The first examples of bifunctional hyperbranched polymers (HBP) with high density ionic liquid (IL) moieties in the main chain and controllable amount of pyrene groups at the chain ends (Py-HBPIL) have been synthesized via a facile three-step procedure, which were then immobilized onto reduced graphene oxide (rGO) via π–π stacking interactions. Py-HBPIL(Br) bearing pyrene groups at 10% of the chain ends allowed the highest immobilization loading of 73% in weight. The resultant Py-HBPIL(Br)@rGO hybrid material displayed much better catalytic activity than ever reported for immobilized IL catalysts for coupling reaction between CO2 and propylene oxide (PO), and it could be reused up to 6 times by simple filtration process without significant decline in activity. Furthermore, the combination of bifunctional HBP and π–π stacking immobilization may provide a general and versatile platform to design highly active, selective and recyclable catalysts for various chemical transformations.

ABSTRACTCarbon nanomaterials (CNMs) have been proposed as promising nanofillers for polymer composites because of their high surface area, structural flexibility, good mechanical strength, and their unique thermal, optical, and electronic properties. However, the strong van der Waals interactions between individual nanoparticles have limited the manipulation of CNMs and restricted their use in many promising fields. The functionalization of CNMs has attracted great interest on synthesis of complex structures, and helped establish different facile, scalable, controllable and low-cost methods to graft well-defined polymers onto the surfaces of CNMs. This review highlights the advances made in recent years on the functionalization chemistry of carbon nanotubes and graphene with polymers by both the “grafting from” and “grafting to” techniques. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 622–631

Fire hazards related to polymer-based thermally conductive composites (PTCs) used in electronic equipment are a significant, but often neglected, risk. Here, we offer a solution by incorporating flame retardant-functionalized graphene (PFR-fRGO) into PTCs using a procedure that improves both their flame resistance and thermal conductivity. Briefly, PFR-fRGO was prepared by covalently grafting a polyphosphoramide oligomer (PDMPD) onto the surface of graphene, which was then introduced in situ into epoxy resin/Al2O3 (EP/Al2O3) composites. As expected, the incorporation of PFR-fRGO not only increased the thermal conduction paths by weakening the settlement of microparticles, but also reduced the interfacial thermal resistance by enhancing interfacial interactions, both of which resulted in an enhancement of the thermal conductivity of the ternary composites. The resultant EP/Al2O3/PFR-fRGO composite exhibited a superior flame retarding ability with dramatic decreases being seen in the high peak heat release rate (PHRR), the total heat release (THR) and the total smoke production (TSP), i.e. 53%, 37% and 57%, respectively, when compared to pure epoxy resin. Additionally, a synergistic flame retarding effect was found in the ternary composite compared to the EP/PFR-fRGO and EP/Al2O3 composites. The remarkable enhancement in flame retardancy was mainly attributed to the catalytic charring effect of PFR-fRGO and the template effect of Al2O3, both of which resulted in the formation of a high strength, thermally stable protective layer in the condensed phase that is able to retard the permeation of heat and volatile degradation products during combustion, slow down the heat release rate and protect the underlying polymer.

A facile method to construct scroll-like nanohybrids combining one dimensional ceramic silicon carbide (SiC) nanowires with 2D graphene oxide (GO) nanosheets is presented. The SiC/GO nanohybrids with an oxygen-containing GO outer surface, which are easily and stably dispersed in water and various organic solvents, can be used as a new type of nanofiller for the preparation of easily dispersed poly(propylene carbonate) (PPC)-based nanocomposites using a simple physical blending procedure. The scroll-like structure of the SiC/GO nanohybrids enhances adhesion and the compatibility of SiC with PPC, while preventing the GO sheets from aggregating face-to-face in the PPC. The PPC-based nanocomposites, incorporated with SiC/GO nanohybrids, show synergistic effects with superior thermal, mechanical, shape memory and barrier properties compared to those made as individual (i.e. SiC or GO enhanced) PPC nanocomposites. An optimal performance PPC–SiC/GO nanocomposite that showed improvements in both the glass transition temperature (Tg) and the thermal degradation temperature (Td) was obtained with 0.1 wt% SiC/GO.

