Trace sorbitol-modified nano-silica: Towards nano-nucleation for poly(L-lactic acid)

Nucleating agents, especially those with small particle sizes, are preferred to boost the nucleation density and crystallinity of poly(lactic acid) (PLA) due to its weak crystallization capability. Organophilicly modified nanofillers hardly alter the nucleation and crystallinity of non-isothermally crystallized PLA. Herein, nano-silica adsorbed trace D-sorbitol (m-SiO2) as a heterogeneous nucleating agent was melt-mixed with poly(L-lactic acid) (PLLA), and the isothermal and non-isothermal crystallization behavior, as well as crystallization kinetics, were investigated. Transmission electron microscopy (TEM) revealed that m-SiO2 was uniformly dispersed in the PLA matrix as 100-300 nm clusters. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) showed that the nucleation rate and density of the non-isothermally crystallized PLLA/m-SiO2 composites were significantly improved. Despite the fact that m-SiO2 does not raise the overall non-isothermal crystallization rate, the crystallization temperature and crystallinity of the PLLA/3%m-SiO2 composite increased from 97.2 °C and 6.8 % for neat PLLA to 108.2 °C and 48.6 % (10 °C/min cooling rate), respectively. The Avrami exponent n of isothermal crystallization remains unchanged, while the crystallization rate increases dramatically. Both isothermal and non-isothermal crystallization have increased activation energies. The heat deflection temperature increased from 59 °C of neat PLLA to 152 °C with a 50 % increase in impact strength.

A Freestanding, Dissolution- and Diffusion-Limiting, Flexible Sulfur Electrode Enables High Specific Capacity at High Mass Loading

The acquisition of stable and high-areal-capacity S cathodes over 10 mA h cm-2 is a critical and indispensable step to realize the high energy density configuration. However, increasing the areal capacity of S cathodes often deteriorates the specific capacity and stability due to the aggravated dissolution of S and diffusion of solvable polysulfides in the thick electrode. Herein, the design of a freestanding composite cathode that leverages 3D covalent binding sites and chemical adsorption environment to offer dissolution-limiting and diffusion-blocking functions of S species is reported. By employing this architecture, the coin cell exhibits excellent cycling stability and an exceptional specific capacity of 1444.3 mA h g-1 (13 mA h cm-2), and the pouch cell configuration manifests a noteworthy areal capacity exceeding 11 mA h cm-2. This performance is coupled with excellent flexibility, demonstrated through consecutive bending cycle tests, even at a sulfur loading of 9.00 mg cm-2. This study lays the foundation for the development of flexible Li-S batteries with increased loading capacities and exceptional performance.

Recent Advances in Bioinspired Hydrogels: Materials, Devices, and Biosignal Computing

The remarkable ability of biological systems to sense and adapt to complex environmental conditions has inspired new materials and novel designs for next-generation wearable devices. Hydrogels are being intensively investigated for their versatile functions in wearable devices due to their superior softness, biocompatibility, and rapid stimulus response. This review focuses on recent strategies for developing bioinspired hydrogel wearable devices that can accommodate mechanical strain and integrate seamlessly with biological systems. We will provide an overview of different types of bioinspired hydrogels tailored for wearable devices. Next, we will discuss the recent progress of bioinspired hydrogel wearable devices such as electronic skin and smart contact lenses. Also, we will comprehensively summarize biosignal readout methods for hydrogel wearable devices as well as advances in powering and wireless data transmission technologies. Finally, current challenges facing these wearable devices are discussed, and future directions are proposed.

Mechanically robust and flame-retardant poly(lactide)/poly(butylene adipate-co-terephthalate) composites based on carbon nanotubes and ammonium polyphosphate

In order to synchronously improve mechanical and flame retardant properties of polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) composites, a series of multifunctional composites containing multi-walled carbon nanotubes (CNTs), ammonium polyphosphate (APP) and a commercial multifunctional epoxy oligomer (MEO) as chain extender were prepared via melt blending. The results show that the optimal flame retardant properties of PLA5-PBAT5/10A/6C composite containing 6 % CNTs and 10 wt% APP, presented the limited oxygen index reached 28.3 % and exhibited a decrease in peak heat release rate (pHRR) and total heat release (THR) to 368 kJ/m² and 72 MJ/m², respectively because of the co-continuous phase, CNTs network and condensed effect of APP. Meanwhile, the construction of co-continuous phases endows PLA5-PBAT5 with better mechanical compared to PLA8-PBAT2 composites. The elongation at break reaches (245.9 %) and notched impact strength (16.5 kJ/m²) of PLA5-PBAT5/10A/6C were higher than the PLA8-PBAT2/10A/6C by 16.0 and 283.7 %.

Polymer-functionalization of carbon nanotube by in situ conventional and controlled radical polymerizations

Functionalization of carbon nanotube (CNT) with polymers has drawn much attention due to its wide range of applications. Polymer-functionalized CNT could exhibit variety of properties, such as responsivity to environmental stimuli, ability of complexation with metal ions, increased dispersibility in different solvents, higher compatibility with polymer matrix, etc. Chemical and physical methods have been developed for the preparation of polymer-functionalized CNT. Polymer chains are chemically bonded to the CNT edge or surface in the chemical methods, which results in highly stable CNT/polymer composites. "Grafting to", "grafting from", and "grafting through" methods are the most common chemical methods for polymer-functionalization of CNT. In "grafting to" method, pre-fabricated polymer chains are coupled with the either functionalized or non-functionalized CNT. In "grafting from" and "grafting through" methods, CNT is functionalized by polymers simultaneously synthesized by in situ polymerization methods. Conventional free radical polymerization (FRP) and also controlled radical polymerization (CRP) are the most promising methods for in situ tethering of polymer brushes onto the surface of CNT due to their control over the grafting density, thickness, and functionality of the polymer brushes. The main focus of this review is on the synthesis of polymer-functionalized CNT via both the "grafting from" and "grafting through" methods on the basis of FRP and CRP routs, which is commonly known as in situ polymerizations. Finally, the most important challenges and applications of the in situ polymer grafting methods are discussed, which could be interesting for the future works.

Super toughened renewable poly(lactic acid) based ternary blends system: effect of degree of hydrolysis of ethylene vinyl acetate on impact and thermal properties

Effect of hydrolysed EVA on PLA ternary blend systems.