Temperature-sensitive Gel Nanofiber Membrane And Colloidal Electrospun Fiber Structure Evolution Mechanism

Electrospinning is one of the methods to prepare continuous nanofibers stably and efficiently.The micro and nanofibrous films prepared by the method have the advantages of high porosity,high specific surface area,fine size stability and light weight.Electrospun nanofibrous films give full play to their merits and are widely used in many fields due to the introduction of interpenetrating network and functional nano-particles.In this paper,the electrospun poly(N-isopropylamide)(PNIPAm)nanofibers were used as matrix,and the cross-linked network of sericin(SS)and genipin was introduced in nanofibers via in situ polymerization,thermo-resposive nanofibrous films with semi-interpenetrating networks were prepared.The best electrospinning conditions,the effect of semi-interpenetrating on thermo-responsivity,thermal stability and mechanical properties of electrospun nanofibrous films were explored.The ultraviolet light cross-linking group was further introduced to prepare nanofibrous membrane with double cross-linked network,and the effect of double cross-linked network on the wettability,swelling rate,size stability and underwater mechanical properties of the nanofibrous films.At the same time,the thermo-responsive microgels poly(NIPAm-co-tBA)were introduced in electrospun PAAm nanofibers,and one-dimensional nanofibers with blackberry-like,spindle-like and necklace-like structures were prepared,the mechanism of evolution of nanofiber structure was elucidated,which provided a theoretical basis for the design and construction of ordered structure of electrospun fibers.The research work mainly includes three parts:In the first part,the electrospun PNIPAm nanofibers were used as matrix,and the cross-linked networks of SS and Genipin were introduced to obtain thermo-responsive nanofibrous films by in-situ polymerization.The research suggests that the introduction of semi-interpenetrating network enhances size stability of fibrous films and the mechanical toughness underwater.The fibrous films have certain applications in the field of intelligent interface,trigger and tissue engineering scaffolds.In the second part,poly(N-isopropylacrylamide-co-benzophenone)(poly(NIPAm-co-ABP))with UV photo-polymerization was prepared by free radical polymerization and was introduced into SS and Genipin network,and then a double cross-linked network of nanofibrous films were prepared by means of electrospinning and UV radiation,our study shows that the best UV irradiation time is 20 min,UV radiation in fibrous film surface to generate hydroxyl,which results in enhacing the wettability to water.The synergistic energy dissipation process of the fiber cross-linked network fracture and the orientation of the fiber and the double cross-linked network fracture were greatly enhanced in the underwater tensile test.In the third part,water-soluble PAAm was used as the raw material,and then the thermo-responsive microgels poly(NIPAm-co-tBA)were introduced through colloidal electrospinning.One-dimensional thermo-responsive nanomaterials with blackberry-like,spindle-like and necklace-like structures were prepared by adjusting the ratio of PAAm and poly(NIPAm-co-tBA).The result shows that when PAAm predominated in the spinning solution,the fibers of blackberry-like were prepared,and when poly(NIPAm-co-tBA)predominated in the spinning solution,the hybrid structure of blackberry-like,spindle-like and necklace-like were prepared.Our research work reveals inherent mechanism of the evolution of fiber structures,which is expected to be applied in the field of structural color fibers.