Preparation And Characterization Of Low Dielectric Constant Polymeric Materials Containing Trifluoromethyl Groups

With the rapid development of the microelectronic industry,the integrated circuits with smaller dimensions lead to resistant-capacitance delay,cross-talk and power dissipation.Circuit loss and time delay can be reduced by decreasing the dielectric constant of materials.Therefore,it becomes vital to develop materials with low dielectric constant.According to the Debye equation,an efficient strategy to obtain low dielectric constant materials is to introduce bulky trifluoromethyl groups into materials,which possess lower polarizability and increased free volume.Moreover,polymers containing trifluoromethyl groups are endowed with enhanced chemical and thermal stability,lower water absorption along with solubility in organic solvents.As a consequence,this dissertation was focused on the relationship between molecule structure and performance of low dielectric constant polymeric materials containing trifluoromethyl groups,which could be divided into three parts:“low dielectric constant epoxy resins containing trifluoromethyl group”,“low dielectric constant poly?arylene ether ketone?s containing trifluoromethyl group”and“ultra low dielectric constant poly?arylene ether ketone?containingphenol and trifluoromethyl groups cured epoxy resin nanofiber mats”.1.Low dielectric constant epoxy resins containing trifluoromethyl groups.A series of hydroquinone containing trifluoromethyl phenyl groups?FHQ?was synthesized via Meerwein reaction.Then the epoxy resins were synthesized through the reaction between FHQ and epichlorohydrin,and cured with diaminodiphenylmethane?DDM?and aminophenyl sulfone?DDS?.The cure kinetics of epoxy resins were investigated by non-isothermal DSC method and the cure conditions were determined from the results.All epoxy resins exhibited excellent thermal stability with glass transition temperature?T_g?above 128 ? and 5%weight loss above 300 ?.Among them,d-FER samples with more trifluoromethyl groups showed better thermal stability(T_d5>320 ?).DDS cured epoxy resins possessed higher thermal stability than that of DDM cured epoxy resins,while DDM cured epoxy resins showed better mechanical,dielectric and hydrophobic performance.For the DDM cured epoxy resins,the flexural strength is 95.55¹52.36 MPa,the flexural modulus is 1.71².65 GPa,the dielectric constant is 2.55³.05,and the water absorption is 0.49%⁰.95%.The dielectric constant and dielectric loss of DDM cured d-FER at 1 MHz are 2.55 and 0.016,and the water absorption is 0.49%,which are much lower than that of other samples.Above all,introducing trifluoromethyl groups into epoxy resins can be a valid strategy to improve the dielectric and hydrophobic performance.2.Low dielectric constant poly?arylene ether ketone?s containing trifluoromethyl groups.To obtain low dielectric constant polymers with higher performance,a series of poly?arylene ether ketone?s containing naphthalene moiety?PNAEK?was prepared through the nucleophilic substitution polycondensation of naphthalene-based difluoroarene and bisphenol monomers.The PNAEKs exhibited good film uniformity,higher T_g?>210??and T_d5?>440 ??,high tensile Young's modulus?1.32¹.51 GPa?.The dielectric constant and dielectric loss of PNAEKs at 1 MHz are 2.37².78 and 0.006⁰.017,respectively.The solubility,thermal stability,dielectric properties and hydrophobicity of PNAEKs were improved by introducing trifluoromethyl groups into polymers.Above all,PNAEK-3 prepared with difluoromethyl phenyl bisphenol exhibited high thermal stability(T_d5=461 ?),low water absorption?0.56%at 80 ??,dielectric constant?2.37?and dielectric loss?0.006?.These results demonstrated that introducing trifluoromethyl groups into PAEK was an efficient way to obtain low dielectric constant materials with excellent performance.3.Ultra low dielectric constant poly?arylene ether ketone?containingphenol and trifluoromethyl groups?HPNAEK?cured epoxy resin nanofiber mats.To improve the toughness of epoxy resins and obtain epoxy resins with ultra-low dielectric constant,a kind of macromolecule curing agent was prepared,and the electrospinning technique was applied to the preparation of porous film.Firstly,HPNAEK containing phenol and trifluoromethyl groups was synthesized via demethylation reaction.For the dense epoxy resin film,the dielectric constant is 3.4 at 1 MHz,the T_g is 237 ?,T_d5 is 354 ?,and the tensile strength and elongation at break are 51.39 MPa and 7.79%,respectively.The dielectric,mechanical and thermal properties of epoxy resin can be greatly improved by HPNAEK.For epoxy resin nanofiber mat?ES-HPNAEK-TMBPER?,it showed good toughness and hydrophobic properties.For example,the elongation at break of ES-HPNAEK-TMBPR is 15.89%;while the water contact angle is 145 ^o.ES-HPNAEK-TMBPER exhibited high T_g?262 ??,low coefficient of thermal expansion?CTE=52 ppm/??,excellent thermal stability(T_d5=347 ?)and ultra-low dielectric constant?1.9 at 1MHz?.As a result,electrospinning technique is an efficient way to prepare materials with ultra low dielectric constant,and the thermal stability,dielectric and hydrophobic properties can be furtherly improved by HPNAEK containing trifluoromethyl and aromatic moieties.