Preparation And Properties Of Low Dielectirc Constant Poly (Aryt Ether Ketone)s Containing Long Aliphatic Side Chains

In recent years, the electronic products are becoming more lightweight andthinner and have the characteristics of high performance and multi-function alongwith the rapid development of electronic information technology in themicroelectronics field. Next generations of microelectronic devices request furtherminiaturized systems. In this context, further reduction in the dielectric constant ofthese materials used as interlayer dielectrics is needed to avoid cross-talk betweenconducting wires and increase signal propagation speed as electronic devices continueto shrink. People are trying to adopt new technologies in the fields of electronicengineering and manufacturing and also replace the original materials with the newmaterials with more excellent performance, and we are concerned about the newpolymer materials with a low dielectric constant (ε) compatible with ε <<3resolution.In particular, poly (aryl ether ketone)s (PAEKs) have achieved an excellent positionamong other thermoplastic polymers by the virtue of their superior properties, such asthermal stability, high heat-distortion temperature, chemical inertness, electricalperformance, and flame retardancy. A variety of approaches of physical and chemicalmodification have been attempted by us in order to reduce the polarizability of amolecule, scilicet the total polarization of a medium, and the number of polarizablepolar molecules unit volume, and finally decrease the dielectric constant of theresulting polymers.First, the aromatic diphenol monomers,4-(1-adamantyl)-1,3-benzene diol(AdRES) and4-(6-(4-hydroxyphenyl)undecan-6-yl)phenol (BISPR5R5),4-(4-(4-hydroxyphenyl)heptan-4-yl)phenol (BISPR3R3) were successfullysynthesized and used to synthesize a new series of poly (aryl ether ketone)copolymers with the same percentage of two diphenol monomers by nucleophilic aromatic substitution polycondensation. The structure of copolymers was confirmedby FTIR and1H NMR spectroscopy and it was found that the copolymers presentedhigh molecular weight, good solubility and hydrophobic nature. The introduction ofthe flexible long aliphatic side chains had negative effect on the glass transitiontemperature and thermal durability of the copolymers, however, the introduction ofrigid pendant adamantyl group improved the thermal properties of the copolymers, sothe temperatures of5%weight loss in N2exceeded450oC and the temperatures of10%weight loss were more than470oC. The introduction of the pendent adamantylgroup and symmetrical long side chains was conducive to the reduction of thedielectric constant, and the dielectric constant was lowered more significantly as thelength of the long aliphatic side chains became longer.Second, we wonder whether the tiny change of the structure of the polymerchains could impact polymer aggregation and its physical properties. A new series ofpoly (aryl ether ketone) copolymers (AdRES-BISPR5R5-PEEKs) with differentpercentages of two diphenol monomers have been successfully synthesized bynucleophilic aromatic substitution polycondensation. The structure of copolymers wasconfirmed by FTIR and1H NMR spectroscopy. By the comparison and the discussionof the results of experiments and tests, we have found that the flexible side chains andthe rigid side group interacted with each other and influenced the basic performanceof the polymer material together. The introduction of the flexible side chains greatlyimproved the toughness and their elongation at break of the polymer films, and didnot reduce their tensile strength and Young’s modulus. Moreover, as the long sidechains’ content increased, the ε value of the polymer films remarkably decreased andeven reached2.5(1MHz) for the100%BISPR5R5-PEEK.Finally, by the observation of the experimental test results, we found that thedielectric constant of all bulk materials is not low enough and the adjustable range islimited because of their own structures and the synthesis methods. Since the dielectricconstant of gases is not much different from that of vacuum ε≈1, the incorporation offree space or pores is an attractive approach to reduce the number of polarizable polarmolecules unit volume and decrease the dielectric constant of films. 4-(6-(4-hydroxyphenyl)undecan-6-yl)phenol (BISPR5R5) was selected. Itssymmetrical structure with low polarity was propitious to reduce the polarity of thepolymer chains and subsequently reduce the dielectric constant of the polymer.Simultaneously the monomer, phenolphthalin (PPL) was selected to copolymerizewith4,4’-difluorobenzophenone (DFB) and BISPR5R5via the nucleophilic aromaticsubstitution polymerization. The inorganic phase and organic phase were connectedtogether covalently by the reaction of the pendant group-carboxyl and the amino ofthe silane coupling agent KH550via the sol-gel process. A series oforganic–inorganic hybrid materials with different percentages of TEOS have beensuccessfully prepared. SEM images were used to confirm the microscopicmorphology of the organic–inorganic hybrid membranes and the porous structure.The mutual penetration of the silica inorganic network structure and the polymermatrix was observed, and the inorganic nanoparticles were homogeneously dispersedthroughout the sample. After HF etching, the porous structure was formed in the thinfilm material. The porous membrane-30%TEOS showed a lower value of thedielectric constant, ε=2.38(at1MHz), than that of100%BISPR5R5-PEEK(ε=2.5at1MHz).