Synthesis Of POSS-based Profragrance And Their Application In The Aromatic Modification Of Electrospun Fibers

Aroma-modified fibers are an everyday product in high demand and mainly consist of a fiber matrix material and aroma material.Traditionally,aroma-modified fibers are made by adding fragrances directly to the fibers,but fragrances have the disadvantages of highly volatile and prone to oxidation and deterioration,resulting in significant losses during processing and use.As fragrance materials continue to develop,researchers are turning their attention to materials that can retard the release of fragrance.Profragrance technology is now a very popular route of fragrance retention.Profragrances have the advantages of high chemical stability and low volatility,releasing fragrances under mild environmental conditions such as hydrolysis,light and oxygen.In order to extend the retention time of profragrance,researchers have investigated the selection of substrate materials,the stability of the chemical bonds attached to the substrate and the design of profragrance composites.Polyhedral oligomeric silsesquioxane(POSS)is a high molecular weight,biocompatible and high temperature resistant material,which makes it an ideal base material for a profragrance substrate.Compared to small molecules,POSS-based profragrance are more effective in fragrance retention.Electrospinning is a relatively simple spinning and shaping process,which can be combined with POSS-based profragrance to produce aromatic fibers that are more stable.This combination can further improve the fragrance retention performance to a certain extent,and thus expand the range of applications.At present,aromatic fibers are generally electrospun by adding a small molecule-based profragrance to the spinning solution,which has a short duration of fragrance release during use.In this paper,three new POSS-based Schiff base profragrances were prepared by reacting anisaldehyde,p-methylbenzaldehyde,benzaldehyde and octa(γ-chloropropyl)polyhedral oligomeric sesquisiloxane(OCAP-POSS)with Schiff base to produce three structurally similar profragrances,POSS-PAA,POSS-MB and POSS-Ben.POSS-PAA was selected and added to polyacrylonitrile solution,which was electrospun to prepare the aromatic fibers(PAN/POSS-PAA nanofibers)with improved fragrance retention properties.The main contents and conclusions of the paper are as follows.(1)Three Schiff base type profragrances(POSS-PAA,POSS-MB and POSS-Ben)were successfully synthesized using different aromatic aldehyde molecules and OCAP-POSS as raw materials via Schiff base reaction.The structures of the profragrances were characterized by NMR,IR and UV-Vis spectroscopy,and the thermal stability of the profragrances was investigated by thermal weight loss.In addition,the kinetics of fragrance release in different pH buffer solutions(5.8,7.0 and 7.9)were also investigated.The results show that the thermal decomposition temperature of all three types of profragrances exceeded 285 ℃,which means that the profragrances have good thermal stability.The structure of the profragrance molecules has a significant effect on their release performance,with the release rate in equilibrium of POSS-PAA and POSS-Ben being57.25% and 33.12%,respectively.And the fragrance release time is in the order of POSS-PAA(29h)> POSS-MB(16 h)> POSS-Ben(12 h).All three profragrances are more stable in alkaline environment and can achieve slow release in acidic sweat,and their release behaviors follow the first-order reaction kinetics characteristics.(2)Then POSS-PAA profragrance was dispersed in polyacrylonitrile solution and the aromatic nanofibers were prepared by electrospinning.The properties of the spinning solution were characterized using a nanoparticle size analyzer and a rheometer;the dispersion of the profragrance in the nanofibers and the fiber diameter distribution were observed by SEM and EDS;the loading rate of the profragrance in the fibers was quantified by thermal weight loss method;and the kinetics of fragrance release in different pH buffer solutions(5.8 and 7.9)were also explored.The results show that POSS-PAA is uniformly dispersed in the spinning solution with a particle size of less than200 nm within 5% addition.The average diameter of electrostatically spun nanofibers decreases with increasing voltage and with increasing POSS-PAA content.When the voltage is 20 k V and the POSS-PAA content is 5%,the average diameter of the electro spun nanofibers was about 355 nm.Compared to direct addition of aromatic aldehydes,the addition of profragrance significantly reduces the loss of fragrance molecules during the electrospinning process.The PAN/POSS-PAA nanofibers gives a sustained release of 14 days with a release rate of 58.4% in a pH = 5.8 buffer solution compared to 28.3% in pH = 7.9 buffer solution,and the release behavior conforms to Korsmeyer-Peppas kinetics.