Mechanical properties of carbon fibre reinforced composites modified with star-shaped butyl methacrylate

This article presents the possibility of strength improvement and energy absorption of carbon fibre reinforced polymer composites by matrix modification. In this study, the mechanical properties of bisphenol-A epoxy matrix and carbon fibre reinforced polymer composites were modified with four different wt.% of star-shaped polymer n-butyl methacrylate (P n-BMA) block glycidyl methacrylate (PGMA). The tensile strength of the epoxy with 1 wt.% star-shaped polymer showed 128% increase in comparison to unmodified epoxy samples. Two different wt.% were then used for the modification of carbon fibre-reinforced polymer composite samples. Tensile tests and low-velocity impact tests were conducted for characterising modified samples. Tensile test results performed showed a slight improvement in the tensile strength and modulus of the composite. Low-velocity impact tests showed that addition of 1 wt.% star-shaped polymer additives increase composite energy absorption by 53.85%, compared to pure epoxy composite specimens. Scanning electron microscopy (SEM) analysis of post-impact specimens displays fracture modes and bonding between the matrix and fibre in the composites. These results demonstrate the potential of a novel star-shaped polymer as an additive material for automotive composite parts, where energy absorption is significant.

Efficient and stable inverted perovskite solar cells with very high fill factors via incorporation of star-shaped polymer

Stabilizing high-efficiency perovskite solar cells (PSCs) at operating conditions remains an unresolved issue hampering its large-scale commercial deployment. Here, we report a star-shaped polymer to improve charge transport and inhibit ion migration at the perovskite interface. The incorporation of multiple chemical anchor sites in the star-shaped polymer branches strongly controls the crystallization of perovskite film with lower trap density and higher carrier mobility and thus inhibits the nonradiative recombination and reduces the charge-transport loss. Consequently, the modified inverted PSCs show an optimal power conversion efficiency of 22.1% and a very high fill factor (FF) of 0.862, corresponding to 95.4% of the Shockley-Queisser limited FF (0.904) of PSCs with a 1.59-eV bandgap. The modified devices exhibit excellent long-term operational and thermal stability at the maximum power point for 1000 hours at 45°C under continuous one-sun illumination without any significant loss of efficiency.

Synthesis of Four-arms Star-shaped PCL-b-PEG as a Potential Amphiphilic Hydrogel

Hydrogel formulations have drawbacks in delivering hydrophobic drugs which can affect its efficiency. Introducing amphiphilic system into hydrogel can overcome this limitation and increase hydrogel effectiveness as a drug cargo. In this study, four arms star-shaped block copolymers with polyethylene glycol (PEG) as hydrophilic block and polycaprolactone (PCL) as hydrophobic block were synthesized via a combination of ring-opening polymerization (ROP) and Steglich esterification. The structures were confirmed by 1H-NMR and FTIR analysis. The polydispersity index (PDI) indices from gas permeation chromatography (GPC) were 1.3 to 1.6 suggesting controlled polymerisation reaction occurred. Average molecular weight analysis, Mn based on 1H-NMR are close to the theoretical value. However, there is a slight difference of Mn between GPC and proton analysis due to the ability of GPC determining Mn for the star-shaped polymer. Both star-shaped polymers possesses high thermal stability (>350 °C) based on thermal decomposition study using TGA analysis. The presence of PEG had increased the hydrophilicity and solubility of the PCL in the hydrogel since an opaque homogeneous formulation form when using the amphiphilic star-shaped polymer. The pH (7.25 ± 0.03) and viscosity (9330 cP) of the formulation are set within the compatibility and suitable for human skin and topical application.

Multi-Responsive Nanocarriers Based on β-CD-PNIPAM Star Polymer Coated MSN-SS-Fc Composite Particles

A temperature, glutathione (GSH), and H2O2 multi-responsive composite nanocarrier (MSN-SS-Fc@β-CD-PNIPAM) based on β-cyclodextrin-poly(N-isopropylacrylamide) (β-CD-PNIPAM) star polymer capped ferrocene modified mesoporous silica nanoparticles (MSN-SS-Fc) was successfully prepared. The surface of the mesoporous silica was first modified by ferrocene (Fc) via a disulfide bond (–SS–) to form an oxidizing and reducing site and then complexed with a β-CD-PNIPAM star shaped polymer through host–guest interactions as a nano-valve to provide temperature responsive characteristics. The structure and properties of the complex nanoparticles were studied by FTIR, TGA, EDS, Zeta potential, and elemental analysis. Doxorubicin (DOX) and Naproxen (NAP), as model drugs, were loaded into nanocarriers to assess drug loading and release behaviour. The release of drugs from nanocarriers was enhanced with an increase of the GSH, H2O2 concentration, or temperatures of the solution. The kinetics of the release process were studied using different models. This nanocarrier presents successful multi-stimuli responsive drug delivery in optimal stimuli and provides potential applications for clinical treatment.