High-Pressure Synthesis and Properties of Aliphatic−Aromatic Polyimides via Nylon-Salt-Type Monomers Derived from Aliphatic Diamines with Pyromellitic Acid and Biphenyltetracarboxylic Acid

Abstract

Two aliphatic series of polyimides having well-defined structures with inherent viscosities of 0.4−2.7 dL g-1 were readily synthesized by the solid-state thermal polycondensation under high pressure of the salt monomers composed of aliphatic diamines having 6−12 methylene units and both pyromellitic acid (PMA) and biphenyltetracarboxylic acid (BPA) under 220 MPa at 250 °C for 5 h. It is noteworthy that the polycondensation proceeded rapidly with the elimination of water in a closed reaction vessel under high pressure, producing high molecular weight polyimides mostly within only 1 h. The thermal behavior (melting temperature and glass transition temperature) and crystallinity of the PMA- and BPA-based polyimides are also discussed in detail.

Preparation of polyimides derived from biphenyltetracarboxylic dianhydrides and aromatic diamines bearing alkylene spacers

“…With a longer alkylene chain the tensile strengths at break and initial moduli decreased due to the flexibility of the alkylene chain. It is interesting to note the "odd-even" behavior of the tensile properties of polymer VIII films similar to the reported behavior of the melting temperatures for these polymers 18 and for analogous aliphatic PIs 26,27 and as reported in the behavior of the tilt bias angle for aliphatic PIs. 28 Thus, tensile strengths at break and initial moduli of polymers with an even number of methylene spacers have larger values than those of polymers with an odd number of methylene spacers.…”

Robust ambient pressure dried polyimide aerogels and their graphene oxide directed growth of 1D–2D nanohybrid aerogels using water as the only solvent

“…The nylon-salt-type monomer is extremely reactive and thus is a reasonable precursor for the preparation of polyimide. 25,26 The process for the green hydrothermal preparation of PI aerogels is shown in Scheme 1, where the dianhydride was rstly hydrolyzed to corresponding tetracarboxylic acid, which was then reacts with triamine TAPB to form the nylon-salt precursor. Due to the poor solubility of TAPB in water, the solution was stirred overnight at room temperature to fulll the salt formation.…”

High-pressure synthesis of aliphatic polypyromellitimides via nylon-salt-type monomers composed of aliphatic diamines and pyromellitic acid diesters

“…Pyromellitic acid (PMA) was prepared by a usual hydrolysis of PMDA with water. 11,15 Pyromellitic acid m-and p-diethyl esters (mPME and PME, respectively) were synthesized according to the reported procedure 8,15 by the reaction of PMDA with absolute ethanol. The separation of the two isomers was achieved by fractional recrystallization from chlorobenzene.…”

“…A series of nylon-salt-type monomers XPME, where X stands for the number of methylene unit in the aliphatic diamine, were prepared by the reported procedure 11,15 by mixing an ethanol solution of an aliphatic diamine with an ethanol solution of PME. Salt monomer 12mPME was synthesized by the same procedure from dodecamethylenediamine and mPME.…”

“…The structure of these salt monomers was confirmed by means of infrared (IR) spectroscopy and elemental analysis. 11,15 Endothermic peak temperatures of the salt monomers XPME, determined by DTA at a heating rate of 10°C/min, are summarized in Table I.…”