Synthesis And Properties Of Crystalline Biphenyl Poly(Arylene Ether Sulfone)

Poly(aryl ether sulfone)(PAES)resin is a kind of high temperature resistant thermoplastic special engineering plastic with excellent comprehensive performance.It has been widely used in the fileds of aerospace,electrical and electronic,energy and water treatment.At present,the mainstream poly(aryl ether sulfone)resin,such as polysulfone(PSF),polyethersulfone(PES)and polyphenylene sulfone(PPSU),are amorphous,which leads to a big gap in the performance of acid and alkali resistance,solvent resistance,friction and wear,mechanical strength between poly(aryl ether sulfone)resin and other crystalline special engineering plastics,such as poly(phenylene sulfide)(PPS)and poly(ether ether ketone)(PEEK).This situation makes PAES cannot be used in harsh conditions such as high humidity,high temperature,chemical corrosive and high-speed rotation and transmission.The regulation of polymer aggregate structure is an important direction in the field of polymer.Generally,the aggregate structure of polymer includes crystalline,liquid crystal,amorphous state and oriented state structure.The aggregate structure of the polymer material is closely related to the performance of the polymer material.Compared with PEEK,the main reason why PAES has an amorphous structure is the presence of sulfone groups in polymer chains.Compared with the ether/ketone structure of PEEK resin,the bond angle of ether bond is inconsistent with the bond angle of the sulfone group,resulting in destruction of the regularity of the molecular chain,so that the common poly(aryl ether sulfone)resin cannot be crystallized.In view of this situation,researchers generally adopt two methods to obtain the crystalline PAES.One is to introduce the side group having a large steric hindrance on the benzene ring ortho to the sulfone group,which could change the bond angle of the sulfone groups close to the bond angle of ethe and thereby increase the regularity of polymer chains.The main disadvantages of this method are the tedious synthesis and the lowered thermal stability of the PAES due to the introduction of large sterically hindered groups.Another method is to introduce a large proportion of rigid groups in polymer chains,such as terphenyl groups,to induce polymer crystallization.Compared with the first method.the synthesis step of the second way is much simpler,but introduction of a large proportion of rigid groups will reduced solubility of the polymer in the solvent,so it is generally difficult to obtain a product with high molecular weight.At the same time,the melting point of the polymer will increase,which is bad for polymer processing.According to the above analysis,the sulfone group is the main reason for the amorphous structure of poly(aryl ether sulfone).From the perspective of molecular design,this paper introduced rigid symmetric groups on both sides of the sulfone group to inhibit its influence on the aggregate structure,and obtained a new semi-crystalline PAES resin containing symmetric bis-phenylene structure.Moreover,the crystallization kinetics and mechanical behavior was studied in this paper.Firstly,two kinds of difluoro monomers and bisphenol monomers with bisphenyl groups were synthesized by Suzuki-Miyaura coupling reaction,and the structure of both two monomers were characterized by NMR and FT-IR.Then the monomers were respectively polymerized with corresponding monomers containing a benzene ring or a biphenyl structure,and finally three kinds of poly(aryl ether sulfone)containing a plurality of biphenyl groups were prepared,which were respectively recorded as DBPPES,DBP-PESDS and PEBDS.By the DSC testing,it was found that the DBP-PES and DBP-PESDS were too symmetrical due to the high proportion of sulfone groups in the molecular structure,though the glass transition temperature exceeded 270 °C.However,there is no evidence of crystal melting,indicating that the two polymers do not have crystallization ability.After testing PEBDS,it was found that PEBDS resin showed obvious crystal melting peak,and XRD test also showed that PEBDS resin had obvious crystal diffraction peak,which proved PEBDS resin had good crystallization ability.The basic properties of PEBDS resin were further characterized in this paper.The test shows that the PEBDS resin in this thesis has excellent solvent resistance and is almost insoluble in all common organic solvents.Therefore,the molecular weight of PEBDS resin was characterized by using m-chlorophenol as solvent.The inherent viscosity of the PEBDS resin is 0.42 d L/g,and the DSC test shows that the glass transition temperature(Tg)is 232 ° C and the melting point(Tm)is 372 ° C.After X-ray diffraction analysis,the crystal diffraction peak of PEBDS resin can be clearly observed.The calculated maximum crystallinity of PEBDS resin can reach 21%,and the crystal melting enthalpy is about 92 J/g.At the same time,the non-isothermal crystallization kinetics of PEBDS resin was studied by Jeziorny method,and the crystallization rate constant and Avrami index of PEBDS resin with different cooling rate were obtained.Due to the solubility of the PEBDS resin,although the product obtained in this paper has a higher molecular weight than other crystalline poly(aryl ether sulfone)s reported in the literature,because of high rigidity of the molecular chain,the toughness of the material is low,which leaded to the resin material could not be processed into test stripsIn order to obtain crystalline poly(aryl ether sulfone)with higher mechanical strength and molecular weight,we have prepared BDP-PEES1,3,5,10 copolymers with different 4,4'-difluorodiphenyl sulfone content.The test found that BDP-PEES3 also has the ability to crystallize,and its Tg and Tm are not significantly different from the homopolymer.After calculation,the maximum crystallinity of BDP-PEES3 is 18%.At the same time,its molecular weight has completely reached the standard of processing into a spline.After tensile bending test,we found that the tensile strength and bending strength of BDP-PEES3 are obviously stronger than ordinary PPSU with similar molecular weight,therefore,this is a new type of resin material with great development prospects and application prospects.