To realize a robust, transparent, and easily processable polymer that is intrinsically selfhealable at room temperature, the following three material design criteria were established: (1) a readily processable and physically tunable base material, (2) a dynamic covalent bond that is operable at room temperature, and (3) optimal self-healing efficiency and mechanical properties.Thermoplastic polyurethane (TPU) is a thermoprocessable elastomer that is widely used as a protective film in the automotive and electronic industries. TPU was selected as the base material to satisfy the first criterion because its chemical structure can be fine-tuned to generate the desired transparency and mechanical properties. [4] Urethane structures containing polytetramethylene ether glycol (PTMEG) have been utilized to prepare shape memory effectassisted self-healing materials. [5] To satisfy the second criterion, an aromatic disulfide bond was selected as the chemical operator. [6] Intrinsic self-healing is chemically driven by noncovalent bonds such as hydrogen bonds, [3c-e,5c,7] metal-ligand, [8] host-guest interactions, [2e,9] or reversible (dynamic) covalent bonds [10] such as Diels-Alder, [11] radical recombination, [12] urea chemistry, [13] olefin metathesis, [14] polysiloxanes, [15] boronic esters, [16] acylhydrazones, [17] and other reactions. [18] Among these, disulfide metathesis has attracted significant attention since it can be activated at moderate temperatures (60-90 °C) and without external stimuli. [5d,19] In particular, an aromatic disulfide-based poly(urea-urethane) shows efficient room-temperature self-healing because aromatic disulfides undergo more efficient metathesis than aliphatic disulfides. [6e,f,20] The third criterion was addressed by optimizing the mechanical properties and self-healing efficiency of TPU through the design of a hard segment of the polymer containing the chemical operator, i.e., an aromatic disulfide moiety. Generally, TPUs with tightly packed hard segments have better mechanical properties but lower self-healing efficiency because the restricted chain mobility hinders disulfide metathesis. [5d,21] Loosely packed hard segments produce the opposite effect. Room-temperature self-healable cross-linked poly(urea-urethane) has an undesirable ultimate tensile strength (UTS) of ≈0.8 MPa with a toughness of ≈13 MJ m −3 . [6e] Other disulfide-containing TPUs have UTS values greater than 10 MPa, but they must be heated above 80 °C to initiate self-healing. [5d] The most important properties of self-healing polymers are efficient recovery at room temperature and prolonged durability. However, these two characteristics are contradictory, making it difficult to optimize them simultaneously. Herein, a transparent and easily processable thermoplastic polyurethane (TPU) with the highest reported tensile strength and toughness (6.8 MPa and 26.9 MJ m −3 , respectively) is prepared. This TPU is superior to reported contemporary roomtemperature self-healable materials and conveniently heals w...

Self-repairable materials strive to emulate curable and resilient biological tissue; however, their performance is currently insufficient for commercialization purposes because mending and toughening are mutually exclusive. Herein, we report a carbonate-type thermoplastic polyurethane elastomer that self-heals at 35 °C and exhibits a tensile strength of 43 MPa; this elastomer is as strong as the soles used in footwear. Distinctively, it has abundant carbonyl groups in soft-segments and is fully amorphous with negligible phase separation due to poor hard-segment stacking. It operates in dual mechano-responsive mode through a reversible disorder-to-order transition of its hydrogen-bonding array; it heals when static and toughens when dynamic. In static mode, non-crystalline hard segments promote the dynamic exchange of disordered carbonyl hydrogen-bonds for self-healing. The amorphous phase forms stiff crystals when stretched through a transition that orders inter-chain hydrogen bonding. The phase and strain fully return to the pre-stressed state after release to repeat the healing process.

The demand for face masks is increasing exponentially due to the coronavirus pandemic and issues associated with airborne particulate matter (PM). However, both conventional electrostatic‐ and nanosieve‐based mask filters are single‐use and are not degradable or recyclable, which creates serious waste problems. In addition, the former loses function under humid conditions, while the latter operates with a significant air‐pressure drop and suffers from relatively fast pore blockage. Herein, a biodegradable, moisture‐resistant, highly breathable, and high‐performance fibrous mask filter is developed. Briefly, two biodegradable microfiber and nanofiber mats are integrated into a Janus membrane filter and then coated by cationically charged chitosan nanowhiskers. This filter is as efficient as the commercial N95 filter and removes 98.3% of 2.5 µm PM. The nanofiber physically sieves fine PM and the microfiber provides a low pressure differential of 59 Pa, which is comfortable for human breathing. In contrast to the dramatic performance decline of the commercial N95 filter when exposed to moisture, this filter exhibits negligible performance loss and is therefore multi‐usable because the permanent dipoles of the chitosan adsorb ultrafine PM (e.g., nitrogen and sulfur oxides). Importantly, this filter completely decomposes within 4 weeks in composting soil.

Various ladder‐like structured poly(phenyl‐co‐methacryl silsesquioxane)s (LPMSQ)s with high molecular weight (Mw = 10,000 ∼ 40,000) were synthesized by direct hydrolysis and polymerization in the presence of base catalyst at 25 °C. Synthesized LPMSQs mainly showed ladder‐like structure and photo‐cure reaction by 100 mW/cm2 (360 nm) for 10 s without any photo‐cure initiators. Chemical composition and structural analysis of the obtained LPMSQs were characterized using 1H NMR, 29Si NMR, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X‐ray diffraction (XRD). Physical properties of LPMSQs before and after photcuring were analyzed by Nanoindentation. Surface modulus increased to 8GPa and hardness of thin films increased from 100 to 400 MPa. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Food packaging requirements of gas barrier and self-cleaning are satisfied with the use of bio-renewable cellulose, chitosan, silica, and sunflower oil.