Organocatalysis for versatile polymer degradation

Abstract

The use of a simple, cheap and effective organocatalyst, has been exploited for the transesterification/degradation of commercial polymers.

The Chemical Recycling of Polyesters for a Circular Plastics Economy: Challenges and Emerging Opportunities

“…[130] This remarkable activity enhancement enabled polymer scope to be expanded to PET and poly(bisphenol A) carbonate (BPA-PC), demonstrating catalyst versatility. McKeown et al [131] recently reported tetramethylammonium methyl carbonate (TMC) as a simple and cheap organocatalyst for versatile polymer degradation including PET, BPA-PC and poly(ɛ-caprolactone) (PCL). Promisingly, 100 % Me-LA yield could be achieved within 1 h at 50°C in THF.…”

“…[44,205,206] Zinc acetate is most commonly employed as a transesterification catalyst; however, magnesium acetate, cobalt acetate, lead dioxide and aryl sulfonic acid salts have also been reported. [189] Recently, McKeown et al [131] reported the first example of organocatalysed PET methanolysis using TMC (Figure 6). Promisingly, DMT could be isolated in good yield (72 %) at temperatures as low as 100°C under ambient pressure, although prolonged reaction times (16 h) were required.…”

Make or break: Mg(ii)- and Zn(ii)-catalen complexes for PLA production and recycling of commodity polyesters

“…91,95 PLA recycling processes include hydrolysis [96][97][98][99][100][101][102][103] and alcoholysis. [104][105][106][107][108][109][110][111][112][113][114][115] Hydrogenation [116][117][118] and hydrosilylation 119 processes exploiting ruthenium and iridium have also been reported. Simple, commercially available metal salts and precursors (e.g.…”

“…111 Organocatalysts have also been exploited in PLA degradation, for example triazabicyclodecene (TBD), 4-(dimethylamino)pyridine (DMAP) and tetramethylammonium methyl carbonate. [112][113][114] McKeown et al 123 recently demonstrated a homoleptic Zn(II)-complex bearing a propylenediamine backbone to be highly active for PLA methanolysis, achieving 84% conversion to Me-LA (Y Me-LA ) within 1 h at 50°C. The corresponding ethylenediamine analogue exhibited significantly reduced activity (Y Me-LA = 12% in 6 h) under comparable conditions (40°C), highlighting the importance of structure-activity relationships.…”

Valorisation of plastic waste via metal-catalysed depolymerisation

“…Despite these systems represent promising “greener” options, they still are in an early development stage. Uses are mainly limited to nitrogen-based catalysts, ionic liquids [ 123 – 124 ] and alcoholysis of oxygen-containing polymers, such as polyesters, polycarbonates and polyamides, i.e., glycolysis of PET, wherein high temperatures and nearly stoichiometric amounts of catalysts are often required to achieve moderate yields of monomers [ 125 – 126 ].…”