A series of nanocomposites based on poly(ε-caprolactone) (PCL) and graphene oxide (GO) were prepared by in situ polymerization. Scanning electron microscopy observation revealed not only a well dispersion of GO but also a strong interfacial interaction between GO and the PCL matrix, as evidenced by the presence of some GO nanosheets embedded in the matrix. Effects of GO nanofillers on the crystal structure, crystallization behavior and spherulitic morphology of the PCL matrix were investigated in detail. The results showed that the crystallization temperature of PCL enhanced significantly due to the presence of GO in the nanocomposites, however, the addition of GO did not affect the crystal structure greatly. Thermal stability of PCL remarkably increased with the addition of GO nanosheets, compared with that of pure PCL. Incorporation of GO greatly improved the tensile strength and Young's modulus of PCL without a significant loss of the elongation at break.
This paper describes the fabrication,characterization and properties of a novel hybrid poly(ethylene glycol)(PEG) based hydrogel via in situ polymerization.The hybrid hydrogel was fabricated by free-radical redox polymerization using ammonium persulfate(APS) and N,N,N′,N′-tetramethylethylenediamine(TEMED) as initiators and N,N′-methylene bisacrylamide(BIS) as cross-linker at 60℃.To create a hybrid hydrogel,0.2% (mass fraction) of MgAl layered double hydroxide(LDH) was added to the aqueous solution by ultrasonic dispersion. The physicochemical properties of hybrid hydrogel under vacuum freeze-drying processing were characterized by Fourier transform infrared(FTIR) spectroscopy,thermal gravimetric analysis(TGA) and scanning electron microscopy(SEM),while swelling kinetics and gel content were calculated.Swelling degree in distilled water varied from 94%—125%with a gel mass fraction of 83%—91%.SEM images showed that the micron pore size of hydrogel could be adjusted within the range of several micrometers by changing the cross-linker mass fraction from 2%to 10%(based on glycol).The results showed that the hybrid hydrogels exhibited excellent physicochemical behavior and might be a promising material for applications in tissue engineering and drug delivery.
Biodegradable poly(butylene succinate) (PBS) and layered double hydroxide (LDH) nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy (TEM), which showed that LDH nanoparticles were found to be well distributed at the nanometer level. The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates. The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however, the crystallization mechanism and crystal structure of PBS remained almost unchanged. In kinetics analysis of nonisothermal crystallization, the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites, whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites. The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis. The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate. The POM showed that the small and less perfect crystals were formed in nanocomposites.
