Dynamics of flow alignment in nanostructured ABC triblock copolymers
- California Institute of Technology, Pasadena, CA (United States)
- Cornell Univ., Ithaca, NY (United States); and others
Nanostructured block copolymers have potential applications in emerging technologies as well as conventional fields, such as novel separation membranes, biomedical materials, optical devices and microelectronics. Recent discoveries of an array of fascinating morphologies in ABC triblocks motivates study of their dynamics and flow aligning behavior since it may provide routes to functional nanostructures that are inaccessible through block copolymers containing just two types of blocks. To better understand the dynamics of ABC triblock copolymers and to control their global order and nanostructures, requires a system that permits systematic variation of the parameters that control microphase behavior: the relative block lengths, the interaction parameters among the blocks and the sequence of blocks in the chain. Triblocks of styrene (S), isoprene (I), and a random copolymer segment of styrene and isoprene (R) provide such a model system. We begin with the case of equal length blocks and with 50:50 of S:I composition in R block so the interaction parameters among three blocks are fixed. Rheo-optical methods are used to examine flow-induced alignment kinetics. Transmission electron microscopy (TEM) and small angle x-ray scattering (SAXS) are used to identify the nanostructures and global order. The local structure of ABC triblocks can be globally aligned using applied fields, especially flow. The interplay of temperature, oscillatory shear frequency and applied strain amplitude are investigated and compared with the previous work on AB diblocks and ABA triblocks. In ABC triblocks, distinct behavior from AB and ABA systems can be expected, not only because of different ordered structures, but also due to difference in the configuration of chains in a three-microphase structure (e.g., the B blocks are always bridges in a three-microphase ordered ABC).
- OSTI ID:
- 602940
- Report Number(s):
- CONF-961108--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Unexpected Consequences of Block Polydispersity on the Self-Assembly of ABA Triblock Copolymers