Preparation and Properties of 2,5-Furandicarboxylic Acid Based Polyimides
Supervisor:fang sheng zhong
In recent years,due to the growing need for sustainable development,the development of bio-based polymers has received more and more attention.Recently,with the development of the aromatic bio-based monomer 5-hydroxymethylfurfural,compounds derived from 2,5-furandicarboxylic acid and 2,5-furandimethanol have been increasingly used for novel bio-based polymers.However,its research in bio-based polyimides is still blank.To further expand the research of 2,5-furandicarboxylic acid and 2,5-furandimethanol in polyimides,this paper is based on 2,5-furandicarboxylic acid-based polyimides.Research work has been carried out in the following areas:1.Two new types of diamines,N,N’-bis(3-aminophenyl)furan-2,5-dicarboxamide(m-FDDA)and N,N’-bis(4-aminophenyl)furan-2,5-dicarboxamide(p-FDDA)were successfully synthesized.Polyimides were successfully synthesized using a conventional two-step method.Research indicates that(1)2,5-furandicarboxylic acid-based polyimides have good thermal stability(Td5% exceeds 400℃).(2)The coefficient of thermal expansion(CTE)increases as the flexible linkage of the aromatic dianhydride increases(CTE value: BPDA < 6FDA < BPADA).(3)With good mechanical properties,the tensile strength and tensile modulus increase as the rigidity of the main chain increases(BPDA> 6FDA> BPADA).(4)Most are soluble in common organic solvents such as m-cresol,NMP,DMAc.(5)p-FDDA-based polyimide(PI)has a higher glass transition temperature(Tg)value than the corresponding m-FDDA-based PI.After introducing furan into the polymer,the rigid planar conformation of the polymer backbone helps the polyimide for a higher Tg;in addition,the p-FDDA-based PI has better thermal stability than the m-FDDA-based PI.2.A novel bio-based fully aromatic diamine N,N’-bis(4-amino-2-(trifluoromethyl)phenyl)furan-2,5-dicarboxamide(TFFDA)was successfully synthesized.And using conventional two-step method,a series of partially bio-based polyimides was successfully synthesized.Research indicates that(1)by comparison among polyimides,it was found that the polymer showed good solubility in commonly used organic solvents such as m-cresol,NMP,DMAc,acetone and THF.(2)The introduction of the pendant trifluoromethyl group reduces the Tg of the polymer.TFFDA-based polyimides have very good thermal stability(Td5% exceeds 400℃).(3)The CTE value of TFFDA-based polyimides generally increases as the flexible linkage of the aromatic dianhydride increases(CTE value: BPDA < 6FDA < BPADA).(4)Polyimide films have good mechanical properties.Among these polyimide films,PI-1-a has the highest tensile strength and tensile modulus(95 MPa and 2.7 GPa,respectively),which is derived from BPDA.(5)The optical transmittance of TFFDA-based polyimide(PI-1-a~PI-1-c)at a wavelength of 500 nm is less than 70%,and the light transmission performance is significantly lower than that of p-FDDA-based polyimide.3.The feasibility of the cross-linking of the furan group in the 2,5-furandicarboxylic acid polyimide backbone with bismaleimide by Diels-Alder reaction was verified.The study found that:(1)The cross-linked polyimide only swells and can not dissolve in m-cresol,NMP,DMAc,acetone and THF,and the extent of cross-linking increases as the content of bismaleimide.(2)Crosslinking can significantly increase the Tg of polyimides.(3)The CTE values of the polyimides after cross-linking(PI-1-10~PI-1-100 and PI-2-100)are further reduced.(4)The mechanical properties including tensile strength and tensile modulus of the polyimide after cross-linking(PI-1-10~PI-1-100 and PI-2-100)has been significantly enhanced.(5)The cross-linking effect caused by the Diels-Alder reaction between the furan group and the bismaleimide weakens the transparency of the polyimide.