CaltechAUTHORS
  A Caltech Library Service

Kinetics of phase transitions in weakly segregated block copolymers: Pseudostable and transient states

Qi, Shuyan and Wang, Zhen-Gang (1997) Kinetics of phase transitions in weakly segregated block copolymers: Pseudostable and transient states. Physical Review E, 55 (2). pp. 1682-1697. ISSN 1063-651X. http://resolver.caltech.edu/CaltechAUTHORS:QUIpre97

[img]
Preview
PDF
See Usage Policy.

1359Kb

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:QUIpre97

Abstract

We study the kinetics of order-disorder and order-order transitions in weakly segregated diblock copolymers using a time-dependent Ginzburg-Landau (TDGL) approach. In particular, we investigate the microstructural change as well as the order-parameter evolution after a sudden temperature jump from one phase to another. Direct numerical simulation of the TDGL equations shows that depending on the extent of the temperature jump, these transitions often occur in several stages and can involve nontrivial intermediate states. For example, we find that transition from the lamellar phase to the hexagonal cylinder phase goes through a perforated lamellar state within a certain temperature range. The numerical results are elucidated by a multimode analysis under the single-wave-number approximation. The analysis reveals that the geometric characteristics of the free energy surface, particularly saddle points and ridgelike features, are responsible for the nontrivial intermediate states on the kinetic pathways. On the basis of this analysis, a generalized kinetic ``phase diagram'' is constructed, which is able to account for all the different scenarios observed in the numerical simulation. Our results are discussed in connection with available experimental observations. In particular, we suggest the possibility that the perforated-modulated lamellar structures obtained by Bates and co-workers [I. W. Hamley, K. A. Koppi, J. H. Rosedale, F. S. Bates, K. Almdal, and K. Mortensen, Macromolecules 26, 5959 (1993); S. Förster, A. K. Khandpur, J. Zhao, F. S. Bates, I. W. Hamley, A. J. Ryan, and W. Bras, Macromolecules 27, 6922 (1994)] may be kinetic, intermediate states rather than new equilibrium phases.


Item Type:Article
Additional Information:©1997 The American Physical Society. (Received 2 August 1996) This research is supported in part by the National Science Foundation (Grant Nos. ASC-9217368 and DMR-9531914) and the Camille and Henry Dreyfus Foundation (Award No. TC-96-063).
Record Number:CaltechAUTHORS:QUIpre97
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:QUIpre97
Alternative URL:http://dx.doi.org/10.1103/PhysRevE.55.1682
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8795
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:17 Sep 2007
Last Modified:26 Dec 2012 09:42

Repository Staff Only: item control page