Synthesis and characterization of hyperbranch polyether on polyimide

Abstract

A hyperbranch polyimide-POSS (Polyhedral Oligomeric SilSesquioxanes) composite was synthesized by a reaction of a bromide-hyperbranch polyther-POSS and a polyimide containing hydroxyl functional group. Hyperbranch polyether was prepared by a reaction of 3,5-dihydroxybenzyl alcohol and MonoChloroIsobutyl-POSS (POSS-Cl) and then convert end then convert end chain hydroxyl group to bromide by carbontetrabromide for the formation of the second layer and the obtained polymer was repeated reacted with the alcohol with same procedure for the formation of the third layer. Thermogravimetric analysis analysis indicated that the thermal degradation (T5%) of hyperbranch polyimide films occurs at 265 to 359 C. The glass transition temperatures of hyperbranch polyimide films are in the range of 324.64C. Regardless of the fixed amount of POSS, the higher layers yield lower dielectric constant and even reduced four times amount of POSS, the third layer still have the lowest dielectric constants. The lowest dielectric constant value for 2.54 can found in third layer of hyperbranch polyimide-POSS composite due to many free volume and loose polyimide structure. The densities of the hyperbranch polyimide correspond to the dielectric constants. The lower is the density, the higher is the free volume and the lower is the dielectric constant. Experimental results indicated that the hyperbranch polyimide-POSS composite exhibited increase solubility compare with pure polyimide.