As alternative flame-retardant additive for polymers, reduced graphene oxide (RGO) is often limited by its poor interfacial compatibility with matrix. In this work, a new flame retardant, containing phosphorous, nitrogen and silicon elements was used to functionalize RGO. The wrapped flame retardant chains induced the improvement in the dispersion and compatibility of RGO in epoxy (EP) matrix. As a result, the mechanical, thermal and flame retardant properties of EP-based composites were significantly improved by adding flame retardant-functionalized RGO. The peak heat release rate, total heat release and total smoke production reduced by 34%, 14% and 30%, respectively, compared to neat resin. Based the char analyses, the enhancement in flame retardancy is attributed to the outstanding char layers with high strength and thermal stability resulting from the template effect of graphene, the charring effect of phosphorus and nitrogen elements and the enhancing effect of silicon element in grafted flame retardant chains.

Organic molecular and polymeric stabilizers are useful for preparing individually dispersed graphene sheets, thus offering new possibilities for the production of nanomaterials. Although exfoliated graphene flakes with good dispersibility can be produced, their use in polymer composites remains limited due to their low stability and mechanical strength. In this work, stable high concentration aqueous dispersions (>10 mg mL−1) of reduced graphene oxide (RGO) sheets were prepared by exfoliation/in situ reduction of graphene oxide (GO) in the presence of cellulose nanocrystals (CNC). The sandwich-like structure formed with the hydrophilic outer surface of CNC forms CNC decorated RGO (CNC–RGO) which is easily dispersed in water with a high thermal stability (>320 °C) comparable to pristine CNC and other common stabilizers. Polyethylene oxide (PEO) based nanocomposites, using fully exfoliated CNC–RGO hybrids, were prepared with a simple procedure. The PEO/CNC–RGO composite films show superior mechanical properties compared to PEO composite films enhanced by other small molecules, polymer dispersants, stabilized RGO or pristine CNC. Not only are the elastic modulus and tensile strength of the composites significantly improved, but their thermal stability is also retained. The hydrothermal dehydration of GO to RGO, using biodegradable and renewable materials such as CNC, offers a “green approach” to large-scale preparation of highly biocompatible and easily dispersed RGO for a range of applications.

Using the versatility of silica chemistry, we describe herein a simple and controllable approach to synthesise two-dimensional (2D) silica-based nanomaterials: the diversity and utility of the resulting structures offer excellent platforms for many potential applications.

Polymer-functionalized reduced graphene oxide (polymer-FG), produced as individually dispersed graphene sheets, offers new possibilities for the production of nanomaterials that are useful for a broad range of potential applications. Although non-covalent functionalization has produced graphene with good dispersibility and a relatively complete conjugated network, there are few reports related to the effective functionalization of reduced graphene oxide (RGO) using a simple, general method. Herein, we report a facile and effective approach for the preparation of polymer-FG from a non-covalently functionalized pyrene-terminal polymer in benzoyl alcohol (BnOH). This aromatic alcohol (BnOH) was used as the liquid medium for the dispersion of graphene oxide (GO) with a pyrene-terminal polymer, and as an effective reductant; this makes the synthesis procedure convenient and the production of polymer-FG easily scalable because the conversion of GO to RGO and the non-covalent functionalization proceed simultaneously. The resulting polymer-FG sheets show organo-dispersibility, high electrical conductivity and good processability, and have a similar grafting density comparable to covalently made materials, thus making them promising candidates for applications such as electrochemical devices, nanomaterials and polymer nanocomposites. Hence, this work provides a general methodology for preparing individually dispersed graphene sheets with desirable properties.

