Theory of polygonal phases self-assembled from T-shaped liquid crystalline polymers

Extensive experimental studies have shown that numerous ordered phases can be formed via the self-assembly of T-shaped liquid crystalline polymers (TLCPs) composed of a rigid backbone, two flexible end chains and a flexible side chain. However, a comprehensive understanding of the stability and formation mechanisms of these intricately nano-structured phases remains incomplete. Here we fill this gap by carrying out a theoretical study of the phase behaviour of TLCPs. Specifically, we construct phase diagrams of TLCPs by computing the free energy of different ordered phases of the system. Our results reveal that the number of polygonal edges increases as the length of side chain or interaction strength increases, consistent with experimental observations. The theoretical study not only reproduces the experimentally observed phases and phase transition sequences, but also systematically analyzes the stability mechanism of the polygonal phases

Asymptotically Compatible Schemes for Nonlocal Ohta Kawasaki Model

We study the asymptotical compatibility of the Fourier spectral method in multidimensional space for the Nonlocal Ohta-Kawasaka (NOK) model, which is proposed in our previous work. By introducing the Fourier collocation discretization for the spatial variable, we show that the asymptotical compatibility holds in 2D and 3D over a periodic domain. For the temporal discretization, we adopt the second-order backward differentiation formula (BDF) method. We prove that for certain nonlocal kernels, the proposed time discretization schemes inherit the energy dissipation law. In the numerical experiments, we verify the asymptotical compatibility, the second-order temporal convergence rate, and the energy stability of the proposed schemes. More importantly, we discover a novel square lattice pattern when certain nonlocal kernel are applied in the model. In addition, our numerical experiments confirm the existence of an upper bound for the optimal number of bubbles in 2D for some specific nonlocal kernels. Finally, we numerically explore the promotion/demotion effect induced by the nonlocal horizon, which is consistent with the theoretical studies presented in our earlier work

A finite element approach to self-consistent field theory calculations of multiblock polymers

Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based on using a spectral approach. While widely successful, this approach has limitations especially in the context of current technologically relevant applications. These limitations include non-trivial approaches for modeling complex geometries, difficulties in extending to non-periodic domains, as well as non-trivial extensions for spatial adaptivity. As a viable alternative to spectral schemes, we develop a finite element formulation of the SCFT paradigm for calculating equilibrium polymer morphologies. We discuss the formulation and address implementation challenges that ensure accuracy and efficiency. We explore higher order chain contour steppers that are efficiently implemented with Richardson Extrapolation. This approach is highly scalable and suitable for systems with arbitrary shapes. We show spatial and temporal convergence and illustrate scaling on up to 2048 cores. Finally, we illustrate confinement effects for selected complex geometries. This has implications for materials design for nanoscale applications where dimensions are such that equilibrium morphologies dramatically differ from the bulk phases

Tuning the corona-core ratio of polyplex micelles for selective oligonucleotide delivery to hepatocytes or hepatic immune cells

Targeted delivery of oligonucleotides or small molecular drugs to hepatocytes, the liver's parenchymal cells, is challenging without targeting moiety due to the highly efficient mononuclear phagocyte system (MPS) of the liver. The MPS comprises Kupffer cells and specialized sinusoidal endothelial cells, efficiently clearing nanocarriers regardless of their size and surface properties. Physiologically, this non-parenchymal shield protects hepatocytes; however, these local barriers must be overcome for drug delivery. Nanocarrier structural properties strongly influence tissue penetration, in vivo pharmacokinetics, and biodistribution profile. Here we demonstrate the in vivo biodistribution of polyplex micelles formed by polyion complexation of short interfering (si)RNA with modified poly(ethylene glycol)-block-poly(allyl glycidyl ether) (PEG-b-PAGE) diblock copolymer that carries amino moieties in the side chain. The ratio between PEG corona and siRNA complexed PAGE core of polyplex micelles was chemically varied by altering the degree of polymerization of PAGE. Applying Raman-spectroscopy and dynamic in silico modeling on the polyplex micelles, we determined the corona-core ratio (CCR) and visualized the possible micellar structure with varying CCR. The results for this model system reveal that polyplex micelles with higher CCR, i.e., better PEG coverage, exclusively accumulate and thus allow passive cell-type-specific targeting towards hepatocytes, overcoming the macrophage-rich reticuloendothelial barrier of the liver

Synthesis and characterization of functional polymeric materials for use in organic photovoltaics

Norbornene-type monomers with pendant oligothiophene donor and perylene diimide acceptor groups were synthesized and polymerized using ring-opening metathesis polymerization (ROMP) to yield donor and acceptor homopolymers. These semiconducting homopolymers were characterized by UV-Vis and fluorescence spectroscopy to determine absorbance maxima, emission and excitation profiles, optical bandgaps, molar absorbtivities, and quantum yields. The electrochemical behavior of the donor and acceptor materials was characterized by cyclic voltammetry to determine the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the organic semiconductors. Donor-acceptor diblock copolymers were synthesized using ROMP. Fluorescence spectroscopy demonstrated increased donor emission quenching with decreasing block length. Random donor-acceptor copolymers demonstrated almost complete quenching of the donor emission, likely due to increased donor-acceptor interfaces for charge transfer. Electron paramagnetic resonance spectroscopy (EPR) confirmed the formation of persistent donor radical cations and acceptor radical anions in the block copolymers. Small-angle X-ray scattering (SAXS) demonstrated bulk microphase separation with domain sizes between 24-28 nm. Furthermore, the formation of crystalline structure within the ordered microdomains was also observed. All of these studies indicate that the designed materials may be useful as the active layer in organic photovoltaic applications. As a route to functional hybrid materials, block copolymers containing a donor-segment and a Lewis-basic oligoethylene glycol segment, for preferential ZnO nanoparticle growth, were synthesized by ROMP. Photophysical and electrochemical characterization demonstrated that the donor electronic properties were maintained upon incorporation into the copolymer. SAXS was used to demonstrate lamellar morphology in bulk films of the symmetric block copolymers. ZnO nanoparticles were synthesized and incorporated into composite thin films with the block copolymers. These composite films demonstrated high photoluminescence quenching, which increased upon thermal annealing, as a result of favorable charge transfer from the photo-excited donor to the ZnO nanoparticles. These studies demonstrate that improved morphology control and self-assembly can increase charge transfer in hybrid materials through increased interfacial area. As an alternative route to directed ZnO nanoparticle growth, a copolymer containing pendant dipicolylamine moieties was synthesized and characterized by photophysical and electrochemical methods.Chemistr