Date of Award

12-1-1996

Degree Type

Thesis

University or Center

Clark Atlanta University(CAU)

Degree Name

M.S.

Department

Chemistry

First Advisor

Dr. Issifu I. Harruna

Abstract

The star-like molecule, 2, 7-diamino-9,9-bis(4-aminophenyl)fluorene, was used to effectively control the orientation of linear polyimide chains so as to prepare star-like polyimide systems that are excellent candidates of improved compressive properties compared to the linear analogues. The synthesis of the central fluorene unit involved the reaction of 2,7-dinitro-9-fluorenone with aniline in the presence of aniline hydrochloride followed by the reduction of the nitro functionalities. The incorporation of this favorable geometric molecule by condensation with the C-terminus of the linear polyimides resulted in the synthesis of three-dimensional polyimides. Polyimide systems exhibiting improved solubility in organic solvents and strong acids, and transitions at lower temperatures were prepared by introducing hexafluoro groups (bis-4,4’-aminophenylhexafluoropropane and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride), and by using a dianhydride (bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride) with reduced symmetry and decreased π-electron density relative to benzene tetracarboxylic dianhydride. An improvement in the solubility of the thermally stable three-dimensional polyimides was observed as a result of a decrease in linearity and an increase in free volume due to the star-like structure of the three-dimensional polyimides.

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