Degradation Mechanism and Kinetics of Thermosensitive Polyacrylamides Containing Lactic Acid Side Chains
摘要:
Diblock copolymers of poly(N-isopropylacrylamide-co-N-(2-hydroxypropyl)methacrylamide lactate) (poly(NIPAAm-co-HPMAm-lactate)) as a thermosensitive block and poly(ethylene glycol) (PEG) as a hydrophilic block form polymeric micelles above the cloud point (CP) of the temperature-sensitive block. Destabilization of these micelles occurs upon hydrolysis of the lactate side chains. Here we report on the degradation kinetics of the HPMAm-mono(di)lactate monomers and their copolymers with NIPAAm. The degradation of the monomers and polymers in their soluble state (thus below their CP) followed normal ester hydrolysis behavior: the degradation rate increased with temperature, pH (from pH 7.5 to 11), and dielectric constant of the medium. Above the CP, where the polymers are in a precipitated state, a significant retardation of the polymer degradation occurred due to a decrease of dielectric constant of the local environment of the precipitated polymer. This study shows that it is possible to predict the rate of formation of HPMAm in NIPAAm-co-HPAIAm-lactate copolymers which results in an increase of the overall hydrophilicity of the polymers and destabilization of polymeric micelles based on poly(NIPAAm-co-HPMAm-lactate).
Chiral alpha- and beta-hydroxy acids such as (S)-lactic acid, (S)-phenyllactic acid, (S)-mandelic acid, or (3R)-3-hydroxybutyric acid have been used as tether groups for intramolecular and diastereoselective [2 + 2] photocycloaddition of 3-oxocyclohexene carboxylic acid derivatives. Total regiocontrol toward the straight adduct and high diastereoselectivities (up to 94%) were observed in the case of
A Versatile Route to Functionalized Dilactones as Monomers for the Synthesis of Poly(α-hydroxy) Acids
作者:Mark Leemhuis、Jan Hein van Steenis、Michelle J. van Uxem、Cornelus F. van Nostrum、Wim E. Hennink
DOI:10.1002/ejoc.200300181
日期:2003.9
A synthetic pathway to functionalized six-membered dilactones structurally analogous to lactide is described. Through the use of orthogonal protecting groups, the synthesis of functionalizeddilactones was performed in a straightforward way by cyanuric chloride-mediated cyclization of the corresponding linear α-hydroxyacid dimers. The synthesis of three different dilactones − methylglycolide, ben
Synthesis of lactide from L-Lactic acid over iso-reticular zeolites derived from Al-UTL
作者:Iunia Podolean、Bogdan Cojocaru、Vasile I. Pârvulescu、Michal Mazur、Sarra Abdi、Jiři Čejka
DOI:10.1016/j.apcata.2023.119379
日期:2023.9
and 7), in the synthesis of lactide from L-Lactic acid as an intermediate for the polylactic acid production. Catalytic tests allowed a thorough understanding of the structure-acidity-activity relationship and the control of the shape selectivity. The lactide and the dimers of the lactic acid were obtained in one step with a high selectivity (>55% for lactide and >70% for the dimer of the lactic).