Soluble conjugated polymers with degenerate ground state derivatives of poly(1,6-heptadiyne)

Abstract

We report the results of initial measurements on two derivatives of poly(1,6-heptadiyne): a di-ketone (PHDK) and a di-ester (PHDE). Both polymers have the degenerate ground state of poly(1,6-heptadiyne); both are soluble in common organic solvents. Electron spin resonance (ESR) measurements on pristine samples place an upper limit of 10−4 spins per monomer for both polymers. At low doping levels, we observe a single doping-induced absorption band at an energy of approximately half the π−π* gap, Eg/2; the doping-induced spectral features were fully reversible. In situ ESR and absorption measurements during doping show that charge is stored predominantly in spinless charge carriers. Because of the inequivalent carbons on the conjugated backbone, the results are discussed in terms of the (A=B)n polymer. Both PHDK and PHDE are relatively stable in air; the strength of the π−π* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value.

Theoretical analysis of conjugated polymers with a degenerate ground state: Type-I and type-II soliton charge storage states in poly(1,6-heptadiyne) and derivatives

“…In the case of poly͑1,6-heptadiyne͒, the doping is simulated by withdrawal of electrons from the molecules, following the experimental studies of p-doped derivatives reported by Pakbaz et al 9 are considered by using different numbers of monomer units within a doubly charged polymer unit cell. In the case of PDPHA, a study of the n doping is performed, first by simply adding electrons to the system, and second by adding both protons and electrons which then allows us to investigate the n-self-doping process in PDPHMA.…”

“…Since the onset for the first optical transition in poly͑di-ethyldipropargylmalonate͒ and poly͑3,3-dipropargyl-2,4-octanedione͒ is measured to be about 1.9 eV ͑with a peak at about 2.3 eV͒, 9 the comparison with VEH-calculated bandgaps indicates that the systems are actually more planar in the solid state than the ϭϪ69°or ϭ47°structures optimized on isolated chains. At the VEH level, the bandgap becomes on the order of 1.9 eV for ϷϮ10°.…”

“…However, experimental data from optical absorption and ESR measurements on p-doped derivatives of poly͑1,6-heptadiyne͒ are consistent with the formation of solitons. 9 Such results would then imply that the chains are in a trans-like conformation, at least after doping, since only TABLE I. AM1 optimized bond lengths ͑in angströms͒ and dihedral angles ͑in degrees͒ for neutral poly͑1,6-heptadiyne͒ and, within parentheses, PDPHA in the cases of: ͑a͒ the fully optimized system; ͑b͒ the forced cis conformer; and ͑c͒ the forced trans conformer. The labeling is according to Fig.…”

“…1. The energetics of the bond-alternation defects 9 are expected to be more complicated than in transpolyacetylene since there are three inequivalent carbons in the backbone as illustrated in Fig. 2.…”

A 160-Femtosecond Optical Image Processor Based on a Conjugated Polymer

“…Measurement of the diffraction efficiency at zero time delay (q) yielded q = lop4. Because the pulsed laser operated at 620 nm, we were pumping into the leading edge of the r-IT* absorption band (10). Consequently, we expected the laser-induced gratings to have contributions from changes in the absorption coefficient (Act) and from changes in the index of refraction (An); the former leads to an amplitude grating and the latter to a phase grating.…”