Xiaowen Zhong

This work reports the preparation of a novel class of lignin reverse micelles (LRM) and their application as a UV-blocking additive for thermoplastics. It is found that when 7 vol % cyclohexane was added into alkali lignin (AL)/dioxane solution, LRM formed. When the cyclohexane amount increased, LRM tended to aggregate and separate from the solutions. LRM films had a water contact angle higher than 80°, in comparison to only 52° of the AL film control sample. Due to hydrophobicity, the miscibility of LRM with high density polyethylene (HDPE) was significantly improved from that of AL with HDPE. Since LRM retained the phenolic hydroxyl structure of AL, the HDPE/LRM samples showed an excellent UV-absorbing performance. Furthermore, the added LRM had little negative influence, but significantly improved the HDPE mechanical properties. With 5 wt % LRM loading, Young's modulus increased from 1066 to 2104 MPa and the elongation at break increased from 671% to 1030%, respectively.

Sodium lignosulfonate reverse micelles (SLRMs) with vesicular structure were prepared by self-assembling in ethanol–water media and applied to encapsulate horseradish peroxidase (HRP). Results showed that sodium lignosulfonate (SL) could not form SLRMs until the ethanol content reached 63% when its initial concentration was 7.5 g L–1. Owing to strong electrostatic repulsion, solid spherical SLRMs gradually swelled to stable vesicular structures with an average size of 240 nm. The shell of the SLRM thickened when NaCl was added to screen the electrostatic interaction. HRP can be effectively encapsulated while retaining its activity in the hydrophilic core of a SLRM. When hydrogen peroxide was added to initiate the catalytic activity of HRP, SL molecules would be polymerized and the structure of SLRMs would be fixed. Furthermore, HRP immobilized in polymerized SLRMs showed high activity at a more acidic pH of 4 and at a lower optimal temperature decrease of 35 °C compared to free HRP. SLRM allows enzymes such as HRP to work at more acidic and lower temperature conditions.

Abstract Aiming to improve the poor miscibility between lignin and non-polar materials, alkali lignin (AL) was self-assembled into lignin reverse micelles (LRM) and blended with high-density polyethylene (HDPE) to fabricate composite films. The particle size of AL increased from 3.5 nm to 130 nm after forming LRM, showing a uniform spherical morphology. The water droplet contact angle increased from 54° to 89°. Optimal and rheological analysis revealed that composite films exhibited good transparency, ultraviolet (UV)-blocking performance and low viscoelasticity after adding the nano LRM. Under the optimal dosage of 5 wt% LRM, the composite film can screen 93% UV rays, and the apparent viscosities, complex viscosities, storage and loss modulus of the mixture were the lowest. Atomic force microscopy (AFM) was used to investigate the molecular interactions between lignin and HDPE. The average adhesion force between LRM and HDPE in dry air was 1.07 mN m −1 , while that between AL and HDPE was 0.77 mN m −1 . AFM experiments fundamentally demonstrated better compatibility between LRM and HDPE, which was beneficial for the improvement of UV-blocking, rheological properties, as well as their processability of LRM/HDPE films.