Zhimei Wei

Porous electrospun ultrafine fibers via a liquid–liquid phase separation method

This communication reported a new simple method to produce porous ultrafine fibers during electrospinning process. It was named liquid–liquid phase separation method. This method required introducing suitable amount of water into electrospun solution to form similar stable three-phase membrane-forming systems previously. Scanning electron microscopy was employed to evaluate the morphology of porous ultrafine fibers. According to the investigation result, porous ultrafine fibers were prepared by this method. Liquid–liquid phase separation caused by the change of the property of three-phase systems of charged jet that was led by the rapid solvent evaporation during electrospinning process was considered as the key role for the formation of porous structure. This method is very simple and it not only lowers the requirement on the solvents but also does not introduce any new component into the fibers. Therefore, this method provides a new simple way to form porous structure during electrospinning process.

Porous Electrospun PES/PEG Ultrafine Fibers for the Removal of Endocrine Disruptors

In this work, porous polyethersulfone (PES)/polyethylene glycol (PEG) ultrafine fibers were prepared via electrospinning technique, and then were used to removing endocrine disrupters from their aqueous solutions. The surface and the internal structures of PES/PEG ultrafine fibers were characterized by scanning electron microscopy (SEM) and the result showed that they were both porous. The porous electrospun PES/PEG ultrafine fibers can remove endocrine disrupters such as biphenyl A (BPA) and biphenyl (BP) effectively. Compared with pure PES ultrafine fibers, PES/PEG ultrafine fibers showed larger adsorption capacity and faster kinetics of uptaking target species. The hydrophilic properties and the porosity of porous PES/PEG ultrafine fibers can be controlled by adding hydrophilic materials such as polyethylene glycol (PEG), which can improve the adsorption properties of porous PES/PEG ultrafine fibers significantly. The results showed that porous electrospun PES/PEG ultrafine fibers had the potential to be used in environmental application and water treatment.

Preparation and drug delivery study of electrospun hollow PES ultrafine fibers with a multilayer wall

The focus of this work was the preparation of hollow ultrafine fibers with a multilayer wall via coaxial electrospinning technology in one step and then studied their drug delivery properties. In this paper, by choosing a suitable dilute hydrophilic polymer solution as the core solution, polyethersulfone (PES) hollow ultrafine fibers with two different layers wall (porous structure layer and dense smooth layer) were formed during coaxial electrospinning process in one step. They showed good drug delivery capacity when curcumin was used as the model drug. There were much larger delivery amounts, more stable release rate, and higher utilization rate of PES hollow ultrafine fibers with a multilayer wall to curcumin than that of PES porous ultrafine fibers. Compared with porous ultrafine fibers, hollow ultrafine fibers with two different layers wall were more suitable to be used as drug delivery materials. Besides, between the two hollow ultrafine fibers with two different layers wall mentioned in this paper, there was much better drug delivery capacity for the hollow fibers produced with the core solution of PVA/DMSO. These results showed that PES hollow ultrafine fibers with two different layers wall have the potential to be used as the drug delivery materials.

A new simple method to prepare hollow PES microspheres

A new simple method for the formation of hollow polyethersulfone (PES) microspheres was reported in this paper. Coaxial electrospraying equipment and nonsolvent precipitating bath were used to produce hollow microspheres in one step. The properties of the core solution affected the formation of hollow PES microspheres. To form hollow microspheres in one step, the core solution should be removed directly by a nonsolvent. Additionally, the core solution should also be used to occupy the internal space of microspheres and form a supporting layer at the interface between the core solution and the shell solution. The supporting layer formed by the micro-phase that was caused by the phase separation of the core or shell solution was the key factor for the formation of hollow PES microspheres. The performance of hollow microspheres produced by this method was excellent. This method provided a new simple way to form hollow polymer microspheres and can be extended to other polymers to prepare hollow microspheres in one step.

