Research on Structures and Properties of Fluorescent Polyarylene Ether Nitriles

Author:Wang Pan

Supervisor:liu xiao bo


Degree Year:2019





Polymer fluorescent materials have attracted much attention in the filed of flexible display,wearable devices,fluorescence sensing,biological diagnosis and treatment due to their advantages of adjustable emission property,molecular design,flexible devices fabrication and etc..After long-term development,polymer fluorescent materials not only have high-efficiency conjugated polymers,such as polyfluorene and polythiophene,but also involving the linear or dedritic non-conjugated polymers containing a large amount of ester groups,hydroxyl groups and amio groups emerging in recent years.With the increasing demand of society,fluorescent polymer materials with excellent comprehensive performance have become an attractive reserach filed.Polyarylene ether nitriles(PEN)is a type of high performace engineering plastics.Thanks to the ether bond and benzene ring in the main chain,and cyano group in the side chain,PEN has a comprehensive properity of high temperature resistance,radiaton resistance,corrosion resistance,easy processing,good mechanical perfoemance and excellent electrical property which makes PEN widely used in aerspace,aircraft,manufacturing,petro chemical and defense military fields.Recenty,PEN had proved as an intrinsic type of blue-emitting fluorescent polymer which give us the basis funfamental to study the fluorencet property of PEN and explore the further fluorenct functional application of PEN.However,there are few systematic reports at present,and the relationship between the structure and the fluorescence property of PEN is still unclear,especially the application of its fluorescence functionalization is in the primary exploration stage.To this end,this thesis will study the fluorescence property of PEN with different structures to reveal the relationship between PEN structure and fluorescence performance.Then,explore the application of fluorescent PEN in the filed of heacvy metal ion detection and bio-imaging.The specific research contents are as follows:1.Taking PEN containing phenolphthalin(PEN-PPL)as the research structure and focusing on the effect of molecular structure and environmental factor on fluorescne performance.In order to clarify the structural advantages of PEN-PPL for fluorescence functionalization,PEN with different molecular structures were slectred for comparison.Trough the analysis of the characterization results of solubility,heat resistance performance,film fabrication ablity,mechanical properties and optical properties,PEN-PPL is proved to be a better one with comprehensive performance.PEN-PPL is not only a fluorescent polymer material with a blue emission,but also a high performance polymer with a 5%thermal decomposition temperature at 422 oC,a glass transition temperature at226 oC,a tensile strength of 84.9 MPa and a good solubity in common weakly polar solvents.The other important is the carboxyl group pendanting in the side chain of provide a rich possibility for further functionalization.Therefore,to the further study of the influence of more structures and environment factors on the optical properties of PEN-PPL.The research variables include solvent,pH,chain orientation,concentration,molecular weight and molecular weight distribution.The influence of molecular weight and molecular weight distribution on the fluorescence performance of PEN-PPL was very important and also concentration dependent.The molecular weight at the low concentration plays a major role in determining the fluorescence performance,while the fluorescence performance most depended on molecular weight distribution under high concentration of PEN.2.In order to further enhance the fluorescence properties of PEN,a series of bifunctional fluorescent PEN were synthesised by introducing different contents of tetraphenylenthene(TPE)structure into the backbone of PEN-PPL.The TPE monomer has a property of aggregated-induced emission effect(AIE),which converted PEN-TPE/PPL into a typical AIE polymer(AIE-PEN)successfully.The fluoresnce intensity of AIE-PEN can be greatly increased in a good-poor mixed solvent system,and its highest AIE factor(αAIE)is 81 times higher.At the same time,the emission peak of PEN-TPE/PPL is red-shifted from420 nm of PEN-PPL to470 nm,the color changs from blue to bright blue-green.In addition,PPL functional structure enables PEN-TPE/PPL to utilize the carboxyl complexed with mental cation,especially Ca2+.The presence of Ca2+can make PEN-TPE/PPL further aggregation by crosslinking reaction.Then the emission intersity can futher enhanced with maximum AIE factor of 7.4 times.The reults show that the bifunctional PEN-TPE/PPL has a better spectral tunablility,a higher fluorescent efficiency,and a higher emission intensity under aggregated state controlled by the coordination of the carboxyl group with metal ion.Thus,bifunctianl PEN-TPE/PPL afford a new way to design high quality intrinsic fluorescent PEN.3.Explore the application of fluorescent PEN in the detection of mercury ion(Hg2+)based on PEN-PPL.Using and the carboyl group fuctionalized bule-emitting PEN-PPL as enery donor and red-emitting Au NCs as energy,a composite of PEN-PPL/Au NCs can be construced through fluorescence resonance energy transfer(FRET).With the increasing of Au NCs content,PEN-PPL/Au NCs’s blue emission is weakened while the red emission is enhanced.Based on the difference of fluorescence response of PEN-PPL and Au NCs to Hg2+of the composite,a FRET-based viculization red-blue dual-emission fluorescence sensing material was prepared.Red emission of Au NCs has an ultrasensitice specific response to Hg2+,which can cuse fluorescence quenching in the presence of very low concentrations.However,the blue emission of PEN-PPL is very stable,the emission didn’t show a significant quenching even in the presence of high concentrations of Hg2+.So,the PEN-PPL/Au NCs composite can play as a red-to-blue fluorescence transition under the presence of Hg2+which can be observed by naked-eye.Finally,the PEN-PPL micro/nano fiber film prepared by electrospinning technology was absorbed with Au NCs to obtain a fluorescent composite film.By testing its fluorescence properties under solid-state,it is shown that the PEN-PPL/Au NCs composite film belongs to a reusable Hg2+rapid recognition solid-state sensing material.4.Explore the application of fluorescent PEN in the field of bio-imaging based on the PEN-TPE/PPL.Using metal ion coordination method and solvent replacement method,PEN-TPE/PPL with AIE performance can be cross-linked with Ca2+to prepare AIE-PEN fluorescent polymeric nanoparticles(AIE-PEN FPNs)which can be stably dispersed in water.The obtained water-dispersed AIE-PEN FPNs have a fluorescence emission peak at 473-477 nm with average hydrodynamic radius range from 173 nm to200 nm.AIE-PEN FPNs have been demonstrated to have good biocompatibility by cytotoxicity experiments.Finally,in vitro cell incubation combined with confocal fluorescence microscopy show that AIE-PEN FPNs enriched in cells with blue fluorescence emission.It indicates that PEN is a kind of fluorescent functionalized high performance polymer material,which has potential application value in the field of bioimaging.