In this study, a nanocalcium silicate (n-CS)/polyetheretherketone (PEEK) bioactive composite was prepared using a process of compounding and injection-molding. The mechanical properties, hydrophilicity, and in vitro bioactivity of the composite, as well as the cellular responses of MC3T3-E1 cells (attachment, proliferation, spreading, and differentiation) to the composite, were investigated. The results showed that the mechanical properties and hydrophilicity of the composites were significantly improved by the addition of n-CS to PEEK. In addition, an apatite-layer formed on the composite surface after immersion in simulated body fluid (SBF) for 7 days. In cell culture tests, the results revealed that the n-CS/PEEK composite significantly promoted cell attachment, proliferation, and spreading compared with PEEK or ultrahigh molecular weight polyethylene (UHMWPE). Moreover, cells grown on the composite exhibited higher alkaline phosphatase (ALP) activity, more calcium nodule-formation, and higher expression levels of osteogenic differentiation-related genes than cells grown on PEEK or UHMWPE. These results indicated that the incorporation of n-CS to PEEK could greatly improve the bioactivity and biocompatibility of the composite. Thus, the n-CS/PEEK composite may be a promising bone repair material for use in orthopedic clinics.

This study proposes a novel and facile method to synthesize high-quality NH 2 -functionalized and carboxylfunctionalized graphene oxide (PPD-CFGO)/polyimide (PI) composite films with high dielectric constant (3), low dielectric loss, high-temperature resistance and outstanding mechanical properties by in situ polymerization. In addition to the partial carboxyl groups located at the edges, the ample hydroxyl and epoxy groups bonded on the basal plane of graphene sheets were exploited to covalently bond to the amines. GO was modified by oxalic acid to obtain carboxyl-functionalized GO (CFGO) before amidation.NH 2 -functionalized CFGO (PPD-CFGO), dispersing well in dimethylacetamide (DMAc), was the initial platform for polymer grafting to improve the CFGO dispersion in the polymer matrix. Partially reduced graphene nanosheets are formed during the imidization process. The PPD-CFGO/PI composite films exhibit high tensile strength (up to 848 MPa) and Young's modulus (18.5 GPa). The thermogravimetric analysis results indicate that the PPD-CFGO/PI composites have good thermal stability below 500 C.The dielectric constant increases up to 36.9 with an increasing amount of PPD-CFGO, higher than that of the pure PI polymer by a factor of 12.5, while the dielectric loss is only 0.0075 and the breakdown strength still remains at a high level (132.5 AE 9.3 MV m À1 ).

The abilities to enhance the degree of orientational freedom of dipole in polymer dielectrics and strengthen the homogeneous dispersion of conductive fillers in matrix are of crucial importance for fabricating composite materials with high dielectric constant, low dielectric loss, low density, and good processability. Compared with conventional main-chain polybenzoxazoles, whose processability and dielectric performance are strictly limited by the conjugated benzoxazole groups on the backbone, improved solubility in dimethylformamide and dielectric constant (4.92) were observed for poly(2-isopropenylbenzoxazole) (P(2-IBO)), due to the high mobility of the dipole (benzoxazole ring) on the side chains. In addition, improved dispersion of conductive graphene nanosheets was achieved by a surface-initiated atom transfer radical polymerization (ATRP) of the N-(2-hydroxyphenyl)methacrylamide (o-HPMAA), the precursor of 2-isopropenylbenzoxazole from reduced graphene oxide (RGO). The nanocomposites of functionalized graphene and P(2-IBO) possess a dielectric constant of 8.35 (approximately 70% higher than that of pure P(2-IBO) at 1 kHz) when the weight fraction of functionalized graphene reaches 0.015, the lowest so far among the reports on dielectric property of the graphene/polybenzoxazole system.

A colloidal lithography method has been developed for patterning nonplanar surfaces. Hexagonal noncontiguously packed (HNCP) colloidal particles 127 nm-2.7 μm in diameter were first formed at the air-water interface and then adsorbed onto a substrate coated with a layer of polymer adhesive ∼17 nm thick. The adhesive layer plays the critical role of securing the order of the particles against the destructive lateral capillary force generated by a thin film of water after the initial transfer of the particles from the air-water interface. The soft lithography method is robust and very simple to carry out. It is applicable to a variety of surface curvatures and for both inorganic and organic colloidal particles.