Development of a novel preparation method for conductive PES ultrafine fibers with self-formed thin PES/CNTs composite layer by vapor treatment

Conductive electrospun fibers have attracted widespread interest in the field of electromagnetics. However, the problem of how to effectively improve the electrical conduction of electrospun fibers has still not been adequately addressed. In this study, a new, simple and effective method was introduced to significantly improve the conductive properties of fibers. PES/PVA fibers with previous addition of 20 wt% PVA were chosen as a matrix due to the large parallel porous structure. The carbon nanotubes (CNTs) were first absorbed by the PES/PVA fibers, and then a thin polymer/CNTs composite layer was self-formed on the surface of the porous fibers by vapor treatment. Most importantly, a CNTs network structure was also formed in this vapor process, which easily gave the porous fibers a significant enhancement in conductivity with only a small amount of CNTs. Electrical conduction tests showed that the conduction of the fibers increased with increasing CNT content, and attained the maximum value when the amount of CNTs was around 7 wt%. The adsorption time and the DMSO vapor treatment time were optimized to obtain the best thin polymer/CNT composite layers. The surface microstructure of the composite layer was observed using scanning electron microscopy (SEM) and TGA. The results showed that this novel, powerful method could potentially be used to prepare novel types of conductive polymer fibers.

Structure Controlling and Adsorption Application of Polyethersulfone Porous Microspheres Prepared via Electrospraying

The focus of this work is to control the structure of electrosprayed polymer microspheres and then study the effect of different structures on the microspheres’ adsorption properties. Scanning electron microscopy (SEM) coupled with image analysis software was employed to evaluate the size distributions and the structure of microspheres. According to the observation and analysis results, two types of polyethersulfone (PES) porous microspheres (perfect sphere-shaped and collapsed) were prepared via electrospraying technology by adjusting the solvent and polymer molecular weight. The porous PES microspheres can remove bisphenol A (BPA) from its aqueous solution effectively. Compared with collapsed microspheres, the rough microspheres had much higher specific surface area and better mobility in the BPA aqueous solution, so it showed a better adsorption capacity than that of collapsed microspheres. The solvent evaporation rate and the occurrence rate of phase separation significantly affect the structure and morphology of microspheres.

Release characteristics and processing-structure-performance relationship of electro-spinning curcumin-loaded polyethersulfone based porous ultrafine fibers

Abstract Polymeric porous ultrafine fibers with different structures as drug carrier could be facilely prepared. However, the drug release characteristics and relevant mechanism of different structural porous ultrafine fibers were not well studied. In the present work, different structural Poly-Ether-Sulfone (PES) based porous ultrafine fibers, namely PES, PES/Poly-Ethylene-Glycol (PEG) and PES/Water were prepared by electro-spinning. Curcumin was chosen as drug model loaded in these fibers. Investigation of curcumin release characteristics was carried out by the total immersion in buffer solution. The surface and inner structure of PES based ultrafine fibers were studied by scanning electron microscopy (SEM) in detail. It is found that there is significant difference in the accumulate release amount and release rate with similar structure. About 92.5% of curcumin released within 600 min for PES/PEG ultrafine fibers and only 58.9% of curcumin flowed out from PES with 1000 min. In order to discuss the fact of this phenomenon, the development structure of PES based porous ultrafine fibers was studied with curcumin release. The results indicated that the curcumin release was directly involved with the structure. For PES/PEG, curcumin around the surface layer released in advance. And then, some penetrable structure emerged with PEG dissolving in the buffer solution, which result in larger specific surface area and more embedded curcumin from the interior structure of the ultrafine fibers diffusing out. For the others, curcumin release only through its own pores of ultrafine fibers. Finally, the processing-structure-performance relationship of PES based porous ultrafine fibers were confirmed by the diversity of porosity and contact angle. The research results demonstrate that PES based porous ultrafine fibers have the potential to be used as drug carrier in the drug delivery according to the practical clinical requirements.