No abstract

We present the effect of organic modifier on crystallinity and nanomechanical properties of polymer clay nanocomposites (PCNs) using two different polymers while maintaining the same nanoclay and organic modifier. Experimental results and interaction energy maps of Polybutylene-Terephthalate- (PBT-) PCN system indicate that the underlying mechanisms of change in crystallinity and improvement in mechanical properties as proposed in altered phase theory are valid. Experimental and molecular simulation studies of PBT-PCN and Nylon6-PCN reveal that a higher crystallinity polymer could require significantly higher attractive and repulsive interaction energies between polymer and organic modifiers to change the crystallinity of the polymer in the PCN significantly and thus improve mechanical properties of the PCN.

No abstract

Summary: Copper‐loaded carboxymethyl‐chitosan (CMCS‐Cu) nanoparticles were successfully prepared by chelation under aqueous conditions. The effect of degree of deacetylation and substitution, the molecular weight of CMCS, CMCS concentration, Cu(II) ions concentration, pH value of the solution, as well as temperature, on the morphology of the yielded particles were systematically investigated. The physicochemical properties of the particles were determined by size and zeta potential analysis, FTIR analysis, DLS, TEM, SEM and XRD pattern. FTIR and XRD revealed that Cu (II) ions and CMCS formed a chelate complex. The size of CMCS‐Cu particles shows a good consistency by DLS, TEM, and SEM. The nanoparticles with the size of about 70 nm have been prepared at 0.13 wt% CMCS, 16 mmol/L Cu(II) ions, pH value 4.56 at 25 °C. The antibacterial activity of CMCS, CMCS‐Cu normal particles with the size of about 1000 nm and CMCS‐Cu nanoparticles with the size of less than 100 nm against Staphylococcus aureus was evaluated by vibration method. Results show that the antibacterial efficiency of nanoparticles reached 99%, which is much more efficient than 68.9% of the normal one and 6.1% of CMCS. CMCS‐Cu nanoparticles were proved to be a good novel antibacterial material.

No abstract

The heterogeneity of bone shape and size variation is modulated by genetic, mechanical, nutritional, and hormonal patterning throughout its lifetime. Microstructural changes across cross sections are a result of mechanistic optimization that results over the years of evolution while being based on universal, time-invariant ingredients and patterns. Here we report changes across anatomical sections of bone with osteogenesis imperfecta (OI) that undermines the work of evolution through genetic mutation. This work examines the microstructure and molecular composition of different anatomical positions (anterior, medial, posterior, and lateral regions) in the diaphysis of an OI human tibia. The study shows that although there is no significant microstructural difference, molecular changes are observed using FTIR revealing differences in molecular composition of the four anatomical positions. In addition, the nanomechanical properties of anterior section of OI bone seem more heterogeneous. The nanomechanical properties of interstitial lamellae in all these bone samples are consistently greater than those of osteonal lamellae. The nanomechanical properties of bone depend on its anatomical section and on the measurement direction as well. Variations in molecular structure with anatomical positions and also corresponding differences in nanomechanical properties are reported. These are compared to those observed typically in healthy bone illustrating the unique influence of OI on bone multiscale behavior which results from an evolutionary process lasting for many years.

No abstract

No abstract