Investigation of glass transition behaviors in poly(amic acid) precursors of semiflexible polyimides by oscillating differential scanning calorimetry
SCIE
SCOPUS
- Title
- Investigation of glass transition behaviors in poly(amic acid) precursors of semiflexible polyimides by oscillating differential scanning calorimetry
- Authors
- Kim, SI; Pyo, SM; Ree, M
- Date Issued
- 1997-12-15
- Publisher
- AMER CHEMICAL SOC
- Abstract
- Aromatic poly(amic acid) precursors always form complexes with dipolar aprotic solvents via strong acid/base interaction and are expected to have relatively high glass transition temperatures (T-g's) which are overlapped with or higher than the imidization temperatures, so that their T-g's could not he determined in spite of their wide usages. In the present study, the measurement of T-g was attempted fur poly(amic acid) precursors of three different aromatic polyimides synthesized in N-methyl-2-pyrrolidone (NMP) from the respective dianhydrides and diamines: poly(4,4'-oxydiphenylene pyromellitamic acid) (PMDA-ODA), poly(p-phenylene 3,3',4,4'-oxydiphthalamic acid) (ODPA-PDA), and poly(p-phenylene benzophenonetetracarboxamic acid) (BTDA-PDA). Phase transitions, as well as imidization reactions in the precursor/NMP mixtures, were measured with varying compositions by a newly developed oscillating differential scanning calorimetry Compositions in the mixtures were determined by proton nuclear magnetic resonance spectroscopy. For solvent-rich mixtures, a melting point depression of the NMP solvent was observed, whereas for precursor rich mixtures, T-g depression was detected. In particular, T-g's measured for the precursor rich mixtures were best fitted by a modified Gordon-Taylor equation as a function of composition, in order to estimate T(g)s of poly(amic acid)s in solvent free, that is, true T-g's of the precursor polymers: 207.4 degrees C for PMDA-ODA, 166.3 degrees C for ODPA-PDA, and 213.2 degrees C for BTDA-PDA precursor. The Kuhn segment length, which is a measure of chain flexibility, was estimated to be 43.3 Angstrom for PMDA-ODA, 34.6 Angstrom for ODPA-PDA, and 34.6 Angstrom for BTDA-PDA. In addition, a phase diagram was constructed Cor the PMDA-ODA precursor/NMP mixture. For the highly dried precursor samples, the chemical repeat unit, was also determined to complex with 1.4-1.7 NMP molecules, depending on the precursors.
- Keywords
- FLEXIBILITY; SCATTERING; BLENDS; IR
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/20928
- DOI
- 10.1021/ma970556f
- ISSN
- 0024-9297
- Article Type
- Article
- Citation
- MACROMOLECULES, vol. 30, no. 25, page. 7890 - 7897, 1997-12-15
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- There are no files associated with this item.
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