Effect of the Lignin Structure on the Physicochemical Properties of Lignin-Grafted-Poly(ε-caprolactone) and Its Application for Water/Oil Separation

Abstract

Lignin-grafted poly(ε-caprolactone) copolymers (lignin-g-PCLs) have shown wide application potentials in coatings, biocomposites, and biomedical fields. However, the structural heterogeneity of lignin affecting the structures and properties of lignin-g-PCL has been scarcely investigated. Herein, kraft lignin is fractionated into four precursors, namely, Fins, F1, F2, and F3, with declining molecular weights and increased hydroxyl contents. Lignin-g-PCLs are synthesized via ring-opening polymerization of ε-caprolactone with lignin and characterized by GPC, FTIR, 1H and 31P NMR, DSC, TGA, and iGC. The mechanical properties, UV barrier, and enzymatic biodegradability of the lignin-g-PCLs are evaluated. Results show that lignin with a higher molecular weight and aliphatic OH favors the copolymerization, leading to lignin-g-PCLs with longer PCL arms. Moreover, lignin incorporation improves the thermal stability, hydrophobicity, and UV-blocking ability but reduces the lipase hydrolyzability of the copolymers. We also demonstrated that the lignin-g-PCL-coated filter paper could successfully separate chloroform–, petroleum ether–, and hexane–water mixtures with an efficiency up to 99.2%. The separation efficiency remains above 90% even after 15 cycles. The structural differences of copolymers derived from the fractionation showed minimal influence on the separation efficiency. This work provides new insights into lignin-based copolymerization and the versatility of lignin valorization.

Surface-Modified S═O Microenvironment Boosts Catalyzed Oxidation of Alcohol via Hydrogen Bond Interactions

“…The special free energies of methanol adsorption were determined using shell polymers POF-ET and POF-S� O (Figure 3C−D). The free energy of methanol adsorption (−ΔG methanol Sp ) of POF-S�O is higher (5.11 kJ/mol) than that of POF-ET (3.41 kJ/mol), indicating a stronger affinity for polar molecules, 47,50,51 highly due to the hydrogen bond (1.7 kJ/mol) between the OH group and the surface S�O groups (Table S2). Furthermore, an in situ DRIFTS study of alcohol adsorption was applied to show the interaction of OH groups with the catalyst shell.…”

“…The incorporation of SO and ethyl groups also results in different surface properties. According to the water contact angles of POF-ET (97°) and POF-SO (∼0°) (Figure S7), it could be observed that the significant difference in the wettability of the two materials is due to the functional group difference. − Meanwhile, inverse-phase gas chromatography (IGC) was employed to characterize the surface energy of the shell to reflect their organophilic properties quantitatively. ,− Several n -alkanes served as the probe molecules to calculate the dispersive surface energy (γ S D ) (Supporting Note 1). POF-ET with a larger γ S D (22.8 mJ/m 2 ) is more organophilic (Table S2), whereas POF-SO displays a smaller γ S D value (15.3 mJ/m 2 ). , …”

Modulation of Methoxyfenozide Release from Lignin Nanoparticles Made of Lignin Grafted with PCL by ROP and Acylation Grafting Methods

“…Conversely, the DP influenced the initiation temperatures of degradation. 20,24 The initial decomposition temperature decreased from 341 to 328 °C when DP decreased from 101 to 22. In this case, the highest and lowest onset temperatures were found for PCL (371.63 °C) and LN (318.47 °C), respectively.…”

“…A trend emerged, showing that as the length of PCL arms increased, the T m of the copolymers approached the T m of PCL. 13,15,20,24 Crystallinity, as measured by DSC, displayed a slight decrease with an increase in the DP of PCL attached to LN. Previous studies either reported an increase in crystallinity with DP 20,22 or no trend.…”

Preparation of pH-responsive reversible wettable surfaces and application for oil-water separation

“…Generally, there are two kinds of materials used in the oil-water separation process: one is superhydrophobic oleophilic material [4][5][6][7][8], this material is used in the case of oil and water separation of density than water, it cannot be separated from the density of oil than water; the other is superhydrophilic underwater oleophobic material [9][10][11][12][13], similar to this material is used in the case of density than water and water separation, it cannot be separated from the density of oil than water. Xie et al [14] obtained lignin-g-PCL by ring-opening polymerization of ε-caprolactone with lignin and investigated the thermal stability, hydrophobicity and UV-blocking ability. In the oilwater separation experiments, it was found that the lignin-g-PCL coated filter paper could successfully separate chloroform, petroleum ether and hexane-water mixtures with an efficiency of 99.2%.…”