Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Q36: Focus Session: Self-assembled Block Copolymers and Soft Nanoparticles in Solution II |
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Sponsoring Units: DPOLY Chair: Zhong-Ren Chen, Ningbo University Room: 211 |
Wednesday, March 4, 2015 2:30PM - 3:06PM |
Q36.00001: Topologically Active Soft Materials for Cellular Delivery Invited Speaker: Cecilia Leal Lyotropic lipid liquid crystalline materials having nanostructures that deviate from the conventional flat bilayer arrangement such 2D hexagonally packed lipid tubes and bicontinous cubic phases have been increasingly recognized as relevant materials for the applications of gene and drug delivery as well as linked to the functionality of cellular organelles comprising lipid-membranes. The simple argument that non-bilayer phases such as bicontinous cubic having 3D nanostructured intertwined channels have a higher surface-to-volume ratio enabling more point contacts with cell surfaces while having a larger encapsulation power to host drug/gene molecules might be insufficient to completely describe the experimental findings. In this work we will show our recent efforts in stabilizing topologically rich lipid-based materials incorporating drugs or nucleic acids in diverse morphologies such as: i) bulk, ii) dispersed in an aqueous solution, iii) as well as thin film coatings. We utilize a combinatorial technical approach including Small/Wide Transmission/Grazing Incidence X-ray Scattering structural characterization and Cell Culture methods to demonstrate that a judicious choice of lipid materials allows an incredibly rich phase behavior in bulk, solution, and thin film platforms. Furthermore, the systems can be tailored to be adaptive in response to a number of environmental cues. The general finding is that lipid-based materials comprising negative Gaussian curvature membranes are able to most efficiently deliver their cargo across cell membranes by lowering the energy cost of forming a membrane pore. These new materials have great potential in the particular field of responsive and self-healing materials for surface-based and systemic drug/gene delivery devices as well as bioadhesive drug delivery. [Preview Abstract] |
Wednesday, March 4, 2015 3:06PM - 3:18PM |
Q36.00002: Control of Nanostructure of Block Copolymer Particles through Size and Aspect Ratio-controlled Nanoparticle Surfactants Kang Hee Ku, Jae Man Shin, Hyunseung Yang, Bumjoon J. Kim Due to the high surface area of nanometer-sized colloidal particles relative to their volume, the interfacial interaction between block copolymer (BCP) chains and surfactant surrounding the emulsion droplet greatly affects the final internal morphology of BCP particles. Convex lens-like functional BCP particle with defect-free porous cylindrical channels was created via precise design of interfacial interactions between Nanoparticle (NP) surfactants and BCPs. The effect of size and aspect ratio of nanorod (NR) surfactants on the shape and internal morphology of BCP particles was systemically investigated using polystyrene-b-poly(4-vinylpyridine), Au NPs, and CuPt NRs. Both size and shape-induced segregation of NPs generated the balanced interfacial interaction between BCPs and water, and this neutralized interface combined with the directionality of solvent generated defect-free, vertically ordered porous channels within the particles. Furthermore, these particles could possess unique optical, chemical and catalytic property by loading various metal nanoparticles into the porous channels. [Preview Abstract] |
Wednesday, March 4, 2015 3:18PM - 3:30PM |
Q36.00003: Multiple Phases of Binary Micellar Crystals Derived from Aqueous Solutions of Charged Block Copolymers Kookheon Char, Seyoung Kim, Soo-Hyung Choi, Sheng Li Amphiphilic block copolymers containing weak polyelectrolyte blocks can induce surface-charged block copolymer micelles (BCMs) in aqueous media and, at the same time, their charge densities can be finely tuned by pH of the media. Polystyrene-\textit{block}-poly(acrylic acid) and polystyrene-\textit{block}-poly(vinyl pyridine) BCMs, whose signs of surface charges are opposite in a relevant pH window, can self-assemble together via electrostatic interactions. By mixing of these charge-tuned BCMs, we obtained binary micellar complexes showing strong crystalline habits and assigned their crystal structures with small-angle neutron scattering and other techniques. We demonstrate multiple phases of binary micellar crystals derived from a set of BCM mixtures of which size and charge ratios are varied. The dependence of the size ratio of individual phases is proven to be different from that of rigid nanoparticles such as inorganic nanocrystals. We believe that this deviation from the hard-matter superlattices is due to the deformability of BCMs based on soft building units. That is to say that BCMs can be readily deformed by the swelling in good solvent and can modify their structure from spheres to other anisotropic shapes while they assemble together. [Preview Abstract] |
