Coaxial‐electrospinning as a new method to study confined crystallization of polymer

Abstract

Coaxial-electrospinning (ES) was used as a new method to fabricate one-dimensional (1D) confinements for studying confined crystallization of poly(ethylene glycol) (PEG). A series of core-sheath ultrafine fibers with PEG as the core and cellulose acetate as the sheath were obtained by coaxial ES. It was found that the uniform core-sheath ultrafine fibers could be fabricated and a (1D) confinement environment, a nanotube with a diameter from 68 to 860 nm, could be obtained by coaxial-ES. When the confinement dimension decreased to be smaller than 120 nm in diameter, the melt temperature (T m ), the crystallization temperature (T c ), the crystallinity (X m ), and the crystal sizes of the PEG were much smaller than those of bulk PEG and when the nanotube was larger than 200 nm in diameter, the T m , T c , X m , and the crystallite sizes of the PEG were close to those of bulk PEG, which suggested that the crystallization of the PEG was influenced by the confinement dimension.

Effect of interface and confinement size on the crystallization behavior of PLLA confined in coaxial electrospun fibers

“…The results of nonisothermal and isothermal crystallization reveal that the crystallizability of C1 composite fiber is enhanced and it crystallizes faster, as compared with bulk PLLA and PLLA fiber. Such a phenomenon is quite unusual, since it is frequently reported that the crystallizability of polymers becomes weaker when they are nano‐spatially confined . The confined polymers usually exhibit a lower T c , as compared with unconfined ones.…”

“…reported some semicrystalline polymers such as poly (ethylene glycol) (PEG), PVDF 29 and polyoxymethylene (POM) under cylindrical confinement formed by coaxial electrospinning and found that the confinement dimension had a great influence on the crystallinity, crystalline structure and crystalline morphology. Their results showed that the crystallizability of PEG confined within cellulose acetate (CA) coaxial electrospun fibers decreased with decreasing confinement size . A transition from β‐crystal to α‐crystal was also observed in the PAN/PVDF core‐sheath nanofibers when PVDF recrystallized from the melt, which was correlated to the confinement effect …”

“…However, PLLA has a shortcoming of relatively slow melt‐crystallization rate, as compared with other semicrystalline polymers such as PEO, PCL, PE and so on. It is widely reported that crystallizability of nano‐spatially confined polymers is weakened, when compared with their bulks . If crystallization of PLLA is also suppressed under nano‐spatial confinement, preparation of crystalline PLLA coaxial fibers would be very difficult.…”

Micro/nano-encapsulation of a phase change material by coaxial electrospray method

“…Moreover, several research groups such as Lee et al [23], Wu et al [24], Zhang et al [25], Lee et al [26], Yu et al [27], and Luo et al [28] worked with coaxial electrospray and did not mention the position of the inner needle tip relative to that of the outer needle. However, the core capillary protruding outside the shell capillary is dependent on the feeding rates of the inner and the outer liquids, the interfacial tension, and the viscosity ratio of the liquids [17,29].…”

Melt electrospinning in a parallel electric field

“…As an efficient, direct, and simple method of producing polymer nanofibers, electrospinning has attracted increasing attention because of its versatility and potential for application in diverse fields . Although the setup, materials, and conditions of electrospinning processes vary, fiber instability often occurs, especially when the jet is near the collector.…”