Pristine poly-DCH

Pristine poly-DCH. Fig. 2 shows the C CP-MAS spectra of unreacted N-dicarbazolyl-2,4-hexadiyne and of the polymerized material. The appearance of a new peak at 129 ppm in the spectrum of poly-DCH, resulting from the formar tion of a double bond, is evident from the spectra. Furthermore, polymerization causes a marked downfield shift of the triple bond resonance(s) from 68.3 and 75.0 ppm in the diacetylenic monomer to 104.3 ppm in poly-DCH. This effect is well-documented for many polycoi jugated systems containing triple bonds (12,21), and presumably reflects an increasing cumulene contribution to the original enyne electronic structure of such systems. 

ESR studies of pristine poly-[l,6-bls(N-carba2olyl)-2,4-hexadlyne](poly-DCH), a member of the general class of materials known as polydlacetylene, of the reaction of poly-DCH with bromine, and of poly-DCHBr, are reported and compared to previously reported ESR studies on similar systems. The ESR studies include measurements of the spectral linewidths, the g-tensors and the relative ESR signal intensity as a function of temperature for poly-DCH and poly-DCHBr,. Briefly, for pristine poly-DCH, two superimposed ESR spectra are observed. The spectral linewidths and g-tensors are Independent of temperature. In contrast, the ESR signal intensity is thermally activated and displays two activation energies. The kinetics of the disappearance of the original ESR spectrum observed in pristine poly-DCH and its replacement with a different ESR spectral envelope is presented as are the kinetic parameters which describe the reaction of poly-DCH with bromine. 

As described In the Introduction and In references 3-5, poly-DCH has been found to react with bromine at 268 K. The purpose of these experiments was to see If there were any free radical Intermediates found during the reaction. Howeyer, none were found. Instead, the radicals observed In pristine poly-DCH disappear and two new radical species at lower concentrations reappear. 

The product of the interaction of chlorine gas with poly-DCH was studied by scanning electron microscopy (SEM) our SEM studies of pristine and brominated poly-DCH were previously rep>orted (lb). A sample at magnification 1500 is shown in Figure 1. Compared to pristine p>oly-DCH, Figure 1 reveals that a fibrous morphology is reUuned, but the fibers of the chlorinated polymer appear thicker and rougher than those of the reactant. 

ESR Studies of the Reaction of Partially Oriented Pristine Polvcrvstalllne Poly-DCH with Bromine... 

ESR was used to monitor the ESR Intensity as a function of time as pristine polycrystalllne poly-DCH was allowed to react with bromine at 268 K. The reaction can be divided Into three phases. 

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