Investigation of Glass Transition Behaviors in Poly(amic acid) Precursors of Semiflexible Polyimides by Oscillating Differential Scanning Calorimetry

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 be determined in spite of their wide usages. In the present study, the measurement of T g was attempted for 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 diffferential 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 the poly(amic acid)s in solvent free, that is, true T g's of the precursor polymers: 207.4 °C for PMDA−ODA, 166.3 °C for ODPA−PDA, and 213.2 °C for BTDA−PDA precursor. The Kuhn segment length, which is a measure of chain flexibility, was estimated to be 43.3 Å for PMDA−ODA, 34.6 Å for ODPA−PDA, and 34.6 Å for BTDA−PDA. In addition, a phase diagram was constructed for 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.

High performance polyimides for applications in microelectronics and flat panel displays

“…111 In addition, the amounts of residual solvents in the precursor polymer specimens were measured by proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy. 111 For a given PAA precursor, T g was measured with varying the content of residual solvent.…”

Synthesis of new aromatic polyimides with various side chains containing a biphenyl mesogen unit and their abilities to control liquid-crystal alignments on the rubbed surface

“…17 For a given poly(amic acid), the relative and specific viscosities were measured at four different concentrations over the range of 0.10 -0.60 g/dL, and the [] value was estimated by extrapolation of the reduced and inherent viscosities to infinite dilution. The [] was determined to be 0.207 dL/g for the ODPA-BP1 PAA, 0.259 dL/g for the ODPA-BM1 PAA, 0.653 dL/g for the ODPA-BO1 PAA, 0.245 dL/g for the ODPA-BP2 PAA, and 0.400 dL/g for the ODPA-MPD PAA.…”

Adhesion of poly(4,4′-oxydiphenylene pyromellitimide) to copper metal using a polymeric primer: Effects of miscibility and polyimide precursor origin

“…For the synthesized precursors, [g] measurements were conducted in NMP at 25.0 8C using an Ubbelohde suspended level capillary viscometer as reported previously [18][19][20] . The measured [g] was 0.880 dL/g for PMDA-ODA PAA and 0.503 dL/g for PMDA-ODA PAE.…”