Master of Science, University of Akron, 2021, Polymer Science

A fundamental understanding of polymer translocation through nanopores is important for various biological phenomena such as the ejection of viral DNA and the transport of proteins, DNA, and RNA through membrane nanopores. Many factors control the phenomenon of polymer translocation. In the present study, we investigated the effect of polymer topology on translocation process. We employed the bead-spring model and Langevin dynamics to simulate poly[n]catenane passing through a nanopore under an external driving force. We varied the number of rings (n), number of beads per ring and also the stiffness of the polymer chain to investigate their relationship with the translocation process. In addition, other important factors such as the diameter and length of the nanopore are also varied and used to develop scaling laws for the translocation of poly[n]catenanes through nanopores.

Committee: Mesfin Tsige (Advisor); Toshikazu Miyoshi (Committee Member) Subjects: Polymers

Doctor of Philosophy, Case Western Reserve University, 2020, Macromolecular Science and Engineering

A new form factor model is introduced to describe small-angle neutron scattering measurements of star polymers that explicitly includes an excluded volume parameter and Flory interaction parameter, χ. Using 3-, 4-, and 6-arm poly(N-isopropylacrylamide), the stretching predicted by the Daoud-Cotton model was found in addition to significant effects of end-group chemistries on χ. These star polymers and their deviations from the ideal conformation were too small to investigate with resistive pulse sensing (RPS). Using RPS of the translocation events of phytoglycogen nanoparticles, dendrimers with uniform density, were found to permeable by using a “hardness” parameter to explain the current blockade, which is confirmed with recent neutron scattering results in the literature. The current blockade response of the viral nanoparticle Qβ is more complicated, suggesting a divergence between ionic and hydrodynamic permeability of the capsid with the ionic permeability of Qβ increasing with salt concentration. The timescale of translocation dwell times for both phytoglycogen and Qβ was found to obey the Stokes-Einstein relation. A Strouhal framework was then used to define the parameter space of RPS experimental conditions in terms of a Strouhal number, Sr. When Sr >> 1, nanoparticle motion is dominated by thermal energy, kBT, and diffusion coefficients derived from dwell times correspond to values derived from dynamic light scattering measurements. For 1 < Sr << 1, the electrophoretic force, QE, applied by the electric field decreases dwell times from Brownian diffusion times. A new model is introduced to relate the rate of this decrease to the hydrodynamic radius, Rh, electrophoretic mobility, μe, electric field, E, and length of the nanochannel, lp. This relationship finds the electrodes must be very close together, at least 1 mm for the low-charge particles measured in this work, for Sr to be in this range. Further application of the model developed in this work will all (open full item for complete abstract)

Committee: Michael Hore (Committee Chair); LaShanda Korley (Committee Member); Svetlana Morozova (Committee Member); Horst von Recum (Committee Member) Subjects: Engineering; Experiments; Materials Science; Nanoscience; Nanotechnology; Physical Chemistry; Physics; Polymer Chemistry; Polymers