Wednesday, March 4, 2015 3:30PM - 3:42PM |
Q36.00004: Structure and Self-Assembly of Thermoreversible Triblock Copolymer Micelles and Gels Vivek Prabhu, Shrinivas Venkataraman, Yi Yan Yang, Jim Hedrick The polymer physics of hierarchical, self-assembled block copolymer solutions remains an active area of research for both advanced materials and biomaterial applications. Of current interest is the development of aliphatic polycarbonates for biomedical applications [1]. For instance, cholesterol-functionalized aliphatic polycarbonate diblock copolymers of polyethylene glycol formed disk and stacked disk-like self-assembled morphologies that are nano-carriers for hydrophobic molecules [2]. The hydrophobic nature of the cholesterol block provides a versatile platform to form complex morphologies in solution. The presentation will describe the phase diagram, structure and dynamics of the micelles and gels formed by well-defined triblock copolymers prepared with cholesterol and fluorene hydrophobic end-groups. The hierarchical structure of these thermoreversible gels as a function of hydrophobic end-group molecular weight was studied by small-angle neutron scattering and static and dynamic light scattering covering nm-to-micron length scales and microsecond-to-second time scales. [1] F. Suriano, O. Coulembier, J.L. Hedrick, P. Dubois, Polym. Chem. 2, 528 (2011). [2] S. Venkataraman, A.L. Lee, H.T. Maune, J.L. Hedrick, V.M. Prabhu, and Y.Y. Yang, Macromolecules 46, 4839 (2013). [Preview Abstract] |
Wednesday, March 4, 2015 3:42PM - 3:54PM |
Q36.00005: BREAK |
Wednesday, March 4, 2015 3:54PM - 4:06PM |
Q36.00006: Assembly of Block Copolymer-Nanoparticles Conjugates Towards Sub-10-nm Hybrid Ordered Nanostructures Zhiwei Lin, Pengtao Lu, Chih-Hao Hsu, Stephen Cheng Precisely controlled locations of nanoparticles (NPs) in block copolymers (BCP) and design of BCP/NPs hybrid nanostructures have attracted numerous research interests over the past several decades. In this work, two series of BC-NP conjugates, composed of a hydrophilic fullerene (AC$_{\mathrm{60}})$ NP tethered with a polystyrene-block-poly(ethylene oxide) (PS-$b$-PEO) at the PS chain end (AC$_{\mathrm{60}}$-PS-PEO) or the junction point (PS-AC$_{\mathrm{60}}$-PEO), were utilized to investigate assemblies of these two series conjugates in the bulk. It was revealed that the incorporation of AC$_{\mathrm{60}}$ NPs induces the nano-phase separation of intrinsically disordered PS-$b$-PEO with low molecular masses. A variety of ordered nanostructures were found including lamellae, double gyroids and cylinders with domain sizes smaller than 10 nm. The different architectures of these conjugates provided evidence of how the NPs are located and distributed within the nano-phase separated structures, and in turn, demonstrated significant effects of these NPs on the stablization of these originally unstable structures. [Preview Abstract] |
Wednesday, March 4, 2015 4:06PM - 4:18PM |
Q36.00007: Giant Molecules based on Precisely Functionalized POSS Nano-atoms: Tuning from Crystals to Frank-Kasper and Quasicrystal Phases Stephen Z. Cheng, Mingjun Huang, Kan Yue, Chih-Hao Hsu, Zhiwei Lin In order to create new functional materials for advanced technologies, precisely control over functionalities and their hierarchical structures as well as orders is vital for obtaining the desired properties. Among all the giant molecules, giant surfactants and giant polyhedra draw us the special focus. Giant surfactants are constructed via tethering polymers tails to the precisely functionalized polyhedral oligomeric silsesquioxane (POSS) or fullerene (C60) molecular nano-particles (MNPs) (so called ``nano-atoms'') heads. The heads and tails thus have drastic chemical differences to impart amphiphilicity. Giant polyhedra were created by integrating polyhedron framework with differently functionalized POSS nano-atoms, which further introduce the designed symmetry breaking of positional interactions. A series of novel giant surfactants with multiple polymer tails and giant tetrahedra are utilized as building blocks to construct into hierarchically ordered superlattice structures ranging from crystals, to Frank-Kasper and quasicrystal phases in the condensed bulk state and thin films. This reveals evidently the interconnections between soft matters and hard matters in sharing their common structures and fundamental knowledge. [Preview Abstract] |
Wednesday, March 4, 2015 4:18PM - 4:30PM |
