Stimuli‐responsive nanoparticles have the potential to improve the delivery of therapeutics to a specific cell or region within the body. There are many stimuli that have shown potential for specific release of cargo, including variation of pH, redox potential, or the presence of enzymes. pH variation has generated significant interest for the synthesis of stimuli‐responsive nanoparticles because nanoparticles are internalized into cells via vesicles that are acidified. Additionally, the tumor microenvironment is known to have a lower pH than the surrounding tissue. In this review, different strategies to design pH‐responsive nanoparticles are discussed, focusing on the use of charge‐shifting polymers, acid labile linkages, and crosslinking.

No abstract

Hybrid composites are currently spearheading in polymer composites field with the promising ability in improving polymer properties. The influence of Eurycoma longifolia (EL)/montmorillonite (MMT) hybrid fillers loading on the mechanical properties of poly(vinyl chloride) (PVC) hybrid composites has been investigated. PVC resin and various additives were first dry-blended using a laboratory blender before being milled into sheets using two-roll mills at 165 C and hot pressed at 180 C and 120 kgm À2 . The mechanical properties of PVC hybrid composites were determined using Izod impact, tensile, and flexural test. The incorporation of EL fiber into PVC matrix improved the flexural modulus, tensile modulus of PVC composites, whereas the tensile strength and impact strength decreased with increasing EL fiber content. The addition of MMT into EL-filled PVC composites has significantly increased the flexural modulus, tensile modulus of PVC hybrid composite compared to PVC composites. However, MMT decreased the flexural strength and impact strength of PVC hybrid composites.

In contrast with all advantages of composite materials, susceptibility of these materials to impact damage became a major concern recently. The aim of this research is to investigate the dynamic response of laminated composite cylindrical shell subjected to pure impact numerically. For this purpose, the impact of a steel ball on composite cylinder is modeled in Abaqus software as a point load and the amount of radial deflection and contact force of the contact point on cylinder surface is recorded for whole period of contact motion. To validate the obtained results they were compared with the exactly the same model in published data. According to obtained results, both of radial deflection and contact force have a parabolic variation during the impact motion. The maximum radial deflection occurs when the striker has its maximum penetration and bouncing back motion is just about to start.

Depolymerization of polycarbonate (PC) is one of the important issues in environment especially in industry field. In this project degradation of PC is done by employing the hydrolysis method using microwave irradiation. PC degradation was carried out under constant amount of tetrahydrofuran (THF) as co-solvent and by using various amount of water (H 2 O) as main solvent and different concentration of sodium hydroxide (NaOH) as catalysts in a microwave reactor for low power and different time. The solid main product bisphenol A (BPA) was analyzed by FTIR and HPLC. It was found that PC degradation is favored by increasing amount of H 2 O, concentration of NaOH and time duration of process. Complete depolymerization was found to occur in 12.5 min when the amount of water was 3.5 g and concentration of NaOH was 0.5 g at 110°C.