Physics of Polymer Gels

Takamasa Sakai

• Publisher: Wiley-VCH
• Year: 2020
• Print ISBN: 9783527346417
• eBook ISBN: 9783527346554
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Physical & Theoretical Chemistry
• Index: Technology & Engineering

Explains the correlation between the physical properties and structure of polymer gels

This book elucidates in detail the physics of polymer gels and reviews their unique properties that make them attractive for innumerable applications. Geared towards experienced researchers and entrants to the field, it covers rubber elasticity, swelling and shrinking, deformation and fracture of as well as mass transport in polymer gels, enabling the readers to purposefully design polymer gels fit for specific purposes.

Divided into two parts, Physics of Polymer Gels starts by explaining the statistical mechanics and scaling of a polymer chains, and that of polymer solutions. It then introduces the structure of polymer gels and explains the rubber elasticity, which predicts the solid-like nature of polymer gels. Next, it describes swelling/deswelling, which can be understood by combining the rubber elasticity and the osmotic pressure of a polymer solution. Large deformation and fracture, and the diffusion of substances in polymer gels, which are essential for practical applications, are also introduced. The last half of the book contains the authors' experimental results using Tetra-PEG gels and provides readers with the opportunity to examine and compare it with the first half in order to understand how to utilize the models to experiments. This title:

* Is the first book dedicated to the physics of polymer gels
* Describes in detail the properties of polymer gels and their underlying physics, facilitating the development of novel, polymer gel-based applications
* Serves as a reference for all relevant polymer gel properties and their underlying physics
* Provides a unified treatment of the subject, explaining the physical properties of polymer gels within a common nomenclature framework
Physics of Polymer Gels is a must-have book for experienced researchers, such as polymer chemists, materials scientists, organic chemists, physical chemists, and solid-state physicists, as well as for newcomers to the field.

Part I
Theories

1
Single Polymer Chain

Takamasa Sakai

Graduate School of Engineering, The University of Tokyo, Tokyo, Japan

1.1 General Features

A polymer gel is a three-dimensional network of polymer chains containing a large amount of solvent (Figure 1.1). When a network structure is formed only by chemical bonding, all the polymer chains are included in a single molecule; one large macromolecule traps a large number of solvent molecules. Let us calculate the molecular weight of a polymer gel. For example, 100 g of a gel with a polymer concentration of 5% contains 5 g of polymer networks. In other words, one molecule has a weight of 5 g. Because the molecular weight is given by the sum of Avogadro's number of weights of individual molecules, the molecular weight of the polymer gel is 3 × 10²⁴ g/mol, which is extremely large. When one stretches a piece of polymer gel, all the chains forming this extremely large macromolecule are stretched, which is why the mechanical properties of polymer gels are predicted based on the simple sum of the contributions of single polymers connected to neighboring chains via crosslinks. Thus, learning the characteristics of a single polymer chain is important for understanding polymer gels. This chapter introduces some methodologies for extracting the universal characteristics of a single polymer chain.

1.1.1 Conformation of a Polymer Chain

A polymer chain is a linear molecule containing a large number of atoms. Prior to considering the shape of a polymer chain, let us focus on the local structure of a polymer composed of four carbons (Figure 1.2). When a carbon–carbon single bond is present between the monomers, the distance between each monomer is approximately 1.5 Å. Additionally, if carbons are connected by a single bond, the bond angle θ is essentially constant at 109.5°. Even if the bond length and bonding angle are constant, rotation around the bond axis, represented by ψ, is allowed, resulting in conformational flexibility. In fact, the value of ψ takes the trans (ψ = 0°) or gauche (ψ = ±120°) stable angles due to steric hindrance.

Let us increase the number of carbons to 100 and consider the shape of the resulting polymer chain. For example, if all the bonds take trans conformations, the polymer chain takes an elongated form with an end-to-end distance of approximately 25 nm. Conversely, if all bonds are in gauche conformations, the polymer chain takes a helical structure, and the end-to-end distance becomes very short. Although these structures can be realized by some specific macromolecules or under specific conditions, conventional polymers contain both trans and gauche forms and have highly complicated structures. However, by applying coarse-graining conce...

Table of contents

• Cover
• Table of Contents
• Preface
• Acknowledgements
• Part I: Theories
• Part II: Experiments
• Index
• End User License Agreement