Steady flow and dynamic viscosity of branched butadiene–styrene block copolymers

Autor: Gerard Kraus, F. E. Naylor, K. W. Rollmann
Rok vydání: 1971
Předmět:
Zdroj: Journal of Polymer Science Part A-2: Polymer Physics. 9:1839-1850
ISSN: 1542-9377
0449-2978
DOI: 10.1002/pol.1971.160091007
Popis: Steady flow and dynamic viscosities were determined for symmetrical linear and starbranched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.
Databáze: OpenAIRE
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