1. Random and Tapered SIBR’s with varying Tg
Aaron Ryba and Dr. Adel Halasa
Na & TMEDA modified SIBR’s polymerized in a batch reactor
4/1/03
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2. Overview Objectives Batch Reaction Conditions Experimental Parameters
Results
Summary
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3. Objectives
Develop a catalyst system that randomizes styrene, isoprene, and butadiene in multiple SIBR’s
Develop a system with the ability to vary the Tg at the same monomer concentration and molecular weight
Develop a system that can be quickly implemented
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4. Batch Reaction Conditions
Polymerization of SIBR
One gallon reactor
Nitrogen atmosphere
Heating coils
Mechanical mixing
~20% Bd/Hexane pmx
~20% Sty/Hexane pmx
~20% Iso/Hexane pmx
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5. Experimental Parameters
Catalyst:
n-Butyl Lithium
Modifiers:
N, N, N1, N1-Tetramethylethylenediamine
Sodium Dodecylbenzene Sulfonate
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6. Experimental Parameters
Simplified System
0.15/1/~2 SDBS
25/50/25 & 35/35/30 SIBR
Rxn Temp = 65°C & 90oC
Polymerization time varying
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7. Results Rxn with n-BuLi/TMEDA Butadiene conversion is fast
at low levels of TMEDA (~0.5 molar ratio)
Styrene conversion is slower than Isoprene
at mid levels of TMEDA (1-2 molar ratio)
Styrene and Isoprene conversion are about equal
at higher levels of TMEDA (>4 molar ratio)
Styrene conversion is faster than Isoprene
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8. Results
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9. Results
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10. Results
With the addition of SDBS at a low level (~0.15 molar ratio) all three monomer conversion rates are about equal
NMR analysis
3,4-PI content varies with change in temp.
Styrene sequencing is not blocky
Bd 1,2/cis-1,4/trans-1,4 ratio remains about the same
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11. Results
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12. Results
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13. Results
Commercially available SDBS was compared to the lab prepared SDBS from Dr. Halasa
Aldrich
Acros
Random SIBR at Tg=-55°C
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14. Results
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15. Results
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16. Results
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17. Summary
SIBR monomer distribution can be controlled with SDBS (random-tapered)
TMEDA with SDBS allows one to vary the Tg of an SIBR while maintaining a random distribution
Rxn temp. has a strong bearing on 3,4-PI content of the polymer
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18. Summary
Low Tg (-55°C) SIBR made with Aldrich SDBS requires additional Lithium due to possible impurities in the SDBS
These polymers w/o TMEDA have a large (~40°C) exotherm, high polydispersity, and a high cement viscosity
These polymers w/ TMEDA have a lower (~10°C) exotherm and lower cement viscosity
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