RESUMO
Modification of lignin plays a crucial role in extending its applications. While chemical functionalization has been extensively applied, exploring the enzyme-catalyzed approach for grafting phenolic molecules presents a promising avenue. Herein, we investigate the controlled laccase-mediated grafting of vanillin onto lignosulfonates (LS) as a sustainable approach to introduce aldehydes into LS, paving the way for further (bio)chemical functionalizations (e.g., reductive amination and Knoevenagel-Doebner condensations). The resulting vanillin-grafted LS is comprehensively characterized (HPLC, SEC, Pyrolysis-GC/MS, FTIR). The study reveals four key steps in the grafting process: (i) vanillin acts as a mediator, generating the phenoxyl radical that initiates LS oxidation, (ii) the oxidation leads to depolymerization of LS, resulting in a decrease in molecular weight, (iii) rearrangement in the vanillin-grafted LS, evidenced by the replacement of labile bonds by stronger 5-5 bonds that resist to pyrolysis, and (iv) if the reaction is prolonged after complete consumption of vanillin, condensation of the vanillin-grafted LS occurs, leading to a significant increase in molecular weight. This study provides valuable insights on the behavior of vanillin and LS throughout the process and allows to identify the optimal reaction conditions, thereby enhancing the production of vanillin-grafted LS for its subsequent functionalization.
Assuntos
Aldeídos , Benzaldeídos , Lignina/análogos & derivados , Benzaldeídos/química , Lignina/químicaRESUMO
This research aims to study a process of steeping in the n-heptane, used for reducing the migration of additives contained initially in toys for babies plasticized with di-octylphtalate (DOP) based on poly (vinyl chloride) (PVC) and stabilized with epoxidized sunflower oil (ESO). Two formulations were carried out at different levels of DOP plasticizers (15% and 45%). The migration tests were conducted in the synthetic saliva in the absence and in the presence of α-amylase with or without agitation at 37° C for 1, 3, and 6 h. The migration phenomenon was studied on the basis of preliminary studies based on the mass variation of the two formulations and where the physico-chemical technical analysis: Fourier-transform infrared spectroscopy (FTIR) and gas chromatography coupled with gas chromatography-mass spectrometry (GC-MS) were performed. This work shows that the presoak method can be used successfully to reduce the migration phenomenon of the additives and to decrease the interactions between the PVC samples and the saliva stimulant. This treatment has allowed a notable decrease of the overall migration of all the additives from saliva. It is noted that the high pH value (7.17) was obtained with the F45% formulation under agitation and in the presence of α-amylase, a mass loss of the order of 0.9004 and a minimum DOP concentration of 0.024 ppm. The analysis by GC-MS provided the DOP chromatograms of the control and the specimens, which have undergone migration tests and treatments. In addition, the amount of DOP, migrated in the case of the F15% and F45%, controls the formulations and was greater than those of the presoaked formulations, which have indicated the efficiency of the applied process. This study shows that migration has taken place, and that the soaking treatment has reduced the migration of all the additives present in the PVC samples.