Low Dielectric Constant Functionalized Polynorbornene: Synthesis And Properties

Three kinds of polymers: poly(norbornene dimethyl dicarboxylate)s, poly(norbornene dicarboxylic acid dialkyl ester)s, and poly(N-substituted nadimide)s, were synthesized by vinyl addition polymerization using palladium(II)-based catalyst from pure exo-monomers, and their structures were characterizated with IR,1H-NMR and GPC etc.The solubility, the glass transition temperatures, the thermal properties and degradation behaviors and the dielectric constants were also investigated and the results were summarized as follows:The resulting polymers such as poly(norbornene dicarboxylic acid dialkyl ester)s (alkyl = Me (PNB-1), Et (PNB-2), Pr (PNB-3) and Bu (PNB-4)), poly(norbornene dimethyl dicarboxylate)s, (carboxylates = acetate (PNB-A), propionate (PNB-B), and butyrate (PNB-C)) showed good solubility in common organic solvents. The solubility in common organic solvent of poly(N-substituted nadimide)s were not as well as poly(norbornene dimethyl dicarboxylate)s and poly(norbornene dicarboxylic acid dialkyl ester)s.The glass transition temperatures of polynorbornene esters were characterizated by DMA. We also gained refractive indexs of polymers, and calculated the dielectric constants of polymers by Maxwell equation. The glass transition temperatures and dielectric constants of solid polymers were found to decrease as the alkyl side-chain length increases for both polymer series. However, poly(norbornene dimethyl dicarboxylate)s showed lower glass transition temperatures and higher dielectric constants, compared with those of poly(norbornene dicarboxylic acid dialkyl ester)s containing the same carbon number of side chain.The thermal properties and degradation behaviors of poly(norbornene dicarboxylic acid dialkyl ester)s and poly(N-substituted nadimide)s were investigated by thermogravimetric analysis in dynamic conditions, the first one high thermal stability up to 330℃, the later one show higher thermal stability up to 430℃. The apparent activation energy and thermal degradation model of poly(norbornene dicarboxylic acid dialkyl ester)s and poly(N-substituted nadimide)s were also estimated repectively. The thermal degradation temperture and the apparent activation energy of poly(norbornene dicarboxylic acid dialkyl ester)s decreases in the order PNB-1>PNB-2>PNB-3>PNB-4 with the increase in size of side chain.The effects of polymerization conditions on the polymerization results by polymerizing norbornene dimethyl propionate and N-cyclohexyl-nadimide were systematically investigated, such as the size of substitutents, molar ratio of monomer to catalyst, solvent polarity, reaction time, and temperature on the polymerization of monomers. It was found the polar properties of solvents have considerable effect on the catalyst activity.