Synthesis and Aggregation Behavior of Poly(arylene alkenylene)s and Poly(arylene alkylene)s Having Dialkoxyphenylene and Aromatic Diimide Groups

Polycondensation reactions of 2,5-dialkoxy-1,4-diiodobenzene with N,N′-ω-dialkenylpyromellitic diimide and N,N′-ω-dialkenyl naphthalenetetracarboxylic diimide in the presence of a Pd­(OAc)₂–NaOAc catalyst produce six polymers containing the two aromatic groups connected alternatingly by alkenylene spacers. ¹H NMR spectrum of a polymer prepared from 2,5-bis­(dodecyloxy)-1,4-diiodobenzene and N,N′-(10-undecenyl)­pyromellitic diimide (poly­(1a-IA)) indicates that the polymerization involves 2,1- and 1,2-insertion of a vinyl group into the Pd–Ar bond in 70:30 selectivity. Matrix-assisted laser deportion/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) spectra of poly­(1a-IA) and a polymer from 2,5-bis­(dodecyloxy)-1,4-diiodobenzene with N,N′-dialkenyl naphthalenetetracarboxylic diimide (poly­(1a-IIA)) contained a series of polymer fragments with M_n up to 4500. Measurement of electrospray ionization MS (ESI-MS) of the polymers revealed formation of cyclic molecules for 1:1 and 2:2 oligomers. Hydrogenations of poly­(1a-IA) by using [Ir­(cod)­(py)­(PCy₃)]⁺PF₆^– (cod = 1,5-cycloctadiene; PCy₃ = tricyclohexylphosphine) catalyst and of poly­(1a-IIA) by a mixture of p-toluenesulfonyl hydrazide (TSH) and tripropylamine (TPA) produce the poly­(arylene alkylene)­s with saturated spacers in 93% degree of hydrogenation. The absorption spectrum of poly­(1a-IA) in CHCl₃ shows an absorption edge at 410 nm, which is at a longer wavelength than that of a mixture of the monomers (370 nm). Light-scattering measurement of the solution (1.00 mmol L^–1) indicates the presence of aggregates with a hydrodynamic radius of 48 nm. The polymers exhibit weak elasticity at room temperature, as determined by dynamic viscoelasticity analysis (DMA), and it becomes negligible on heating to 75–80 °C (polymer with pyromellitic diimide groups) and 110–122 °C (polymer with naphthalenetetracarboxylic diimide groups). The above properties of the polymers are attributed to attractive interaction between the electron-rich alkoxyphenylene and the electron-deficient aromatic diimide groups both in solution and in the solid state.