Stimuli‐responsive shape‐transforming hydrogels have shown great potential toward various engineering applications including soft robotics and microfluidics. Despite significant progress in designing hydrogels with ever more sophisticated shape‐morphing behaviors, an ultimate goal yet to be fulfilled is programmable reversible shape transformation. It is reported here that transient structural anisotropy can be programmed into copolymer hydrogels of N‐isopropylacrylamide and stearyl acrylate. Structural anisotropy arises from the deformed hydrophobic domains of the stearyl groups after thermomechanical programming, which serves as a template for the reversible globule‐to‐coil transition of the poly(N‐isopropylacrylamide) chains. The structural anisotropy is transient and can be erased upon cooling. This allows repeated programming for reversible shape transformation, an unknown feature for the current hydrogels. The programmable reversible transformation is expected to greatly extend the technical scope for hydrogel‐based devices.

Stress-free two-way shape memory polymers (2W-SMPs) capable of reversible shifting between two distinct shapes are versatile platforms for the development of future smart devices. However, it is challenging to prepare stress-free 2W-SMPs with good actuation performance and shape programmability from single-component semicrystalline polymers. Herein, we demonstrate a straightforward and universal strategy for preparing 2W-SMPs through self-nucleated crystallization (SNC) of semicrystalline polymers. SNC enables the formation of two types of crystals in the 2W-SMPs, annealed and primary crystals, which function as the skeleton phase and actuation phase, respectively. We achieved a high reversible actuation strain of 17.6% and a good reprogrammability of the SNC-treated polymer networks. Complex shape transformations were obtained, and smart devices were fabricated from the SNC-treated networks by using a locally designed folding and kirigami structure. The SNC strategy provides a generalized approach to improve the 2W-shape memory behavior of semicrystalline polymers.

A Cu(ii)–pyridyl complex was in situ synthesized and immobilized onto silica microspheres as a highly effective Fenton-like catalyst at near-neutral pH.

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Switching temperature (T sw) is a key parameter governing the service condition of shape memory polymers (SMPs). However, tuning T sw of SMPs often requires sophisticated synthesis or intricate processing. Herein, we report a simple yet effective strategy to prepare the SMPs with tunable T sw and good reconfigurability by using the cocrystalline polyesters as the reversible phase. The cocrystallizable copolyesters with rearranged sequences were prepared by the transesterification of mixed polyester diols and then photo-cross-linked to achieve the SMP networks. Cocrystallization of copolymer blocks endows the SMP networks tunable melting point and relatively high crystallinity, affording the network good shape fixing and recovery ability at body temperature. Besides, the dynamic nature of transesterification, that enables the network to have good shape reconfigurability, allows for the easy processing of SMPs with complicated shapes. The reconfigurable SMPs capable of actuating at the body temperature show great potential for use as biomedical devices.

Widespread application prospect of thermo-responsive hydrogels requires the materials enabling robust mechanical properties and tunable responsiveness. Herein, we report the robust thermo-responsive physical hydrogels with tunable network structure and responsiveness...

Antibiotics are emerging contaminants due to their potential risks to human health and ecosystems. Poor biodegradability makes it necessary to develop effective physical-chemical methods to eliminate these contaminants from water. The cobalt-modified MCM-41 was prepared by a one-pot hydrothermal method and characterized by SAXRD, N adsorption-desorption, SEM, UV-Vis DR, and FTIR spectroscopy. The results revealed that the prepared 3% Co-MCM-41 possessed mesoporous structure with BET surface areas at around 898.5 mg. The adsorption performance of 3% Co-MCM-41 toward levofloxacin (LVF) was investigated by batch experiments. The adsorption of LVF on 3% Co-MCM-41 was very fast and reached equilibrium within 2 h. The adsorption kinetics followed the pseudo-second-order kinetic model with the second-order rate constants in the range of 0.00198-0.00391 g mg min. The adsorption isotherms could be well represented by the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm equations. Nevertheless, D-R isotherm provided the best fit based on the coefficient of determination and average relative error values. The mean free energy of adsorption (E) calculated from D-R model was about 11 kJ mol, indicating that the adsorption was mainly governed by a chemisorption process. Moreover, the adsorption capacity was investigated as a function of pH, adsorbent dosage, LVF concentration, and temperature with help of respond surface methodology (RSM). A quadratic model was established, and an optimal condition was obtained as follows: pH 8.5, adsorbent dosage of 1 g L, initial LVF concentration of 119.8 mg L, and temperature of 31.6 °C. Under the optimal condition, the adsorption capacity of 3% Co-MCM-41 to LVF could reach about 108.1 mg g. The solution pH, adsorbent dosage, LVF concentration, and a combination of adsorbent dose and LVF concentration were significant factors affecting the adsorption process. The adsorption thermodynamic functions were also determined. The negative ΔH (-33.50 kJ mol) and ΔS (-43.57 J mol K) suggested that the adsorption was an exothermic process accompanied by decreasing disorder. This study may indicate that 3% Co-MCM-41 is a promising adsorbent for removing emerging pollutants of LVF from water.

Development of effective organocatalysts for the living ring‐opening polymerization (ROP) of lactones is highly desired for the preparation of biocompatible and biodegradable polyesters with controlled microstructures and physical properties. Herein, a new class of hydrogen‐bond donating bisurea catalysts is reported for the ROP of lactones under solvent‐free conditions. ROP of lactones mediated by the bisurea/7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (MTBD) catalyst exhibits a living/controlled manner, affording the polymers and copolymers with the well‐defined structure, predictable molecular weight, narrow molecular weight distribution, and high selectivity for monomer at low catalyst loadings at ambient temperature. The possible mechanism of bisurea/MTBD‐catalyzed ROP of lactones is proposed, in which the bisurea activates the carbonyl group of lactones while MTBD facilitates the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding. Moreover, the poly(ε‐caprolactone‐co‐δ‐valerolactone) [P(CL‐co‐VL)] random copolymers with various compositions were synthesized using the bisurea/MTBD catalyst. The measurements of thermal properties and crystalline structure demonstrate that the CL and VL units are cocrystallized in the crystalline phase of P(CL‐co‐VL) copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 90–100