Performance And Preparation Of Hyperbranched Epoxy Resin By Thiol-maleimide Click Reaction

Epoxy resin has excellent physical and chemical properties,which is widely used in aerospace,electronic information and other fields.Epoxy resin can also be used as shape memory materials,but it is difficult to prepare epoxy resin for shape memory materials and it is with low mechanical strength.Hyperbranched epoxy resin has the highly branched structure of hyperbranched polymer and the advantages of traditional epoxy resin,which is expected to solve the problems of difficult preparation and low mechanical strength of traditional epoxy resin shape memory materials.In this paper,the thiol-maleimide click reaction,which has advantages of mild reaction conditions,high selectivity and high yield,is used to introduce imide structure into the hyperbranched molecular skeleton,and then the thiol-ene click reaction is used to prepare a series of hyperbranched epoxy polymers with different functions.The mechanical strength and shape memory properties of the hyperbranched epoxy resin film are studied,and the influence factors and rules of hyperbranched epoxy resin on the properties of bisphenol-A epoxy resin(DGEBA)were discussed.The specific research contents are as follows:Hyperbranched epoxy resins with different molecular weights(ETMP-n,n=6,9,11)were prepared from aliphatic ternary thiol(TMMP),N,N'-4,4'-diphenylmethyene bismaleimide(BMI)and allyl glycidyl ether(AGE),their shape memory properties and their effects on DGEBA properties were studied.Thiol-terminated hyperbranched polymers(BTMP-n,n=6,9,11)with different molecular weights were prepared by thiol-maleimide click reaction between TMMP and BMI,and then ETMP-n were synthesized by thiol-ene click reaction between BTMP-n and AGE.The molecular structure and molecular weight of BTMP-n and ETMP-n were characterized and confirmed by infrared spectroscopy(FT-IR),hydrogen nuclear magnetic resonance spectroscopy(~1H NMR),matrix assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS)and gel permeation chromatography(GPC).The cationic curing agent(B100)was used to cure ETMP-n,and cured films of ETMP-n with shape memory function.The fastest shape recovery time of ETMP-n cured films is 480 ms and the shape memory test(4 cycles)was carried out by dynamic thermomechanical analyzer(DMA).Various characterization results show that the ETMP-n films have excellent shape memory performance,the recovery rate and the fixity rate are above 83.45%and 83.74%,respectively.After introducing imide structure,the tensile strength of ETMP-n cured films can reach 27.63MPa.After 5 cycles of shape memory cycles,the tensile strength can still maintain 90.52%,and the thermal stability is good.ETMP-n were added to DGEBA to prepare the ETMP-n/DGEBA hybrid resin.ETMP-n have good compatibility with DGEBA,and the effects of ETMP-n on the macro-properties and microstructure of DGEBA were studied.With the contents of ETMP-n in ETMP-n/DGEBA increased,the mechanical properties of ETMP-n/DGEBA increased at first and then decreased,and the mechanical properties showed the same rule with the increase of molecular weight of ETMP-n.When the proportion of ETMP-9 in the ETMP-n/DGEBA is 12 wt%,the mechanical properties of the hybrid resin have maximum values,and the impact,bending and tensile strength of the hybrid resin are2.38,1.48 and 1.78 times higher than those of pure DGEBA,respectively.The microscopic morphology and free volume of the ETMP-n/DGEBA were analyzed by SEM,AFM,DMA and TMA.The results show that its strengthening and toughening mechanism belongs to“in situ”reinforcing and toughening mechanism.Secondly,in order to obtain membrane materials and hybrid resins with higher strength,hyperbranched epoxy resins(ETHP-n,n=6,9,11)with different functions were prepared from nitrogen heterocyclic ternary thiol(THMP),BMI and AGE.Their shape memory properties and their effects on the properties of DGEBA were studied.Thiol-terminated hyperbranched polymers(BTHP-n,n=6,9,11)with different molecular weights were prepared from THMP and BMI by thiol-maleimide click reaction,then ETHP-n were prepared through the thiol-ene click reaction between BTHP-n and AGE.FT-IR,~1H NMR,MALDI-TOF-MS and GPC characterizations were used to confirm the molecular structure and molecular weight of BTHP-n and ETHP-n.B100 was used to cure ETHP-n,and cured films of ETHP-n with shape memory function.The fastest shape recovery time of ETHP-n cured films is 430 ms and the shape memory test(7 cycles)was carried out by DMA.Various characterization results show that the ETHP-n films The cured ETHP-n films have better shape memory performance and tensile strength than the cured ETMP-n films,the fixity rate and the recovery rate are above 97.98%and 97.24%,respectively,the maximum tensile strength is 31.15 MPa and the tensile strength retention rate is 87.19%.The effects of ETHP-n on the macroscopic properties and microstructure of DGEBA were studied.ETHP-n and DGEBA can form a homogeneous system.With the increase of the proportion of ETHP-n in the ETHP-n/DGEBA,the mechanical properties of ETHP-n/DGEBA increased at first and then decreased,and the mechanical properties showed the same rule with the increase of molecular weight of ETHP-n.When the proportion of ETHP-9 in the ETHP-n/DGEBA is 12wt%,the mechanical properties of the ETHP-n/DGEBA have maximum values.The impact,bending and tensile strength of the hybrid resin are 2.12,1.43 and 1.70 times higher than those of the pure DGEBA,respectively,and they are all higher than that of12%ETMP-9/DGEBA.The microscopic morphology and free volume of the ETHP-n/DGEBA were analyzed by SEM,AFM,DMA and TMA.The results show that its strengthening and toughening mechanism belongs to“in situ”reinforcing and toughening mechanism.The preparation method of a series of hyperbranched epoxy polymers with different molecular weight and topological structure is simple and efficient.The hyperbranched epoxy resin has high mechanical strength and good shape memory properties and can obviously improve the mechanical properties of DGEBA,which provides a theoretical basis for the preparation of high strength hyperbranched epoxy resin-based shape memory materials and a new method for the reinforcing and toughening of DGEBA.