RESUMEN
The current insufficient recycling of commodity polymer waste has resulted in pressing environmental and human health issues in our modern society. In the quest for next-generation polymer materials, chemists have recently shifted their attention to the design of chemically recyclable polymers that can undergo depolymerization to regenerate monomers under mild conditions. During the past decade, ring-closing metathesis reactions have been demonstrated to be a robust approach for the depolymerization of polyolefins, producing low-strain cyclic alkene products which can be repolymerized back to new batches of polymers. In this review, we aim to highlight the recent advances in chemical recycling of polyolefins enabled by ring-closing metathesis depolymerization (RCMD). A library of depolymerizable polyolefins will be covered based on the ring size of their monomers or depolymerization products, including five-membered, six-membered, eight-membered, and macrocyclic rings. Moreover, current limitations, potential applications, and future opportunities of the RCMD approach will be discussed. It is clear from recent research in this field that RCMD represents a powerful strategy towards closed-loop chemical recycling of novel polyolefin materials.
RESUMEN
Soft and stretchable force sensors are widely used for health monitoring, robotics, prosthetics, and other applications. Soft force sensors with the capability of measuring both normal and shear force could offer even greater functionality and provide more information, particularly in the field of biomechanics. In this work, a new solid-state force sensor is proposed that can measure both normal and shear forces at the same time. The soft and stretchable sensor was fabricated using an ionic liquid (IL)/polymer network. Two separate IL-based polymer membranes were used to detect normal and shear forces. Sensor architecture and electrical wiring for normal, shear, and combined sensing were developed, and various material compositions for different sensor layers were investigated to find the combination that could achieve the optimum sensor performance. A basic material formulation for carbon nanotube-based electrodes, the IL/polymer network, and polymeric insulation layers was proposed. To configure a combined (normal and shear) sensor, separate sensors for normal and shear deformations were first designed and investigated. Later, a combined sensor was fabricated using a mold via screen printing, photocuring, and thermal curing. The combined sensor was evaluated under different force conditions. The results show that the sensor can reliably measure normal and shear forces. Moreover, the findings demonstrate a way to successfully modulate the sensitivity for normal and shear sensing by varying the material composition or geometric configuration, which provides flexibility for application-specific designs.