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 Polymer Review
Overview Objectives Batch Reaction Conditions Experimental Parameters Results Summary Polymer Review
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 Polymer Review
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 Polymer Review
Experimental Parameters Catalyst: n-Butyl Lithium Modifiers: N, N, N1, N1-Tetramethylethylenediamine Sodium Dodecylbenzene Sulfonate Polymer Review
Experimental Parameters Simplified System 0.15/1/~2 SDBS 25/50/25 & 35/35/30 SIBR Rxn Temp = 65°C & 90oC Polymerization time varying Polymer Review
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 Polymer Review
Results Polymer Review
Results Polymer Review
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 Polymer Review
Results Polymer Review
Results Polymer Review
Results Commercially available SDBS was compared to the lab prepared SDBS from Dr. Halasa Aldrich Acros Random SIBR at Tg=-55°C Polymer Review
Results Polymer Review
Results Polymer Review
Results Polymer Review
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 Polymer Review
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 Polymer Review