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:
ABA-type “tapered” block copolymers of α-methylstyrene (monomer A) and butadiene were prepared using four commercially available dilithio initiators. Polymerizations were run at 25°C in benzene solvent, or at 40°C with butadiene dissolved in neat α-methylstyrene. Although α-methylstyrene has a rather low ceiling temperature, triblock copolymers could be made at these temperatures by using α-methylstyrene concentrations well in excess of the [M]e values at the respective temperatures. Its concentration was such that molecular weights of at least 15,000-20,000 for the A blocks could be attained. The course of the copolymerization at 40°C was followed, showing that copolymers containing about 40% α-methylstyrene could be formed in 4-8 hr, depending on the initiator used. They showed the usual behavior of triblock thermoplastic elastomers, with tensile strengths 〉 3000 lb/in.2 at 24°C. However, because of the high Tg of poly(α-methylstyrene) (172°C), they also had tensiles of several hundred lb/in.2 at 100°C, unlike comparable polymers with polystyrene end blocks, which have practically no strength at this temperature. Microstructures of polybutadienes made with these initiators are also given.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1978.070221017
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