Title page for ETD etd-32398-61326


Type of Document Dissertation
Author Yang, Jinlian III
Author's Email Address jimyang@vt.edu
URN etd-32398-61326
Title PART I: SYNTHESIS OF AROMATIC POLYKETONES VIA SOLUBLE PRECURSORS DERIVED FROM BIS(A-AMININITRILE)S PART II: MODIFICATIONS OF EPOXY RESINS WITH FUNCTIONAL HYPERBRANCHED POLY(ARYLENE ESTER)S
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Dorn, Harry C.
McGrath, James E.
Riffle, Judy S.
Tanko, James M.
Gibson, Harry W. Committee Chair
Keywords
  • polymerization
  • synthesis
  • polyketones
  • aminonitriles
  • poly(arylene ester)s
  • modifications
  • toughening
  • epoxies
  • functionalization
  • hyperbranched
Date of Defense 1998-02-25
Availability unrestricted
Abstract
Part I: This part of the dissertation describes a new approach to high molecular weight aromatic polyketones via soluble precursors derived from bis(a-aminonitrile)s. Bis(a-aminonitrile)s were easily synthesized from dialdehydes and secondary amines in very high yield by the Strecker reaction. Polymerization of bis(a-aminonitrile)s with activated dihalides using NaH as base in DMF yielded soluble, high molecular weight polyaminonitriles, which were hydrolyzed in acidic conditions to produce the corresponding polyketones. A novel approach to the synthesis of high molecular weight wholly aromatic polyketones without ether linkages or alkyl substituents in the polymeric backbones was demonstrated. These polyketones displayed excellent thermal properties and solvent resistance. A very efficient synthesis for diphenol and activated dihalide monomers containing keto groups was also developed based on a-aminonitrile chemistry. Novel activated dihalide monomers were obtained in quantitative yields. This method is suitable for any activated dihalide by reaction with 2 equivalents of 4-fluorobenzylaminonitrile and NaH, followed by hydrolysis to produce a new monomer with two more p-fluorobenzoyl units. For the synthesis of polyaminonitriles containing ether linkages in the polymeric backbone, only low to medium molecular weight polymers were obtained. The model studies proved that the carbanions of the aminonitriles can react with ether linkages to form more stable phenoxide anions and cause the termination of the polymerization.

Part II: Functional hyperbranched poly(arylene ester)s were synthesized by thermal polymerization of 5-acetoxyisophthalic acid or 3,5-diacetoxybenzoic acid. Carboxylic terminated hyperbranched copolyesters were also synthesized by copolymerization of 5-acetoxyisophthalic acid and 3-hydroxybenzoic acid using different molar ratios of these two monomers. Both carboxylic acid and phenolic terminated hyperbranched polyesters were functionalized with different reactive groups. The carboxyl terminated hyperbranched poly(arylene ester)s were successfully used to modify inherently brittle epoxy resins. The hyperbranched polymers were chemically incorporated into the epoxy networks using triphenylphosphine (TPP) as a catalyst and 4,4'-diaminodiphenyl sulfone (DDS) as a curing agent. The chemistry and the proper formation of crosslinked networks were confirmed by solution 1H NMR, solid state CPMAS 13C NMR, kinetic FTIR spectroscopes and gel fraction analysis. Fracture toughness was improved without sacrificing thermal properties. The fracture toughness K1C values of the modified epoxies were found to be a function of the percentage loading, the molecular weights and the proportion of linear units of hyperbranched polyesters. Because the carboxylic acid terminated hyperbranched poly(arylene ester)s were immiscible with the commercially available epoxy EPON 828, the percentage loadings of hyperbranched modifiers were limited and the processibility of epoxy resins was difficult, especially at high percentage loadings of hyperbranched modifiers. These problems could be solved using phenolic terminated hyperbranched poly(arylene ester)s, which are more soluble in epoxy resins.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  1.pdf 123.49 Kb 00:00:34 00:00:17 00:00:15 00:00:07 < 00:00:01
  10.pdf 313.62 Kb 00:01:27 00:00:44 00:00:39 00:00:19 00:00:01
  11-.pdf 183.88 Kb 00:00:51 00:00:26 00:00:22 00:00:11 < 00:00:01
  2-3.pdf 39.31 Kb 00:00:10 00:00:05 00:00:04 00:00:02 < 00:00:01
  4.pdf 245.93 Kb 00:01:08 00:00:35 00:00:30 00:00:15 00:00:01
  5.pdf 284.74 Kb 00:01:19 00:00:40 00:00:35 00:00:17 00:00:01
  6.pdf 308.52 Kb 00:01:25 00:00:44 00:00:38 00:00:19 00:00:01
  7.pdf 122.86 Kb 00:00:34 00:00:17 00:00:15 00:00:07 < 00:00:01
  8-9.pdf 72.54 Kb 00:00:20 00:00:10 00:00:09 00:00:04 < 00:00:01
  cover_abs_tab_of_con.pdf 75.02 Kb 00:00:20 00:00:10 00:00:09 00:00:04 < 00:00:01

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.