Renewable Bio-Based Polymers and Degradable Functional Polymers

In this dissertation, polymers derived from renewable bio-based resources and degradable functional polymers with stimuli-responsive properties by various polymerization techniques were investigated. The properties of these polymeric materials were characterized and discussed. In Chapter 1, the overall background and recent development of renewable bio-based polymers as well as degradable stimuli-responsive polymers was introduced. Major research objectives of my doctoral work were described. The first section of the dissertation, on the preparation of renewable bio-based polymers was provided from Chapter 2 to Chapter 4. In Chapter 2, the preparation of novel polymers derived from renewable gum rosin by atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization was described. Chapter 3 described the preparation of different rosin containing polycaprolactone (PCL) by a combination of ring-opening polymerization (ROP) and click chemistry. The rosin containing PCL showed excellent hydrophobicity, elevated glass transition temperature, low water uptake and full degradability. Also the polymers exhibited good biocompatibility and low cytotoxicity, suitable for potential biomedical applications. In Chapter 4, sustainable graft copolymers derived from renewable cellulose, rosin and fatty acid as novel thermoplastic elastomers were accomplished by ATRP and mechanical properties of the polymers were characterized by tensile stress-strain and creep compliance testing. The second part of the dissertation is the preparation and characterization of degradable salt-responsive polymers. In Chapter 5, degradable cationic random copolymers containing a PCL skeleton and quaternary ammonium side groups were synthesized by a combination of ring-opening polymerization and copper-catalyzed click reaction. These random copolymers exhibited ion strength-dependent solubility in water. In salt-free water or water with low ionic strength, random copolymers were completely soluble while in high salt concentration solution, the solubility of random copolymers decreased. Also these cationic random copolymers showed good degradability in dilute acid solution. Chapter 6 described the preparation of high molecular weight cationic salt-responsive bottle-brush polymers by ring-opening polymerization, ring-opening metathesis polymerization, and click reaction. These cationic bottle brush polymers exhibited not only good salt responsive properties but also better mechanical properties due to the high molecular weight of the polymers. Both the random copolymers and bottle brush polymers with salt responsive properties showed potential applications in personal hygiene products. Finally, a summary is given in Chapter 7. In addition, some suggestions about future research directions on the renewable polymer materials and degradable stimuli-responsive polymers are provided

Imaged based fractal characterization of micro-fracture structure in coal

We acknowledge financial support from the National Natural Science Foundation of China (41830427; 41472137), the Petro China Innovation Foundation (2018D-5007-0101), the Key research and development project of Xinjiang Uygur Autonomous Region (2017B03019-1), the Royal Society Edinburgh and National Natural Science Foundation China (NSFC 41711530129), and the Foreign Experts’ Recruiting Program from the State Administration of Foreign Experts Affairs P.R. China.Peer reviewedPostprin

Caveolin-1 Plays a Crucial Role in Inhibiting Neuronal Differentiation of Neural Stem/Progenitor Cells via VEGF Signaling-Dependent Pathway

In the present study, we aim to elucidate the roles of caveolin-1(Cav-1), a 22 kDa protein in plasma membrane invaginations, in modulating neuronal differentiation of neural progenitor cells (NPCs). In the hippocampal dentate gyrus, we found that Cav-1 knockout mice revealed remarkably higher levels of vascular endothelial growth factor (VEGF) and the more abundant formation of newborn neurons than wild type mice. We then studied the potential mechanisms of Cav-1 in modulating VEGF signaling and neuronal differentiation in isolated cultured NPCs under normoxic and hypoxic conditions. Hypoxic embryonic rat NPCs were exposed to 1% O2 for 24 h and then switched to 21% O2 for 1, 3, 7 and 14 days whereas normoxic NPCs were continuously cultured with 21% O2. Compared with normoxic NPCs, hypoxic NPCs had down-regulated expression of Cav-1 and up-regulated VEGF expression and p44/42MAPK phosphorylation, and enhanced neuronal differentiation. We further studied the roles of Cav-1 in inhibiting neuronal differentiation by using Cav-1 scaffolding domain peptide and Cav-1-specific small interfering RNA. In both normoxic and hypoxic NPCs, Cav-1 peptide markedly down-regulated the expressions of VEGF and flk1, decreased the phosphorylations of p44/42MAPK, Akt and Stat3, and inhibited neuronal differentiation, whereas the knockdown of Cav-1 promoted the expression of VEGF, phosphorylations of p44/42MAPK, Akt and Stat3, and stimulated neuronal differentiation. Moreover, the enhanced phosphorylations of p44/42MAPK, Akt and Stat3, and neuronal differentiation were abolished by co-treatment of VEGF inhibitor V1. These results provide strong evidence to prove that Cav-1 can inhibit neuronal differentiation via down-regulations of VEGF, p44/42MAPK, Akt and Stat3 signaling pathways, and that VEGF signaling is a crucial target of Cav-1. The hypoxia-induced down-regulation of Cav-1 contributes to enhanced neuronal differentiation in NPCs

