Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session W12: Beyond the Linear Block Copolymer Phase DiagramInvited
|
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Ang-Chang Shi, McMaster University Room: Room 235 |
Thursday, March 9, 2023 3:00PM - 3:36PM |
W12.00001: Continuous Transition of Close-packed Structures of Block Copolymer Micellar Colloid Invited Speaker: Sangwoo Lee We investigated close-packed structures of strongly segregated block copolymer micellar colloids using X-ray scattering and simulation-based scattering pattern analysis. Our experimental phase diagram reveals a phase domain of continuously varying polytypic close-packing structures from FCC to HCP in the concentration parameter space. The stability of the polytypic close-packed crystals was tested with crystal growth, and the crystals with nearly perfect random stacking of 2D-HCP layers (RHCP) were found stable. We attribute the stability of the RHCP crystals to the equal thermodynamic preference for the FCC and HCP lattices. Because close-packed structures of equal spheres are the archetypes of all polytypic crystal systems with permutable 2D-HCP layer stacking choices, the stable RHCP crystals of micellar colloids may indicate the universal stability of RHCP orders in the crystal systems with competing preference for the FCC and HCP lattices. Indeed, RHCP orders have been widely observed from other polytypic systems, such as cobalt, ice, and hard-sphere colloids, which are known to form FCC and HCP orders in the phase space. |
Thursday, March 9, 2023 3:36PM - 4:12PM |
W12.00002: Unraveling the Phase Behavior of Block Copolymer Materials Invited Speaker: Christopher M Bates The recent discovery of Frank–Kasper phases in block copolymer melts has reinvigorated the study of fundamental phase behavior. This presentation will discuss the role of molecular design, equilibrium thermodynamics, and kinetics in driving the formation of both classical and unconventional mesophases such as A15. In addition, a simple and scalable strategy based on automated chromatography will be described to accelerate the characterization of phase diagrams by fractionating a small number of as-synthesized samples into large libraries spanning a wide range of compositions. The ability to efficiently explore phase space using commercially available chromatography systems should prove broadly useful in the study of multiblock polymers with increasingly complex sequences that are designed to tailor the structure and properties of soft materials. |
Thursday, March 9, 2023 4:12PM - 4:48PM |
W12.00003: Ordered states in diblock copolymer blends Invited Speaker: Kevin D Dorfman When cooled below their order-disorder transition, diblock copolymers adopt an ordered, nanostructured state that optimizes the competition between interfacial tension and chain stretching subject to the constraint of constant density. This presentation will discuss predictions from self-consistent field theory (SCFT) for blends of AB and B'C diblock copolymers, where the prime indicates a (potentially) different degree of polymerization, for the case where the segregation strength between the A and C blocks is strong. In such a system, ordered states that could be produced by blending must outcompete macrophase separation into AB-rich and B'C-rich phases. The first part of the presentation will focus on cases where the diblock copolymers produce a body-centered cubic phase in their neat melt state. We predict the emergence of a Laves phase that appears as a non-ideal line compound state at strong segregation. The complete phase diagram of this "block copolymer alloy" bears a striking resemblance to metallic alloys. The second part of the presentation will focus on systems where the two diblock copolymers form double-gyroid network phases in their neat melt state. An alternating gyroid morphology is predicted to be metastable in such a blend, but may be realizable via solvent annealing owing to the small free energy difference with the macrophase separated state. Addition of a miniscule amount of ABC tetrablock terpolymer stabilizes the alternating gyroid through a surfactant-like interaction that bridges between the A-network and the C-network. A common theme that emerges in this work is a focus on destabilizing the macrophase separated states to produce robust blended morphologies. |
Thursday, March 9, 2023 4:48PM - 5:24PM |
W12.00004: Non-native block copolymer morphologies via blending and layering Invited Speaker: Kevin G Yager Self-assembly of block copolymers efficiently yields nanoscale morphologies. Yet the most easily-accessible morphologies—such as lamellae and cylinders—are comparatively simple. Future materials will equire nanostructures more complex than those afforded by the canonical diblock-copolymer equilibrium phase diagram. This talk will discuss non-equilibrium strategies for generating non-native morphologies. Blending of copolymer chains can be used to stabilize otherwise high-energy configurations, opening the door to a new set of morphologies. Additional control can be applied by using directed assembly strategies. Chemical templates can select among competing morphologies in the blends, alongside the usual pattern registration. Layering of copolymer thin films provides an additional control mechanism. Layering essentially 'primes' the system into a contrived initial state, forcing the system to evolve through a set of non-equilibrium morphologies during annealing. Finally, we will discuss how the complex and high-dimensional parameter spaces associated with these strategies can be efficiently explored using autonomous experimentation, wherein machine-learning algorithms guide discovery. |
Thursday, March 9, 2023 5:24PM - 6:00PM |
W12.00005: Topological Effect on Self-Assembly of High Interaction Parameter Block Copolymers Invited Speaker: Rong-Ming Ho Block copolymers (BCPs) with high χ value, polystyrene-block-polydimethylsiloxane (PS-b-PDMS), have drawn intensive attention due to their rich phase behaviors. Lamellar phase with an interdigitating chain packing can be found in the PS-b-PDMS where a superlattice structure can be formed in a diblock but the star-block (PS-b-PDMS)n (n = 3 and 4) might constrain the superlattice formation due to configurational topology. Owing to the high χ value of the PS-b-PDMS, metastable cubic network phases including double primitive phase (DP), double diamond phase (DD) and double gyroid phase (DG) can be obtained from a single-composition, lamellar PS-b-PDMS. The order-order transitions from DP (hexapod network) to DD (tetrapod network), and finally to DG (trigonal planar network) are attributed to the reduction on the degree of packing frustration (entropic penalty) within the junction (node), different to liquid crystals. By taking advantage of the topological effect with increasing the arm number (star-block (PS-b-PDMS)n (n = 6)), it is possible to overcome the packing frustration, giving higher accessibility for the formation of network phases. It is highly appealing to exploit the forming network phases as templates for fabrication of metamaterials. Controlling the orientation of nanostructured BCP thin films is essential for BCP lithography. According to conventional wisdom, the orientation of BCP thin films is mainly determined by molecular interactions (enthalpy-driven orientation). By taking advantage of the entropic effect due to the topology of star-block copolymers, it is feasible to regulate the entropic contribution with the number of arms, giving self-assembled PS-b-PDMS thin films with perpendicularly oriented PDMS cylinders. With combination of configurational topology effect (entropy effect) and surface air plasma treatment or vacuum effect (enthalpy effect) to create a neutral air surface, it is possible to give the formation of the film-spanning perpendicular cylinders upon thermal annealing through self-alignment mechanism. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700