Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

Abstract

Inside Cover: In article number 2000571 by Brad H. Jones and coworkers, linear and crosslinked polyurethanes are prepared from traditional isocyanates and new polyols containing unsaturated moieties designed to favor ring‐closing olefin metathesis and concomitant cleavage of the molecule. These polyurethanes are found to be efficiently depolymerized upon exposure to second generation Hoveyda–Grubbs catalyst under ambient conditions. The depolymerization products are multi‐vinyl/cycloalkene species that can be re‐polymerized.

Controllable Degradation of Polyurethane Thermosets with Silaketal Linkages in Response to Weak Acid

“…Despite numerous successes in broad applications, the excessive consumption of PU products is leading to an increasingly severe problem of polluting waste. For example, nearly 1.3 million tons of PU waste ends up in American landfills or incineration each year because of their limited life span, which is clearly inconsistent with the desire of globally sustainable development. , For the sake of harmonious coexistence between man and nature, appropriate green methods are emerging to adopt for credible degradation and reutilization of PU waste. , However, due to the remarkably stable nature of carbamate bonds and the chemical cross-linking network in PU products, it seems considerably difficult to obtain an environmentally friendly depolymerization of the cross-linked PU thermosetting materials. , In general, the degradation of PU wastes is mainly achieved by the chemical decomposition of carbamate bonds in their backbone, including alcoholysis, hydrolysis, acidolysis, pyrolysis, aminolysis, and so on. − On one hand, the degradation process routinely requires harsh conditions such as hyperthermal with temperatures ranging from 200 to 800 °C or vicious acid/base digestion. On the other hand, the control over the degradation rates is challenging, as the hydrolysis of carbamate bonds and ester bonds is unmanageable, which limits the availability of chemical recyclization.…”

Chemical recycling of polyolefins via ring-closing metathesis depolymerization

“…Capitalizing on the low RSEs of cyclohexene and cyclopentene, the Jones lab developed a clever synthetic approach to depolymerizable polyurethanes. 47 They began the study by designing two diol monomers which contain unsaturated alkenes in a configuration favoring ring-closing metathesis to cyclohexene and cyclopentene derivatives. These diol monomers were incorporated into the polymer backbone by their polycondensation with diisocyanates and triisocyanates, generating linear and crosslinked polyurethanes, respectively.…”

Effect of the Crosslinking Degree on Self‐Healing Poly(1,2,3‐Triazolium) Adhesive

“…Since then, more vitrimer materials were designed and synthesized. [ 15–17 ] In addition of transesterification, the others include vinylogous urethanes, [ 18–21 ] thiol exchange, [ 22 ] olefin metathesis, [ 23–25 ] dioxaborolanes, [ 26 ] and silyl ethers. [ 27 ]…”