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Dissertation: „Studies of poly(L-lactide) and L-lactide alcoholysis reactions catalysed by metal alkoxides” mgr Dominik Jerzy Bykowski Supervisor: prof. dr hab. Piotr Sobota The subject of this PhD dissertation regarding the investigation of the reaction of poly(L-lactide) and L-lactide alcoholysis which is catalysed by specific metal alkoxides. The effect of the catalyst, amount and type of alcohol, conditions concerning to both solvent used and temperature upon the reaction of PLLA and L-LA alcoholysis. Furthermore, the selectivity of the products formation was discussed. Recently, a great interest in the field of synthesis and usage of the chemicals has been paid to environmentally friendly substances derived from renewable sources. Ecological approach in this aspect is intensively studied by so-called „green chemistry”. Poly(lactide) (PLA) is a aliphatic polyester obtained from renewable sources, and is intensively used in the pharmaceutical and medical industries and in the production of packages devoted to food products. The performed alcoholysis reactions of PLLA and L-LA showed significant catalytic activity of metal alkoxides. The compounds based on lithium, sodium, potassium, magnesium, calcium, zinc and aluminum metal centers were used as catalysts for the alcoholysis reactions of PLLA and L-LA. Ethanol, methanol, and other alcohols such as n-propanol, isopropanol, n-butanol and allyl alcohol were used in alcoholysis reactions, whereas dichloromethane, toluene and ethyl lactate served as solvents. In the study a commercially available high-weight PLLA in the form of granules was used. Applying these catalysts and alcohols, the alkyl lactates and lactyllactates were obtained in high yields. For obtained ethyl (S)-lactate (EtlacH) optical purity was determined, what confirmed the lack of adverse racemization reaction in the PLLA alcoholysis process. Performed studies clearly showed that both the amount and ratio of reagents [catalyst]: [polymer]: [alcohol] used in the reaction have a significant impact on rate and selectivity of the alcoholysis process and on the formation of lactic acid esters. It is worth noting that using an excess of alcohol significantly reduces the step of the polyester chain fragmentation and allows for determination of the thermodynamic equilibrium in the reaction mixture between lactic and lactyllactic acid esters. In the reaction with 10 equivs of ethanol (in relation to lactic acid units in the polymer [-CH(CH3)COO-]) after 1 h reaction resulting the mixture which contains 18% of ethyl lactate, 63% of ethyl lactyllactate and 19% of oligomeric products of PLLA fragmentation. Extending the reaction time to 3 h allow to complete consumption of polyester and obtain ethyl lactate with 96% overall yield. The reaction carried out with the ratio of the reagents [Mg(OEt)2] : [PLLA] : [EtOH] = 1 : 100 : 500 proceeds much more slowly. The reaction mixture contained 31% of lactic acid oligomers after 1 h. Increased reaction time to 3 h caused the reduction of oligomers amount to 4%, and the quantity of the esters of lactic and lactyllactic acids equalled 78 and 18%, respectively. A similar course of alcoholysis reaction was also observed for other alcohols. In the case of PLLA alcoholysis process that was proceeded rapidly in the presence of metal alkoxides such as LiOEt and KOEt, the complete conversion of PLLA into ethyl esters of lactic and lactyllactic acid was observed after 1 h. Here, no catalytic activity of zinc, aluminum and sodium alkoxides was observed, and the lower reactivity of Ca(OEt)2 was affected due to aggregation of these compounds in the presence of ethyl alcohol. Further investigations revealed that prepared in situ magnesium alkoxides Mg(OR)2 have an optimum activity in PLLA and L-LA alcoholysis reactions and allow to obtain alkyl lactates under mild conditions, in a shorter period of time and with higher yield. Studies of alcoholysis reaction in which ethyl lactate (hydroxyester) was used both as a solvent and reactant were also carried out and allowed to eliminate toxic substances from the reaction system. Furthermore, the alcoholysis reactions of L-LA with different alcohols were performed. Compounds such as hydroxyesters: methyl and ethyl lactate, and alcohols containing chlorine and fluorine (2-chloroethanol and 2,2,2-trifluoroethanol), allyl alcohol having a carbon-carbon double bonds (C=C) and long-chain aliphatic alcohols (C10-C16) were used. It has been shown that in the presence of hydroxyesters: ethyl lactate and methyl lactate alkyl esters of lactic acid trimer R(lac)3H are formed. These studies have additionally shown that during L-LA alcoholysis reaction, the self-condensation of RlacH with formation of ROH and R(lac)2H occurs. Alcoholysis reactions of L-LA carried out in the presence of 2-chloroethane, 2,2,2-trifluoroethanol and allyl alcohol allowed to obtain 2-chloroethyl and 2,2,2-trifluoroethyl lactyllactates, and allyl lactate. Reactions of L-LA conducted in the presence of long chain alcohols (C10-C16) were similar and allowed to yield the corresponding -esters of lactic acid. In the last part of this work, the reactions of L-LA with fatty acids (C10-C16) and their lithium salts were performed, which resulted in ω-esters of lactic acid. The developed method for the synthesis of lactic acid esters can be used for the preparation of alkyl lactates on a laboratory scale and in the long term to develop a technological process of PLA recycling.