Preparation Of Piperazine-containing Cross-linked Polymers Via Michael Addition And Their Complexing Fuction With Metal Ions

Michael addition reaction is a kind of synthesis reaction in line with green chemistry because of its mild reaction conditions,high atomic availability or economy and no by-products.It has been mostly used in the modification of small compounds,the synthesis of dendritic polymer and other fields,but it is seldom used to prepare crosslinked polymers.The excellent properties of cross-linked polymers such as solvent resistance,thermal stability and high strength make them play an increasingly important role in our daily life.In this paper,the piperazine structure was introduced into the crosslinked polymers via aza-Michael addition.On the one hand,without any catalyst in the preparation process,the reaction is efficient and environmentally friendly.On the other hand,the cross-linked polymers containing piperazine structure have complexation effect with metal ions,which makes them of great practical value in solvent detection,sewage treatment and other aspects.A series of piperazine-containing cross-linked polyamides and polyether-b-epoxy resin copolymers were synthesized from anhydrous piperazine as raw materials.The complexation of them with metal ions was studied.The main research contents are as follows:1.A linear polyamide(t-AA-PA)with acrylamide terminal groups was prepared by the Michael addition reaction of piperazine(PZ)and N,N-methylene bisacrylamide(MBA).1,4-butanediamine(BDA),1,6-hexanediamine(HDA),and 1,8-octylenediamine(ODA)were used as cross-linkers,and a further Michael reaction of them with t-AA-PA was conducted to form cross-linking structure.A series of cross-linked polyamides(P-cPAs)with piperazine units were synthesized.The effects of cross-linker chain length on the properties were studied.The results showed that P-cPAs has crystallinity.With the increase of carbon length,the glass transition temperature(Tg),crystallization temperature(Tc)and melting temperature(Tm)all decrease somehow.The mechanical tensile strength of P-cPAs also decreases,but the overall tensile strength is still higher than 20 MPa;The elongation at break increases gradually,reaching up to 89%.At the same time,the initial thermal decomposition temperature of P-cPAs decreases from 274? to 270? and the residual rate also decreased from 17%to 5.5%.By complexing P-cPAs with cobalt ions(Co2+),a series of cross-linked polyamides with coordination of cobalt ions(cPAC-Co2+s)were prepared and their related properties were studied.The results showed that cPAC-Co2+s lost crystallizing ability due to the complexation with Co2+,but the Tg increased by about 35? compared with P-cPAs.In addition,the introduction of Co2+ gives the materials excellent solvatochromic property,which enables them to change color rapidly when cPAC-Co2+s encounter water or methanol.These cPAC-Co2+ s are easy to prepare.The synthetic method is friendly to the environment and has great application value in the field of solvent detecting sensors.2.In the previous chapter,when Co2+ was introduced into the crosslinked polyamides,the texture of the materials became hard and brittle,and the complexation effect on enhancing mechanical properties can not be shown.In this chapter,a Michael addition of PZ and polyethylene glycol dimethacrylate(PEGDMA)was firstly conducted to prepare a polyether prepolymer A(Pre A)terminated with piperazinyl units.A ring-opening reaction of PZ with 1,4-butanediol diglycidyl ether(BDDE)was conducted to prepare several prepolymers B(Pre Bs)terminated epoxy groups.Then,Pre A and different Pre Bs were copolymerized to synthesize piperazine-containing linear polyether-b-epoxy copolymers(P-b-Es).Finally,a series of piperazine-containing cross-linked polyether-b-epoxy copolymers(c-P-b-Es)were obtained by the cross-linking reaction of c-P-b-Es with multifunctional 1,4-bis(3-aminopropyl)piperazine(BAPZ)via Michael addition.The effect of different piperazinyl content on its properties was also studied.The results showed that the solubility of c-P-b-Es in good solvents decreased gradually with the increase of piperazinyl content and remained between 12%and 8%.The mechanical properties of c-P-b-Es were improved but is still not high.The maximum tensile strength is only 1.1 MPa and the elongation at break is 115%,c-P-b-Es had no crystallization property and their Tg increased with the increase of piperazinyl content,but all of them were lower than-5?.c-P-b-E complexes(r-c-P-b-ECs)were prepared by complexing c-P-b-Es with Co2+and drying.After complexing,the Tg was significantly increased by about 60?.The mechanical properties are greatly enhanced by 20 times.The maximum mechanical properties reaches 25 MPa and the maximum elongation at break is more than 100%.At the same time,r-c-P-b-ECs also have excellent solvatochromic performance.In addition,the porous membranes of c-P-b-Es were also prepared.Their chemisorption on heavy metal ions such as Co2+,copper(Cu2+)and zinc(Zn2+)in solution was studied.The optimal pore numbers and pore size of c-P-b-E porous membranes for metal ions adsorption were investigated.5 wt%dilute hydrochloric acid was used to recover the heavy metal ions absorbed in the porous membranes.The research on the function of crosslinked block copolymers absorbing heavy metal ions brings a broad application prospect in solvent-detection sensor,removal of heavy metal ions,and sewage treatment.