC were increased by 4% and almost 0.2%, respectively, compared with other three popular predictors: DISOPRED, DISOclust, and OnD-CRF. The selected features may shed some light on the understanding of the formation mechanism of disordered structures, providing guidelines for experimental validation.