Title page for ETD etd-02022007-133644


Type of Document Dissertation
Author Joseph, William Dale
URN etd-02022007-133644
Title Synthesis and characterization of high performance polybenzoxazoles
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
McGrath, James E. Committee Chair
Gibson, Harry W. Committee Member
Riffle, Judy S. Committee Member
Tanko, James M. Committee Member
Ward, Thomas C. Committee Member
Keywords
  • Polymerization
  • Polymers
Date of Defense 1993-08-05
Availability restricted
Abstract

High molecular weight poly(hydroxy amide)s and polybenzoxazoles possessing a variety of backbone compositions have been synthesized via low temperature polycondensation and a novel catalytic cyclization reaction. Preliminary experiments involved the synthesis of poly(hydroxy amide)s and polybenzoxazoles based on a bisphenol-A aminophenol and isomeric acid chlorides. The polymers exhibited Tg's around 280°C, limited solubilities and only fair thermo-oxidative stabilities. In an effort to improve these properties. fluorinated monomers were investigated. A number of novel fluorinated monomers and commercial monomers were incorporated into poly(hydroxy amide)s and polybenzoxazoles using the above mentioned polymerization/cyclization techniques. Enhanced solubilities, glass transition temperatures and thermooxidative stabilities were realized. Difficulties encountered during the polymerization of the fluorinated monomers prompted the study of polymerization conditions. Results of these studies indicate that the electronic environment about the bis(o-aminophenol)s and acid chlorides dictates the ability of these monomers to participate in an ester forming side reaction. Physical and spectroscopic evidence was presented to support this conclusion. Investigations were also conducted to determine optimum cyclization conditions. It was shown that pyridine hydrochloride and p-toluenesulfonic acid monohydrate were active cyclization catalysts when used in conjunction with an azeotroping solvent, such as toluene or 0- dichlorobenzene. In general, complete cyclization of the oxazole rings could be achieved in as little as 6 hours at 175°C. Unfortunately, generic cyclization conditions were not found. Additionally, phenylethynyl terminated polybenzoxazoles were successfully synthesized using the above techniques. Molecular weight control and phenylethynyl incorporation were confirmed by spectroscopic, thermal and mechanical analyses.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
[VT] LD5655.V856_1993.J677.pdf 21.01 Mb 01:37:14 00:50:00 00:43:45 00:21:52 00:01:52
[BTD] next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.