Rigid rod polymers with flexible side chains, 4. Synthesis, structure and phase behaviour of polyimides prepared from pyromellitic anhydride and 2,5‐di‐n‐alkoxy‐1,4‐phenylene diisocyantes

Abstract

A series of rigid rod polyimides 1 af derived from pyromellitic anhydride (PMDA) and 2,5di-n-alkoxy-l,4phenylenediamine containing flexible alkoxy side chains with 4 to 16 carbon atoms was prepared by solution polycondensation. As demonstrated by model experiments full conversion to the imide structure is achieved by reaction of PMDA with 2,5-dialkoxyphenylene diisocyanate, the latter compound being blocked by imidazole. The best solvent for the polycondensation, found in the course of the model reaction, is 1,3-dimethyl-2-oxo-perhydropyrimidine together with 4dimethylaminopyridine as an accelerator. Wide-angle X-ray diffractograms showed that all polyimides under consideration here are highly crystalline at room temperature. The occurrence of a sharp reflection at the region of low angles together with its higher orders demonstrates the presence of a layered structure. The layer spacing was found to increase linearly with the length of the alkyl side chains. Polyimides bearing long side chains (n 2 10) exhibit two broad endotherms in the DSC analysis. As is revealed by wideangle X-ray analysis the fiist transition is related to a disordering process of the side chains. The second transition leads to a layered high-temperature phase akin to the modification (B) found in a recent study of a similar rigid polyester bearing flexible side chains. a) Part 3: Cf.3). b, Part of the thesis of M. Wenzel. 0025-1 16X/87/%03.00

Tuning the solubility of hepta(p-benzamide)s via the monomer sequence

“…It is believed that such side chains act like a covalently attached solvent, allowing for a gain in entropy upon dissolution of the oligomer or polymer. [19][20][21][22][23] The fine structural balance between solubility and aggregation has been exploited in the field of organogelators. 24 For gelation to be oberseved an aggregation or supramolecular polymerization needs to occur in order to achieve the required high connectivity of the individual gelator molecules.…”

“…28 However, covalently attached side chains typically increase solubility of otherwise insoluble oligomers and polymers. [19][20][21][22][23] We rationalized that in the case of hexyloxy-substituted oligo(p-benzamide)s, the side chain not only acted as a covalently attached solvent but also as an intramolecular hydrogen bond acceptor, thereby rendering two neighboring phenyl rings perfectly coplanar. In the case of the hepta(2-hexyloxy-pbenzamide) all amide N-H groups can form hydrogen bonds to neighboring hexyloxyethers and thus render all phenyl rings in the heptamer perfectly coplanar (Figure 1, bottom).…”

Transport and Electro‐Optical Properties in Polymeric Self‐Assembled Systems

“…Unfunctionalized PPP is not soluble and does not melt. However, incorporating a dense set of side-chains leads to "hairy rods" [261][262][263], i.e. a comb-shaped architecture, where the mutual aggregation of the rods is reduced by the side-chain spacers [264,265].…”

Polyimides based on aromatic diisocyanates containing pendent flexible alkoxy chains and aromatic dianhydrides: Synthesis, characterization, and liquid‐crystal alignment properties

“…These are (1) diamine modification, [10][11][12] (2) dianhydride modification, 9 and (3) diisocyanate modification. [13][14][15][16][17][18] The purpose of this study was to synthesize aromatic polyimides based on meta-oriented aromatic diisocyanates containing pendent flexible alkoxy chains of various carbon lengths by polycondensation with commercially available aromatic dianhydrides and to study the effect of pendent flexible alkoxy chains on the properties of the resulting polyimides. 5-Alkoxy-1,3-phenylenediisocyanates, namely, 5-butyloxy-1,3phenylenediisocyanate (BPDC), 5-octyloxy-1,3-phenylenediisocyanate (OPDC), 5-dodecyloxy-1, 3-phenylenediisocyanate (DDPDC), and 5-hexadecyloxy-1,3phenylenediisocyanate (HDPDC), were synthesized and polycondensed with aromatic dianhydrides, namely, 4,4 0 -oxydiphthalic anhydride (ODPA), 3 , chloroform, and m-cresol were reagent grade and were purified as per literature procedures.…”