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Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
Published on: June 20, 2019
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Dodecagonal quasicrystalline order in a diblock copolymer melt
Timothy M Gillard1, Sangwoo Lee2, Frank S Bates3
1Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455;
Summary
Researchers discovered a dodecagonal quasicrystalline state (DDQC) in a block copolymer melt. This metastable state forms from a supercooled liquid and transforms over time into a stable phase, offering insights into aperiodic order.
Area of Science:
- Materials Science
- Polymer Science
- Condensed Matter Physics
Background:
- Block copolymers form ordered structures in melts.
- Quasicrystalline states exhibit non-periodic atomic arrangements.
- Understanding phase transitions in polymers is crucial for material design.
Purpose of the Study:
- To investigate the formation and stability of a dodecagonal quasicrystalline state (DDQC) in poly(isoprene-b-lactide) diblock copolymer melts.
- To characterize the temperature and time dependence of phase transitions.
- To explore the relationship between material properties and the emergence of quasicrystalline order.
Main Methods:
- Small-angle X-ray scattering (SAXS) measurements were used to analyze the structure of the copolymer melt.
- Experiments involved rapid cooling from above the order-disorder transition temperature (TODT).
- Time-resolved studies were conducted at various sub-transition temperatures.
Main Results:
- A metastable dodecagonal quasicrystalline state (DDQC) was observed below 40 °C, forming from a supercooled disordered state.
- The DDQC state transforms over time into the thermodynamically stable Frank-Kasper σ phase.
- Phase formation kinetics are strongly temperature-dependent, with longer times required at lower temperatures.
- A transition from ergodic liquid to non-ergodic glassy solid occurs around 40 °C, coinciding with DDQC formation.
Conclusions:
- The study reveals the formation of a novel DDQC phase in a model block copolymer system.
- The DDQC state is a temporally transient, metastable phase seeded by the development of glassy dynamics.
- Model block copolymers provide a unique platform for studying the origins and stability of aperiodic order in condensed matter.
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