Preparation And Properties Of Phenolphthalein-based Poly Aryl Ether Resins Containing Isopropyl Groups

Poly aryl ether resin is a kind of high-performance special engineering plastic with excellent comprehensive performance and occupies an important position in the fields of rail transportation,new energy,sewage treatment,military weapons and aerospace due to its advantages of radiation resistance,creep resistance,high strength,impact resistance,and high thermal stability.In addition to the above advantages,its low dielectric constant can effectively reduce the crosstalk and power consumption generated between circuit links,which has good application potential in the field of interlayer electronic packaging materials for ultra-large-scale integrated circuits,and is of great research value especially in the context of the 5G information era.However,the poor solubility,high hot working temperatures and high melt viscosity of poly aryl ether resins usually make them unfavorable for industrial processing,and are limiting factors for their development in the field of electronic packaging materials.The amorphous phenolphthalein-based poly aryl ether resins prepared by introducing a non-coplanar phenolphthalein structure into poly aryl ether resin not only have high glass transition temperature（T_g）,good mechanical properties and good solubility,but also the lactone ring structure of phenolphthalein provides a reactive site for functional modification of its monomer,allowing the molecular structure to be designed in more diverse ways.But there is still a gap between the dielectric constant of phenolphthalein-based poly aryl ether resins with traditional structure and the standard for low dielectric constant dielectric materials（ε＜3.0）,so it is of great significance to effectively reduce its dielectric constant for its application in dielectric materials.However,relatively little research has been done to modify traditional phenolphthalein-based poly aryl ether resins to reduce dielectric constant,and there is still a considerable research space for the preparation of low dielectric constant phenolphthalein-based poly aryl ether resins with excellent overall performance based on the molecular design approach.In order to solve the above research problems,this paper takes the structural design and synthesis of phenolphthalein-based bisphenol monomers as the starting point,and designs and synthesizes high purity phenolphthalein-based bisphenol monomer with different side group structures by optimizing the experimental parameters;Subsequently,phenolphthalein-based poly aryl ether ketones（iPrPEKC）,poly aryl ether sulfone（iPrPESC）and poly aryl ether nitrile resins（iPrPENC）containing isopropyl groups were prepared on this basis from high purity bisphenol monomers（iPrPHT）via the S_N2 nucleophilic substitution reaction,the influence of the aggregated structure of polymer chains and the variation of the inter-chain free volume on the thermal stability,mechanical and dielectric properties of polymers has also been investigated from a microscopic perspective;Finally,based on the structural and performance advantages of iPrPEKC,two series of copolymers with different monomer ratios were prepared by introducing a low polarizability group and a group with a large space volume into the molecular structure of iPrPEKC,respectively.The effects of different molecular designs and the relative content of structural units in copolymers on the mechanical properties,thermal stability,dielectric properties and microstructure of the materials were investigated.The main results are as follows:1.A suitable experimental scheme was developed by exploring the experimental conditions,and phenolphthalein-based bisphenol monomers（sub-PP）with high purity and different side groups were successfully prepared.The crude monomer product was purified by recrystallisation and the optimum solvent mixture ratio for recrystallisation was determined by experiments.The synthesis and purification scheme solved the problems of low purity of the target product sub-PP due to by-products and the product can not be purified due to its high viscosity,resulting in a high yield of sub-PP,which can be easily prepared in large quantities.The purity of the purified sub-PP was greater than 97%for all five different structures,demonstrating the feasibility of the experimental scheme.2.Based on the structural characteristics,yield and purity of the five prepared sub-PPs,iPrPHT containing isopropyl groups in the ortho position of the two phenolic hydroxyphenyl rings was selected as the raw material and polymerized with a dihalogen monomer containing a ketone group,a sulfone group and a cyano group,respectively,to prepare phenolphthalein-based poly aryl ether ketone（iPrPEKC）,poly aryl ether sulfone（iPrPESC）and poly aryl ether nitrile（iPrPENC）containing isopropyl groups.The effects of the isopropyl groups on the thermal,mechanical,solubility,dielectric properties and microstructure of the three resins were studied and summarized.The results show that the isopropyl groups can significantly reduce the thermal stability,mechanical properties and dielectric constant of the polymer.The aggregation state of the polymer molecular chains and the free volume between the chains were analyzed and it was found that all three resins have an amorphous structure and that a larger volume of isopropyl groups increases the distance between the molecular chains（d）,the free volume（v）and the free volume fraction（f_v）,the increase in the d value weakens the interchain interaction forces,leading to a decrease in the thermal and mechanical properties,and also provides the three resins with good solubility and lower dielectric constants.In addition,the polarity of the groups in the molecular structure also affects the dielectric constant of the polymer.In the case of both isopropyl groups,the dielectric constant of the iPrPEKC resin containing ketone carbonyl group at 1 MHz（2.81）is lower than that of the iPrPESC and iPrPENC resins containing sulfone and cyano groups（3.11 and 2.86）.3.The presence of-CF₃ groups consisting of C-F bonds with low polarizability and fluorene groups consisting of aromatic rings in the molecular chain can effectively improve the dielectric properties of the polymer and reduce the dielectric constant of the polymer.Based on the structural and performance advantages of iPrPEKC resin,two series of copolymers with different structural unit ratios,iPrBPAF and iPrBPFL were prepared by introducing 4,4’-（Hexafluoroisopropylidene）diphenol（BPAF）and4,4’-（9-fluorenylidene）diphenol（BPFL）structural units into their molecular structures respectively.It was found that with the increase of the relative content of BPAF and BPFL structural units,v and f_v of the iPrBPAF and iPrBPFL series copolymers first increased and then decreased,while the dielectric constant of the copolymer at 1 MHz first decreased and then increased.The mechanism of reducing the dielectric constant of the copolymer was clarified,and the effect of the variation of BPAF and BPFL content on the distribution of free volume pores and the dielectric constant of the copolymers was investigated.The iPrBPFL series copolymers maintain good dielectric properties at high frequencies.iPrBPFL-60 has a dielectric constant in the range of 2.63to 2.71 at 10 to 42 GHz and can achieve the standard for low dielectric constant interlayer dielectric materials.In conclusion,this thesis has prepared a new type of phenolphthalein-based poly aryl ether resin containing isopropyl groups through molecular design,which effectively improves the dielectric properties of phenolphthalein-based poly aryl ether resin,solves the problem that the dielectric properties of such materials do not meet the applicable standards for low dielectric constant interlayer dielectric materials,providing some research ideas and references for the development of new low dielectric constant poly aryl ether materials.