Many of the unique properties of a conventionally crosslinked shape memory network are not found at the same time, and this is a large challenge for the development of advanced shape memory functional materials. In this work, a topologically well-controlled network shape memory poly(ethyl methacrylate) (CN-SMPEMA) is designed and fabricated by introducing two tetra-armed functional structures simultaneously as well-defined structure units to promote switch segment and net-point uniform distribution via the combined technology of the unique controllable atom transfer radical polymerization (ATRP) and copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC). Compared with conventionally crosslinked networks, the as-prepared CN-SMPEMA not only exhibits a combination of excellent mechanical properties, shape fixity, shape recovery ratios and outstanding cycling stability, but also displays rapid recoverability. Additionally, a feasible molecular mechanism for the shape memory effect of the CN-SMPEMA system is analyzed and proposed. We anticipate that such a topologically well-defined network shape memory material with multiple excellent properties will broaden the practical application range of acrylate-based shape memory polymer materials.
Xiaohui Yu,Yong Zheng,Haopeng Zhang,Yufei Wang,Xiaoshan Fan,Tianxi Liu
To meet various practical requirements and enhance human experience, hydrogels possessing multifunctionality are of great significance for flexible wearable sensors. Herein, a novel strategy has been developed to fabricate nanocomposite hydrogels with a combination of excellent stretchability, rapid recoverability, self-healing, and outstanding adhesiveness. The PAAc/SiO2-g-PAAm nanocomposite hydrogels were facilely prepared through the polymerization of acrylic acid (AAc) using SiO2-g-polyacrylamide core–shell hybrid nanoparticles (SiO2-g-PAAm) as the dynamic cross-linking center. The densely dynamic hydrogen bonds between PAAc matrices and grafted PAAm chains could reversibly be destructed and reconstructed to dissipate a large amount of energy. Due to this unique feature, the formulated hydrogels showed a wide spectrum of desirable properties, including skin-mimetic modulus, excellent stretchability (1600%), exceptional self-healing properties (96.5% at ambient temperature), and fast recoverability. The sensors fabricated with the prepared hydrogels exhibited a high detection sensitivity in the strain range from 50% to 500% with a gauge factor value of 5.86, rapid response time, and good antifatigue performance. Depending on the outstanding adhesiveness, this sensor could attach to different substrates to release the real-time motion monitoring. In the practical wearable sensing test, various human motions, including tiny-scaled swallowing, laughing, and speaking, as well as large-scaled wrist, elbow, and knee movements during basketball shooting, could be sensed. These demonstrations heralded the potential application of our sensor in accurate and long-term human motion monitoring.
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