Chunmei Zhang

The graphene‐based aerogel microspheres (GAMs) with a flow‐induced microchannel structure were prepared by a combination of emulsification method with the in situ freeze‐drying process, followed by thermal reduction. A uniform orientation microchannel structure can be found on the surface of the large GAMs. While, multi‐orientation microchannels were observed on the small GAMs. The effective reduction of the GAMs was confirmed by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X‐ray photoemission spectroscopy. The hydrophobic GAMs were highly porous with a bulk density ranging from 4.30 to 7.74 mg/cm³ and exhibited excellent absorption performance for various types of organic solvent and oils. The absorption capacities of the GAMs for oil/solvent ranged from 67 to 133 times to their initial weight, showing great potential applications in oil and chemical spill/leak cleanup.

The graphene nanosheets (GNS)/polydimethylsiloxane (PDMS) composite films with out-of-plane dielectric actuation behavior were prepared through a layer-by-layer spin coating process. The GNS-PDMS/PDMS composite films with 1~3 layers of GNS-PDMS films were spin coated on top of the PDMS film. The dielectric, mechanical, and electromechanical actuation properties of the composite films were investigated. The dielectric constant of the GNS-PDMS³/PDMS composite film at 1 kHz is 5.52, which is 1.7 times that of the GNS-PDMS¹/PDMS composite film. The actuated displacement of the GNS-PDMS/PDMS composite films is greatly enhanced by increasing the number of GNS-PDMS layers. This study provides a novel alternative approach for fabricating high-performance actuators with out-of-plane actuation behavior.

Lactide-Caprolactone copolymer (LACL) was added to a Polylactide/Poly(ε-caprolactone) (PLA/PCL) blend as a compatibilizer through solution mixing and the casting method. The melt crystallization behavior and crystalline morphology of PLA, PLA/PCL, and PLA/PCL/LACL were investigated using differential scanning calorimeter (DSC) and polarized optical microscopy (POM), respectively. The temperature of the shortest crystallization time for the samples was observed at 105 °C. The overall isothermal melt crystallization kinetics of the three samples were further studied using the Avrami theory. Neat PLA showed a higher half-time of crystallization than that of the PLA/PCL and PLA/PCL/LACL blends, whereas the half-time of crystallization of PLA/PCL and PLA/PCL/LACL showed no significant difference. The addition of PCL decreased the spherulite size of crystallized PLA, and the nuclei density in the PLA/PCL/LACL blend was much higher than that of the PLA and PLA/PCL samples, indicating that LACL had a compatibilization effect on the immiscible PLA/PCL blend, thereby promoting the nucleation of PLA. The spherulites in the PLA/PCL and PLA/PCL/LACL blend exhibited a smeared and rough morphology, which can be attributed to the fact that PCL molecules migrated to the PLA spherulitic surface during the crystallization of PLA.

Blends of poly(lactic acid)/polycaprolactone (PLA/PCL) were electrospun under various conditions to study the influence of solution concentration, feed rate and voltage supply on the morphology of the nanofibers. To improve compatibility and to help produce fine electrospun nanofibers, an L-lactide/caprolactone (LACL) copolymer was introduced as a compatibilizer in the PLA/PCL blends. It was found that the solution concentration was a principal governing factor. The mean diameter of the fibers increased with the solution concentration, feed rate and voltage. Too high of a concentration and feed rate caused the fibers to stick to each other. A slow feed rate, 10% solution concentration, and 20 kV voltage were capable of producing thin, smooth and uniform fibers. Preliminary biocompatibility assays of the nanofibers were conducted with NIH 3T3 cells. The cells grown on the nanofiber blend exhibited spindle-like morphologies. The addition of PCL and LACL copolymer was found to improve the biocompatibility of PLA nanofibers, suggesting their potential application as cell culture scaffolds.

In this paper a series of di-block copolymers of L-lactide and (meth)acrylate [(M)A, representing methyl methacrylate, tert-butyl acrylate and 2-ethylhexyl acrylate] were synthesized by varying the molecular weight of the polylactide (PLLA) macroinitiator and the structure of the (meth)acrylate monomers. The glass transition temperature, crystallinity and thermal stability of copolymers with different poly(meth)acrylate [P(M)A] blocks were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results indicated that the glass transition temperature of the copolymers could be tuned by changing the chain structure and chain length of the P(M)A blocks. Besides, the crystallization of the copolymers was inhibited by the introduction of P(M)A blocks, and the toughness of the copolymers could be tuned. It is noted that the thermal stability of the copolymers depended on the type of P(M)A blocks and the PLLA/P(M)A blocks ratio. Furthermore, the microphase separation of copolymers in thin films was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the results showed that the composition of copolymers significantly affected the surface morphology of the block copolymer thin films.

In this study, a new method of fabricating conductive NR nanocomposites was proposed. Graphene oxide (GO) was obtained through oxidization and exfoliation of graphite and was employed as a reinforcing nanofiller for natural rubber (NR). GO/NR nanocomposites with different concentrations of GO were prepared by a latex mixing and casting method. The nanocomposites were characterized by Raman spectroscopy and TEM, and the thermal and mechanical properties were evaluated by TGA, DSC, tensile testing, and DMA. The results showed that the nanocomposite showed a segregated “weblike” morphology. The addition of GO slightly decreased the glass transition temperature of NR and improved the thermal stability of the material. The tensile strength and storage modulus of the nanocomposites significantly increased with the GO contents, indicating GO had a strong reinforcing tendency on NR. The electrically conductive reduced graphene oxide (r‐GO)/NR nanocomposites were obtained by immersing GO/NR nanocomposites in a hydroiodic (HI) acid aqueous solution for reduction. HI acid can efficiently reduce the GO into graphene in 2 h at 60°C. The volumetric electrical conductivity of the nanocomposites increased with the r‐GO contents, and the conductivity of the 5% r‐GO/NR nanocomposite was as high as 1 S/m, which showed its promising application as stretchable electrical conductors and elastomers. POLYM. COMPOS., 38:E199–E207, 2017. © 2016 Society of Plastics Engineers