Stevensbaun8549

Glycopolymers based on dextran are frequently prepared via ATRP, whereas the use of RAFT polymerization is strangely limited due to the difficult synthesis of Dextran-based macromolecular chain transfer agent (DexCTA). The aim of this work is to establish a controlled and reproducible methodology for its preparation. Direct esterification of the hydroxyl dextran functions is the most common method. Our study shows that this latter leads to a very low degree of functionalization. As alternative, we report a reproductible multistep strategy consisting of oxidation, amination, and amidation reactions. Various DexCTAs with tunable degree of substitution (respectively 0.025, 0.045, and 0.06) were successfully prepared. As proof of concept, one of the DexCTAs was involved in the photo-mediated RAFT polymerization of hydroxypropyl methacrylate in DMSO to prepare amphiphilic Dex-g-PHPMA glycopolymers, which can self-assemble in water into monodisperse spherical nano-objects. MTT assays revealed the biocompatibility of all dextran derivatives. The target of the study is to improve the yield and the colloidal stability of cellulose nano-crystals (CNC) that is obtained through maleic acid hydrolysis. Herein, a facile/ green approach to prepare CNC with high yield and colloidal stability from bamboo fibers is presented. Ball mill pretreatment can break down and open up the structure of bamboo fibers, thus exposing more hydroxyl groups on the surface of pulp fibers and increasing the access of acid molecules into pulp fibers. The maleic acid molecules can easily hydrolyze cellulose, thus releasing more crystalline parts; maleic acid anhydride can react with hydroxyl groups to generate more -COOH groups on CNC. The yield of resultant CNC was 10.55-24.50 %, which was much higher than 2.80 % of the control. The study put forward a facile approach to prepare CNC with high yield and colloidal stability, and paves a possible way for industrialization of CNC production. Production and potential application of chitooligosaccharide is reported in this study. Chitooligosaccharide was produced by enzymatic hydrolysis of chitosan using Bacillus cereus chitosanase. The chitooligosaccharide was characterized, and its prebiotic activity together with the antioxidant activity were evaluated and compared to marketed standard and chitosan. Additionally, its stability in yoghurt was monitored. The produced chitooligosaccharide was water soluble with molecular weight of 2.005 kDa and higher degree of acetylation. Bioactivity results cleared the chitooligosaccharide has potent prebiotic plus antioxidant activity with poor stability in yoghurt. Subsequently, encapsulation of chitooligosaccharide into nanoparticles and microparticle were assessed to enhance its stability. Our results indicated that nanoparticles with size 100 nm maintained 96.83 + 1.2 % of chitooligosaccharide in yoghurt during shelf life compared to 45.09 ± 2.5 % for microparticle (850 μm). Finally, the sensory evaluation favored the yoghurt containing chitooligosaccharide nanoparticles over free chitooligosaccharide or chitooligosaccharide microparticle, which suggest nanoparticles as potential formula to boost the chitooligosaccharide stability in yoghurt. The pectin from tomato peel waste (TPP) was employed as tin corrosion inhibitor with the aim to enhance the knowledge regarding the application of natural inhibitors, instead synthetic, and reducing the waste disposal for value-added biopolymers production. To evaluate the TPP anticorrosion activity the commercial apple pectin (CAP) was also utilised. The gravimetric tests show that the highest inhibitive impact (η) of 75.9 % (CAP) and 73.9 % (TPP) are gained at concentration of 20 g L-1. By electrochemical, potentiodynamic polarization and impedance spectroscopy measurements, the maximum η (60.05-65.5 %) are reached at lower concentration (4 g L-1), due to tendency of pectins to form viscous solution. The prominent decreases in current density with the shifts of potential in the cathodic direction revealed that pectins provided cathodic protection of tin surface. Similar inhibition impact of pectins, and fine agreement between applied methods confirmed their suitability against tin corrosion. An antioxidant-active polysaccharide (WMP) with a molecular weight of 26.91 kDa was isolated from Mentha haplocalyx Briq by water extraction, ethanol precipitation and gel filtration. According to HPLC, methylation, GC-MS, and 1D/2D nuclear magnetic resonance spectroscopy, WMP is a heteropolysaccharide composed of Gal (84.2 %), Glc (9.8 %), Man (2.8 %) and Ara (3.2 %) with (1→6)-α-d-Galp and (1→4, 6)-α-d-Galp residues in the backbone and (1→6)-α-d-Galp and (1→6)-α-d-Glcp residues in the branch. The branch point was located at C-4 of (1→4, 6)-α-d-Galp residue with a branching degree of 19.71 %. WMP showed remarkably high scavenging ability for 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals, ferrous ion chelating activity and ferric reducing powder in vitro. In vivo result showed that WMP oral administration substantially increased the activities of antioxidant enzymes, including SOD, GSH-Px and CAT, and decreased MDA levels in the serum and liver of d-Gal-induced aging mice. Therefore, WMP can be an effective natural antioxidant. Microencapsulated phase change composite materials (MPCMs) with cellulose nanocrystals-composited poly (methyl methacrylate) (PMMA) as shell and n-eicosane as core was facially prepared via Pickering emulsion assisted solvent evaporation approach. PMMA and n-eicosane were dissolved in chloroform as the oil phase. Protein Tyrosine Kinase inhibitor Cellulose nanocrystals (CNC) can efficiently stabilize oil - in - water (O / W) emulsion, and the core-shell ratio will affect the thermal properties of MPCMs, study found that the optimal core-shell ratio was 12 and encapsulation ratio reached 58.2 %. The PMMA encapsulated MPCMs displayed a regular spherical shape sized in the range of 5-10 micrometers. They had favorable thermal stability and melting enthalpy of up to 150.8 J/g. Results of the thermal cycling tests showed melting enthalpy of MPCMs were maintained by over 99 % after 100 heating-cooling cycles. The proposed Pickering emulsion assisted solvent evaporation approach provides a potential way for industrial production of microencapsulated phase change materials.