Preparation And Performance Of Sulfur-containing Hyperbranched Polymers With Controllable Microstructure By Thiol-X Click Reaction

Hyperbranched epoxy resins,as an important thermoset resins,can be used to improve specifically the toughness and strength of common epoxy resin.However,microstructure and performance controllability of hyperbranched epoxy resin is a key problem in epoxy resins field.In this work,we have tuned microstructure and performance of epoxy resins via thiol-X click reaction with high yield,no by-products and high selectivity.Microstructure(epoxy value and degree of branching)of hyperbranched epoxy resins were regulated by thiol-epoxy and thiol-ene click reaction,which controlled performance of diglycidyl ether of bisphenol-A(DGEBA).We have studied the effects of epoxy value and degree of branching on rheological,mechanical and thermal properties of hyperbranched epoxy resins/DGEBA hybrid resins.The quantitative relationship between microstructure and the performance of hybrid resins was built.Firstly,thiol-ended aliphatic hyperbranched polymers(THBP-n,n=3,6,9 and 12)with different thiol founctionalities were synthesized by an esterification reaction between hydroxyl-ended aliphatic hyperbranched polymers and 3-mercaptopropionic.The chemical structure and molecular weight of THBP-n were characterized and verified through FT-IR,~1H NMR and matrix-assisted laser desorption-ionization time-of-flight mass(MALDI-TOF-MS)spectra.Thiol-epoxy crosslink structures were obtainedthroughmixingTHBP-nwithDGEBAbyusing2,4,6-tris(dimethylaminomethyl)phenol as accelerator.And the mechanical and thermal properties of cured materials have been discussed.The results showed that the impact,tensile and flexural strength of the cured materials increased first and then decreased with an increase in THBP-n thiol functionality.As the thiol functionality of THBP-n increases,the thermal degradation and glass transition temperatures of cured materials increased.The morphology of the cured materials were analyzed by SEM and DMA techniques.The reinforcing and toughening mechanism can be explained by an in-situ reinforcing and toughening mechanism.Secondly,the aliphatic hyperbranched epoxy resins(EHBP-n,n=3,6,9 and 12)and aromatic hyperbranched epoxy resins(EHPP-n,n=3,6,9 and 12)with different epoxy values were obtained by thiol-ene click reaction,basing on hydroxyl-ended aliphatic and aromatic hyperbranched polymers as the main raw materials,respectively.The molecular weight and structure of EHBP-n and EHPP-n were confirmed by MALDI-TOF-MS,FT-IR and ~1H NMR spectra.The effects of epoxy value and content of EHBP-n and EHPP-n on performance of EHBP-n/DGEBA and EHPP-n/DGEBA hybrid resins were studied.The flowability of EHBP-n/DGEBA and EHPP-n/DGEBA hybrid resins increased with an increase in epoxy value and content of EHBP-n and EHPP-n.With the increase of epoxy value and content of EHBP-n and EHPP-n,the mechanical performance of EHBP-n/DGEBA and EHPP-n/DGEBA hybrid resins first increased and then decreased,reaching the maximum values at the content about 9?wt%.With the increase of epoxy value of EHBP-n or EHPP-n,the thermal degradation temperature of hybrid resins increased slightly,but the glass transition temperature of hybrid resins increased first and then decreased.The reinforcing and toughening mechanism and morphology of the hybrid resins were also researched by SEM and DMA techniques.Finally,nitrogen-phosphor skeleton hyperbranched epoxy resins(NPEHP-n,n?=?0,0.5,1.0)with different degrees of branching(DB)were prepared by a thiol-ene Michael addition reaction.Their molecular weight,structure,particle size and shape were characterized by MALDI-TOF-MS,FT-IR,~1H NMR,dynamic light scattering(DLS)and molecular simulation techniques.The particle size decreased gradually as the DB of NPEHP-n increased.An increase in flowability were observed when the content and DB of NPEHP-n in hybrid resin were increased.With an increase in DB of NPEHP-n,the tensile,flexural strength and glass transition temperature of hybrid resins decreased,but the impact strength increased.The reinforcing and toughening mechanism of NPEHP-n/DGEBA hybrid resins were studied by SEM and DMA,indicating in accordance with in-situ reinforcing and toughening mechanism.