Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A59: Bridging New Polymer Chemistry and Polymer PhysicsInvited
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Sponsoring Units: DPOLY Chair: Justin Kennemur, Florida State Univ Room: LACC Petree Hall D |
Monday, March 5, 2018 8:00AM - 8:36AM |
A59.00001: Precise Associating Polymers Exhibit New Morphologies and Promising Properties. Invited Speaker: Karen Winey Acid- and ion-containing polymers have specific interactions that produce both acid- or ion-rich aggregates arranged in hierarchical nanoscale morphologies and remarkable bulk properties. Untangling the correlations between the primary structure of such associating polymers and their morphologies and properties has long been a challenge in polymer physics, because most acid- and ion-containing polymers have random sequences of polar and non-polar monomeric units. New synthetic methods increasingly produce polymers with greater molecular precision that provide greater uniformity of and control over the hierarchical morphologies and even yield new morphologies. Specifically, we have studied a series of precise polyethylenes synthesized by acyclic diene metathesis (ADMET) chemistry that have functional groups evenly spaced along linear polyethylenes. We have established design rules connecting these precise polymers to particular hierarchical morphologies and have discovered a variety of new morphologies. This talk will discuss the mechanical properties of precise acid- and ion-containing polyethylenes, particularly the morphological transformations that correlated with strain hardening during tensile deformation. In addition, this talk will highlight a precise sulfonated polyethylene that exhibits well-controlled chain folding to produce a highly uniform morphology with high proton conductivity. Above 65% relative humidity at 40°C the proton conductivity through these layers is on par with Nafion 117. Finally, the talk will include comparisons between precise, nearly precise and random polymers to assess the impact of polymer microstructure. |
Monday, March 5, 2018 8:36AM - 9:12AM |
A59.00002: Computationally Driven Design of Soft Materials Invited Speaker: Andrey Dobrynin Mimicking the mechanical properties of soft biological tissues is vital for medical implants, tissue engineering, soft robotics, and wearable electronics. However, the unique combination of softness, strength, and toughness is difficult to recreate in synthetic materials. Current design strategies are predominantly Edisonian - exploratory mixing of assorted polymers, crosslinking schemes, and solvents, which is both inflexible in application and imprecise in property control. We develop a computationally driven approach for design of soft materials with solvent free network architecture. This approach is based on the theoretical and computational studies of the mechanical properties of networks made of graft polymers such as combs and bottlebrushes. In particular, it is demonstrated that the graft polymers in a melt behave as ideal chains with effective Kuhn length. Our analysis shows that the effective Kuhn length of the graft polymers is a universal function of the crowding parameter, describing overlap between neighboring macromolecules. This model of graft polymers is applied to model mechanical properties of networks of graft polymers in linear and nonlinear deformation regimes and to correlate network’s mechanical response with architectural and chemical structure of the network strands. This approach is verified by replicating elastic materials with mechanical properties of jellyfish, lung, and arterial tissue in PDMS networks of combs and bottlebrushes. This technique lays the foundation for a computationally driven materials design that will enable encoding of a broad range of mechanical properties of soft materials in solvent free elastomers. |
Monday, March 5, 2018 9:12AM - 9:48AM |
A59.00003: Structure, Properties, and Function in Periodically Sequenced Poly(lactic-co-glycolic acid)s Invited Speaker: Tara Meyer Despite the deep understanding of the connection between sequence and properties in biological copolymers, synthetic challenges have inhibited the development of a sophisticated understanding of structure and function in non-biological systems. We have prepared a library of poly(lactic-co-glycolic acid)s and have investigated how properties, especially hydrolytic degradation, depend on sequence. Our studies have shown that while some properties depend only slightly on sequence (Tg, modulus), others are extremely sensitive (swelling, hydrolytic degradation). We are now beginning to explore how sequence errors affect properties. In particular, we will present data that demonstrate that some properties follow a dopant model, where even small error rates are meaningful, while other characterisitics are controlled by a dominant material model, where a threshold of contamination must be attained before property changes become significant. |
Monday, March 5, 2018 9:48AM - 10:24AM |
A59.00004: Dynamic Order-Order Transitions and Kinetic Surface Trapping of Unique Morphologies for Sub-10 nm Nanostructured Ultrathin Films of Sugar-Polyolefin Conjugates Invited Speaker: Lawrence R. Sita Living coordinative chain transfer polymerization (LCCTP) is a new polymerization process that can provide access to a large variety of end-group functionalized polyolefins (x-PAOs) of very narrow polydispersity and tunable degree of polymerization from readily available and inexpensive α-olefin monomers. These x- PAOs now establish a new category of hydrophobic building block for the development of amphiphilic materials that self-assemble in both solution and the solid-state to produce an assortment of highly-ordered nanostructured morphologies. This talk will present the results of our most recent investigations regarding the synthesis and characterization of low molecular weight sugar-polyolefin conjugates that engage in unique dynamic temperature-driven order-order phase transitions involving several different sub-10 nm nanostructured morphologies within the bulk solid state and ultrathin films. Using a variety of techniques, including atomic force microscopy (AFM) and grazing incident small angle X-ray scattering (GISAXS), we have been able to establish formation of a long-lived bicontinuous gyroid morphology of a sugar-polyolefin conjugate within a sub-100 nm thick film through apparent kinetic surface trapping. |
Monday, March 5, 2018 10:24AM - 11:00AM |
A59.00005: The design of block copolymers and the control over their structures for energy storage Invited Speaker: Guoliang Liu Herein we describe a method for controlling the mesoporous nanostructures in block copolymers and their subsequently converted porous carbons. We systematically investigated the self-assembly behavior of polyacrylonitirle-block-polymethyl methacrylate (PAN-b-PMMA) after thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA microphase-separated into globular nanostructures, and the globular nanostructures evolved into various morphologies after thermal or solvent annealing. Surprisingly, after thermal annealing and pyrolysis, the pore size and center-to-center spacing of the mesoporous carbon thin films increased significantly with the increasing annealing temperature, which differed from most block copolymers. In addition, the choice of solvent during solvent annealing strongly influenced the block copolymer nanostructures and the pore size of mesoporous carbon thin films. The porous carbon structure was applied as electrodes in supercapacitors and exhibited outstanding surface area-normalized capacitance and gravimetric capacitance. |
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