A new structural design and tailored morphology of polymer-functionalized graphene (polymer-FG) are employed to optimize composite polymer electrolytes (CPEs). The ionic transfer conditions including Li salt dissociation, amorphous content and segmental mobility are significantly improved by incorporating polymer-FG, especially that having a polymeric ionic liquid (PIL) and a polymer brush structure [PIL(TFSI)-FGbrush]. Electrical shorts are eliminated due to the presence of the functionalized polymer on reduced graphene oxide (RGO) and a minimal amount of polymer-FG in the PEO/Li+ polymer electrolytes (PEs). Polymer-FG with PIL brushes increases significantly the Li ion conductivity of PEO/Li+ PE by >2 orders of magnitude and ∼20-fold at 30 °C and 60 °C with high Li salt loading (O/Li = 8/1), respectively. Furthermore, significant improvements in mechanical properties are observed where only 0.6 wt% addition of the PIL(TFSI)-FGbrush led to more than 300% increase in the tensile strength of the PEO/Li+ at an O/Li ratio of 16/1. Li-ion battery performance was evaluated with the CPE containing 0.6 wt% of PIL(TFSI)-FGbrush, resulting in superior capacity and cycle performance compared to those of the PEO/Li+ PE. Thus, we believe, embedding minimal amounts of structurally and morphologically optimized polymer-FG nano-fillers can lead to the development of a new class of SPEs with high ionic conductivity for high performance all-solid-state Li-ion batteries.

An effective chemical strategy for the synthesis of polymer–ionic liquid (IL) electrolytes with ion-conducting channels, physically modulated by variously dimensioned IL-functionalized carbon materials (IL-FCMs) including carbon black (CB), multi-walled carbon nanotubes (MWCNT) and reduced graphene oxide sheets (RGO) is reported, enabling a fundamental understanding of the relationship between carbon structures and ion transport behavior. The risk of electrical shorts is eliminated by the presence of IL groups on the surfaces of CMs and only minimal amounts of the IL-FCMs (⩽1.0 wt.%) in the polymer/IL composite electrolytes (e.g., polymer matrix filled with 1.0 wt.% IL-FCMs has a conductivity of ∼10−7 S cm−1 at 100 °C). Increase in ion transport within the reorganized ion channels of the composite polymer electrolytes (CPEs) is confirmed by the enhanced ionic conductivity and low activation energy for through-plane and in-plane ionic conduction at different temperature (40–160 °C). Maximum improvement in the ionic conductivity (150–300% at 100 °C) can be achieved by optimizing the carbon structure and the loading ratio, which leads to highly ionic conductive polymer/IL composite electrolytes for practical applications.

•2D nanoplates within porous structures create 3D ion conductive network that increase ion mobility and lead to high ionic conductivity.•The surface porosity of 2D nanofillers in combination with a PIL grafting improves the CPEs’ IL immersion and retention properties.•Optimized CPEs exhibit high ionic conductivity, which is on the same order of magnitude as that offered by other reinforced CPEs, while only requiring a small IL loading.•Li/LiFePO4 cells with PIL/IL/PIL-FMSiNP CPE are capable of delivering high capacity during charge/discharge cycles.The structural design of ion-conducting channels within polymer electrolytes (PEs) is of prime importance if their transport properties, especially in high performance electrochemical devices, must be optimized. Although many efforts have been directed towards enhancing the transport properties of PEs through nanoscopic modification, few investigations have successfully used nanofillers to achieve enhanced target ion conduction in composite polymer electrolytes (CPEs). In this work, we show that the transport properties of polymeric ionic liquid (PIL)-based PEs can be optimized by the incorporation of 2D silica nanofillers and that desirable transport properties result from the inclusion of abundant, shorter, continuous and interconnected ion transfer pathways created by a combination of grafted PIL and mesoporous structures in 2D silica nanofillers. The presence of PIL-functionalized mesoporous silica nanoplates (PIL-FMSiNP) increases the ionic conductivity of PIL/IL PEs by 1130% at room temperature (~30 °C) while significantly decreasing the ion transport activation barrier (ca. 10 kJ mol−1). Such nanofillers simultaneously confer both high ionic conductivity [(~10−3 S cm−1 at 130 °C) with only a small amount of IL loading (15 wt%)], and excellent IL immersion and retention properties to PIL/IL PE. The CPE's favorable transport properties make it well-suited for the fabrication of electrochemical devices including Li batteries, fuel cells, dye-sensitized cells, and supercapacitors. Preliminary Li battery tests have shown that Li/LiFePO4 cells with PIL/IL/PIL-FMSiNP CPE are capable of delivering 135.8 mA h g−1 capacity at 60 °C during 30 charge/discharge cycles, suggesting that their capacity and capacity retention are superior to cells using unmodified PIL/IL PE (50.0 mA h g−1).The transport properties of polymeric ionic liquid (PIL)-based PEs can be optimized by the incorporation of 2D silica nanofillers and that desirable transport properties result from the inclusion of abundant, shorter, continuous and interconnected ion transfer pathways created by a combination of grafted PIL and mesoporous structures in 2D silica nanofillers.

