纤维素类材料表面性能的最新综述

Surface Properties of Cellulose and Cellulose

Derivatives: A Review

Qing Shen

State Key Laboratory for Modification of Chemical Fibers and Polymers and Department of Polymer Materials and Engineering, Donghua University, 2999 Renming Road, N, 201600 Songjiang, Shanghai, China The rapidly increasing interdisciplinary research on cellulose

and cellulose derivatives, as well as the broad use of these

materials, makes a basic understanding of their properties

important. The surface properties of cellulose and cellulose

derivatives play an important role in numerous applications.

This review compiles the surface properties data reported in

the literature on cellulose and its main derivatives, cellulose

ethers and cellulose esters, with a focus on the surface free

energy, the Lewis acid–base properties, and the Hamaker

constant. Because Lewis acid–base interactions can be

described using a variety of theories and/or scales, a

comparison of surface properties data obtained using different

acid–base scales is made and discussed. The influence of the

main structural properties of cellulose and cellulose

derivatives, such as the degree of polymerization, the

crystallinity index, and the degree of substitution, on the

surface properties of the materials is also is discussed.

Introduction

Cellulose is the most abundant natural polymer, and has been used by mankind for centuries. It is the main structural component of plant cell walls, as has been shown by the removal of lignin and extractives from plant tissue. Cellulose is a semicrystalline linear polysaccharide of β-1,4-linked D-glucopyranose (1–3). In its native form, it typically has a degree of polymerization, DP, between 10,000 and 15,000 glucose residues, depending on its origin. Cellulose occurs as a partly crystalline, partly amorphous material, and the degree of crystallinity has been found to depend on the cellulose source; for example, cotton has a high degree of crystallinity, whereas wood has a lower one (4). Cellulose can be derived from plant or bacterial sources. The best known example of a bacterial source is Acetobacter xylinum, which produces extracellular cellulose as a small pellicle extending from its cell (4).

Cellulose has been widely studied, and consequently our understanding of its nature and behavior is considerable. Moreover, many of the basic principles of polymer chemistry and physics were worked out in the course of investigating cellulose, and these studies have led to an understanding of the behavior of other natural and synthetic polymers (5).

Because cellulose and its derivatives have been broadly applied in various areas, e.g., liquid penetration, diffusion, adsorption, coatings, foods, paper-making, and chemical engineering (6–7), and because many of these applications rely on the interfacial behavior of cellulose, an understanding of the surface properties of cellulose is important.

In this review, we aim to summarize the information reported in the literature on the Hamaker constant, surface free energy, and Lewis acid–base properties of cellulose and its main derivatives, i.e., cellulose ethers and cellulose esters. Since various measurement methods are available for determining or estimating the surface properties data with respect to different acid–base theories and scales (8–9), a comparison of the data obtained on the basis of different theories and scales is presented.

Methods for Evaluating the Surface Properties of Cellulose

and Cellulose Derivatives

Methods for Evaluating the Hamaker Constant

The Hamaker constant is an important parameter in surface chemistry because it strongly depends on the interactions between materials. Among the