Regeneration of polycondensation of wholly aromatic poly(azomethine)s with 1,5- or 2,6-substituted naphthalene moiety in main chain

Abstract

Wholly aromatic poly(azomethine)s with 1,5‐ or 2,6‐substituted naphthalene moiety in the main chains were prepared in aprotic polar solvents or m‐cresol under various reaction conditions. In the polymerization of 1,5‐diaminonaphthalene with terephthalaldehyde, the polymer that synthesized in (HMPA/DMSO) at room temperature for 24 h by adding 5 wt % of calcium chloride and a very small amount of p‐toluenesulfonic acid showed the highest reduced viscosity in all of the polymers from 1,5‐diaminonaphthalene. The reduced viscosity of poly(azomethine)s synthesized from 2,6‐diaminonaphthalene with 2,6‐diformylnaphthalene in m‐cresol and with terephthalaldehyde in HMPA/DMSO were ηred = 0.35 and 0.36, respectively. The thermal analysis showed the poly(azomethine)s had high thermal stability and the glass‐transition temperatures of these polymers are about 250 °C. The X‐ray diffraction showed that they are partially crystalline. They could be polymerized again by second stage polycondensation in polyphosphoric acid. The reduced viscosities of the obtained polymers were about 2–5 times as high as that of the pristine polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1064–1072, 2000

Synthesis and photophysical study of a conjugated–non-conjugated oligoazomethine

“…On the other hand, these features are also responsible for the low solubility of polyazomethines, hindering its processing, applications and even the study of their properties. The most employed strategies to improve solubility are the modification of the chain itself, like the insertion of lateral ramifications or flexible segments as alkyl or alkoxy groups along the backbone [5,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Inserting bulky substituents act in separating or twisting the polymer chain [28], inserting flexibilizing groups such as ether or isopropyl bridges [13].…”

Self-Assembling Polycondensation of 4-Aminobenzaldehyde. Preparation of Star-Like Aggregates of Cone-Shaped Poly(azomethine) Crystals

“…In order to improve their intractability, several approaches such as the introduction into the main chain of flexible aliphatic segments, bulky lateral substituents or fluorine groups have been attempted so far. [9][10][11][12] We have been studying on the morphology control of intractable polymers during solution polymerization, and succeeded in preparing the whiskers of poly(poxybenzoyl) and other aromatic polyesters by polymerization in liquid paraffin (LPF). [13][14][15][16][17][18] These whiskers are formed by the reaction-induced crystallization of oligomers during solution polymerization.…”

“…One of reasons is that aromatic poly(azomethine)s are precipitated in the solution during polycondensation because of the low solubility. 12 Much effort was devoted recently to preparing soluble and fusible aromatic poly(azomethine)s in many different ways. [19][20][21] However, the modification of polymer chain structures sacrifices their essential properties derived from their straight rigid-rod structures.…”

,Polyazomethines. Synthesis, properties and applications (review)

“…Отклонение от этого диапазона рН может влиять на скорость реакции. Азометины ряда альдиминов, как правило, образуются в форме Е-изомеров [2]: В публикациях последних лет при синтезе оснований Шиффа в случаях, когда в качестве карбонильной компоненты использовали малоактивные салициловый и 2-гидроксинафталевый альдегиды, для ускорения реакции и повышения выхода азометинов (до 91-99%), в качестве катализатора было предложено использовать соляную, п-толуолсульфоновую [3] или муравьиную кислоты [4].…”