Dibutylamine dba

The 4,4′-methylene diphenyl diisocyanate (MDI) and a mixture (about 80:20) of 2,4- and 2,6-toluene diisocyanates (TDI) were provided by Elantas Europe S.r.l. and stored at − 18 °C. Reagent grade triethylamine (TEA), benzylamine (BA) and dibutylamine (DBA) were purchased from Sigma Aldrich. Acetone-d₆ was purchased from Sigma Aldrich.
HPLC water was purified using the Milli-Q system. HPLC grade acetonitrile was purchased from Sigma Aldrich. Technical grade acetonitrile and n-hexane were purchased from Carlo Erba. Technical grade dry tetrahydrofuran (THF) was purchased from Sigma Aldrich.
Three batches of PA were provided by Elantas Europe S.r.l. Samples have a mean viscosity of 1100 mPa s and a mean dry content of 22.9% (solvent used is NMP). Three samples were chosen corresponding to three batches produced over a year (Table 1). One batch was marked as anomalous as slightly greater quantities of MDI and TDI were added during the condensation step of the synthesis process to achieve final specifications.Table 1

PAs sample provided by Elantas Europe S.r.l.

Sample name	Production date	Abnormality
PA 1	August 2020	Yes
PA 2	January 2021	None
PA 3	April 2021	None

The molecular structures of the standards were confirmed by ¹H-NMR, recorded on a Varian Mercury plus 400 system at 400 MHz^{25 (link),26 (link)}.

Fatty Acid Methyl Ester of Very High Oleic Sunflower Oil (FAMEVHOSO) with 3.32 mmol double bond/g was kindly supplied by the ITERG group (Canéjan, France). The FAMEVHOSO is composed of 83% of oleic acid. Table S1 presents the distribution of fatty methyl esters of unsaturated FAMEVHOSO. Glacial acetic acid (AA), toluene (99%), H₂O₂ 30%, ethyl acetate (99%), and ethanol (99.9%) were obtained from Fisher Scientific (Illkirch-Graffenstaden, France). Amberlyst^® 15H (strongly acidic cation exchanger dry), Amberlite^® IR120H (strongly acidic hydrogen form), CDCl₃, phenylisocyanate (98%), dibutylamine (DBA) (99.5%), HBr (48% in water), HCl (37% in water), and diethylamine (99%) (DEA) were provided by Sigma-Aldrich (Saint-Quentin-Fallavier, France). ethanol absolute (EtOH) was purchased from VWR (Briare, France). All of the chemicals were used without any purification.