ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Owing to the low Tg of polystyrene, the mechanical properties of polystyrene-block-poly-butadiene-block-polystyrene (SBS) thermoplastic elastomers drop steeply above 60°C. To overcome this behavior, many research groups have considered the replacement of styrene (S) by α-methylstyrene (MS). We also attempted the synthesis of copolymers with a central polybutadiene (poly B) block and rigid blocks consisting of polystyrene (poly S) and poly(α-methylstyrene) (poly MS) blocks. Starting from a dilithium initiator, difunctional poly B's with low 1,2 content (10%) were prepared and toluene was added. After addition of a small amount of styrene, MS was added in the presence of a 15% (in vol) of THF at T ≤ -40°C. The copolymers did not have the expected structure and poor mechanical properties resulted, which were, however, still measurable at 120°C. These results probably resulted from secondary reactions involving the MS carbanions. To identify these reactions and to control the polymer structure, the synthesis of multiblock copolymers was carried out with a monofunctional polybutadienyllithium to which were added successively S and MS (in a mixture of hexane and benzene as solvent). MS was added at low temperature in the presence of small amounts of THF or at room temperature after addition of TMEDA. These attempts were unsuccessful, the copolymer being always multimodal as a result of unwanted coupling reactions involving terminal double bonds. The synthesis of elastomers using a coupling reaction of poly MS-poly S-poly B was also considered but the yield in poly B was low since termination reactions involving the polar additive occurred. © 1994 John Wiley & Sons, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1994.070541007
Permalink
