Preparation Of Ordered Polyacetylene By Solid-State Polymerization In Nanoscale Confinement

In press, in Chemistry of Materials (doi.org/10.1021/acs.chemmater.9b03644).

The theory that underlies the reason for this article is addressed in "Bond Alternation In Infinite Periodic Polyacetylene: Dynamical Treatment Of The Anharmonic Potential," then the history of the material is exhaustively reviewed in "Polyacetylene: Myth and Reality" (open access, so you've no excuse to not read it). The preparation of the starting material, di-iodo-butadiene, C4H4I2, in urea, is published in "Commensurate Urea Inclusion Crystals With The Guest (E,E)-1,4-Diiodo-1,3-Butadiene."

I'm also very happy to be able to officially acknowledge my use of the Syracuse University Academic Virtual Hosting Environment (AVHE) as part of this work, which was involved in everything from periodic DFT calculations and the anharmonic treatment of polyacetylene on the electronic structure side, to cleaning up crystal cells of the polyacetylene-urea complexes for the generation of images in VMD and UberPOV – why just make a picture when you can, at least, make a method-consistent one?

As an aside, this is also my first experience using GIMP for a production-quality graphic – in this case, in the form of a proposed journal cover image (below. We'll see if it gets accepted in the coming month or so).

This GIMP use was instigated by originally formatting my MPB post-repair to Case-sensitive APFS three years ago, for which Photoshop refused to install with a widely-posted but little-addressed "Case-sensitive drives not supported" error (for which the Adobe solution remains "don't do that"). After a small learning curve, I'm pleased to say that GIMP is a hell of a program, well worth the price, and is just as pleasant an experience in Ubuntu 18.04 as it is in OS X 10.15 – a tidy sum saved each year for the 0.2% of features actually needed in either program to do the above.

Steluta A. Dinca, Damian G. Allis, Michael D. Moskowitz, Michael B. Sponsler, Bruce S. Hudson

Abstract: We report a novel, highly effective strategy for controlling the synthesis of polyacetylene as a guest in an organic host crystal by monitoring in situ an elimination–condensation polymerization reaction. Specifically, in this process, the polymer material is forced to have its chains extended and aligned such that translational periodicity applies, producing a bond alternation potential that has a symmetric double minimum. The synthetic approach used is photochemical elimination of iodine from a conjugated diene, (E,E)-1,4-diiodo-1,3-butadiene, which forms a commensurate and fully ordered urea inclusion compound. Photochemical cleavage of the terminal C–I bonds results in elimination of iodine from the single crystal and formation of C–C bonds between adjacent radicals to produce the conjugated 1,8-diiodo-1,3,5,7-octatetraene and subsequent longer polyene species. The combination of in situ crystal mass-loss measurements and vibrational Raman spectroscopy demonstrates clearly the presence of new polyene chains and loss of iodine from the urea substructure. The first few product oligopolyenes exhibit very strong Raman scattering with the most intense vibrational features decreasing in frequency for longer chains approaching an asymptotic limiting frequency that mimics the behavior of conjugated polyenes of known lengths from previous vibrational Raman studies. With extensive irradiation, the mass loss approaches that anticipated from the crystal stoichiometry and, at the same time of irradiation, the Raman intensity largely disappears. These results demonstrate that the reaction reported here proceeds to completion, leading to a quasi-one-dimensional array of isolated polyacetylene chains that are constrained to be in a continuous extended, all-trans conformation within the tunnels formed by the urea crystal lattice.

And Happy Leap Day (a first after nearly 20 years of this domain existing).

Free Astronomy Magazine – January-February 2020 Issue Available For Reading And Download

Above: On ancient Mars, water carved channels and transported sediments to form fans and deltas within lake basins. Examination of spectral data acquired from orbit show that some of these sediments have minerals that indicate chemical alteration by water. Here in the Jezero Crater delta, sediments contain clays and carbonates. Credit: NASA/JPL-Caltech/MSSS/JHU-APL

The most recent issue of Free Astronomy Magazine (January-February 2020) is available for your reading and downloading pleasure at www.astropublishing.com (click the link to go directly to the issue).

Feature articles this month include (1) a great read on the history of the discovery of the (dwarf) planet Pluto, (2) SOFIA confirming the collision of two planets in an old star system, and (3) details about the landing site selection of Jezero Crater for Mars 2020 (with an image from the article featured about and downloadable from www.jpl.nasa.gov…PIA23239).

For those wanting a quick look at what the issue has to offer, the Table of Contents is reproduced below.

The web browser-readable version: www.astropublishing.com/1FAM2020/

Jump right to the PDF download (14 MB): January-February 2020

Free Astronomy Magazine – November-December 2019 Issue Available For Reading And Download

The most recent issue of Free Astronomy Magazine (November-December 2019) is available for your reading and downloading pleasure at www.astropublishing.com (click the link to go directly to the issue).

As editor-in-chief Michele Ferrara alludes to early in his "flexible concept" article on page 38, there's been quite the transition into the study of exoplanets and the potentials for habitability as a way to more credibly have the discussion about alien life.

His article on page 22 is worth the read for those who think it's not a question of "if" but of "how often?"

For those wanting a quick look at what the issue has to offer, the Table of Contents is reproduced below.

The web browser-readable version: www.astropublishing.com/6FAM2019/

Jump right to the PDF download (14 MB): November-December 2019