Matching Items (2)
Description
The properties of block polymers (BPs) are intricately coupled to the dynamic and rich nature of the nanostructured assemblies which result from the phase separation between blocks. The introduction of strong secondary forces, such as electrostatics and hydrogen bonding, into block polymers greatly influences their self-assembly behavior, and therefore affects their physical and electrochemical properties often in non-trivial ways. The recent surge of work expanding scientific understanding of complex spherical packing in block polymers (BPs) has unlocked new design space for the development of advanced soft materials. The continuous matrix phase which percolates throughout spherical morphologies is ideal for many applications involving transport of ions or other small molecules. Thus, determining the accessible parameter range of such morphologies is desirable. Bulk zwitterion-containing BPs hold great potential within the realm of electroactive materials while remaining relatively untapped. In this work, architecturally and compositionally asymmetric diblock polymers were prepared with the majority block having zwitterions tethered to side chain termini at different ratios. Thermally reversible Frank-Kasper phases are observed in multiple samples with significant signs of kinetic arrest and influence. The kinetic influences are validated and described by the temperature-dependent static permittivity. Polyzwitterions combine the attractive features of zwitterions with the mechanical support and processability of polymeric materials. Among these attractive features is a potential for superior permittivity which is limited by the propensity of zwitterions to pack into strongly associating structures. Block polymer self-assembly embodies a plethora of packing frustration opportunities for optimizing polyzwitterion permittivity. The capabilities of this novel approach are revealed here, where the permittivity of a polyzwitterionic block is enhanced to a level comparable to that of pure liquid zwitterions near room temperature (εs ~ 250), but with less than a third the zwitterion concentration. The mechanistic source of permittivity enhancement from a single zwitterion-tethered block polymer is realized deductively through a series of thermal pathways and control sample experiments. Tethered zwitterions within the mixed block interface are frustrated when subject to segmental segregation under sufficient interfacial tension and packing while non-interfacial zwitterions contribute very little to permittivity, highlighting the potential for improvement by several fold.
ContributorsGrim, Bradley James (Author) / Green, Matthew (Thesis advisor) / Long, Timothy (Committee member) / Richert, Ranko (Committee member) / Jin, Kailong (Committee member) / Seo, S. Eileen (Committee member) / Arizona State University (Publisher)
Created2024
Temperature and polarizability effects on electron transfer in biology and artificial photosynthesis
Description
This study aims to address the deficiencies of the Marcus model of electron transfer
(ET) and then provide modifications to the model. A confirmation of the inverted energy
gap law, which is the cleanest verification so far, is presented for donor-acceptor complexes.
In addition to the macroscopic properties of the solvent, the physical properties of the solvent
are incorporated in the model via the microscopic solvation model. For the molecules
studied in this dissertation, the rate constant first increases with cooling, in contrast to the
prediction of the Arrhenius law, and then decreases at lower temperatures. Additionally,
the polarizability of solute, which was not considered in the original Marcus theory, is included
by the Q-model of ET. Through accounting for the polarizability of the reactants, the
Q-model offers an important design principle for achieving high performance solar energy
conversion materials. By means of the analytical Q-model of ET, it is shown that including
molecular polarizability of C60 affects the reorganization energy and the activation barrier
of ET reaction.
The theory and Electrochemistry of Ferredoxin and Cytochrome c are also investigated.
By providing a new formulation for reaction reorganization energy, a long-standing disconnect
between the results of atomistic simulations and cyclic voltametery experiments is
resolved. The significant role of polarizability of enzymes in reducing the activation energy
of ET is discussed. The binding/unbinding of waters to the active site of Ferredoxin leads
to non-Gaussian statistics of energy gap and result in a smaller activation energy of ET.
Furthermore, the dielectric constant of water at the interface of neutral and charged
C60 is studied. The dielectric constant is found to be in the range of 10 to 22 which is
remarkably smaller compared to bulk water( 80). Moreover, the interfacial structural
crossover and hydration thermodynamic of charged C60 in water is studied. Increasing the
charge of the C60 molecule result in a dramatic structural transition in the hydration shell,
which lead to increase in the population of dangling O-H bonds at the interface.
(ET) and then provide modifications to the model. A confirmation of the inverted energy
gap law, which is the cleanest verification so far, is presented for donor-acceptor complexes.
In addition to the macroscopic properties of the solvent, the physical properties of the solvent
are incorporated in the model via the microscopic solvation model. For the molecules
studied in this dissertation, the rate constant first increases with cooling, in contrast to the
prediction of the Arrhenius law, and then decreases at lower temperatures. Additionally,
the polarizability of solute, which was not considered in the original Marcus theory, is included
by the Q-model of ET. Through accounting for the polarizability of the reactants, the
Q-model offers an important design principle for achieving high performance solar energy
conversion materials. By means of the analytical Q-model of ET, it is shown that including
molecular polarizability of C60 affects the reorganization energy and the activation barrier
of ET reaction.
The theory and Electrochemistry of Ferredoxin and Cytochrome c are also investigated.
By providing a new formulation for reaction reorganization energy, a long-standing disconnect
between the results of atomistic simulations and cyclic voltametery experiments is
resolved. The significant role of polarizability of enzymes in reducing the activation energy
of ET is discussed. The binding/unbinding of waters to the active site of Ferredoxin leads
to non-Gaussian statistics of energy gap and result in a smaller activation energy of ET.
Furthermore, the dielectric constant of water at the interface of neutral and charged
C60 is studied. The dielectric constant is found to be in the range of 10 to 22 which is
remarkably smaller compared to bulk water( 80). Moreover, the interfacial structural
crossover and hydration thermodynamic of charged C60 in water is studied. Increasing the
charge of the C60 molecule result in a dramatic structural transition in the hydration shell,
which lead to increase in the population of dangling O-H bonds at the interface.
ContributorsWaskasi, Morteza M (Author) / Matyushov, Dmitry (Thesis advisor) / Richert, Ranko (Committee member) / Heyden, Matthias (Committee member) / Beckstein, Oliver (Committee member) / Arizona State University (Publisher)
Created2019