Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Y63: Structured Polymers and Their Advanced Morphological CharacterizationsLive
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Sponsoring Units: DPOLY Chair: Julie Albert, Tulane Univ |
Friday, March 19, 2021 11:30AM - 11:42AM Live |
Y63.00001: Mechanisms of Directional Polymer Crystallization Alejandro Krauskopf, Andrew Jimenez, Elizabeth Lewis, Bryan D Vogt, Alejandro J Muller, Sanat Kumar Zone annealing is adapted here to crystalline polymers. Almost 50 years ago, Lovinger and Gryte postulated that for a polymer undergoing zone annealing, at steady state, the crystal growth rate of the polymer equals the velocity at which the sample is being pulled through the temperature gradient. They also implied that there is a critical velocity below which the crystal growth rate dominates over nucleation, and that directional crystallization can therefore only occur below this critical velocity. In this work, we perform analyses of SAXS, DSC, and CPOM of zone annealed PEO in order to examine these postulates. The steady-state ansatz is validated with our long period data, and an analysis of Herman’s orientation function shows that there exists a transitional region around a critical velocity where a coexistence of oriented and isotropic domains occurs. Below this critical velocity, directional crystallization is achieved, while above it, the mechanism is more similar to that of conventional isotropic isothermal crystallization. |
Friday, March 19, 2021 11:42AM - 11:54AM Live |
Y63.00002: Investigating topological and group contribution predictive schemes for the heat capacity of polyzwitterions Andrew Clark, Michael Rosenbaum, Yajnaseni Biswas, Ayse Asatekin, Peggy Cebe The specific heat capacity (cp) for six zwitterionic polymers were measured using differential scanning calorimetry (DSC). Poly(sulfobetaine methacrylate) (PSBMA), poly(sulfobetaine acrylate) (PSBA), poly(ethyl sulfobetaine methacrylate) (PESBMA), poly(sulfobetaine methacrylamide) (PSBMAm), poly(sulfobetaine 2-vinylpyridine) (PSB2VP) and poly(sulfobetaine 4-vinylpyridine) (PSB4VP) were synthesized with changes of chemical structure in order to study effects of either the polymer backbone or the side group. Temperature modulated DSC (TMDSC) in scanning mode as well as quasi-isothermal (QI) TMDSC were used to determine cp. The glass transition for PSBA and PESBMA was measured for the first time. PSBMA, PSBMAm, PSB2VP and PSB4VP thermally degrade prior to the glass transition allowing for measurement only of the solid-state cp. Theoretical values of solid state cp were calculated for the polyzwitterions using topological and group contribution methods and compared to the measured values. The modelled cp accurately predicts only PSB2VP and PSB4VP. The discrepancy between the measured and predicted cp values is likely due to the reduction of vibrational degrees of motion in the solid state for some of the polyzwitterions. |
Friday, March 19, 2021 11:54AM - 12:06PM Live |
Y63.00003: Twins in tubular networks: (422) double gyroid twin & (222) double diamond twin Xueyan Feng, Edwin Thomas Triply periodic double gyroid (DG) and double diamond (DD) network phases have unique photonic properties as well as superior charge and/or mass transport along with outstanding mechanical properties arising from their 3D continuous morphology. Determination of the nature of defects (e.g. grain boundaries) in these phases is critical for further understanding/improving material performance. Slice-and-view scanning electron microscopy tomography enabled identification of coherent twins in polystyrene-b-polydimethylsiloxane (PS-PDMS) block copolymers. The DG structure was formed from a 43-29.5 kg/mol sample cast from toluene and the DD structure was obtained from a 51-35 kg/mol sample cast from chloroform. In the DG phase, the boundary is a (422) twin while the twin plane in the DD phase is identified as (222). The reconstructions show that the inter-material dividing surface (IMDS) is smooth and continuous across the twin plane with the formation of new types of boundary nodes and loops. The network topology and the IMDS curvature distribution, surface/volume ratio etc. of the twin boundary regions are compared with the corresponding morphological descriptors measured in the adjacent, ordered DG and DD grains and suggest both boundaries are of low energy. |
Friday, March 19, 2021 12:06PM - 12:18PM Live |
