Homogeneous ring opening graft polymerization of ɛ-caprolactone onto xylan in dual polar aprotic solvents

Hemicelluloses-based sprayable and biodegradable pesticide mulch films for Chinese cabbage growth

In this study, one high-performance hemicelluloses (HC)-based sprayable and biodegradable pesticide mulch film was developed. Firstly, HC was transesterified with vinyl acetate (VA) to improve its solubility and film-forming ability. Then abamectin (ABA) was encapsulated by β-cyclodextrin (β-CD) to endow mulch film persistent anti-pesticide activity. After that, sodium alginate (SA) and gelatin were added to develop the mechanical performances of the mulch film. As a result, the obtained mulch film showed good characteristics, with optimum mechanical strength, elongation at break, water vapor permeability (WVP), swelling ratio (SR), and weight loss (biodegradability) of 7.9 ± 0.3 MPa, 43.6 ± 2.0 %, 2.1 ± 0.1 × 10^-11 g mm m^-2 s^-1 kPa^-1, 73.8 ± 2.0 %, and 69.3 %, respectively. After covering with mulch film, the soil moisture and temperature were developed to 90.8 % and 19.3 ± 0.2 °C, respectively, which could facilitate Chinese cabbage growth, with optimum germination rate of 98.6 ± 6.4 %.

Constructing a Novel Xylan-Based Film with Flexibility, Transparency, and High Strength

Xylan-based films have great potential to replace petroleum-based polymers used for packaging and coatings due to their excellent biocompatibility, biodegradability, and good gas barrier properties. However, fabricating a xylan-based film with flexible, transparent, water-proof, and excellent mechanical properties is an enormous challenge. Herein, we manufactured a series of degradable films with adjustable properties via solution-casting using a water-soluble xylan derivative. This is the first report of a pure xylan-based film with high performance, requiring no additives. The tensile strength of the xylan-based film could be controlled by adjusting the aldehyde content, which varied from 105.0 to 132.6 MPa. The smallest initial water contact angle of the xylan-based films is 93.26°, indicating that these films are hydrophobic. This work shows a simple and viable route toward manufacturing xylan-based films with high tensile strength, flexibility, and transparency, which can be used for packaging materials and coatings.

Poly(ε-caprolactone) grafted cashew gum nanoparticles as an epirubicin delivery system

Polysaccharide based copolymers have been the focus of several research, particularly for the development of drug delivery systems. This study reports on the preparation of nanoparticles from an amphiphilic copolymer obtained by the poly(ε-caprolactone) graft in the structure of cashew gum, via ring-opening polymerization. The synthesis of copolymers was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The copolymers exhibit self-organization capability in water, with critical association concentration of 42 and 50 μg mL^-1. The nanoparticle hydrodynamic diameters (212 and 202 nm) revealed a decreasing trend with increasing poly(ε-caprolactone) graft percentage. Epirubicin was used as an anticancer drug model and incorporated into the nanoparticles. The encapsulation efficiency reached 50% and 5.0% drug load. Nanoparticles showed an epirubicin controlled release profile, with maximum release of 93.0 ± 4.0% in 72 h, as well as excellent biocompatibility, according to hemolysis and cytotoxicity assays.

Basic understanding of the color distinction of lignin and the proper selection of lignin in color-depended utilizations

Lignin based materials and chemicals with outstanding sustainability have drawn increasingly attentions. However, the dark color of lignin limits the utilization in color-depended fields. In this work, the factors that influence the color of lignin were investigated and mechanisms were illustrated by GPC, NBO, 2D HSQC, XPS, SEM, and visible light spectrum. It is found that the condensed structures were mainly separated at higher pH due to its high molecular weight and low solubility. The condensation contributes to the conjugation and unsaturation, which resulted in the dark-color of the lignin precipitated at high pH value. The oxidation is not crucial for the color darkening of lignin in drying, it is the micro aggregation that dominantly determined the color degree. The concentration of chromophore was decreased owing to the decrease of bulk density (caused by the alleviation of aggregation), which endowed lignin with the bright seeing macroscopically. Notably, the selection of light-colored lignin needs to be individually considered regarding different use, since the dominating factors that influence the color at solid or solution are totally different. In summary, this work offers guidance for acquiring light-colored lignin and helps people select the light-colored lignin properly regarding utilizations.

Organic Catalysis for Ring-Opening Graft Polymerization of p-Dioxanone with Xylan in Ionic liquid

Recently, organic catalysis has become a powerful alternative to the use of more traditional metal-based catalysts. In this study, 4-dimethylaminopyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were applied to mediate the ring-opening graft polymerization (ROGP) of p-dioxanone (PDO) with xylan-based hemicelluloses in ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). Excellent control of the molar ratio of the catalyst to anhydroxylose units (AXU) in xylan was found for a good tuning of the weight percent gain (WPG) of xylan-graft-poly(p-dioxanone) (xylan-g-PPDO) copolymers. As a result, the maximum WPG of xylan-g-PPDO copolymers was 431.07% (DMAP/AXU of 2/1), 316.72% (DBU/AXU of 0.2/1), and 323.15% (TBD/AXU of 0.2/1), respectively. The structure of xylan-g-PPDO copolymers was characterized with FT-IR and NMR. The thermal properties of copolymers were investigated using thermogravimetric analysis (TGA/DTG) and differential scanning calorimetry (DSC), and a significant difference was observed regarding the transition temperature (Tg), melting temperature (Tm), and crystallization temperature (Tc).

Synthesis of Thermoplastic Xylan-Lactide Copolymer with Amidine-Mediated Organocatalyst in Ionic Liquid

Ring-opening graft polymerization (ROGP) of L-Lactide (L-LA) is a practical method of altering the physical and chemical properties of lignocellulose. Previous studies have mainly investigated cellulose and tin-based catalysts, particularly of tin(II) 2-ethylhexanoate (Sn(oct)2), at high temperatures and reported low graft efficiencies. In the present study, ROGP of L-LA was successfully achieved on xylan-type hemicelluloses in ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl) using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an effective organic catalyst. Mild reaction condition (50 °C) was used to limit transesterification, and thus enhance the graft efficiency. The hydroxyl groups on xylan acted as initiators in the polymerization, and DBU, enhanced the nucleophilicity of the initiator and the propagating chain. Xylan-graft-poly(L-Lactide) (xylan-g-PLA) copolymer with a degree of substitution (DS) of 0.58 and a degree of polymerization (DP) of 5.51 was obtained. In addition, the structures of the xylan-g-PLA copolymers were characterized by GPC, FT-IR and NMR, confirming the success of the ROGP reaction. Thermal analysis revealed that the copolymers exhibited a single glass-transition temperature (T g), which decreased with increasing molar substitution (MS). Thus, modification resulted in the graft copolymers with thermoplastic behavior and tunable T g.