Structure And Dynamics Of Confined Polymers

Polymers are essential to biology because they can have enough stable degrees of freedom to store the molecular code of heredity and to express the sequences needed to manufacture new molecules. Through these they perform or control virtually every function in life. Although some biopolymers are created and spend their entire career in the relatively large free space inside cells or organelles, many biopolymers must migrate through a narrow passageway to get to their targeted destination. This suggests the questions: How does confining a polymer affect its behavior and function? What does that tell us about the interactions between the monomers that comprise the polymer and the molecules that confine it? Can we design and build devices that mimic the functions of these nanoscale systems? The NATO Advanced Research Workshop brought together for four days in Bikal, Hungary over forty experts in experimental and theoretical biophysics, molecular biology, biophysical chemistry, and biochemistry interested in these questions. Their papers collected in this book provide insight on biological processes involving confinement and form a basis for new biotechnological applications using polymers. In his paper Edmund DiMarzio asks: What is so special about polymers? Why are polymers so prevalent in living things? The chemist says the reason is that a protein made of N amino acids can have any of 20 different kinds at each position along the chain, resulting in 20 N different polymers, and that the complexity of life lies in this variety.

Thelocal relaxations of polymers in cylindrical confinement are measured experimentally using QENS. When polystyrene is confined in cylindrical nanopores, the segmental relaxations slow down non-monotonically with pore size. This trend is also observed for EISF, which measured the fraction of non-diffusing hydrogen within the probing time scale of QENS. At last, we found that when d/R ee > 2, hydrogen has the lowest MSD. When the pore size is decreasing to 2 > d/Ree > 1, MSD is slightly higher but still lower than that for bulk PS. When the pore size is further decrease to d/Ree

The study of the structure and dynamics of polymers confined by solid surfaces, enhances our knowledge about the properties of composite materials. The topic has been a desired area of study given the development of its applications. In such systems, the macromolecules are responsible for the general performance of the whole system. Therefore, understanding the effect of the confinement on the structure and dynamics of polymers is crucial for the advancement of the field. It has been shown that conformations and dynamics of polymer melts confined to thin films and flat surfaces as well as cylindrical pores are altered in comparison with the bulk. The change in properties depends on several factors including but not limited to the geometry of confinement. In our research, we study the effects of both the nanoscopic confinement and curvature on the dynamics and properties of a chemically realistic united atom model of a 1,4-Polybutadiene (PBD) melt using Molecular Dynamics (MD) simulations. Therefore, we divide our work into two systems: one with a PBD melt confined in a cylindrical nanopore and the other with a PBD melt surrounding a cylindrical nanorod. In both systems, the effects induced by the confinement on the melt's structure and dynamics on several scales are examined and compared.

The rapidly-developing field of confined polymers is reviewed in this volume. Special emphasis is given to polymer aspects of this interdisciplinary problem. Taken together, the contributions offer ample evidence of how the field of polymer science continues to evolve with the passage of time. The topics revolve around the tendency of surfaces to impede chain relaxation and to stimulate new sorts of chain organization. These have been implicated in a variety of spectacular phenomena. Here is a listing of authors and affiliations: K. Binder (Johannes Gutenberg-Universität Mainz, Germany); P.-G. de Gennes (College de France, France); E.P. Giannelis, R. Krishnamoorti, and E. Manias (Cornell University and University of Houston, USA); G.S. Grest (Exxon Research and Engineering Co., USA); L. Leger, E. Raphael, and H. Hervet (College de France, France); S.-Q. Wang (Case Western Reserve University, USA).

Nanoparticles (NPs) grafted with organic layers form hybrids able to retain their unique properties through integration into the mesoscopic scale. The organic layer structure and response often determine the functionality of the hybrids on the mesoscopic length scale. Using molecular dynamics (MD) simulations, we probe the conformation of luminescent rigid polymers, dialkyl poly(p-phenylene ethynylene)s (PPE), end-grafted onto a silica nanoparticle in different solvents as the molecular weights and polymer coverages are varied. We find that, in contrast to NP-grafted flexible polymers, the chains are fully extended independent of the solvent. In toluene and decane, which are good solvents, the grafted PPEs chains assume a similar conformation to that observed in dilute solutions. In water, which is a poor solvent for the PPEs, the polymer chains form one large cluster but remain extended. The radial distribution of the chains around the core of the nanoparticle is homogeneous in good solvents, whereas in poor solvents clusters are formed independent of molecular weights and coverages. As a result, the clustering is distinctively different from the response of grafted flexible and semiflexible polymers.

Representing the wide breadth academic disciplines involved in this ever-expanding area of research, this reference provides a comprehensive overview of current scientific and technological advancements in soft materials analysis and application. Documenting new and emerging challenges in this burgeoning field, Soft Materials is a unique and outsta

A physical, mechanism-based presentation of the plasticity and fracture of polymers, covering industrial scale applications through to nanoscale biofluidic devices.

This book gives detailed information about the fabrication, properties and applications of nanoporous alumina. Nanoporous anodic alumina prepared by low-cost, simple and scalable electrochemical anodization process due to its unique structure and properties have attracted several thousand publications across many disciplines including nanotechnology, materials science, engineering, optics, electronics and medicine. The book incorporates several themes starting from the understanding fundamental principles of the formation nanopores and theoretical models of the pore growth. The book then focuses on describing soft and hard modification techniques for surface and structural modification of pore structures to tailor specific sensing, transport and optical properties of nano porous alumina required for diverse applications. These broad applications including optical biosensing, electrochemical DNA biosensing, molecular separation, optofluidics and drug delivery are reviewed in separated book chapters. The book appeals to researchers, industry professionals and high-level students.

Polymers exhibit a range of physical characteristics, from rubber-like elasticity to the glassy state. These particular properties are controlled at the molecular level by the mobility of the structural constituents. Remarkable changes in mobility can be witnessed with temperature, over narrow, well defined regions, termed relaxation processes. This is an important, unique phenomenon controlling polymer transition behaviour and is described here at an introductory level. The important types of relaxation processes from amorphous to crystalline polymers and polymeric miscible blends are covered, in conjunction with the broad spectrum of experimental methods used to study them. In-depth discussion of molecular level interpretation, including atomistic level computer simulations and applications to molecular mechanism elucidation, are discussed. The result is a self-contained approach to polymeric interpretation suitable for researchers in materials science, physics and chemistry interested in the relaxation processes of polymeric systems.

This thesis focuses on the investigation of models of locally stiffpolymers in the melt by molecular dynamics simulations. Two simulation modelsare used: a generic polymer model with only the stiffness entering as aparameter characterizing specific polymers band a detailed atomisticmodel of trans-polyisoprene. The statics and dynamics of wormlike chain polymers in the melt can beobserved. The blob concept is suitable as static description. Localorientations depend on stiffness weakly. The reptation model for long chains in the melt is no longer able to fully describe the dynamics. Long chains move as if confined to tubes. Yet, this motion depends considerably onstiffness. Chains of intermediate stiffness move already only along their contour. The behavior of double-quantum NMRexperiments could be reproduced qualitatively. It is nolonger possible to define an entanglement length for stiffer chains ina simple way. Dynamic structure functionsand primarily visualizations indicate as well that the chain motion iseffectively confined to a tube. The atomistic polyisoprene model was compared with differentexperiments. Experimental results could be reproduced qualitatively. Finally, the model-free mapping of time and length scales of the twodifferent models was a success with respect to reorientation behavior.