TA/Cu-XCM@βCNC nanocarrier is developed for crop protection, the introduced system enables pH-responsive controlled delivery, enhances deposition and prevents pesticide leakage.
A graft copolymer was synthesized by graft copolymerization of starch with styrene (St) and butyl acrylate (BA), using ferrous sulfate-hydrogen peroxide redox initiation system. The starch was pregelled in the presence of acrylonitrile (AN) in aqueous alkali at high temperature before graft polymerization. Major factors affecting the polymerization reaction were investigated. It was found that a graft copolymer with higher percentage conversion (PC), graft efficiency (GE) and graft percentage (GP) was obtained by controlling the initiator concentration, concentration, and ratio of monomers and polymerization temperature. The optimum conditions were as follows: H 2 O 2 concentration, 12%; monomer concentration, 120%; St/BA ratio, 1 : 1; polymerization temperature, 65 C. Fourier transform infrared spectroscopy and NMR analyses were used to gain information on the structure of the products. It was demonstrated that St, BA, and AN had been successfully grafted onto starch and ACN had been saponified into ACONH 2 and ACOO À to a certain degree when pregelling. Scanning electron microscope micrographs showed the coarse structure and broad network. The graft polymerization took place on the surface of starch granule and led to amorphization of the starch structure. Graft polymer had better thermal stability and was endowed with pseudo-plasticity. It was observed that the starch graft copolymer offers good properties such as water resistance as surface-sizing agent.
The lignin−carbohydrate complexes (LCCs) typically present in the liquors produced in the pre-hydrolysis of biomass cause severe difficulties in downstream fractionation. To address this issue, a series of LCC samples were accessed from solutions obtained from the pre-hydrolysis of extractive-free pine wood meal (H-LCC) and compared with LCC obtained from the corresponding residues (B-LCC). Chromatographic and spectroscopic techniques revealed that 8.2% of the lignins were degraded at 160 °C, resulting from the breakage of β-O-4′ linkages during pre-hydrolysis. Meanwhile, (reactive) hemicelluloses were mainly removed from the fibers' cell walls. Some hemicelluloses in the prehydrolysis liquor, such as glucomannans, were associated with degraded lignin fragments via ether and ester bonds. However, the newly formed LCCs were pH-labile and underwent rapid hydrolysis. Overall, we reveal details about LCC formation and degradation during pre-hydrolysis at given temperatures, critically important in efforts to improve biomass processing and valorization.
The diversity of hemicellulose oligomers enables many potential applications, but controlling yield and oligomer molar mass is challenging. Oligomer production by hydrolysis of softwoods was investigated, and the evolution of molar mass was described by a population balance model. A two-dimensional calibration method enabled measurement of broadly distributed oligomer molar mass and concentration simultaneously by size exclusion chromatography. The model describes the full evolution of oligomers from initial solubilization from the softwood, depolymerization to ever-smaller molecules, and final generation of degradation products. Maximum yield and the corresponding reaction conditions for each molar mass interval were predicted. It is likely that the bonds of insoluble hemicellulose break randomly to form soluble oligomers. This may be related to the distribution of acidic groups within the softwood matrix. The soluble oligomers tend to break near the middle of the chain to produce smaller oligomers. This work provides new insights into the relative reactivity of hemicellulose intermediates to facilitate future conversion technologies.
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