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Morphology and Dynamics of Catenanes in Dilute Solutions MORPHOLOGY AND DYNAMICS OF CATENANES IN DILUTE SOLUTIONS AND AT LIQUID/LIQUID INTERFACE A Thesis Presented to The Graduate Faculty at the University of Akron In Partial Fulfillment Of the Requirements for the Degree Master of Science Saeed Akbari December, 2018 i MORPHOLOGY AND DYNAMICS OF CATENANES IN DILUTE SOLUTIONS AND AT LIQUID/LIQUID INTERFACE Saeed Akbari Thesis Approved: Accepted: _______________________ _________________________ Advisor Dean of the college Dr. Mesfin Tsige Dr. Ali Dhinojwala ________________________ _________________________ Committee Member Dean of the Graduate School Dr. Andrey Dobrynin Dr. Chand Midha ________________________ __________________________ Department Chair Date Dr. Tianbo Liu ii ABSTRACT Catenanes as mechanically interlocked polymers possess distinct, well-defined topological interactions and, as a result, exhibit a variety of unique properties. Template- directed synthesis is responsible for the high yield syntheses of these structures40. However, little is known about the interfacial and physical properties of this class of polymers. As proved many times in other polymeric systems, Molecular dynamics simulation can be used to characterize them. Among the limited studies, Wang, et.al quantified the influence of topological constraints on the structural and dynamic behavior of different topologies of ring polymers. They found that catenane topologies have larger flexibility than any of the single chain systems, indicative of the larger structural deformations that these large complexes can sustain53. We will present simulation results on the morphology and dynamics of linear, ring and catenane polymers in dilute solutions. Pure poly (ethylene oxide) (PEO), pure polystyrene (PS) and diblock of PEO and PS catenanes in a select group of solvents are examined. The effect of solvent quality on morphology and dynamics is also investigated. Flexibility caused by different polymer type, different chain structure and different interaction of chains with solvents has the dominant role in determining morphological and dynamical properties of the polymers. The behavior of diblock catenane at an interface of two immiscible solvents provided interesting morphological and dynamical understanding. An interesting dynamics of the two blocks, both translational and rotational, has been observed iii at the liquid/liquid interface. At the interface, the flexibility of the rings also plays a major role in relative rotation of the rings. iv ACKNOWLEDGEMENTS First of all, I wish to express my sincere gratitude to my advisor, Dr. Mesfin Tsige, for his guidance and help throughout my 2-year-graduate study. I feel extremely lucky to work closely with him. I have learned a lot from him, not only on various aspects of molecular dynamics simulation, but also on how to be a hard working person. Then I also would like to thank Dr. Andrey Dobrynin for his helpful comments as my committee member. I also would like to thank my group members, Iskinder Arsano, Dr. Selemon Bekele and Alankar Rastogi for being my great friends and kindly helping me with the research. Last but not least, I would like to thank my wife and my parent for their love, support and encouragement. v TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii CHAPTER I. INTRODUCTION ........................................................................................................... 1 II. SIMULATION METHODS ........................................................................................... 8 III.STRUCTURAL PROPERTIES OF PEO AND PS IN DIFFERENT TOPOLOGIES 15 3.1 Rg plots of various topologies ........................................................................................ 19 3.2 VMD images of various topologies................................................................................ 21 IV. DYNAMICAL PROPERTIES OF PEO AND PS IN DIFFERENT TOPOLOGIES 28 4.1 Translational diffusion and global rotation ................................................................... 30 4.1.1 peo (wat): .................................................................................................................... 30 4.1.2 peo (tol): ...................................................................................................................... 33 4.1.3 ps (wat): ...................................................................................................................... 34 4.1.4 ps (tol): ........................................................................................................................ 35 4.1.5 Hetero catenane at Liquid/Liquid interface............................................................ 40 4.2 Relative rotation ................................................................................................................ 42 V. CONCLUSION ............................................................................................................ 45 REFERENCES ................................................................................................................. 47 APPENDIX ....................................................................................................................... 53 vi LIST OF TABLES Table Page Table 1. Rg2 values for different group of samples based on different topologies for last 4 ns of NVT simulation..................................................................................................... 17 Table 2. Relative rotation of rings of catenanes at various frame intervals and at the entire 4 ns of simulation for a) homo catenanes and b) hetero catenanes. .................................. 43 vii LIST OF FIGURES Figure Page Figure 1 Synthesis of poly[n]catenane 3 via assembling 1 and 2 into a metallosupramolecular polymer (MSP), followed by ring-closing to yield a poly[n]catenate (i.e., metallated poly[n]catenane) and demetallation40. ............................................................................................. 3 Figure 2. Plateau heights H for the linear, isolated ring, 2-ring catenane assembly, and other ring structures. H is a measure of deformability or flexibility of the system53........................................ 6 Figure 3. Cartoon and VMD images of constructed ps topologies as (a) linear chain, (b) ring, (c) catenane comprising two identical interlocked rings, and (d) hetero catenane comprising two different interlocked rings. ............................................................................................................. 10 Figure 4. Scheme of peo/ps hetero catenane at water/toluene interface. In this figure toluene solvent is in the upper portion of the box while and water is in the lower portion of the box. The green ring is peo and the blue ring is ps. ........................................................................................ 12 Figure 5. Rg2 plots of a) peo and b) ps at Liquid/Liquid interface of ps/peo hetero catenane during 20 ns of NVT simulation................................................................................................................ 16 Figure 6. Rg2 plots of a) peo (wat), b) peo (tol), c) ps (wat), and d) ps (tol) in last 4 ns of NVT simulation. In all cases green line is for linear chain, red is for ring, blue is for homo catenane and purple is for hetero catenane. ......................................................................................................... 20 Figure 7. VMD images of a) peo/peo (wat) and b) peo/peo (tol) .................................................. 22 Figure 8. Three representative snapshots of solvated peo at zero _top., small _mid., and large _bottom. pulling force. Hydrogen bonds between water molecules and peo oxygen atoms are marked through dashed lines68. ...................................................................................................... 23 viii Figure 9. VMD images of ps/ps (wat) and ps/ps (tol). In order to clearly see the collapsed and expansion mode of the ps rings, the backbone images are also included. a1) backbone of ps/ps (wat), a2) ps/ps (wat), b1) backbone of ps/ps (tol), and b2) ps/ps (tol) ......................................... 24 Figure 10. VMD images of peo/ps (wat) and peo/ps (tol). In order to clearly see the collapsed and expansion mode of the ps rings, the backbone images are also included. a1) backbone of peo/ps (wat), a2) peo/ps (wat), b1) backbone of peo/ps (tol), and b2) peo/ps (tol) ................................... 25 Figure 11. Rg2 plots of peo and ps of peo/ps hetero catenane at liquid/liquid interface. In this figure, red line is for ps, and blue line is for peo. ......................................................................... 26 Figure 12. 3D plot of center of mass motion in the simulation box during 20 ns NVT simulation for a) peo/ps hetero catenane at water/toluene interface and b) peo/peo catenane at toluene. ....... 29 Figure 13. a) Translational motion and b) global rotation of various topologies of peo in water. In both cases green line is for linear chain, red is for ring, blue is for homo catenane and purple is for hetero catenane............................................................................................................................... 31 Figure 14. Translational motion of peo/peo (wat), ps/ps (wat), and peo/ps
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