Syntheses and X‐Ray Structures for Model Compounds of a Pyrimidinediyl‐Based Rigid‐Rod Aromatic Polyamide

Abstract

( I 7.X.91 j A variety of model compounds for the pyrimidinediyl-based rigid-rod polyamide poly[imino-(pyrimidine-2,5-diy1)-imino-tetraphthaloyl] (PPYMT) was prcpared. in order to comparc their conformations to several model compounds of the related, fully aromatic polymer poly0,-phenyleneterephthalamide) (PPTA). In particular, thc structures (of N-(2-pyrimidyl)benzamide (PY MB) and its complexed form bis[N-(pyrimidin-2-yI)benramide]nickel(ll) dichloride (NiPYMB) were determined by X-ray diffraction. The molecular packing in these crystals pro. in order ]to investigate the influence of intermolecular interactions on the properties of polymers of type 1. The difference in molecular constitution between 1 and 2 does not significantly change the geometry of the polymer chains, and a preliminary investigation of fiber packing indicates that similarities between the two do exist [7]. The pyrimidine rings in the polymer may be seen as functional groups for complexation of the polymer with transition-metal cations such as Fe", Co'+, Cu2+, or Ni'+. Complexation of the polymer can thus be used to 'cross-link' polymer chains aligned in a parallel fashion and might lead to fibers with changed mechanical properties.Information about the conformation of the polymer in the solid state is not easy to obtain [7]. Thus, we synthesized small model compounds which correspond to dimer and trimer segments of 2. The N-(pyrimidin-2-yl)benzamide (3) and its complexed form bis[N-(p~nimidin-2-yl)benzamide]nickel(ll) dichloride (4) were prepared and crystallized for X-ray diffraction. The trimer model compounds N , N -bis(pyrimidin-2-yl)benzene-1,4-dicarboxamide (5) and its nonsymmetric analogue N,N'-(pyrimidine-2,5-diyl)bis-[benzamide] (6) were also prepared and crystallized, but the metallated forms could not

The influence of CH bond polarization on the self-association of 2-acylaminopyrimidines by NH/CH···O/N interactions: XRD, NMR, DFT, and AIM study

“…It is worth mentioning that in Cambridge Structural Database (CSD) only three similar structures were found revealing that the bifurcation of hydrogen bond in pyrimidine derivatives is not common. These contain aromatic CHÁÁÁN/O [39,40] or OHÁÁÁN/O [41] contacts.…”

An investigation of novel approaches in order to provide crosslinked fully aromatic polyamide chains

“…A comparison between the X-ray structures of corresponding model compounds of PPYMT and PPTA shows close agreement 47) .…”

“…All solutions for spinning trials were prepared similarly by dissolving about 1 g of polymer as powder with sufficient amounts of H 2 SO 4 (100 wt.-%) to form homogenous solu- 47) for details tions of 12.5 wt.-%. All solutions were stirred at 0 8C for approximately 4 h, with a low-shear threaded stirrer to avoid mechanical degradation effects.…”

“…Chemical structure of constitutionally disordered PPYMT (5) was investigated. X-ray structure analysis of the model compound bis-[N-(2-pyrimidyl)benzamide]nickel(II) dichloride showed that the crosslinking of polymer chains in PPYMT fibers by complexation is possible 47) . Fig.…”

“…Fig. 2 shows an idealized picture of how the crystal structure of the model compound complexation 47) superimposes over the polymer chain structure.…”