Cross-linked networks that selectively and controllably disassemble on-demand via cascading bond cleavage

Abstract

Cross-linked polymeric networks are found in numerous consumer, medical, and industrial materials. However, these materials require harsh chemical treatments to degrade their covalently bonded and tangled matrix of chains, often leading to environmental and safety issues. Herein, we describe the first networks, silyl-containing polyurethanes, which are highly cross-linked, rigid, and possess good thermal stability, yet will disassemble in multiple directions via cascading bond cleavage upon exposure to a selective chemical stimulus. These materials are formed from aliphatic polyisocyanates and synthesized silyl-diols with varying electrophilicity and chain lengths, and disassembly is initiated by reaction with mild fluoride ion to release small molecules via slightly different mechanisms, which enables the time of disassembly to be controlled. These silyl-containing polyurethanes are resistant to disassembly with strong acid and base, which demonstrates their selectivity and robustness compared to other degradable cross-linked materials.