Chapter 26
Poly(alkyl/aryloxothiazenes), [N=S(O)R]
n
New Direction in Inorganic Polymers 1
Downloaded by NORTH CAROLINA STATE UNIV on October 29, 2012 | http://pubs.acs.org Publication Date: November 18, 1994 | doi: 10.1021/bk-1994-0572.ch026
Aroop K. Roy , Gary T. Burns, Stelian Grigoras, and George C. Lie
2
Mail Stop 500, Dow Corning Corporation, Midland, MI 48640-0995
The thermally-induced condensation polymerization of appropriately substituted N-silylsulfonimidates and free sulfonimidates affords the new sulfur(VI)-nitrogen backbone inorganic polymers, poly(alkyl/aryloxothiazenes), [N=S(O)R] . A novel synthetic approach, involving a facile restructuring of sulfonamides without affecting the oxidation state of sulfur, was utilized in the preparation of the polymer precursor N-trimethylsilylsulfonimidates, Me SiN=S(O)R (OR ). These N-silylated sulfonimidates readily undergo desilylation with methanol to yield free sulfonimidates, HN=S(O)R (OR ). In some respects, the free sulfonimidates appear to be superior "monomers" for the synthesis of the tide polymers. Both homopolymers and copolymers are accessible from the condensation polymerization. The first examples of this new class of polymers have been characterized by GPC, DSC, TGA, NMR, and elemental microanalysis. Theoretical calculations have also been performed on poly(methyloxothiazene), [N=S(O)CH ] . n
1
2
3
1
2
3 n
Over the past two-and-a-half decades, efforts to develop new inorganic backbone polymers have steadily intensified. Two primary reasons account for this rising interest. First, materials requirements for advancing technologies have precipitated the need to look beyond primarily carbon-based polymers. Second, unique charac teristics of the commercially successful poly(siloxanes) and the tremendous versatility and significant commercial potential of the poly(phosphazenes) have heightened awareness of the potential of inorganic polymers as sources for new materials. For precisely the first reason mentioned above, we became interested in deve loping a new polymer system based on an inorganic backbone. A literature search indicated that polymers with an alternating sulfur(VI)-nitrogen backbone, consisting of the repeat unit —N=S(0)X—, would be excellent candidates for exploratory research and development. Of several reasons supporting this choice, two were critical from a synthetic perspective. First, during the early 1960s polymers where X = F, N H were 2
1 2
Corresponding author Current address: 1014 Cumberland Court, Vernon Hills, IL 60061
0097-6156/94/0572-0344$08.00/0 © 1994 American Chemical Society In Inorganic and Organometallic Polymers II; Wisian-Neilson, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1994.
26. ROY ET AL.
Polyfalkyl/aryloxothiazenes), [N=S(0)R]
345
n
patented and briefly described (1-3), and the synthesis of a polymer with X = Ph was inferred from condensation reactions (4,5). Second, the sulfur-nitrogen repeat unit bears strong structural resemblances to the phosphorus-nitrogen repeat unit in poly(phosphazenes). These suggested the possibility of using guidelines from phos phazene chemistry for synthesizing the S-N polymers that we have chosen to call poly(oxothiazenes), in analogy with poly(phosphazenes). For our studies, we decided to initially focus on the polymers [N=S(0)R] 1 with alkyl and aryl substituents attached to sulfur through direct sulfur-carbon bonds. Since polymers 1 would be structurally analogous to the poly(alkyl/arylphosphazenes), [N=PR ] , which are synthesized by a condensation polymerization route (6,7), it appeared reasonable that an analogous polycondensation process might allow access to the S-N polymers 1. Thus, we adopted a retrosynthetic approach for the synthesis of 1. It was obvious that the polycondensation precursor would have to be n
Downloaded by NORTH CAROLINA STATE UNIV on October 29, 2012 | http://pubs.acs.org Publication Date: November 18, 1994 | doi: 10.1021/bk-1994-0572.ch026
2
n
Polymer 1
