Structural and Mechanical Hysteresis at the Order-Order Transition of Block Copolymer Micellar Crystals

Structural and Mechanical Hysteresis at the Order-Order Transition of Block Copolymer Micellar Crystals

Concentrated solutions of a water-soluble block copolymer (PEO)20-(PPO)70-(PEO)20 show a thermoreversible transition from a liquid to a gel. Over a range of concentration there also exists an order-order transition (OOT) between cubically-packed spherical micelles and hexagonally-packed cylindrical...

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Bibliographic Details
Main Authors: Theresa A. LaFollette, Lynn M. Walker Walker
Format: Article
Language:English
Published: MDPI AG 2011-01-01
Series:Polymers
Subjects:
pluronic
block copolymer
order-order transition
SANS
SAXS
rheology
hysteresis
Online Access:http://www.mdpi.com/2073-4360/3/1/281/
Description
Summary:Concentrated solutions of a water-soluble block copolymer (PEO)20-(PPO)70-(PEO)20 show a thermoreversible transition from a liquid to a gel. Over a range of concentration there also exists an order-order transition (OOT) between cubically-packed spherical micelles and hexagonally-packed cylindrical micelles. This OOT displays a hysteresis between the heating and cooling transitions that is observed at both the macroscale through rheology and nanoscale through small angle neutron scattering (SANS). The hysteresis is caused by the persistence of the cubically-packed spherical micelle phase into the hexagonally-packed cylindrical micelle phase likely due to the hindered realignment of the spherical micelles into cylindrical micelles and then packing of the cylindrical micelles into a hexagonally-packed cylindrical micelle phase. This type of hysteresis must be fully characterized, and possibly avoided, for these block copolymer systems to be used as templates in nanocomposites.
ISSN:2073-4360

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