Preparation And Characterization Of POSS-Cored Epoxidized Star-Shaped Polymer And Giant Surfactants

Polyhedron oligomeric silsesquioxane,which can be abbreviated as POSS and expressed by the general formula(RSiO1.5)n,is a nanoscale cage compound.It has been widely used in the preparation of organic-inorganic hybrid materials because of some characteristics,including rigid three-dimensional structure,rich surface chemistry,good heat resistance and mechanical properties.In this work,two kinds of POSS-based epoxidized star-shaped polymers and amphiphilic giant surfactants are synthesized by living anionic polymerization,ring-opening polymerization and "Click" chemistry.(1)Anionic synthesis and characterization of epoxidized eight-arm star-shaped polyisopreneAfter many years of development and application,high-vacuum living anionic polymerization has been widely used by researchers in the preparation of complex topological polymers.In this part,the living(polyisopryl)lithium(PI-Li)is first synthesized in cyclohexane by high-vacuum living anionic polymerization using sec-butyllithium as the initiator and isoprene as the monomer.Subsequently,PI-Li is used to react with the octavinyl polyhedral oligomeric silsesquioxane(OVPOSS)also in cyclohexane to produce an eight-arm star-shaped polyisoprene(8PI-POSS)in one pot.The purified 8PI-POSS is obtained after fractionation precipitation,and then characterized by nuclear magnetic resonance(1H-and 13C-NMR),gel permeation chromatography(GPC),matrix-assisted laser desorption/ionization time-of-flight(MALDI-TOF)mass spectroscopy and Fourier transform infrared spectroscopy(FT-IR),respectively.Finally,the epoxidized star-shaped polyisoprene(8EPI-POSS)is obtained by the oxidation reaction of 8PI-POSS catalyzed by HCOOH/H2O2.The 8EPI-POSS polymer is also characterized by 1H-and 13C-NMR,GPC and FT-IR analyses,respectively.Moreover,the thermal decomposition temperature of the polymer is measured by thermogravimetric analysis(TGA).(2)Preparation of the giant surfactants by combination of ring-opening polymerization and "Click" chemistryGiant surfactants,which shaped like small-molecule surfactants,is a kind of macromolecule with special structures.It consists of a hydrophilic "head" group and a hydrophobic polymeric "tail" chain.In this part,the double bond in OVPOSS molecule was partially oxidized and hydrolyzed to form one hydroxyl group at first,and the POSS derivative(VPOSS-OH)with one hydroxyl group and seven vinyl groups is isolated by column chromatography;Subsequently,VPOSS-OH is then used to polymerize e-CL under the catalysis of Sn(Oct)2 via ring-opening polymerization,producing polycaprolactone end-capped with heptavinyl POSS(VPOSS-PCL);Finally,VPOSS-PCL is used to respectively react with 2-mercaptoethanol,3-mercaptopropionic acid and cysteamine hydrochloride via UV-induced thiol-ene "click" reaction,resulting in three giant surfactants 7HO-POSS-PCL,7HOOC-POSS-PCL and 7NH3C1-POSS-PCL.The polymers are then characterized by 1H/13C-NMR,GPC and MALDI-TOF mass spectroscopy,and the thermal decomposition temperature are tested by TGA analysis.In addition,the morphology and particle size of nanopaticles formed by the giant surfactants in aqueous solution are preliminary characterized by TEM and DLS analysis.