An electron spin resonance study of poly(α‐ethynylnaphthalene) polymerized with [Rh(norbornadiene)Cl]₂ and WCl₆ as catalysts

Abstract

Poly( a-ethynylnaphtha1ene)s (PENAPs) obtained with the Rh complex [Rh(norbornadiene)Cl], as a stereoregular polymerization catalyst of monosubstituted acetylene monomers and WCl, were studied by using the electron spin resonance (ESR) method to inspect the geometrical structure with respect to the C=C bond in the main chain where x-radicals called solitons may be stabilized in the conjugated polymer chain. In PENAP obtained as the immobile unpaired electrons were found to be stabilized in the polymer chain, indicating a short and restricted conjugated chain, i.e., formation of a cis-transoid polymer. In PENAP obtained with WCI, as catalyst more mobile unpaired electrons were found to be stabilized in the conjugated polymer chain not only at room temperature but also at lower temperature, indicating the presence of a n-conjugated main chain, i. e. of a trans-transoid polymer. Moreover it was found, interestingly, that the clearly resolved ESR spectrum with the hyperfine structure (soliton) could be observed at higher temperature, i. e., ca. 300 "C.

Pressure-inducedcis totrans isomerization of aromatic polyacetylenes prepared using a Rh complex catalyst: A control of ?-conjugation length

“…It is also noteworthy that the extremely long conjugated trans sesequences, (C|C) n , n Å 20-40, thus allowing of motional narrowing of the unpaired electrons quences necessary for the nonlinear organic materials, especially large x (3) 16 can be easily genercreated by the rotational scission of the cis double bonds as we reported previously. 3 Thus, the obated by such compression with no heat treatment and the side reactions are minimized in this proserved g value and line width change are useful features for estimating the content of geometrical cess.…”

“…2 It has been proposed that the effect of the solvents is to promote In a previous article we reported that phenylacetthe efficient dissociation of the dimer complex ylene (PA), 1 its homologues, 2 a-naphthylacety-[Rh(NBD)Cl] 2 into the monomeric species, which lene, 3 and alkylpropiolates, 4,5 and pentynoate 6 may be an important initiation species for this can be stereospecifically polymerized in the prespolymerization, 1,7 as shown in Scheme 1. Further, ence of a Rh complex, [Rh(norbornadiene)Cl] 2 , the structural differences observed between poly-[Rh(NBD)Cl] 2 , when triethylamine (TEA) or an pentynoates prepared with the Rh complex cataalcohol is used as the polymerization solvent and lyst and with metathesis catalysts such as WCl 6 that the helical cis-transoid isomer were selecwas interpreted in terms of the difference in geotively formed in high yields under mild conditions.…”

Synthesis and properties of poly(1-naphthylacetylene) and poly(9-anthrylacetylene)

“…[Rh(nbd)Cl] 2 -Et 3 N also gave an insoluble polymer, which is consistent with the previous result. 11 It is well known that Rh catalysts afford stereospecific polymers with cis-transoidal structure and that Mo catalysts generally lead to the formation of cis-rich polymers.…”

“…2 Successful synthesis of high molecular weight polyarylacetylenes with wide conjugation as well as high solubility has been limited to the polymerization of 1-naphthylacetylene (1-NA) by W catalysts. 10,11 However, detailed information on the polymerization behavior of 1-NA is not available until now.…”

Synthesis and properties of widely conjugated polyacetylenes having anthryl and phenanthryl pendant groups

“…The resulting soluble polymer was found to possess a wide conjugation in its main chain. 8,9 Earlier we reported that phenylacetylene polymerizes in high yield in the presence of W-based catalysts, giving a soluble brown-colored polymer with molecular weight about 10 4 . 10 Poly(phenyl-acetylene), however, does not possess a very wide conjugation.…”