WTCHUANG | nsrrcsrd

Wei-Tsung Chuang (莊偉綜), Ph. D.

Associate Research Scientist

Materials Science Group

Office: Room S207, R&D Building

Tel: +886-35780281-7125

Education

2000－2004 Ph.D. in Department of Polymer Engineering, National Taiwan University of Science and Technology (NTUST), Taiwan.

Employment

2015－ Associate Scientist, NSRRC

2010－2014 Assistant Scientist, NSRRC

2005－2009 Postdoctoral researcher, NSRRC

Research Interest

My research interest centers on the structures and phase transitions of soft materials. I have designed many special instruments to extend the capability of sample environment control for small- and wide-angle X-ray scattering (SWAXS) end stations, such as a low-temperature chamber, temperature control of rapid quenching and electric filed etc.. I also integrated other experimental techniques, including differential scanning calorimeter, testing machine, dielectric spectra, rheometer to enable simultaneous measurement. Such an integrated multifunctional end station opens many new research fields for NSRRC users and domestic industrial applications. Using SWAXS combined with other instruments, I have explored several topics, including:

(1) Self-assembly structures of supramolecular block copolymers.

(2) Crystalline morphologies and crystallization kinetics in polymers.

(3) Phase transition of bent-core liquid crystals.

(4) Gelation of glycolipids.

(5) Hierarchical structures of Bio-inspired materials

Several achievements in structural research within the past four years concern mainly soft materials. I have investigated the self-assembly behavior of dendron-jacketed block copolymers; an interesting hierarchical structures and order-order phase transformation under a thin-film stretching was observed with in-situ measurement of SAXS. using time-resolved SAXS integrated with in situ stretching device with simultaneous stress-strain measurements, we illustrated an order-order transformation of PS-b-P4VP(TOB)x from body-centered-cubic (BCC), face-centered-cubic (FCC) to tetragonally perforated layers (TPL), when the local LC phase was tuned through bilayer smectic A (SmA2), distorted, then reoriented to hexagonally packed columnar (HEXcol) phases (Figure 1). The FCC-packed PS domains can be manipulated to extend epitaxially along direction <110>, via thermal stretching and annealing, resulting in an order-order transition FCC to TPL. The associated mechanism was discussed on the basis of interplay between local LC ordering and a global microphase separation of block copolymers. We emphasize that the designated route for the TPL trapping relies critically on the subsequent local and global packing, modulated via stretching and annealing. An underlying prerequisite of the structural trapping is the large dendron grafting density, allowing a sufficient LC packing strength of the DJBCP for rigid columnar LC domains.

Figure 1 2D SAXS patterns in situ covering two q-ranges of a PS-b-P4VP(TOB)0.7 film subjected to subsequent stretching and annealing: from the as-cast film, (a) & (b), to ~two-fold stretching at 120 oC, (c) & (d), followed by stress releasing and annealing for 6 h at 85 oC, (e) & (f). Reflections in the small-q region are indexed according to BCC (a), distorted FCC (c), and TPL structures (e). Reflections in the large-q region are indexed according to Sm (b)&(d) and HEXcol (f) LC phases. Shown in the insets of (b), (d), and (e) are also the corresponding 2D WAXS patterns, with circled zones indicating the orientations of TOB stacking. The film-stretching direction is along Z (or qz), as indicated. PS, P4VP, and TOB domains are respectively coded in red, green and blue.

Bent-core liquid crystals have received much attention since the discovery of their polar switching. Configurational effects of bent-core molecules strongly influence the mesophase formation, resulting in eight main mesophases, denoted B1–B8. The complex of hydrogen-bonded bent-core molecules with the branched siloxane units exhibited SmCG-type phase transitions (Figure 2). We determined the leaning angles of these SmCG-type (B8) phases using synchrotron-based SAXS and WAXS measurements in situ under dc electric fields. To probe the origin of the SmCG-type phase transitions, we have examined the relation between the variation of the leaning angle and the interplay between the thermal stability of hydrogen bonds and microsegregation of the siloxane units, and evidenced the rare SmCG-type phase transitions with X-ray scattering, infrared (IR), and Raman spectra in situ. Our experimental result provided direct evidence to prove the theoretical prediction of the SmCG phase by de Gennes (Nobel laureate in physics, 1991). Our finding provides the first example of the SmCG phase in liquid-crystalline physics. The SmCG phase can be of potential applications, owing to its unique electro-optical properties demonstrated in this study.

