Rigid rod polyamides based on 2,2′,6,6′‐tetrasubstituted biphenyls: Synthesis, characterization, and structures

Abstract

SYNOPSISPolyamides based on 4,4'-diamino-2,2',6,6'-tetrasubstituted biphenyls and phenylterephthalic acid have been synthesized, and the structures and properties of this series of polymer have been studied. It is shown that the polymers have a n amorphous structure although some degree of short-range order is present. This class of polymer, while consisting of comparatively stiff rodlike molecules, demonstrates high solubility and low glass transition temperatures. The behavior is due to the combination of the noncoplanar conformation of the twisted biphenyl and the fact that they have bulky side groups in the 2,2'-and 6,6'positions that weaken the interchain interactions (like hydrogen bonding and van der Waals forces) and frustrate parallel packing of the polymer chains. 0

Soluble Oligoaramide Precursors—A Novel Class of Building Blocks for Rod–Coil Architectures

“…[10] Scheme 1. Synthesis of soluble OPBA precursors: i) acetone, dimethyl aniline; ii) methanol, ammonium formate, Pd/C; iii) thionyl chloride; iv) 1. acetone, 1, dimethyl aniline, 2. water; v) thionyl chloride; vi) 1. acetone, N-methyl pyrolidinone, 3, dimethyl aniline, 2. water; vii) thionyl chloride.…”

Structure of semirigid polyamides with bulky groups in backbone

“…Small molecules and monomers were synthesized according to the procedure described in the literature 10. Biphenyl, succinoyl chloride, adipoyl chloride, sebacoyl chloride, and dodecanedioyl dichloride were obtained from Aldrich.…”

“…This is based on the argument that if rigid chain polymers have bulky groups at intervals along them as with tetrasubstituted biphenyls, they can only display parallel packing of the rodlike molecules at the expense of considerable internal voids with the consequent energy penalty. Hence, the packing should assume nonparallel (random) form 10. A potential application of rigid chain non‐liquid‐crystalline polymers is in the area of molecular composites.…”

Rigid-Rod Polyamides and Polyimides Derived from 4,3‘‘-Diamino-2‘,6‘-diphenyl- or Di(4-biphenylyl)-p-terphenyl and 4-Amino-4‘‘-carboxy-2‘,6‘-diphenyl-p-terphenyl

“…Rigid-rod polymers are well accepted as heat-resistant materials with high mechanical strength, giving easily lyotropic solutions. − However, they present usually infusibility and limited solubility, properties which decrease their processability and restrict further applications. To overcome this problem, various monomers carrying pendent groups have been polymerized or copolymerized leading to polymers with enhanced solubility. − …”