Research On Synthesis And Adsorption Performance Of Polycarbonate Resins With Cross-linked Structure

Aiming at the resolution to gradually severe pollutions of solvent-included organic compounds,an effective approach to it should be relied on the usage of oil-absorbing resins.On the one hand,the absorption mechanism to organic solvents lies in the self-swelling of the oil-absorbing resin.On the other hand,the selective absorption of one organic pollutant necessarily depends on the complicated interactions between it and the oil-absorbing resin.Therefore,besides the requirements of relatively high stability,cost-effective synthesis,large adsorption capacity and good selectivity for the selected oil-absorbing resin,the reproducible using and the recycling of absorbed material should also be highly considerable,from which,the development of new kinds of oil-absorbing resin with desirable adsorption capacity and good selectivity is attracting much attention during the practical treatment of organic pollutants.In consideration of the flexible structure of most oil-absorbing resins characteristic of long-range disorder,its specific skeleton can stretch out and draw back with absorption or desorption to organic compounds.Herein,using the o1 igmers prepared from the condensation of 4-butanediol(BD),1,5-pentanediol(PD)or 1,6-hexanediol(HD)with diethyl carbonate(DEC)as the flexible unit,its further trans-esterification reaction with one of the selected cross-linkages(1,3,5-benzenetricarboxylate(BTB),1,3,5-Benzenetrimethanol(BTM)or3-Aminopropyltriethoxysilane(APTES)),gives the series of new cross-linked polycarbonate resin,respectively.Meanwhile,besides the characterization by 1H NMR,solid 13 C NMR,solid 29 Si NMR,Fourier Transform infrared spectroscopy(FT-IR),X-ray powder diffraction(PXRD),elemental analysis(EA),BET Specific surface area test,and SEM analysis,their thermal stability was also checked from thermogravimetric analysis(TGA).Moreover,the detailed exploration on the correlation between the structure and the swelling behavior to organic solvents,and the absorption performance on BPA at relatively low concentration,the synthesized polycarbonate-type oil-absorbing resins endow a new platform to sorbents for both organic solvents and pollutant BPA.The detailed content of the thesis is shown as follows.Firstly,with BD,PD or HD and DEC as the co-polymerizable monomers,the series of linear aliphatic polycarbonates(Mw = 104 g/mol;PBC based BD,PPC based PD and PHC based HD)were obtained from an improved two-step trans-esterification procedure,respectively.In comparison with the direct condensation,the two-step trans-esterification processing was adopted,where the reaction temperature of 130 °C,the reaction time of 1.5 h were carried out in the presence of N2 atmosphere to control the-OH/-CH3 of 1.1:1 for the oligomer during the first-step trans-esterification,while in the second step,chain-growth took place in dependence of the reaction temperature of 190 °C,the reaction time of 6 h and the retained pressure of0.01 MPa.GPC results showed that the Mw of all the obtained polycarbonates could be up to104 g/mol,and especially 25054 g/mol was for PBC.Furthermore,PXRD analysis showed that all the obtained PBC,PPC and PHC are typically characteristic of semi-crystalline with the degree of crystallinity of 30.8%,25.4% and 21.0%,respectively.Secondly,using the oligomer from the direct condensation of BD,PD or HD with DEC at the reaction temperature of 130 °C for 1.5 h as the flexible unit,the cross-linking agent BTB or BTM was used to give two series of as polycarbonate resins,respectively.Their swelling behaviors showed they could freely self-swell in non-polar organic solvents of chloroform,dichloromethane,tetrahydrofuran,benzene and toluene,while did not work in polar solvent of water,ethanol or methanol.Worthy of noting,the cross-linked polycarbonate based on BTB-inducement and the oligomer from BD and DEC had the highest swelling efficiency of3099% to chloroform.By contrast,in BTM-induced systems,the swelling efficiency of2022% for chloroform could be observed for the oligomer from BD and DEC.On the other hand,the two series of cross-linked polycarbonate resins exhibited appreciated absorption efficiency to low concentration BPA in water,in which,the one from BTB-based and the oligomer with HD and DEC displayed an attractive adsorption efficiency of 86.4% to BPA,while a relatively higher adsorption efficiency(90.1%)to BPA was exhibited for the the cross-linked polycarbonate based on BTM-inducement and the oligomer from PD and DEC.Thirdly,using the series of linear aliphatic polycarbonates(Mw = 104 g/mol;PBC based BD,PPC based PD and PHC based HD)obtained from an improved two-step trans-esterification procedure as the flexible unit,two series of as polycarbonate resins characteristic of relatively longer stretching unit were also obtained in dependence of the cross-linking agent BTB or BTM,respectively.Similarly,the swelling performance of the two series cross-linked polycarbonate resins was also strictly relied on the polar character of one organic solvent.Interesting enough,the chain-growth of the flexible unit had a positive effect on the swelling efficiency to non-polar solvents,where the cross-linked polycarbonate based on BTB-inducement and the oligomer PPC from PD and DEC had the highest swelling efficiency of 6933% to chloroform.In contrast,in BTM-induced systems,the swelling efficiency of 3897% for chloroform could also be observed for the oligomer PPC.Fourthly,also based on the series of linear aliphatic polycarbonates(Mw = 104 g/mol;PBC based BD,PPC based PD and PHC based HD)obtained from an improved two-step trans-esterification procedure,the input of 3-aminopropyltriethoxysilane(APTES)resulted in the formation of another series of cross-linked polyester resins.However,despite the similar swelling rule as above mentioned,the distinctively lower swelling performance,such as the highest swelling efficiency of 753% to chloroform,was observed,which probably should be due to the relatively high cross-linking density arising from the flexible APTES-induced chain-twisting and chain-interweaving.Nonetheless,because of the enriched hydrogen bonding donated from the-NH2 groups from APTES,all the APTES-based cross-linked polyester resins endowed significantly higher adsorption efficiencies(the highest 94.5% for PHC)to BPA is 94.5%.Finally,through the direct condensation of flexible aliphatic 1,3-propanediol(1,3-PD),BD,PD,HD or rigid 1,4-benzenedimethanol(BDM),BTM or 1,3,5-trihydroxy benzene(THB)with 1,3,5-Benzenetricarboxylic acid chloride(BTCAC),the series of cross-linked and/or porous polycarbonate resins were developed,respectively.The correlation between the structure and the absorption to BPA showed that both the rigidity and the porosity of the polycarbonate resins were beneficial for absorption performance of BPA,in which,the BTM-induced polycarbonate resin with the average inner diameter of 149 nm,the specific surface area of 43.5 m2/g could effectively absorb BPA in an absorption efficiency of 65.4%.