Li Chengkai, Zhao Wuchao, He Jianghua, Zhang Yuetao
State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin, China, 130012.
SINOPEC Beijing Research Institute of Chemical Industry, Beijing, China, 100013.
Angew Chem Int Ed Engl. 2024 Apr 15;63(16):e202401265. doi: 10.1002/anie.202401265. Epub 2024 Mar 12.
It remains challenging to synthesize all-(meth)acrylic triblock thermoplastic elastomers (TPEs), due to the drastically different reactivities between the acrylates and methacrylates and inevitable occurrence of side reactions during polymerization of acrylates. By taking advantage of the easy structural modulation features of N-heterocyclic olefins (NHOs), we design and synthesize strong nucleophilic tetraphenylethylene-based NHOs varying in the number (i.e. mono-, dual- and tetra-) of initiating functional groups. Its combination with bulky organoaluminum [BuAl(BHT)] (BHT=bis(2,6-di-Bu-4-methylphenoxy)) constructs Lewis pair (LP) to realize the living polymerization of both acrylates and methacrylates, furnishing polyacrylates with ultrahigh molecular weight (M up to 2174 kg ⋅ mol) within 4 min. Moreover, these NHO-based LPs enable us to not only realize the control over the polymers' topology (i.e. linear and star), but also achieve triblock star copolymers in one-step manner. Mechanical studies reveal that the star triblock TPEs exhibit better mechanical properties (elongation at break up to 1863 % and tensile strength up to 19.1 MPa) in comparison with the linear analogs. Moreover, the presence of tetraphenylethylene group in the NHOs entitled the triblock TPEs with excellent AIE properties in both solution and solid state.
合成全（甲基）丙烯酸三嵌段热塑性弹性体（TPEs）仍然具有挑战性，这是因为丙烯酸酯和甲基丙烯酸酯之间的反应活性差异巨大，并且在丙烯酸酯聚合过程中不可避免地会发生副反应。通过利用N - 杂环烯烃（NHOs）易于结构调制的特点，我们设计并合成了具有不同引发官能团数量（即单、双和四）的强亲核四苯乙烯基NHOs。它与大位阻有机铝[BuAl(BHT)]（BHT = 双（2,6 - 二叔丁基 - 4 - 甲基苯氧基））组合形成路易斯对（LP），以实现丙烯酸酯和甲基丙烯酸酯的活性聚合，在4分钟内得到超高分子量（M高达2174 kg·mol）的聚丙烯酸酯。此外，这些基于NHO的LP使我们不仅能够实现对聚合物拓扑结构（即线性和星形）的控制，还能一步合成三嵌段星形共聚物。力学研究表明，与线性类似物相比，星形三嵌段TPEs表现出更好的力学性能（断裂伸长率高达1863％，拉伸强度高达19.1 MPa）。此外，NHOs中四苯乙烯基团的存在使三嵌段TPEs在溶液和固态中均具有优异的聚集诱导发光（AIE）性能。
