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Full-Text Articles in Engineering Science and Materials

Effects Of Nanoscale Aggregation On Mechanical Properties And Local Dynamics Of Precise Acid- And Ion-Containing Polymers, Luri Robert Middleton Jan 2016

Effects Of Nanoscale Aggregation On Mechanical Properties And Local Dynamics Of Precise Acid- And Ion-Containing Polymers, Luri Robert Middleton

Publicly Accessible Penn Dissertations

Acid- and ion-containing polymers have interchain interactions that alter polymer behavior at the nano, micro, and bulk length scales. Strong secondary-bonds act as thermo-reversible physical crosslinks between chains which drive self-assembly. Tuning theses interactions can modify bulk polymer properties including stiffness, toughness, melt viscosity, resilience, clarity, abrasion resistance and puncture resistance. Furthermore, understanding and improving the relevant factors that control transport properties would have vast implications on developing solid polymer electrolytes (SPEs) for technologically important applications including water desalination, ion exchange membranes and microelectronics. This thesis explores the structure – processing – morphology - property relationships of acid and ionic functionalized polymers.

Improvements ...


First Principles Studies Of Magnetic Oxides, Spin-Driven Ferroelectricity, And The Effect Of Polarization In The Chemistry Of Functional Heterointerfaces, Diomedes Saldana-Greco Jan 2016

First Principles Studies Of Magnetic Oxides, Spin-Driven Ferroelectricity, And The Effect Of Polarization In The Chemistry Of Functional Heterointerfaces, Diomedes Saldana-Greco

Publicly Accessible Penn Dissertations

Achieving accurate description and understanding of the chemical and physical properties of complex materials enables the further development of their technological applications. Employing density functional theory (DFT) with rotationally invariant Hubbard corrections, we present an extensive study of binary manganese oxides modeling their noncollinear spin patterns and computing their electronic structures in agreement with experimental results. Leveraging on our success in predicting accurately magnetic properties, we explore the noncollinear cycloidal magnetic order in CaMn$_{7}$O$_{12}$, which breaks inversion symmetry generating one of the largest spin-driven ferroelectric polarizations measured to date. Based on a generalized spin-current model ...


Multiscale Simulations Of Dynamics Of Ferroelectric Domains, Shi Liu Jan 2015

Multiscale Simulations Of Dynamics Of Ferroelectric Domains, Shi Liu

Publicly Accessible Penn Dissertations

Ferroelectric materials exhibiting switchable polarization have been used as critical components in electronics, memory, actuators and acoustics, and electro-optics. The applications of ferroelectric materials heavily rely on the interactions between the polarization and external perturbations, such as electric field, stress, and temperature. It is therefore crucial to understand the dynamics of ferroelectric response at finite temperature. Despite the tremendous advance of computational power and the success of first-principles methods, large-scale simulations of dynamics in oxides at finite temperature can still only be performed using classical atomistic potential. We first develop a model potential based on principles of bond-valence and bond-valence ...


The Optoelectronic Properties Of Surface-Modified Semiconductor Nanocrystal Solids, Earl D. Goodwin Jan 2015

The Optoelectronic Properties Of Surface-Modified Semiconductor Nanocrystal Solids, Earl D. Goodwin

Publicly Accessible Penn Dissertations

Colloidal semiconductor nanocrystals have emerged as fascinating new materials and gained interest in the last 30 years because of their size, shape, and compositionally tunable electronic and optical properties as well as their potential to serve as artificial atoms. Challenges and opportunities have arisen when assembling nanocrystals into nanocrystal solids for electronic and optoelectronic applications, largely because of the significant influence of nanocrystal surface chemistry on the electronic, optical, and structural properties of nanocrystal solids. In order to assemble nanocrystal solids for high performance devices, we must understand and be able to control the effects of nanocrystal surface organic capping ...