Unsaturated organosilicon polymers via acyclic diene metathesis (ADMET) condensation polymerization
The design and synthesis of unsaturated organosilicon polymers prepared via acyclic diene metathesis (ADMET) condensation polymerization is presented. Well-defined high molecular weight polymers with known alkene end groups result from ADMET, which is only possible when Lewis acid free metathesis alkylidenes of the type, M=CHR(N-2, 6-C[sub 6]H[sub 3]-i-Pr[sub 2])[OCMe(CF[sub 3])[sub 2]][sub 2] (M = W or Mo), are employed as catalysts. Various carbosiladienes and carbosiloxadines were designed and synthesized in order to ascertain the specific monomer structural requirements dictated by this polymerization method. Bis(allyl)tetramethyldisiloxane underwent quantitative cyclization when treated with the molybdenum alkylidene giving the 7-membered cyclosiloxalkene. Cyclization is avoided if the monomer is designed so as to kinetically disfavor the cyclized product. An extension of the methylene groups between the olefin and the siloxane linkage or extension of the siloxane linkage results in facile polymerization to new high molecular weight unsaturated polycarbosiloxanes with low glass transition temperatures and good thermal stability. Hydrosilation oligomerization was used to synthesize and [alpha],[omega]-telechelic diene macromonomer which underwent clean ADMET polymerization to high molecular weight. In some cases, cyclic products are observed at the end of the polymerizations due to a kinetically slow back-biting mechanism when cyclic products are favored. Cyclic products are only observed at the end of the polymerizations where a postcondensation resting state had been established involving ring/chain equilibria. A discriminate co-condensation between a well defined unsaturated polycarbosiloxane oligomer and an aromatic diene monomer was also demonstrated. Complete synthesis, characterization and behavior is discussed for these new organosilicon polymers.
- Research Organization:
- Florida Univ., Gainesville, FL (United States)
- OSTI ID:
- 6887937
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360601* -- Other Materials-- Preparation & Manufacture
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
CHEMICAL PREPARATION
CHEMICAL REACTIONS
DEHYDROCYCLIZATION
DIENES
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
POLYENES
POLYMERIZATION
SILANES
SILICON COMPOUNDS
SILOXANES
SYNTHESIS