Synthesis And Properties Of Polyimides Containing Bulky And Twisted Moieties

Polyimides play a critical role in modern industry due to their excellent comprehensive properties.However,traditional polyimides can't fulfill the requirement of emerging applications,such as flexible display and gas separation.Thus,a series of monomers and polyimides with twisted and bulky moieties were prepared,and their properties were systematically investigated in this dissertation.The major findings are as follows:1.Three bio-based dianhydrides were synthesized using bio-renewable creosol as the raw material,and then three series of polyimides were prepared through the polycondensation of these dianhydrides with petroleum-or bio-based diamines.The bio-based contents of these polymers ranged from 31.8 to 56.4%.The 5%weight loss temperatures(T5%)and glass transition temperatures(Tg)of the bio-based polyetherimides(PI-? and PI-? series)were 406-553 ? and 213-235 ?,respectively,while PI-? series with dioxin segments exhibited a Tg of 378-424?,T5%of 490-508? due to the existence of fused aromatic rings.The tensile strength,modulus,and elongation at break of these polyimides were 70-115 MPa,1.80-2.8 GPa,and 3.5-20.4%,respectively.The abovementioned results indicated that these bio-based polyimides have comparable thermal and mechanical properties to those from petroleum-based monomers,such as Ultem(?)and Kapton(?),and showed certain potential application in the fields of film and engineering plastics.2.Three series isomeric polyimides were prepared through the polycondensation of 5(6)-Amino-1-(4-aminophenyl)1,3,3-trimethylindane(DAPI)with aromatic dianhydride including PMDA,MPDA,4,4'-BPDA,3,4'-BPDA,3,3'-BPDA,4,4'-BTDA and 3,4'-BTDA.All the polymers show good solubility in conventional organic solvents.The Tg and T5%of polyimides were in the range of 329-465? and 484-507?,respectively.The tensile strength,modulus and elongation at break of these polyimides were 76-100 MPa,1.5-2.3 GPa and 7.6-15.3%,respectively.Polymers derived from isomeric dianhydrides exhibit slightly lower Tg and inferior mechanical properties compared with the polymers derived from traditional dianhydrides due to reduced chain rigidity and linearity,as well as lower molecular weights.Polyimides derived from isomeric BPDAs and PMDAs exhibited higher thermal resistance than those from isomeric BTDAs.PMDA-DAPI showed the highest thermal resistance with Tg up to 465?.Generally,the gas permeability of isomeric polyimides is significantly improved without sacrificing perm-selectivity.Isomeric polyimide showed improve gas separation performance relative to those from traditional dianhydrides.Copolyimide derived from 3,4'-BPDA and 3,3'-BPDA exhibited improved CO2/CH4 performace approaching the 1991 Robeson upper bound.3.Three diamines(ADMDA,DMADMDA and FADMDA)containing amantane structure were synthesized by a two-step reaction of 1-adamantanol with acetaniline or its derivatives.Three series of semi-alicyclic polyimides were prepared by polymerization of these diamines with commercial aromatic or alicyclic dianhydrides.The Tg and T5%of polyimides were in the range of 285-440? and 444-540?,respectively.The cut-off wavelength(?cut-off)of the polyimides was observed to fall in the range 275-361 nm.The transmittance at 400 nm(T400)was higher than 80%except for 6FDA-ADMDA.Polyimides exhibited L*values of above 90,a*values of below zero,b*values in the range 1.07-5.09 and YI values in the range 1.99-8.33,indicating their outstanding optical transparency.4.Four diamines(CANAL-1',CANAL-2,CANSCAL-1 and CANSCAL-2)were synthesized through Catalytic Arene-Diene Annulation using norbornadiene and 5-norbomene-2-spiro-?-cyclopentanone-?'-spiro-2"-5"-norbornene as raw materials.Four series of colorless polyimides were prepared using these diamines and commercial dianhydrides as the monomers.The polyimides exhibited good solubility in various organic solvents.The Tg and T5%of polyimides derived from CANAL diamines were in the range of 418-480? and 450-488?.The DSC results of CANSCAL-derived polymers indicated that thermal decomposition occured at around 330?.The tensile strength,modulus and elongation at break of CPI films from CANAL diamines were 76-100 MPa,1.5-2.3 GPa and 7.6-15.3%,respectively.The tensile strength,modulus and elongation at break of CPI films from CANSCAL diamines were 51-98 MPa,1.5-2.7 GPa and 7.6-33.5%,respectively.The mechanical properties of CPI films derived from CANAL-1' and CANSCAL-1 diamines were better than those from CANAL-2 and CANSCAL-2 due to their stronger inter-and intra-molecular interactions.Polyimides based on CANAL diamines exhibited a moderate CTE value range from 34.3-66.2 ppm/K,and cut-off wavelength range from 282-343 nm.The light transmittance at 400 nm for these polyimides exceeds 80%except for those based on 6FDA and BTA.The cut-off wavelength of polymers based on CANSCAL diamines range from 280-339 nm,the transmittance at 400 nm exceeds 78%except those based on 6FDA and BTA.Polyimide CpODA-CANAL-1' exhibited optimal comprehensive performance with a Tg of 462?,the transmittance at 400 nm up to 84%,CTE as low as 34.3 ppm/K,and the tensile strength,modulus and elongation at break of the film are respectively 87 MPa,2.1GPa and 15.3%.