Figure 2 Combined GISAXS and GIWAXS patterns of a surface-aligned sample of hydrogen-bonded complex at various temperatures: (a) modulated ribbon structure (Sm G2); (b) undulated bilayer structure (USmCG2); (c) bilayer structure (SmCG2); (d) monolayer structure (SmCG). Model: yellow, green and blue lines indicate oligosiloxane units, alkyl chains and aromatic cores, respectively. The light grey part of the inset in (a) shows the molecular organization at a side view along direction a (right) and a front view along the normal direction of the a-c plane (left).

Selected Publication

1. Directing the Interfacial Morphology of Hierarchical Structures of Dendron-Jacketed Block Copolymers via Liquid Crystalline Phases W.-T. Chuang,* T.-Ya Lo, Y.-C. Huang, C.-J. Su, U-S. Jeng,* H.-S. Sheu, and R.-M. Ho Macromolecules 47, 6047 (2014).

2. Formation of mesomorphic domains associated with dimer aggregates of phenyl rings in cold crystallization of poly(trimethylene terephthalate) J.-B. Jheng , W.-T. Chuang,* P.-D. Hong*, Y.-C. Huang , U-S. Jeng , C.-J. Su , G.-R. Pan Polymer 54, 6242, (2013).

3. Intra- and intermolecular hydrogen bonds enhance the fluoride-responsiveness of functionalized glycolipid-based gelators Cheng-Che Tsai, W.-T. Chuang,* Y.-F. Tsai,* J.-T. Li, Y.-F. Wu, and C.-C. Liao J. Chem. Mater. B. 1, 819 (2013).

4. Wei-Tsung Chuang,* Yen-Chih Huang, Chun-Jen Su, U.-Ser Jeng* and Hwo-Shuenn Sheu, “Successive order–order transitions of the hierarchical morphology of a dendron-jacketed block copolymer via subsequent stretching alignment and self-assembly” Soft Matter, 8, 11163-11168 (2012).

5. New SmCG Phases in a Hydrogen-Bonded Bent-Core Liquid Crystal Featuring a Laterally Attached Siloxane Terminal Group W.-H. Chen, W.-T. Chuang,* U-S. Jeng, H.-S. Sheu, and H.-C. Lin,* J. Am. Chem. Soc. 133 , 15674 (2011).

6. Formation of Mesomorphic Domains and Subsequent Structural Evolution during Cold Crystallization of Poly(trimethylene terephthalate) W.-T. Chuang,* W.-B. Su, U.-S. Jeng,* P.-D. Hong,* C.-J. Su, C.-H. Su, Y.-C. Huang, K.-F. Laio, and A.-C. Su Macromolecules 44, 1140 (2011).

7. Crystallization kinetics and structure of poly(trimethylene terepthalate)/ monolayer nano-mica nanocomposites A.-N. Khan, P.-D. Hong*, W.-T. Chuang,* K.-S. Shih Mater. Chem. Phys., 110, 93-99 (2010).

8. Tetragonally Perforated Layer Structure Induced by Columnar Liquid Crystalline in Supramolecular complexes of Polystyrene-block-Poly(4-vinylpyridine) with 4'-(3,4,5-trioctyloxybenzoyloxy)benzoic acid W.-T. Chuang, H. S. Sheua, U. S. Jeng, J. J. Lee, H. H. Wu and P. D. Hong Chem. Mater. 21, 975 (2009).