Chlorinated poly-DCH

Figure 1. SEM of chlorinated poly -DCH (gain of ca 12 Cl per repeat unit), 1500X.

Solid PDA have not had an extensive reaction chemistry largely due to their van der Watds tight-packed structures which effectively preclude diffusion of potentially reactive liquids and gases (. Recently (17), reactions of poly-DCH (2c) with electrophiles have led to modified materials which are homogeneous on microscopic examination. The reactions are anisotropic. Bromination resulted in a crystal-to-crystal transformation, while chlorination and nitration have led to amorphous solids to date. The scope of such reactivity is clearly of interest. 

Recently, we observed that the PDA from l,6-di-N-carbazolyl-2,4-hexadiyne (2a), i.e., poly-DCH (2), reacts with assorted gaseous and liquid species to give modified materials which appear homogeneous on microscopic examination (1). Our studies to date of the interaction of chlorine, bromine, and iodine with single crystals of poly-DCH are presented herein. 

We have found that poly>DCH may be chlorinated by liquid or gaseous chlorine, solutions of chlorine in dichloromethane, and by aqua regia. Poly-DCH is inert to refluxing thionyl chloride, and reaction with chlorine gas sufficient to introduce 6 Cl atoms per repeat unit leads to an inhomogeneous material. 

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. 

Given the reactions described above for poly-DCH with chlorine and bromine, it is natural to seek reactivity with iodine. In the course of the above work, we had noted that poly-DCH single crystals were inert to iodine vapor at 20 C and to heating with a ten-fold molar excess of iodine at 125-130 C for 16 hr. 

Interaction of Poly-DCH With Liquid Chlorine. To liquid chlorine (5 ml) was added poly-DCH (57.4 mg) and the mixture was kept in a dry-ice/acetone bath for 22 hours, after which the remmning liquid chlorine was swept into a trap containing aqueous NaOH. The resultant orange solid, found to be amorphous by x-ray diffraction, was washed with dichloromethane to give 107 mg of product. This FTIR spectrum of this material exhibited tdssorption, inter alia, at 1440, 1085, 852, 799, and 744 cm, and its diffuse reflectance exhibited a broad maximum at ca 410 nm which tailed to beyond 600 nm. The materitd was partially soluble in hot dimethylformamide. 

In the present study we have used this method to clarify the course of bromination of poly-DCH. Preliminary results have also been obtained on the chlorination and nitration of this polymer. Information about the chemical structure... 

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