Y63.00004: Combining spectroscopy with DFT for optical models of polarized RSoXS to reveal molecular alignment in nanostructures Victor Manuel Murcia, Brian Collins Polarized Resonant Soft X-ray Scattering (pRSoXS) is uniquely sensitive to local molecular orientation regardless of crystallinity, making it a powerful tool in characterizing various types of nanostructures. Unfortunately, it is difficult to interpret the scattering patterns due to a lack of appropriate optical models. Building block models (BBM), used to measure global orientation in X-ray absorption spectroscopy (XAS) won’t work for pRSoXS as it assesses differences in local ordering and means that XAS measurements alone will not provide enough information for an optical model. We have developed a model that combines angle-dependent XAS with density functional theory (DFT) to algorithmically create a biaxial optical tensor for molecules. We first show how the uniaxial approximation (UA) can be applied to the scattering anisotropy (SA) of Copper(II)Phthalocyanine (CuPc) films as measured by pRSoXS by expanding upon the BBM informed by DFT calculations. Then we show how the UA fails to describe the SA measured on poly-3-hexylthiophene (P3HT) films implying the need for a lower symmetry model. By combining DFT calculations with XAS, a model that enables extraction of additional details of local molecular orientation through pRSoXS can be developed |
Friday, March 19, 2021 12:18PM - 12:30PM Live |
Y63.00005: Highly Conductive, Reconfigurable Nanocomposites of a Nanostructured Carbon Material and a Dynamic Polymer Network Zhen Sang, Qing Zhou, Frank Gardea, Svetlana Sukhishvili Utilizing high aspect ratio nanofillers with exceptional electrical conductivity opens the opportunities for the fabrication of multifunctional conductive polymer composites (CPCs). However, achieving fine filler dispersion for advanced nanocomposite performance has remained challenging. Here, we report a fine dispersion of a carbon nanostructured material assisted by liquefication of dynamic polymer network dissociation via a temperature-reversible Diels-Alder (DA) reaction. The resulting DA polymer composites (DAPCs) demonstrate an ultra-low percolation threshold (0.04 wt. %) and high electrical conductivity of 4 S/m at only 1 wt. % filler loading. Dissociation of DA bonds under low-power electrical-assisted fast heating enables efficient healing of the composite networks. Moreover, the 3D printed DAPC network shows a unique shape memory behavior which can be reprogramed by tuning stereochemistry of DA attachments. This work introduced a new approach to address major challenges in polymer nanocomposites including good filler dispersity, enhanced electrical and mechanical properties, and 3D printability of CPCs. |
Friday, March 19, 2021 12:30PM - 12:42PM Live |
Y63.00006: Structural Characterization of Heterogeneities in Highly Loaded Particle Composites Fabricated via Direct Ink Writing Karla Wagner, Dong June Jang, Sungwoo Jang, Blair Brettmann, Naresh N Thadhani Additive manufacturing (AM) via pneumatic direct ink write (DIW) extrusion offers the ability to print tailored highly solids loaded polymer composites. The AM process inherently introduces heterogeneities such as particle aggregation, porosity, periodicity, and anisotropy across several length scales. Heterogeneities such as these can be difficult to predict and their effect on material properties is not yet well understood. Therefore, this work investigates the influence of processing parameters, polymer binder, and the ratio of volume fractions of solids with a bimodal size distribution on structural heterogeneity. Two polymer binders are investigated: bisphenol A glycidyl methacrylate (BisGMA)/triethylene glycol dimethacrylate (TEGDMA) and 55k Polyvinylpyrrolidone (PVP). Silica beads of two diameters, 10 μm and 170 μm, are mixed with a binder (at ratios of 15:85, 35:65, 65:36, and 85:15 by volume) to give a total solids loading of 61.4% by volume. Non-destructive imaging is performed via X-ray micro computed tomography. By quantitatively characterizing the microstructure from these images, heterogeneities will be investigated and connected to processing and material parameters. |
Friday, March 19, 2021 12:42PM - 12:54PM Live |
Y63.00007: Formation of difuran-diketopyrrolopyrrole adsorption layers on graphite probed in molecular simulations Moufdi Hadjab, Vladyslav Savchenko, Olga Guskova In this computational work, we investigate the adsorption layers of N-unsubstituted difuran-diketopyrrolopyrroles (DPP). Three conformational states differing in their dipole moments are distinguished. The adsorption layers are obtained during in-silico self-assembly on graphite surface through intermolecular hydrogen bonding in all-atom MD simulations. Two experimental processes are reproduced in the modelling: the vacuum deposition of the molecules one-by-one and the construction of the adlayers using the spin-coating technique. In all simulated systems, the formation of stable supramolecular polymers is observed which build the ordered carpets on the surface. However, the binding energetics, the strength and the type of the hydrogen bonding, and diffusion of the molecules on graphite are highly sensitive to the molecular conformation. We quantify each of these characteristics and provide a molecular picture of difuran-DPP adlayers relevant for organic field-effect transistor applications. |
