Upcycling of Poly(lactic acid) Waste: A Valuable Strategy to Obtain Ionic Liquids

With the aim to investigate new strategies for upcycling of plastic waste, we performed aminolysis of poly(lactic acid) (PLA), using N,N-dimethylethylenediamine (DMEDA), N,N-dimethylpropylenediamine (DMPDA), and 3-aminopropylimidazole (API) as nucleophiles. The N-substituted lactamides obtained were alkylated by using alkyl halides differing in alkyl chain length, obtaining organic salts that in most cases behaved as ionic liquids (ILs). Both aminolysis of PLA and alkylation of amides were carried out taking into consideration the basic principles of the holistic approach to green chemistry, applied at a laboratory scale, and carefully selecting the nature of the reaction solvent, temperature range, and amount of reagents. Organic salts obtained from the alkylation of N-substituted lactamides were investigated to determine their glass or solid–liquid transitions and their thermal stability. Furthermore, cytotoxicity toward normal lung fibroblasts was also assessed. Data collected show that the proposed strategy represents a valuable protocol to upcycle plastic waste, using it as starting material to obtain alternative solvents of potential industrial relevance.


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Table S2.Conversion, yield and selectivity values for the aminolysis of PLA in the presence of different nucleophiles.Results are evaluated on the ground of the holistic approach to Green Chemistry (Flag). 2

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Table S3.Optimisation of reaction condition for the alkylation of [N 113 -Lac] in the presence of butyl or dodecyl iodide at 70 °C, for 24h.

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Table S4.Glass transition (T g ) and melting temperature (T m ), thermodynamic parameters determined by DSC measurements relevant to salt synthesised.

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Table S5.IC 50 values relevant to the ILs obtained.

Materials
bromobutane, 1-bromododecane, methanol, ethanol and ethyl acetate were obtained from commercial sources and used without further purification.

General procedure for the alkylation of lactamides
The amide and the suitable alkyl halide (1.5 eq.) were solubilized in EtOH (2 mL) in a reaction vial.
The resulting solution was heated to 70 °C for the reaction times reported below.
Subsequently, the solvent was evaporated at reduced pressure.Then, the residue obtained was washed (3x 5 mL) with ethyl acetate or diethyl ether.In particular, diethyl ether was used to wash the

Figure S5. 1 H
Figure S5.1  H spectrum in CDCl 3 of the residue of alkylation, to recover iodododecane.Benzoic acid was added as internal standard.

Table S2 .
Conversion, yield and selectivity values for the aminolysis of PLA in the presence of different nucleophiles.Results are evaluated on the ground of the holistic approach to Green Chemistry (Flag).2

Table S3 .
Optimisation of reaction condition for the alkylation of [N 113 -Lac] in the presence of butyl or dodecyl iodide at 70 °C, for 24h.

Table S4 .
Glass transition (T g ) and melting temperature (T m ), thermodynamic parameters determined by DSC measurements relevant to salt synthesised.