16-11-2012, 04:27 PM
METATHESIS POLYMERISATION
[attachment=39829]
Introduction -
In 1950s polymer was introduced by Karl Ziegler known as Ziegler-Natta catalysis for polymerizations of ethylene.
Robert H. Grubbs got involved in metathesis in 1972 and also proposed a metallacycle intermediate.
Schrock entered the olefin metathesis field in 1979 as an extension of work on tantalum alkylidenes.
What is Metathesis?
Metathesis, a word meaning “change places.”
It entails the redistribution of fragments of alkenes(olefins) by the scission.
Regeneration of carbon - carbon double bonds.
Acyclic Diene Metathesis Polymerization:
Acyclic diene metathesis or ADMET is a special type of olefin metathesis used to polymerize terminal dienes to polyenes.
The new double bonds formed can be in cis- or trans-configuation, the exact ratio depends on the monomer and catalyst structures.
Wagener reported that 1,5-hexadiene and 1,9-decadiene can polymerized by this method.
Ring Opening Metathesis Polymerization(ROMP)
Ring-opening metathesis polymerization (ROMP) is a chain growth polymerization process where a mixture of cyclic olefins is converted
to a polymeric material.
Any unsaturation associated with the monomer is conserved as it is converted to polymer.
Advantages of metathetical polymerisazation
1.Polymeric material can be prepared under control condition.
2.High efficiency of catalyst.
3.Very narrow molecular weight distribution can be obtained; Mw/Mn approaching 1.0
4.Unsaturation remain conserved i.e. For rubbery material
Curing process is easy.
Disadvantages :
1) Though metathetical reaction reversible sometimes doesn’t undergo polymerization.
2) Orgnometallic catalysts is difficult to handles ;needs specially environments.
i.e. Inert atmosphere.
3)Intermolecular chain transfer result to lower Mol. Wt.
Conclusion:
Ring-opening metathesis polymerization (ROMP) has emerged as a powerful and broadly applicable method for synthesizing macromolecular materials .
Polymer like poly-1,5hexadiene, polyoctene can be prepared by metathesis polymerization.
Several varieties of poly norbornene can be obtained by this method.
[attachment=39829]
Introduction -
In 1950s polymer was introduced by Karl Ziegler known as Ziegler-Natta catalysis for polymerizations of ethylene.
Robert H. Grubbs got involved in metathesis in 1972 and also proposed a metallacycle intermediate.
Schrock entered the olefin metathesis field in 1979 as an extension of work on tantalum alkylidenes.
What is Metathesis?
Metathesis, a word meaning “change places.”
It entails the redistribution of fragments of alkenes(olefins) by the scission.
Regeneration of carbon - carbon double bonds.
Acyclic Diene Metathesis Polymerization:
Acyclic diene metathesis or ADMET is a special type of olefin metathesis used to polymerize terminal dienes to polyenes.
The new double bonds formed can be in cis- or trans-configuation, the exact ratio depends on the monomer and catalyst structures.
Wagener reported that 1,5-hexadiene and 1,9-decadiene can polymerized by this method.
Ring Opening Metathesis Polymerization(ROMP)
Ring-opening metathesis polymerization (ROMP) is a chain growth polymerization process where a mixture of cyclic olefins is converted
to a polymeric material.
Any unsaturation associated with the monomer is conserved as it is converted to polymer.
Advantages of metathetical polymerisazation
1.Polymeric material can be prepared under control condition.
2.High efficiency of catalyst.
3.Very narrow molecular weight distribution can be obtained; Mw/Mn approaching 1.0
4.Unsaturation remain conserved i.e. For rubbery material
Curing process is easy.
Disadvantages :
1) Though metathetical reaction reversible sometimes doesn’t undergo polymerization.
2) Orgnometallic catalysts is difficult to handles ;needs specially environments.
i.e. Inert atmosphere.
3)Intermolecular chain transfer result to lower Mol. Wt.
Conclusion:
Ring-opening metathesis polymerization (ROMP) has emerged as a powerful and broadly applicable method for synthesizing macromolecular materials .
Polymer like poly-1,5hexadiene, polyoctene can be prepared by metathesis polymerization.
Several varieties of poly norbornene can be obtained by this method.