In an effort to increase the mechanical properties of lignin-based carbon fibers, carbon nanotubes grafted with lignin (CNTs-g-L) were synthesized by grafting lignin molecular chains onto the surface of CNTs to improve the interfacial adhesion between CNTs and lignin chains. The addition of CNTs-g-L improved the melt spinnability of lignin, and continuously spooled Lignin/CNTs-g-L melt spun fibers and their carbonized fibers were obtained. The interaction between CNTs-g-L and lignin phases improved the thermal stability of lignin but disordered the graphitic structure of lignin-based carbon fibers. The well-orientated CNTs-g-L increased the tensile strength of lignin-based carbon fibers from 171.2 MPa to 289.3 MPa when 0.5% CNTs-g-L was incorporated. However, due to voids generated by the breakage of chemical links in the functionalized CNTs, the tensile strength of carbon fibers obtained thus decreased with further increases in the CNTs-g-L content.

•Preparing PANi-co-PPy on the surface of the rGO sheets by in situ chemical oxidative polymerization.•Achieving high thermal stability and especially electrochemical performances.•Benifiting from its unique structure, intrinsic properties and synergistic effect among the three components.Poly(aniline-co-pyrrole) was coated on the surface of reduced graphene oxide (rGO) through in situ chemical oxidative polymerization of aniline and pyrrole monomers. For comparison, rGO/polyaniline (PANi) and rGO/polypyrrole (PPy) were also prepared under the similar reaction condition, respectively. The resulting nanocomposites were characterized by field-emission scanning electron microscopy, atomic force microscopy, Fourier transform infrared and Raman spectrometry, and thermogravimetric analysis. Ultrathin layers of conducting polymers on the surface of rGO not only provide more electrochemically active sites but also shorten the distance for ion and electron transport, benefiting from the existence of strong interactions between polymeric chains and rGO. Besides, rGO in the composite can also provide an electron transfer path due to its excellent conductivity and high surface area. What is more, rGO/Copolymer exhibits the highest thermal stability and superior electrochemical stability among these composites, benefiting from its specific chemical structures, intrinsic electrochemical properties of three components, and more importantly, the synergistic effect in the composite. In 1 M Na2SO4 electrolyte, the specific capacitance of rGO/Copolymer was 541 F g−1 at the scan rate of 1 mV s−1, and 283 F g−1 at the scan rate of 20 mV s−1, respectively, which is larger than those for rGO/PANi and rGO/PPy. After 500 cycles, capacitance retention was 86% for rGO/Copolymer. These demonstrate that rGO/Copolymer can be applied as a high-performance electrode material for electrochemical supercapacitors.

Green nanocomposites were prepared by adding well-dispersed cellulose nanocrystals (CNCs) into bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix. Simultaneous enhancements on the mechanical property and thermal stability of PHBV after reinforcement of CNCs were achieved. Compared to neat PHBV, a 149% improvement in tensile strength and 250% increase in Young's modulus can be obtained for the resulting nanocomposites with 10 wt.% CNCs, more importantly, the T0, T5%, Tmax and Tf increased by 51.4, 36.5, 47.1 and 52.9 °C, respectively. This was due to a combination of CNCs reinforcement in the polymeric matrix, and especially the formation of strong intermolecular hydrogen bonding interactions through achieving the excellent dispersion of CNCs in the PHBV matrix via the solvent exchange procedure, as a result, the formation of six-membered ring ester during the degradation process of PHBV was clearly suppressed.Graphical abstractHighlights► Achieving the homogenous dispersion of CNCs in the PHBV matrix through solvent exchange procedure. ► Observing a significant enhancement on the mechanical property and thermal stability of PHBV/CNC nanocomposites. ► Studying the underlying mechanism of simultaneous enhancement on the physical properties of PHBV. ► Optimizing the processing conditions of completely renewable polymeric nanocomposites and their final properties.

The copolymerization of grafting poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) onto ethyl cellulose (EC) was carried out through the homogeneous acylation reaction between EC as a backbone and telechelic OH-terminated PHBV oligomer as side chains in 1,2-dichloroethane by using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent and dibutyltin dilaurate as catalyst. The resulting copolymers were studied by using NMR, FT-IR, WAXD, DSC, and contact angle measurements. It is found that with the increasing of the HDI/PHBV fraction, a transition exhibition occurred on crystallization behavior and hydrophobic properties, which could be modulated through controlling the lengths and grafting densities of PHBV side chains. Compared with those of neat PHBV, the degree of crystallinity for EC-g-PHBV1.8 decreased from 58.1% to 39.1%, the maximum decomposition temperature increased from 259.6 to 266.3 °C, and the contact angle increased from 60.1° to 95.7°.Highlights► Preparing a series of biodegradable EC-g-PHBV copolymers. ► Controlling the side-chain length and grafting density of the copolymers. ► Obtaining expected crystallinity and hydrophobicity of the copolymers.

The green nanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with various cellulose nanocrystals (CNCs) contents were prepared by solution casting method. The effects of CNCs on the crystallization behavior, spherulitic morphology, crystal structure and hydrophilic property of PHBV were studied by differential scanning calorimeter (DSC), polarized optical microscope (POM), wide-angle X-ray diffraction (WAXD) and static water contact angle measurement. It is found that the CNCs act as an effective nucleation agent for crystallization of PHBV, inducing an increase in the melt crystallization temperature of the nanocomposites. A study of the non-isothermal crystallization kinetics further illustrated that overall crystallization rate of PHBV in the nanocomposites was faster than that of neat PHBV, but exhibited a decrease in the crystallinity and the spherulite size of PHBV. Furthermore, the contact angle decreased from 60.1° for neat PHBV to 32.5° for the nanocomposites with 10% CNCs (mass fraction).

A kind of well-defined organic nanoparticle composite polyacrylamide (PAAm) hydrogels (OC gels) are successfully fabricated using in-situ free-radical polymerization with polystyrene (PS) nanoparticles as the cross-linker. These gels show excellent mechanical properties for the uniform dispersion of the organic cross-linker which is prepared by emulsifier-free emulsion polymerization. In addition, a particular swelling behavior is also revealed due to the introduced hydrophobic PS nanoparticles. Both the mechanical and swelling properties show obvious changes with various contents of PS nanoparticle and acrylamide (AAm) monomer in the initial reaction solution. The mechanism for OC gels formation is proposed, and it is validated that the hydrogen bonding interaction among polymer chains also plays an important role in the network formation in addition to the combination of the mutual termination of the attached radical chains on vicinal particles. Besides, the facile route is feasible to design stabilized and functional hydrogels with excellent mechanical properties without affecting the original properties of hydrogels.

A kind of well-defined organic nanoparticle composite polyacrylamide (PAAm) hydrogels (OC gels) are successfully fabricated using in-situ free-radical polymerization with polystyrene (PS) nanoparticles as the cross-linker. These gels show excellent mechanical properties for the uniform dispersion of the organic cross-linker which is prepared by emulsifier-free emulsion polymerization. In addition, a particular swelling behavior is also revealed due to the introduced hydrophobic PS nanoparticles. Both the mechanical and swelling properties show obvious changes with various contents of PS nanoparticle and acrylamide (AAm) monomer in the initial reaction solution. The mechanism for OC gels formation is proposed, and it is validated that the hydrogen bonding interaction among polymer chains also plays an important role in the network formation in addition to the combination of the mutual termination of the attached radical chains on vicinal particles. Besides, the facile route is feasible to design stabilized and functional hydrogels with excellent mechanical properties without affecting the original properties of hydrogels.