Molecular zipper effect macromolecular elastomer: East China University Professor Qu Hui big team

Mechanical properties of the elastomer determine its applicability and industrial prospects, mechanical strength and ductility has been a trade-off where the elastic polymer, the challenge is how best to trace the modifier to greatly improve the traditional elastomeric materials Mechanical behavior. In recent years, due to the rise of the chemical mechanical bonds, supramolecular chemists developed a mechanical interlock structure into the polymer network to increase its mechanical ductility strategy, called \”Molecular pulley\” ([ . 123] Sci Adv 2018, 4, eaat7629;. Science 2017, 357, 279), i.e., by a mechanical bond between the polymer chains and a large ring body is maintained in the stretched elastomeric material the crosslinking process. However, how to simultaneously improve the mechanical strength and stretchability of challenges remain, because the conventional example only improves the stretchability of the material, the mechanical strength is limited. Recently, College of Chemistry and Molecular Engineering, East China University of Technology, Nobel scientist Professor Feilin Jia\’s Joint Research Center Qu Tai-fai team innovatively proposed a \”molecular zipper\” unique concept, while improving the mechanical strength and the tensile properties of the elastomer, made progress in the field of supramolecular polymeric elastomer. relevant outcomes to \”An Ultra-Strong and Highly Stretchable Polyurethane Elastomer Enabled by a Zipper-Like Ring-Sliding Effect\” in the title, published in the \” Advanced Materials \”. (DOI: 10.1002 / adma.202000345) which team will be prepared polyrotaxane skillfully incorporated crosslinker having hydrogen-rich domain deposited polyurethane network having both host-guest interactions and hydrogen bonding supramolecular polymer network . Using a very small amount (0.5 mol%) of the intended rotaxane polyurethane crosslinker can improve the mechanical strength of 950%, the elongation increases 650%, 4470% can improve the fracture. (FIG. 1) of this zippered slip ring sliding urethane mechanical properties the best currently reportedRing-based elastomer.

华东理工大学曲大辉教授团队:高分子弹性体中的分子拉链效应 FIG. 1 molecular mechanism proposed fastener polyurethane network crosslinked polyrotaxane.
Researchers at room temperature simply by doping intended polyrotaxane crosslinked polyurethane network, then the solvent was evaporated, to give a transparent film excellent properties. After a series of stretching experiments were performed and the mechanical properties of the polyurethane crosslinker concentration relevant Quasi rotaxane. 0.5 mol% of the maximum intended rotaxane make up the mechanical strength of the polyurethane 45.06 MPa, maximum elongation rate of 1890%. And a large excess quasi rotaxane they undermine the group of hydrogen bonding, interference double balanced structure crosslinked network, resulting in poor mechanical properties. In addition, the strain rate increases result in reduced elongation at break, indicating the presence of energy dissipation mechanisms. Stress-strain curve indicates that, since the polymer network of hydrogen bonds dissipation effect of the slip ring, the mechanical properties of the crosslinked polyrotaxane proposed elastomeric significantly improved compared to pure urethane. (FIG. 2)
华东理工大学曲大辉教授团队:高分子弹性体中的分子拉链效应 FIG. 2 (a) of FIG stretched film; (b) stress-strain curve of different concentrations of polyurethane intended crosslinked polyrotaxane; (c) a different rate tensile curves; (D ) with different polyurethane stress-strain curve of a crosslinking agent; (e) with different polyurethane crosslinker can break / elongation comparison chart; (f) a slip ring supramolecular elastomeric properties comparison chart.
Fourier transform infrared spectroscopy and X-ray diffraction pattern indicates the formation of hydrogen bonds between the polymer chain and the crosslinking of polymer chains with a rotaxane intended effect of hydrogen bonding and ordered aggregation segments structure. Notably, the diffraction peak width polyurethane intended rotaxane crosslinking after stretching show hydrogen bonds break under mechanical stretching action, formation of amorphous domains. Mechanical properties and structural characterization on, researchers believe that increasing the tensile properties attributable to polyrotaxane intended long distance movement on the polymer chains, increasing the mechanical strength since the main object is intended to interact than hydrogen rotaxane Solutions having higher dissociation energy. Also proposed rotaxane causes the slide break the hydrogen bonds between the polymer chains, increasing the energy barrier of the chain sliding. Dynamic mechanical analysis further confirmed the proposed polyurethane crosslinked polyrotaxane having more stable rheological properties and lower the glass transition temperature. (FIG. 3)
华东理工大学曲大辉教授团队:高分子弹性体中的分子拉链效应 FIG. 3 IR spectrum FIG local contrast (a) polyurethane; (b) X-ray diffraction polyurethane FIG comparison; (c) a polyurethane schematic drawing; (d)Dynamic mechanical analysis graph (e) of the polyurethane.
In conclusion, the researchers succeeded in a similar slide fastener proposed rotaxane polyurethane network in combination with a crosslinking agent containing hydrogen crystal domains, to obtain both high strength and high drawability supramolecular elastomeric material, wherein the key mechanism into the polymer network synergistic effect of the slip ring and the hydrogen of crystalline domains. This new strategy will promote the development of chemical mechanical key to high performance elastomeric material, and further used in flexible electronics, software robots. The work by the

doctoral Shichen Yu, Dr. Zhang Qi Under the guidance of Professor Qu Tai-fai of complete, and has been Tian Academy of Sciences careful guidance. This work was supported by the National Natural Science Foundation of major projects, basic science centers, Shanghai and other major science and technology project funds, characterization work has been the strong support Analysis and Testing Center of East China University of Technology.

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