Synthesis and characterization of polyetherimides containing multiple ether linkages and pendent pentadecyl chains

Abstract

A new aromatic diamine, namely 4-(4-(4-(4-aminophenoxy)-2-pentadecylphenoxy)phenoxy)aniline, was synthesized and polycondensed with aromatic dianhydrides to obtain processable polyetherimides containing multiple ether linkages and pendent pentadecyl chains. 4-(4-(4-(4-Aminophenoxy)-2-pentadecylphenoxy)phenoxy)aniline (APPPA) was synthesized starting from cashew nut shell liquid-derived bisphenol, i.e. 4-(4-hydroxyphenoxy)-3-pentadecylphenol, by nucleophilic substitution reaction with 4-chloronitrobenzene followed by reduction of the formed 4-(4-nitrophenoxy)-1-(4-(4-nitrophenoxy)phenoxy)-2-pentadecylbenzene. Three new polyetherimides containing multiple ether linkages and pendent pentadecyl chains were synthesized by one-step high-temperature solution polycondensation of APPPA in m-cresol with three aromatic dianhydrides, i.e. 3,3',4,4'-oxydiphthalic anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Inherent viscosities and number-average molecular weights of the polyetherimides were in the ranges 0.66-0.70 dLg-1 and 17100-29700gmol-1 (gel permeation chromatography, polystyrene standards), respectively, indicating the formation of reasonably high molecular weight polymers. The polyetherimides were soluble in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, pyridine, m-cresol, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethylsulfoxide, and could be cast into transparent, flexible and tough films from their solutions in chloroform. The polyetherimides exhibited glass transition temperatures (Tg) in the range 113-131°C. The lowering of Tg could be attributed to the combined influence of flexibilizing ether linkages and pentadecyl chains which act as 'packing-disruptive' groups. The temperature at 10% weight loss (T10), determined from thermogravimetric analysis in nitrogen atmosphere, was in the range 460-470°C demonstrating good thermal stability. The virtues of solubility and large gap between Tg and T10 mean that the polyetherimides containing pendent pentadecyl chains have possibilities for both solution as well as melt processability.