Q36.00008: Kelvin Problem and Sphericity Metric in the Packing Structures of Soft Particles Sangwoo Lee, Chris Leighton, Frank Bates Attractive hard spheres are known to prefer to form close-packing structures. In contrast, soft particles develop non-close packing structures, e.g., body-centered cubic (BCC), which Kelvin proposed a century ago as the array of densely packed monodisperse soft particles with lowest surface area per unit volume. Remarkably, nearly all packing structures by self-assembled soft particle domains in surfactants, dendrimers, and block polymers are also non-close-packed and appear a set of common symmetries. We found this commonality can be reasoned based on careful observations on the equilibration process occurring in the formation of a Frank-Kasper $\sigma $-phase in a poly(1,4-isoprene-$b$-DL-lactide) diblock polymer specimen. The formation of a low symmetry $\sigma $-phase occurred by statistically selective mass-exchanges between particle domains, which resulted in volume multiplicity and this process eventually lowered the surface area per unit volume, i.e., better sphericity of particle domains. This example demonstrates that the isovolume condition in the Kelvin problem, which also was assumed in the Weaire-Phelan (A15) structure is not necessary for the natural systems. [Preview Abstract] |
Wednesday, March 4, 2015 4:30PM - 4:42PM |
Q36.00009: Tunable Encapsulation Structure of Block Copolymer Coated SWNTs in Aqueous Solution Youngkyu Han, Suk-kyun Ahn, Zhe Zhang, Gregory S. Smith, Changwoo Do Nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical property of SWNT-block copolymer have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well as irreversibly by adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and $\pi $ orbitals of SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer. Our result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure. [Preview Abstract] |
Wednesday, March 4, 2015 4:42PM - 4:54PM |
Q36.00010: Pickering emulsion stabilized by highly luminescent carbon nanodots Minxiang Zeng, Zhengdong Cheng Graphene quantum dots as a novel form of nanocarbons have been attracting increasing interest in the past decade owing to their low cytotoxicity, chemical inertness, cost effectiveness, and biocompatibility. However, few work has been done regarding applying carbon-based quantum dots in surfactant synthesis. The diversity and facility of surface chemistry on graphene quantum dots make them strong candidate as novel amphiphilic materials. The tunable assembly of graphene surfactant dots were synthesized and stabilized emulsions of water/oil were investigated. Also, the amphiphilicity of graphene quantum dots is tunable upon various organic functional groups. The ease synthesis of chemically modified graphene quantum dots could enable new opportunities in applying carbon-based materials on solution processing, such as enhanced oil recovery. [Preview Abstract] |
Wednesday, March 4, 2015 4:54PM - 5:06PM |
Q36.00011: Preparation of uniform-sized block copolymer particles by membrane emulsification Jaeman Shin, Minsoo Kim, Gi-Ra Yi, Bumjoon Kim Block copolymer (BCP) particles have been intensively studied due to their unique internal and surface structures, but their applications have been limited mainly due to inherent polydispersity in the particle size arising from the fabrication technique. Here, monodisperse polystyrene-\textit{block}-polybutadiene (PS-b-PB) BCP particles with unique internal morphology were successfully prepared using Shirasu Porous Glass membrane emulsification. Systematic study on the process parameters in the membrane emulsification, such as membrane pore size, operation pressure, and surfactant concentration was performed to obtain the uniform-sized BCP particles, which generally showed coefficient of variation (CV) value under 10{\%}. Moreover, we successfully extended our method of membrane emulsification to other polystyrene-\textit{block}-poly(4-vinylpyridine) (PS-b-P4VP) particles, in which P4VP domains were selectively metallized, producing uniform-sized BCP hybrid particles. [Preview Abstract] |
Wednesday, March 4, 2015 5:06PM - 5:18PM |
Q36.00012: Highly luminescent polymer particles driven by thermally reduced graphene quantum dot surfactants Hyunseung Yang, Dong Jin Kang, Kang Hee Ku, Han-Hee Cho, Chan Ho Park, Junhyuk Lee, Doh C. Lee, Pulickel M. Ajayan, Bumjoon J. Kim We report the use of highly luminescent graphene quantum dots (GQDs) as efficient surfactants to produce Pickering emulsions and novel polymer particles. To generate the GQD surfactants, the surface properties of 10 nm sized, non-reduced GQDs (nGQDs), which have strong hydrophilicity, were synthesized and modified in a systematic manner by the thermal reduction of oxygen-containing groups at different treatment times. In stark contrast to the behavior of the nGQDs, thermally reduced GQDs (rGQDs) can produce highly stable Pickering emulsions of oil-in-water systems. To demonstrate the versatility of the rGQD surfactants, they were applied in a mini-emulsion polymerization system that requires nanosized surfactants to synthesize submicron-sized polystyrene particles. In addition, the use of rGQD surfactants can be extended to generating block copolymer particles with controlled nanostructures. Particularly, the polymer particles were highly luminescent, a characteristic produced by the highly fluorescent GQD surfactants, which has great potential for various applications, including bioimaging, drug delivery, and optoelectronic devices. To the best of our knowledge, this is the first report in which nanosized GQDs were used as surfactants. [Preview Abstract] |
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