Friday, March 19, 2021 12:54PM - 1:06PM Live |
Y63.00008: Temperature-Driven Grafted Nanoparticle Penetration into Polymer Melt: Role of Enthalpic and Entropic Interactions. Aparna Swain, Nimmi Das A, Nafisa Begam, Arpan Bhattacharyya, Jaydeep Basu, Sivasurender chandran, Michael sprung Polymer grafted nanoparticles (PGNPs) based ultra-thin membranes are coupled to some substrates, the role of membrane–substrate interactions, nanoparticle (NP) penetration into soft matter systems are indispensable for numerous applications ranging from targeted nanoparticle-based drug delivery to generating hybrid polymer nanocomposite materials. Understanding their mechanical and thermal stability, as well as their plethora of applications. Dynamical parameters are studied using X-ray photon correlation spectroscopy, X-ray reflectivity, and the results are correlated with molecular dynamics simulations. Here we report thermal stability, membrane flexibility when the temperature of the system is below the glass transition temperature and the penetration of NP increased toward the glass transition temperature of underlying films. We report two independent pathways of PGNP penetration depending upon the enthalpic interaction between the grafted chains of PGNP monolayer (top layer) and the chains of a polymer film (bottom layer) onto which the layer is transferred. The extent of PGNP penetration, membrane dynamics are improved upon increasing the entropic and enthalpic compatibility between PGNPs and the underlying bulk layer. |
Friday, March 19, 2021 1:06PM - 1:18PM Live |
Y63.00009: Effects of conformational chirality on the lamellar morphology in block copolymers Natalie Buchanan, Julia Provenzano, Poornima Padmanabhan Block copolymer self-assembly for model polymers adopting random-coil conformations has been extensively studied and is well-understood. Recent advances in polymer synthesis have led to the development of a new class of polymer molecules capable of adopting conformational chirality, that can also result in novel chiral morphologies such as helices and single gyroids. In this study, we use particle-based simulations to investigate the phase behavior of model block copolymers exhibiting conformational chirality. A wide range of conformations between random-coil and perfect helices are obtained by tuning the angular and dihedral interactions in a bead-spring model. Conformational chirality of the molecules is quantified by the average helicity and correlated with the average end-to-end distance. The self-assembly of these molecules into the lamellar morphology is investigated and effects of chain helicity and end-to-end distance on the thermodynamics (order-disorder transition) and material properties (domain spacing) are elucidated. |
Friday, March 19, 2021 1:18PM - 1:30PM Live |
Y63.00010: Orthogonal Nanoprobes for One- and Two-Color Optical Super-Resolution Microscopy Imaging of Distinct Nanodomains in Composite Diblock Copolymer Thin Films Dana Chapman, Joshua A Hinckley, Jacob Erstling, Ulrich Wiesner Optical super-resolution microscopy (OSRM) methods provide fluorescence imaging capabilities below the diffraction limit of light. While this novel set of techniques has been rapidly applied to biology, its adoption in soft matter has been considerably slower. This gradual implementation is due in large part to the lack of probes able to orthogonally label and provide super-resolution images of e.g. polymer nanostructures in the condensed state. Here, we introduce a novel class of ultrasmall aluminosilicate nanoparticles ("aC’ dots") employed in stochastic optical reconstruction microscopy (STORM) with a single excitation source and without specific aqueous imaging buffers. Tailoring both encapsulated dye and aC’ dot surface chemistry affords straightforward protocols for multicolor OSRM on diffraction-limited features of chemically dissimilar BCP nanodomains, paving the way for multiplexed OSRM analysis of polymer nanostructures. |
Friday, March 19, 2021 1:30PM - 1:42PM Live |
