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Aggregation behavior of a new series of ABA triblock copolymers bearing short outer A blocks in B-selective solvent: from free chains to bridged micelles.

Authors :
Giacomelli FC
Riegel IC
Petzhold CL
da Silveira NP
Stepanek P
Source :
Langmuir : the ACS journal of surfaces and colloids [Langmuir] 2009 Jan 20; Vol. 25 (2), pp. 731-8.
Publication Year :
2009

Abstract

A combination of dynamic (DLS) and static (SLS) light scattering measurements was employed to study the self-assembly behavior of a new series of triblock copolymers bearing poly[5-(N,N-diethylamino isoprene)] (PAI) short outer blocks and polystyrene (PS) as the major middle block. Previously, it was verified that PAI outer blocks can be quaternized leading the formation of crew-cut aggregates in water (Riegel, I. C.; Eisenberg, A.; Petzhold, C. L.; Samios, D. Langmuir 2002, 18, 3358). Herein, we focus on the copolymer's ability in the nonquaternized version to undergo self-aggregation in dimethylformamide (DMF), a selective solvent for the middle block. Light scattering measurements showed that formation of well-defined flowerlike micelles is likely to occur. Aggregates with a relatively narrow distribution, small average size, and number of aggregation ranging from 21 to 39 chains/micelle were experimentally observed. The results also suggested that approximately 5-6 polymeric units per each short outer block are needed to induce aggregation. The middle block length governs the size of the micelles and influences the number of aggregation of the resultant particles as well. Furthermore, when the polystyrene middle block was particularly long (degree of polymerization DP > 600), dynamic and static light scattering measurements suggested the formation of bridged micelles in an open structure in concentrations as low as 15 mg mL-1.

Details

Language :
English
ISSN :
0743-7463
Volume :
25
Issue :
2
Database :
MEDLINE
Journal :
Langmuir : the ACS journal of surfaces and colloids
Publication Type :
Academic Journal
Accession number :
19177644
Full Text :
https://doi.org/10.1021/la8026732