Different surfactants are introduced to study the diameter and morphology transformation characteristics of electrospun nanofiber. Surfactants increase the net charge density and instability motion of charged jet. The instability motion provides a good way to stretch the charged jets into finer ones, by which the beaded structures are also prevented. Ultrafine nanofiber with average diameter less than 65 nm can be fabricated. The nanofiber diameter decreases with the increase of surfactant concentration in polymer solution. The nanofibers with anionic surfactant sodium dodecyl sulfate (SDS) have the smallest diameter. The cationic surfactant hexadecyl trimethyl ammonium bromide (HTAB) plays the best role to prevent the formation of beaded structures in nanofibers, and helps to increase the uniformity of electrospun nanofiber. The effects of surfactants on the nanofiber diameter and morphology have been studied, which would promote the industrial application of ultrafine polymeric nanofibers.

No abstract

A multi nozzle electrospinning spinneret with assistant sheath gas was designed to realize the multi jets injection, by which the production rate of nanofiber can be promoted. The sheath gas around the nozzle decreased the surface charge density, and provided an excess stretching force to increase the motion speed of charged jet. The diameter of charged jet was also decreased by the sheath gas further. On the other hand, the sheath gas also reduced the mutual disturbance among charged jets, by which stable multi jets injection can be gained. The stretching force increased along with air pressure of sheath gas. Then, both of the nanofiber diameter and the critical voltage required for jet injection decreased with the increase of air pressure. With the increase of sheath gas pressure, the uniformity of electrospinning nanofiber can be also improved. As sheath gas pressure increased from 0kPa to 50kPa, the critical voltage required for the jet injection from multi nozzle decreased from 5kV to 0.3kV, meanwhile the averaged diameter of electrospinning nanofiber decreased from 472.80nm to 230.60nm. Multi nozzles electrospinning spinneret with sheath gas provided an excellent way to increase the production speed of nanofiber, and promoted the application of electrospinning technology.

No abstract

An ionic polymer metal composite (IPMC) is a kind of electro-active polymer. Due to the properties of low driving voltage, large deformation, flexibility and lightness, it is becoming one of the more popular from a diversity of smart materials. In this study, a novel structure of Nafion® film is proposed to improve the performance of an IPMC. IPMC samples with a gradient structure in thickness are fabricated and their performance is investigated to confirm the validity of the gradient structure. The deformation displacement and the blocking force are compared under AC and DC voltage by experiments. The results indicate that the structure of gradient in thickness would improve the performance both in deformation displacement and blocking force.