Y63.00011: Atomistic investigation on the effect of different counterions and associated bridging mechanism in polyelectrolyte brush. MD Turash Haque Pial, Harnoor Sachar, Siddhartha Das The structural behavior of a polyelectrolyte (PE) brush layer is highly sensitive to the valence of the screening counterions. Multivalent screening counterions are known to reduce the brush height and collapse the brush layer. This collapse is hypothesized to be the effect of multivalent ion-induced "bridging". Such multivalent-counterion-induced bridging has been studied using coarse-grained molecular dynamics (MD) simulation that fails to incorporate appropriate atomistic understanding. In this study, we have performed all-atom MD simulations of polyelectrolyte brush grafted systems with different counterions and salt. We observe that the bridging phenomenon, which was previously thought to occur only in presence of multivalent counterions, occurs even in the presence of monovalent counterions. We also discover that the size of a counterion plays a vital role in bridging: larger counterions cause more interchain bridging. In this study, therefore, we have provided an atomistic-level exploration of the physical factors dictating the counterion- induced bridging. Our findings will be helpful for designing PE grafted surfaces for biomedical and sensing applications. |
Friday, March 19, 2021 1:42PM - 1:54PM Live |
Y63.00012: Probing Stretchable Features of Conjugated Polymer from Molecular Level to Mesoscale with Soft X-Ray Spectroscopy and Scattering Wenkai Zhong, Gregory Su, Guillaume Freychet, Feng Liu, Cheng Wang Great advances have been made in stretchable/flexible organic electronics in recent years. However, the chemical and morphological developments when the organic thin film is under stretching and releasing are still undetermined. In this work, we used N2200 as a prototype polymer to investigate the stretchable features on the molecular level and mesoscale during tensile testing. Bulk-sensitive total fluorescence yield (TFY) spectra with theoretically simulated x-ray absorption spectra can uncover the fingerprint of the molecular behaviors induced by strains. Real-time resonant soft x-ray scattering (RSoXS) can probe the mesoscale characteristics associated with anisotropy and domain size. Furthermore, extending the soft x-ray scattering to tender x-ray scattering can provide new insight into the chain packing when the polymer is with strains. |
Friday, March 19, 2021 1:54PM - 2:06PM On Demand |
Y63.00013: Crystallization and phase behavior in hybrid organic-inorganic diblock and triblock copolymers with salt Gurmukh Sethi, Saheli Chakraborty, Irune Villaluenga, Nitash Balsara Polymer electrolytes are a promising avenue to enable lithium metal anode batteries. Copolymer electrolytes have highly tunable nanostructures containing ion-conducting domains and mechanically rigid domains. The phase behavior of 2 poly(ethylene oxide) -b-polyhedral oligomeric silsesquioxane (PEO-POSS) diblock copolymers and 1 polyhedral oligomeric silsesquioxane -b-poly(ethylene oxide) -b-polyhedral oligomeric silsesquioxane (POSS-PEO-POSS) triblock copolymer mixed with lithium bis(trifluoromethane)sulfonimide salt are presented. While self-consistent field theory suggests that triblock copolymer architectures stabilize the disordered phase, the opposite case is true. Further, though we expect the increase of chain length stabilizes the ordered phases, we observe a wider disordered window in the larger diblock copolymer system. We postulate that POSS crystallization plays a large role in the phase behavior. POSS domains organize into well-ordered crystals in the triblock copolymer/salt mixtures, while POSS domains remain weakly crystalline or amorphous in the diblock copolymer systems. |
Friday, March 19, 2021 2:06PM - 2:18PM On Demand |
Y63.00014: The Effects of Regioregularity on the Thermotropic Liquid Crystalline Phase Transitions of Poly(3-dodecylthiophene) Hyeonjung Park, Moon Jong Han, Youngkwon Kim, Eun Ji Kim, Dong Ki Yoon, Hyeong Kim, Bumjoon Kim We investigate the thermotropic liquid crystalline (LC) phase transition of regioregularity (RR)-controlled poly(3-dodecylthiophene) (P3DDT). Controlling RR of the P3DDT from 95 to 65% provides significantly altered strength of the LC interactions while maintaining the chemical structures the same. As the RR decreases, the P3DDT exhibits progressively decreased phase transition temperatures under polarized microscopy due to weaker interchain interactions. In the X-ray scattering and thermal analysis, the melting of side-chain and backbone leads to entering the nematic and isotropic phases, respectively. Furthermore, as RR decreases, the ratio of Form II/Form I polymorphs increases. Considering the faster breakdown of Form II upon heating, larger Form II/Form I can promote lower transition temperature. Molecular design of the RR provides an effective approach to control the LC interactions and the morphologies of the conjugated polymers. |
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