Facile Synthesis of Cx(AB)yCx Triblock Silicone Copolymers Utilizing Moisture Mediated Living‐End Chain Extension

• Published in: Macromolecular chemistry and physics Vol. 220; no. 8
• Main Authors: Schneider, Alyssa F., Laidley, Elizabeth, Brook, Michael A.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.04.2019
• Subjects: Addition polymerization; Aromatic compounds; Atmospheric moisture; Block copolymers; Catalysis; Chains (polymeric); Chemical properties; Condensates; Condensation polymerization; Copolymers; Ethers; Hydrolysis; Inert atmospheres; living condensation polymerization; Organic chemistry; Piers–Rubinsztajn reaction; Polymerization; silicone; Silicone resins; SiH hydrolysis
• ISSN: 1022-1352; 1521-3935
• DOI: 10.1002/macp.201800575

The physical and chemical properties of silicone block copolymers depend upon the block size and chemical characteristics. Silicone block copolymer synthetic procedures typically involve chain‐growth polymerization techniques that are difficult to control, require low temperatures, inert atmospheres, etc., and which are subject to polymer chain redistribution; the latter process broadens dispersity and leads to the formation of cyclic monomers that must be removed. Once formed, tuning the size of the individual blocks is challenging. The controlled one‐pot synthesis of organosilicone Cx (AB)y Cx triblock copolymers with aryl rich cores is demonstrated by exploiting the Piers–Rubinsztajn reaction and a hydrolysis/condensation polymerization, both using B(C6F5)3 catalysis. A fast Piers–Rubinsztajn reaction between HSi‐terminated silicones and aryl phenyl ethers leads preferentially to the formation of the aryl‐rich core. Subsequent addition of HSi‐terminated silicones permits controlled chain extension of the flanking homosilicone blocks via a slower hydrolysis/condensation facilitated by atmospheric moisture and leads in one pot, two steps to clean Cx (AB)y Cx triblocks. The products are surprisingly resilient to hydrolysis. B(C6F5)3 catalyzes the Piers–Rubinsztajn reaction and hydrolysis/condensation reactions of hydrosilanes. Combining the two processes allows the one‐pot synthesis of a central alternating comonomer block followed by the slower, living assembly of flanking silicone blocks, leading to Cx (AB)y Cx triblock copolymers.