Xinhang Wang

Linear polymeric ionic liquids as phase-transporters for both cationic and anionic dyes with synergic effects

A series of linear polymeric ionic liquids were synthesized from synthetic polyester (PEP) and the following anion exchange reactions. The structure and properties of the obtained polymeric ionic liquids were characterized by 1H NMR, FTIR, TGA and solubility tests. It was found that the obtained polymeric ionic liquid [PEP-MIM]DBS containing a cationic imidazole group and anionic DBS on the side chain was soluble in chloroform and was demonstrated to be a very effective transporter for the anionic dye methyl orange (MO) and cationic dye methylene blue (MB) from the water phase to the chloroform phase individually as well as simultaneously. The transfer efficiency reached 92% for MO and 80% for MB in the phase-transfer of the single dye. In addition, the phase-transfer experiments of the MO/MB mixed solution showed that the absence of MO improved the transfer efficiency of MB by 20% compared with the single solution.

Surface functionalization of cellulose nanocrystals with polymeric ionic liquids during phase transfer

In this study, the cellulose nanocrystals (CNCs) were prepared by method of acid hydrolysis, while the polymeric ionic liquid (PIL) [PEP-MIM]DBS was synthesized by epichlorohydrin, o-phthalic anhydride as well as N-methylimidazole then anion exchanged by sodium dodecyl benzene sulfonate. It was demonstrated that [PEP-MIM]DBS could modify CNCs by non-covalent interaction to change its surface properties, such as amphiphilicity. The chemical structure of the composite CNCs/[PEP-MIM]DBS was characterized via FTIR, 13C NMR, TGA, XRD, etc. Moreover, the properties and applications were characterized through a series of dispersion experiments, contact angle tests, FE-SEM, etc. This study showed that the PIL-modification improved the dispersion of CNCs in non-polar organic solvents with their chemical structure integrated.

Synthesis and Characterization of Novel Thermotropic Aromatic-Aliphatic Biodegradable Copolyesters Containing D,L-Lactic acid (LA), Poly(butylene terephthalate) (PBT) and Biomesogenic Units

In this study, the copolyesters based on 4-hydroxybenzoic acid (HBA) and vanillic acid (VA), lactic acid (LA) and poly(butylene terephthalate) (PBT) were synthesized via melt polymerization and fully characterized by various measurements. The influences of content of HBA and VA units on thermal behavior, structure and degree of crystallinity of copolyesters were discussed in more detail. It was found that the copolymerization of aliphatic and aromatic units together could make the best use of advantages of the respective polyesters. Moreover, the copolyesters with more than 40 mol% of HBA and VA units could show liquid crystallinity in broad temperature range.

Full pH-range responsive hyperbranched polyethers: synthesis and responsiveness

In order to impart full pH-range responsiveness within biocompatible hyperbranched polyethers, new amphiphilic polyethers, i.e. HPMHO–Amines and HPMHO–Carboxys, which have a molecular structure similar to hyperbranched PEG, were prepared through ring-opening polymerization and modified by amination or carboxylation. Because of the existence of hydrophobic core and ionization of weak acidic and basic groups on the surface, these hyperbranched polyethers showed reversible pH-response in aqueous solution. The responsive pH values covered the complete pH range and could be readily adjusted by only changing the degree of modification. Cellular experiments showed that these pH-responsive hyperbranched polyethers had low cytotoxicity, indicating this novel full pH-range responsive hyperbranched polyether would be a promising functional material for physiological and pH-relevant bio-applications.

Nonisothermal and isothermal oxidative degradation behavior of thermotropic liquid crystal polyesters containing kinked bisphenol AF and bisphenol A units

The polyester P–bisphenol AF 2.5 (BPAF 2.5) and P-bisphenol A 2.5 (BPA 2.5) with low melting temperature and high glass transition temperature can be obtained by introducing 2.5 mol% BPAF/BPA and terephthalic acid (TA) units respectively into the molecular chain of poly(oxybenzoate-co-oxynaphthoate) (P-HBA70). In this study, the nonisothermal and isothermal oxidative degradation behavior of polyester P-BPA2.5 and P-BPAF2.5 were investigated comparatively with parent polyester P-HBA70 by thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy measurements. The introduction of BPAF/BPA units into the molecular chain of P-HBA70 strongly influenced the degradation behavior of polyesters. Four multiple heating rate methods including Kissinger, Kim–Park, Flynn–Wall–Ozawa, and Friedman methods were applied to evaluate the dynamic thermal stability successfully. The following order of the activation energy values: P-BPAF2.5 > P-HBA70 > P-BPA2.5 can be found for the three samples. However, from the results obtained by the standard isoconversional method, the P-BPA2.5 showed a better thermal stability as compared to P-BPAF2.5 under isothermal atmosphere.

Preparation, structure, and properties of melt spun cellulose acetate butyrate fibers:

The melt spinning of cellulose acetate butyrate (CAB) without any additives is realized according to the thermal and rheological properties of cellulose acetate butyrate raw material. Thermogravimetric analysis reveals that thermal degradation of cellulose acetate butyrate occurs at 275℃ in oxygen. Rheological tests show that cellulose acetate butyrate is a strong shear thinning pseudoplastic fluid. The melt viscosity of cellulose acetate butyrate is found to be relatively sensitive to temperature change and cellulose acetate butyrate melt is difficult to flow until the temperature reaches 230℃. However, thermal degradation of cellulose acetate butyrate during spinning cannot be completely avoided even when the spinning temperature is 230℃. The orientation of cellulose acetate butyrate fibers can be improved by increasing the spinning draw ratio during the spinning process or by hot drawing during the drawing process. Crystallization of cellulose acetate butyrate fibers is facilitated by improving molecular orientation. Owing to the improved orientation and crystallinity, the tensile strength and initial modulus of cellulose acetate butyrate fibers are enhanced. The cellulose acetate butyrate fiber achieves the highest degree of orientation and crystallinity by drawing at 135℃, showing the highest tensile strength at 1.42 cN/dtex. Moreover, dyeing experiments show that the cellulose acetate butyrate fiber can be dyed with a disperse dye and the suitable dyeing temperature is in the range of 80∼90℃.