Using the versatility of silica chemistry, we describe herein a simple and controllable approach to synthesise two-dimensional (2D) silica-based nanomaterials: the diversity and utility of the resulting structures offer excellent platforms for many potential applications.

Fire hazards related to polymer-based thermally conductive composites (PTCs) used in electronic equipment are a significant, but often neglected, risk. Here, we offer a solution by incorporating flame retardant-functionalized graphene (PFR-fRGO) into PTCs using a procedure that improves both their flame resistance and thermal conductivity. Briefly, PFR-fRGO was prepared by covalently grafting a polyphosphoramide oligomer (PDMPD) onto the surface of graphene, which was then introduced in situ into epoxy resin/Al2O3 (EP/Al2O3) composites. As expected, the incorporation of PFR-fRGO not only increased the thermal conduction paths by weakening the settlement of microparticles, but also reduced the interfacial thermal resistance by enhancing interfacial interactions, both of which resulted in an enhancement of the thermal conductivity of the ternary composites. The resultant EP/Al2O3/PFR-fRGO composite exhibited a superior flame retarding ability with dramatic decreases being seen in the high peak heat release rate (PHRR), the total heat release (THR) and the total smoke production (TSP), i.e. 53%, 37% and 57%, respectively, when compared to pure epoxy resin. Additionally, a synergistic flame retarding effect was found in the ternary composite compared to the EP/PFR-fRGO and EP/Al2O3 composites. The remarkable enhancement in flame retardancy was mainly attributed to the catalytic charring effect of PFR-fRGO and the template effect of Al2O3, both of which resulted in the formation of a high strength, thermally stable protective layer in the condensed phase that is able to retard the permeation of heat and volatile degradation products during combustion, slow down the heat release rate and protect the underlying polymer.

A new structural design and tailored morphology of polymer-functionalized graphene (polymer-FG) are employed to optimize composite polymer electrolytes (CPEs). The ionic transfer conditions including Li salt dissociation, amorphous content and segmental mobility are significantly improved by incorporating polymer-FG, especially that having a polymeric ionic liquid (PIL) and a polymer brush structure [PIL(TFSI)-FGbrush]. Electrical shorts are eliminated due to the presence of the functionalized polymer on reduced graphene oxide (RGO) and a minimal amount of polymer-FG in the PEO/Li+ polymer electrolytes (PEs). Polymer-FG with PIL brushes increases significantly the Li ion conductivity of PEO/Li+ PE by >2 orders of magnitude and ∼20-fold at 30 °C and 60 °C with high Li salt loading (O/Li = 8/1), respectively. Furthermore, significant improvements in mechanical properties are observed where only 0.6 wt% addition of the PIL(TFSI)-FGbrush led to more than 300% increase in the tensile strength of the PEO/Li+ at an O/Li ratio of 16/1. Li-ion battery performance was evaluated with the CPE containing 0.6 wt% of PIL(TFSI)-FGbrush, resulting in superior capacity and cycle performance compared to those of the PEO/Li+ PE. Thus, we believe, embedding minimal amounts of structurally and morphologically optimized polymer-FG nano-fillers can lead to the development of a new class of SPEs with high ionic conductivity for high performance all-solid-state Li-ion batteries.