Wettability regulation and mechanism of PLCL microfiber nonwoven materials
Electrostatic spinning technology is an efficient method for the preparation of nanofiber materials.The fiber materials produced by this method have high porosity and specific surface area,and their fiber structure can mimic the extracellular matrix,making them an ideal material for promoting repair and regeneration of damaged parts in tissue engineering.PLCL is a synthetic polymer material with high biosafety and degradability,and is widely used in tissue engineering and drug delivery.However,the poor hydrophilicity and poor biocompatibility of PLCL electrospun fiber materials limit their applications.The hydrophilicity of composite or pure PLCL fiber materials is often improved by mixing them with hydrophilic natural or synthetic polymer materials or post-treating PLCL microfiber nonwoven materials.However,the composite fiber material made by the former method is unstable in structure and prone to phase separation,and some of the natural polymer materials have large brittleness and poor flexibility,resulting in poor mechanical properties of the composite material.By contrast,the composite fiber material made by the latter method is unstable in effect,and is prone to being hydrophobic from being hydrophilic after a period of use.By changing the ratios of hexafluoroisopropanol(HFIP)and trifluoroacetic acid(TFA)in the electrostatic spinning solution,the wettability of poly(propylene lactone-caprolactone)(PLCL)microfibrous nonwoven materials was changed in a one-step method without adding any hydrophilic components or finishing.PLCL was dissolved in a solvent mixture of HFIP and TFA and then electrostatically spun,and it was found that the average fiber diameter decreased from 1.036 μm to 0.611 μm with the increase of TFA content from 0 to 100％,and the contact angle decreased from 121° in the droplet method to 46° in the bubble method.The infrared spectra,thermogravimetric curves,X-ray diffraction curves,and nuclear magnetic hydrogen spectra of the materials were further tested to investigate the mechanism of the phenomenon.The experimental results showed that the addition of TFA shortened the chain segment of PLCL macromolecule and reduced the number of hydrophobic ester groups,which led to the decrease of fiber diameter and the increase of hydrophilicity of the material.Nevertheless,the addition of TFA did not change the thermal stability of the material as a whole,and did not produce new chemical structures,and the hydrolysis occurred firstly in the amorphous region of the PCL molecule.It is proved that hydrophilic PLCL microfiber nonwoven materials can be prepared simply and efficiently by changing the solvent ratio.PLCL microfiber nonwoven materials can be applied to tissue engineering dressings,and inoculating epidermal cells or fibroblasts based on the polymer scaffold material can be used to repair patients'wound to increase the degree of active growth factor secretion.Since hydrophilic materials are easier for cell adhesion and biocompatible,improving the wettability of PLCL microfiber nonwoven materials is one of the keys to expanding their applications.
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