Higher performance polyurethane-organoclay nanocomposites

A series of polyurethane (PU)-organoclay nanocompositcs were synthcsised by swelling organically-modified layered silicate (organoclay) in a polyol with subsequent polymerisation. The techniques of wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), Fourier transform infer-red spectroscopy (FTIR), modulated differential scanning calorimetry (MDSQ, contact angle measurement and tensile test were used to investigate the effect of addition of organoclay on curing dynamics, phase structure, tensile properties, dynamical mechanical thermal analysis (DMTA), fatigue durability and surface properties of PUs. FTIR and MDSC revealed that the addition of organoclay has an important influence on curing process of PUs. With increasing organoclay, the reaction between -OH group in polyol and- NCO in isocyanate became fast. WAXD and TEM results showed that PU-organoclay nanocomposites prepared in this research were intercalated materials ones. The addition of organoclay has significant influences on the phase structure of PUs. SAXS results revealed that the long period (average thickness of soft and hard segment) decreased with increasing organoclay. Contact angle measurements showed that the organoclay can affect the surface properties of PU nanocomposites. The addition of organoclay resulted in the decrease in surface energy. AFM results revealed that the adhesion force of the surface of PU nanocomposites decreased with increasing organoclay. Tensile strength and elongation of PUs at break were improved significantly by incorporating organoclay. The tensile strength increased up to 100%, and elongation increased up to 120%. At high soft segment content, with increasing organoclay, the modulus decreased slightly, and at low soft segment content, the modulus increased with increasing organoclay. The addition of organoclay improved significantly thermal stability of PUs. Fatigue measurements uggestedt hat the fatigue durability can significantly be improved by incorporating organoclay. A nanospring concept for understanding the enhancemenht as been proposed

Evaluation and Error Correction of the ECMWF Subseasonal Precipitation Forecast over Eastern China during Summer

Subseasonal-to-seasonal (S2S) prediction is a highly regarded skill around the world. To improve the S2S forecast skill, an S2S prediction project and an extensive database have been established. In this study, the European Center for Medium-Range Weather Forecasts (ECMWF) model hindcast, which participates in the S2S prediction project, is systematically assessed by focusing on the hindcast quality for the summer accumulated ten-day precipitation at lead times of 0–30 days during 1995–2014 in eastern China. Additionally, the hindcast error is corrected by utilizing the preceding sea surface temperature (SST). The metrics employed to measure the ECMWF hindcast performance indicate that the ECMWF model performance drops as the lead time increases and exhibits strong interannual differences among the five subregions of eastern China. In addition, the precipitation forecast skill of the ECMWF hindcast is best at approximately 15 days in some areas of Southeast China; after correcting the forecast error, the forecast skill is increased to 30 days. At lead times of 0–30 days, regardless of whether the forecast error is corrected, the root mean square errors are lowest in Northeast China. After correcting the forecast error, the performance of the ECMWF hindcast shows better improvement in depicting the quantity and temporal and spatial variation of precipitation at lead times of 0–30 days in eastern China. The false alarm ratio (FAR), probability of detection (POD), and equitable threat score (ETS) reveal that the ECMWF model has a preferable performance at forecasting accumulated ten-day precipitation rates of approximately 20∼50 mm and indicates an improved hindcast quality after the forecast error correction. In short, adopting the preceding SST to correct the summer subseasonal precipitation of the ECMWF hindcast is preferable

The Application of a Desktop NMR Spectrometer in Drug Analysis

A desktop NMR spectrometer was used to qualitatively analyze samples in drug-related cases in order to enhance the accuracy of the results and identify new drugs. Twelve known drugs and their derivatives were used to establish the parameters, conditions, and procedures for the methods and validate the feasibility and reliability of the methods. First, 1-D and 2-D NMR data for these 12 drugs and their derivatives were obtained in detail using a 600-MHz NMR spectrometer to create a data library. Next, some of these 12 drugs were analyzed using a Picospin 80 MHz desktop NMR spectrometer to set up the analytical procedure and method. With the procedure and method established, real case samples were analyzed and the data were compared to those obtained by a standard method. The results indicate that the desktop NMR spectrometer is a reliable and promising approach that can be used in criminology to quickly identify whether or not samples contain illegal drugs

Poly(hydroxyethyl methacrylate)-based composite cryogel with embedded macroporous cellulose beads for the separation of human serum immunoglobulin and albumin

A novel super-macroporous monolithic composite cryogel was prepared by embedding macroporous cellulose beads into poly(hydroxyethyl methacrylate) cryogel. The cellulose beads were fabricated by using a microchannel liquid-flow focusing and cryopolymerization method, while the composite cryogel was prepared by cryogenic radical polymerization of the hydroxyethyl methacrylate monomer with poly(ethylene glycol) diacrylate as cross-linker together with the cellulose beads. After graft polymerization with (vinylbenzyl)trimethylammonium chloride, the composite cryogel was applied to separate immunoglobulin-G and albumin from human serum. Immunoglobulin-G with a mean purity of 83.2% and albumin with a purity of 98% were obtained, indicating the composite cryogel as a promising chromatographic medium in bioseparation for the isolation of important bioactive proteins like immunoglobulins and albumins

Chromatographic adsorption of serum albumin and antibody proteins in cryogels with benzyl-quaternary amine ligands.

The preparation and characterization of mixed-mode adsorbents for a typical separation purpose are of great importance in bioseparation areas. In this work, we prepared a new monolithic cryogel with a combination of ion-exchange and hydrophobic functions by employing benzyl-quaternary amine groups. The fundamental cryogel properties, protein equilibrium adsorption isotherm and chromatographic adsorption in the cryogel were measured experimentally. The results showed that, by using bovine serum album as the model protein, the dual functional cryogel has protein binding capability even in salt solution and the buffer with pH close or below the protein isoelectric point due to both the electrostatic and hydrophobic interactions. A capillary-based adsorption model was developed, which provided satisfied insights of the microstructure, axial dispersion, mass transfer as well as protein adsorption characteristics within the cryogel bed. The chromatographic isolation of bioactive proteins from rabbit blood serum was carried out by the cryogel. Immunoglobulin G antibody with a purity of 98.2% and albumin with a purity of 96.8% were obtained, indicating that the cryogel could be an interesting and promising adsorbent in bioseparation areas