Yali Ji

Solubility of a High Molecular-Weight Bacterial Cellulose in Lithium Chloride/N,N-dimethylacetamide Solution

High molecular-weight bacterial cellulose (BC) was found to be soluble in a lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solvent system with a maximal concentration of 3 wt% if an activation procedure was performed beforehand. The granular BC was not favored and had to be ground to powders before dissolution. To facilitate subsequent dissolution, an activation procedure consisting of stewing the BC samples at 45°C–50°C in DMAc containing dissolved KMnO4 was adopted. It was found that a swelling temperature of 45°C was preferred, for about 4 h, but continuous, constant temperature heating during dissolving procedure was unfavorable, possibly due to the instability of the intermediate complex formed between the Li+ ion and the carbonyl oxygen of DMAc. However, the BC sample would be gradually dissolved if placed at room temperature for a long enough time.

Preparation, Characterization, and Rheological Properties of Dibutyrylchitin

Dibutyrylchitin was prepared by an acylating reaction in a heterogeneous system with butyric anhydride as an acylating agent and perchloric acid as a catalyst. The effects of the preparation conditions, including chitin grain size, reaction temperature, and reaction time, on conversion ratio of chitin to dibutyrylchitin are discussed in detail. By adjusting reaction time and reaction temperature, dibutyrylchitin with an adequate intrinsic viscosity could be obtained. Steady-state rheological measurement was also performed and the results revealed that concentration, temperature, and shear rate had a great influence on the rheological properties of dibutyrylchitin/dimethylformamide solutions. Thus, a suitable spinning condition could be determined from the rheological analyses.

Submicron Ion-Exchange Fibers of Polystyrene and Styrene-Butadiene-Styrene Copolymer Blends

In the present study, submicron ion-exchange fibers (IEFs) of polystyrene (PS) and its blends with styrene-butadiene-styrene block copolymer (SBS) were prepared by electrospinning and postsulfonating modification. Scanning electron microscopy (SEM) images showed that the diameters of the fibers enlarged significantly after treatment and the surfaces become rougher. Mechanical properties analysis showed that the electrospun fibers (EF) and the IEFs from PS/SBS blend fabrics possessed better mechanical performances than those from pure PS. The ion-exchange capacity (IEC) of 4.35 mmol/g and and copper ions (Cu2+) adsorption value of 3.08 mmol/g for IEFs from PS/SBS blends were both higher than that of IEFs from pure PS and the conventional IEFs produced by coating or grafting fibrous substrates with functionalized resins or monomers. Dynamic adsorption experiments were made to test the behavior of adsorption for Cu2+. The results of dynamic adsorption experiments with Cu2+ showed that the IEFs from PS/SBS would quickly purify 3000 ml waste water containing Cu2+ (100 mg/L), and the removal rate for Cu2+ reached 96.5% even at the flow rate of 12 ml/min. The study provided an absorbent with a high dynamic adsorption capacity for removing Cu2+ from waste water.

Degradable Bioelastomers Prepared by a Facile Melt Polycondensation of Citric Acid and Polycaprolactone-diol

Abstract Citrate-based bioelastomers have great potentials in various biomedical fields. An appropriate selection of diol monomers could tune their properties to fulfill different application requirements. Herein, polycaprolacone diol (PCL-diol) was selected as the diol monomer to fabricate poly(caprolactone-diol citrate) (PCC) degradable bioelastomers by a one pot melt polycondensation coupled with subsequent thermosetting or post-polymerization. The catalyst-free polycondensation reaction was confirmed by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1HNMR) spectroscopy. The properties of the PCC elastomers were explored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), uniaxial tension tests, dynamics mechanical analysis (DMA), water-contact angle and in-vitro degradation measurements. The results showed that the molar ratio of monomers and thermosetting conditions had significant effects on the ultimate properties of the PCC elastomer. By regulating monomer ratio and thermosetting temperature the crosslink density ranged from 32 ± 6 mol/m3 to 292 ± 18 mol/m3, the tensile strength ranged from 171 ± 28 KPa to 977 ± 112 KPa, Young’s modulus ranged from 252 ± 36 KPa to 1737 ± 212 KPa, ultimate elongation ranged from 70 ± 9% to 260 ± 32%, the static-water-contact-angle was in the range of 65.4 ± 1.8 ∼ 91.0 ± 0.9° and the weight loss of the PCC elastomer in phosphate buffered saline (PBS) (pH =7.4) was in the range of 30 ∼ 100 wt% after 8 weeks degradation. An elastic and compressible, porous scaffold was fabricated via a salt leaching method, which has potential use in soft tissue grafts.

Crystallization Behavior of PEO in Nano‐Structured PEO‐b‐PS/PPO Blends

Blends of poly (ethylene oxide)‐b‐polystyrene (PEO‐b‐PS) diblock copolymer and poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) homopolymer were obtained by solution blending, and the morphologies of PEO dispersed nanoparticles in PPO/PS matrix were observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The isothermal crystallization kinetics was studied using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Nonisothermal crystallization kinetics was studied using DSC. The results showed that PEO segments were easier to crystallize in the blend than in the copolymer probably due to the interfaces of PPO acting as nucleation sites to promote the crystallization of PEO. The crystallization of PEO blocks destroyed the pre‐existing microdomain structure even though the glass transition temperature of the matrix was much higher than the crystallization temperature.