Study On Fluorescent Aramid Fibers Based On Aggregation-induced Emission By Microfluidic Spinning

Fluorescent fiber is widely used as a functional fiber in anti-counterfeiting and decoration fields.However,most of fluorescent fibers are based on fibers such as polyvinyl alcohol,polypropylene,polyester and other fibers.There are few reports on the preparation of fluorescent aramid fiber.As a high-performance fiber,aramid fiber plays a huge role in industrial filter materials,special protective clothing,etc.Therefore,research on fluorescent aramid fiber is expected to expand its application in anti-counterfeiting safety,military,decoration and so on.In this paper,poly(m-phenylene isophthalamide)(PMIA)was used as the polymer material to prepare fluorescent fiber,EtOxPy,EtAmPy,HPNC and HPPC were selected as Aggregation-induced Emission(AIE)fluorescent materials,and a series of fluorescent-colored PMIA fibers were prepared by microfluidic spinning technology.The fluorescence and mechanical properties of fibers were discussed.PMIA spinning solution blended with EtOxPy or EtAmPy AIE dye was used as the core flow solution,and the N,N'-2 dimethylacetamide(DMAc)and water solutions with different volume ratios were used as the sheath flow solution.Two types of fluorescent PMIA fibers,EtOxPy-PMIA and EtAmPy-PMIA,were prepared by microfluidic spinning.The effects of the flow rate of core and sheath flow,the ratio of DMAc and water and the concentrations of CaCl2 in the sheath flow on the fiber were specifically studied.Results indicated that the EtOxPy-PMIA and EtAmPy-PMIA fibers showed excellent and long-lasting fluorescence properties,and the internal structure of the fiber could be porous or solid by changing spinning parameters.The diameter of the fiber could be adjusted within 21.1 ?m to 52.1 ?m,and the mechanical properties of fibers were changed differently as well.Based on 1-naphthaldehyde and 1-pyrene formaldehyde,two kinds of naphthalene derivative HPNC and fluorene derivative HPPC were designed and synthesized.The UV-vis spectra showed that the absorption peaks of HPNC and HPPC were dominated by naphthalene and fluorene rings in the molecule,respectively.Aggregation-induced luminescence studies demonstrated that the two compounds have typical AIE properties and excellent solid-state luminescence properties.The mechanism of solid-state luminescence was due to the radiation transition caused by the restricted intramolecular rotation,which results in an increase in the quantum yield of the aggregate state and enhanced fluorescence.HPNC-PMIA and HPPC-PMIA fibers were prepared by using PMIA solution blended with HPNC and HPPC powders as the core flow solution,and solution with different volume ratios of DMAc and water as the sheath flow solution.The morphology of the fibers stretched with different times were observed by SEM and optical microscopy,and the change in the fluorescence intensity after stretching was measured.These results demonstrated the mechanical properties,fluorescence intensity,and morphology of the fibers changed with the stretch times.HPNC-PMIA and HPPC-PMIA fibers performed good sewability and the fluorescence intensity was 63.4%and 74.4%of the original fibers after six months,enabling long-term use of fluorescent properties.