Okamoto Hiroshi, Sogabe Atsushi, Honda Satoshi
MIRAI Technology Institute, Shiseido Co. Ltd, 1-2-11 Takashima, Nishi-ku, Yokohama, Kanagawa, 220-0011, Japan.
Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Commun Chem. 2024 Mar 21;7(1):61. doi: 10.1038/s42004-024-01140-3.
Organocatalytic ring-opening polymerization (ROP) is a versatile method for synthesizing well-defined polymers with controlled molecular weights, dispersities, and nonlinear macromolecular architectures. Despite spectacular advances in organocatalytic ROP, precision synthesis of polysiloxanes remains challenging due to the mismatch in polarity between highly polar initiators and nonpolar monomers and polymers and the difficulty in suppressing the formation of scrambling products via transetherification reactions during ROP of cyclic siloxanes. Here, we describe a binary organocatalytic ROP (BOROP) of hexamethylcyclotrisiloxane (D3) employing organic bases as catalysts and (thio)ureas as cocatalysts. The BOROP of D3 using triazabicyclodecene (TBD) and (thio)ureas generates polydimethylsiloxanes (PDMSs) with narrow dispersity (M/M < 1.1). Despite the similar basicities of TBD and 1,8-bis(tetramethylguanidino)naphthalene (TMGN), which is known as a proton sponge, a unitary organocatalytic system using TMGN was inactive for the ROP of D3. When the TMGN was paired with acidic urea, the BOROP of D3 yielded PDMSs with narrow dispersity (M/M < 1.1). Data suggest that the synergetic effect of TMGN and urea is results in an unprecedented activation-deactivation equilibrium between dormant and propagating species. The benefits of the present BOROP system are demonstrated by the formation of PDMS elastomers with more uniform network structures that are highly stretchy and have excellent mechanical properties.
有机催化开环聚合（ROP）是一种通用的方法，用于合成具有可控分子量、分散度和非线性大分子结构的明确聚合物。尽管有机催化ROP取得了显著进展，但由于高极性引发剂与非极性单体和聚合物之间的极性不匹配，以及在环状硅氧烷的ROP过程中难以抑制通过醚交换反应形成的无规产物，聚硅氧烷的精确合成仍然具有挑战性。在这里，我们描述了一种以有机碱为催化剂、（硫）脲为助催化剂的六甲基环三硅氧烷（D3）的二元有机催化ROP（BOROP）。使用三氮杂双环癸烯（TBD）和（硫）脲对D3进行BOROP反应可生成分散度窄（M/M＜1.1）的聚二甲基硅氧烷（PDMS）。尽管TBD和1,8-双（四甲基胍基）萘（TMGN，一种质子海绵）的碱性相似，但使用TMGN的单一有机催化体系对D3的ROP反应无活性。当TMGN与酸性尿素配对时，D3的BOROP反应产生了分散度窄（M/M＜1.1）的PDMS。数据表明，TMGN和尿素的协同作用导致了休眠物种和增长物种之间前所未有的活化-失活平衡。具有更均匀网络结构、高弹性且具有优异机械性能的PDMS弹性体的形成证明了当前BOROP体系的优势。
