High‐resolution NMR spectra and phase equilibria in poly(phenylacetylene)‐diluent mixtures

Abstract

The C‐13 NMR spectra of partly crystalline poly(phenylacetylene) (PPA) in CDCl3 CCl4 are rather well resolved and the peaks can be matched with those of 1, 3,5‐triphenylbenzene. A different, less‐well‐resolved C‐13 spectrum is characteristic of a disordered PPA obtained by heating. We conclude that crystalline PPA has the chain conformation of a cis‐cis‐oid helix. This interpretation is consistent with the proton NMR spectra and is supported by the fluorescence spectra, which can display two bands, one concluded to be characteristic of the cis‐cis‐oid conformation, the other of chain conjugation in the disordered polymer. Phase equilibria of PPA in the presence of chloroform were determined and are represented as those of the quasiternary mixture cis‐cis‐oid helix, disordered polymer, and chloroform.

Precise synthesis of monosubstituted polyacetylenes using Rh complex catalysts. Control of solid structure and π-conjugation length

“…Hexagonal polymer chains packed in a column are also conjectured to be rotated in each column where the molecular axis distance, i. e., the c-axis, cannot be estimated because of being effectively an infinite one 36) . The helicoidal 1 a polymers with a rigid and rodlike structure have been postulated by Ehrlich and his group 37) . They reported that the crystalline 1a polymer which was repeatedly treated with a mixture of CDCl 3 and CCl 4 displayed birefringence due to a liquid crystallike order, although the crystalline structure of the 1 a polymer has not been identified by them.…”

“…It appears that the polymer chains which are packed in the hexagonal column may be helical chains which stabilize the columnar structure. The helical structure of the 1 a polymer has been described by Sanford et al 37) , Simionescu et al 46) , and recently by us 19) using molecular mechanic calculations. The calculations support that the cis-transoid structure of 1 a polymer is helical as has been previously deduced.…”

Cis-trans isomerization and13C-NMR chemical shift of polyphenylacetylene

“…In the MO calculations, we take account of not only planar zigzag configurations such as cis-transoidal, trans-cisoidal, and transtransoidal forms, but also the same deflected configurations as the TGЈTGЈ-type for the trans chain in poly(vinylidene fluoride) reported by Hasegawa et al 19 The cis-cisoidal forms of the chain was not used in the calculation, because the steric hindrance of phenyl groups in PPA chain did not allow the considerable helical structure of the chain. 6,8,17 Figure 1 shows the backbone geometry of the same deflected trans chain conformation projected on a perpendicular plane and a perpendicular axis to its axis. The deflected angle of corresponds to the dihedral angle between two double bonds in the main chain.…”

“…The two kinds of 13 C peaks in the spectrum of deflected trans-PPA are attributed from the phenyl group and the main chain, because pyrolysis byproducts of triphenylbenzene and low molecules were removed completely. 6,17 Comparing the respective peaks of the deflected trans-PPA with those of the cis-PPA, peak 1 shifts downfield by 0.24 ppm, but peak 2 becomes broader and shifts upfield by 3.07 ppm. Table I lists the chemical shift values of the two peaks and the respective chemical shift variations, ⌬␦s, for cis-and deflected trans-PPAs.…”

Mutual conversion between stretched and contracted helices accompanied by a drastic change in color and spatial structure of poly(phenylacetylene) prepared with a [Rh(nbd)Cl]2-amine catalyst

“…During the past two decades, bidentate rhodium complexes, for example, [Rh(nbd)Cl] 2 (nbd: norbornadiene), Ziegler–Natta catalyst, Fe(acac) 3 ‐AlH( i ‐Bu) 2 , Luttinger's catalyst, RhCl 3 ‐LiBH 4 , Wilkinson's catalyst, RhCl(PPh 3 ) 3 , and metathesis catalysts such as WCl 6 or MoCl 5 , have been developed as important stereoregular polymerization catalysts for phenylacetylene (PA) together with other substituted acetylene (SA) monomers to obtain substituted polyacetylenes (SPA)s, which are known to have helical cis ‐ transoid structures. Furthermore, the propagation species, that is, a monodentate Rh species from the bidentate Rh complex catalyst, has been generated in situ when triethylamine (TEA), alcohol, or aqueous alcohol was used as a cocatalyst or as the polymerization solvent .…”