Cellulose Surface Chemistry

download Cellulose Surface Chemistry

of 149

  • date post

    14-Sep-2014
  • Category

    Documents

  • view

    115
  • download

    0

Embed Size (px)

Transcript of Cellulose Surface Chemistry

SURFACE CHEMISTRY OF CELLULOSEfrom natural fibres to model surfaces

PROEFSCHRIFTter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de Rector Magnificus, prof.dr. R.A. van Santen, voor een commissie aangewezen door het College voor Promoties in het openbaar te verdedigen op maandag 21 februari 2005 om 16.00 uur

door

Eero Jaakko Kontturigeboren te Espoo, Finland

Dit proefschrift is goedgekeurd door de promotoren: prof.dr. J.W. Niemantsverdriet en prof.dr. T. Vuorinen Copromotor: dr. P.C. Thne

CIP-DATA LIBRARY TECHNISCHE UNIVERSITEIT EINDHOVEN Kontturi, Eero J. Surface chemistry of cellulose : from natural fibres to model surfaces / by Eero J. Kontturi. Eindhoven : Technische Universiteit Eindhoven, 2005. Proefschrift. ISBN 90-386-2876-5 NUR 913 Trefwoorden: oppervlaktechemie / natuurlijke vezels; cellulose / dunne lagen; spincoatingsproces / polymeermengsels; morfologie / oppervlakteanalyse; atomaire krachtmicroscopie; AFM Subject headings: surface chemistry / natural fibers; cellulose / thin films; spin coating process / polymer blends; morphology / surface analysis; atomic force microscopy; AFMPrinted at Universiteitsdrukkerij, Eindhoven University of Technology.

CONTENTSList of Abbreviations Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 General Introduction.......................................................................... 1 Hardware............................................................................................ 17 Characterization of Industrial Pulp Samples......................................39 Laboratory Recycling of a Representative Pulp Species................... 61 Cellulose Model Surfaces Simplified Preparation and Characterization by XPS, ATR-IR, and AFM................................... 77 Open Films of Nanosized Cellulose AFM and Quantitative Information........................................................................................ 91 Trimethylsilylcellulose / Polystyrene (TMSC/PS) Blends as a Means to Construct Cellulose Domains on Cellulose........................111 Outlook and Conclusion.................................................................... 129 Summary............................................................................................ 136 Samenvatting......................................................................................138 Yhteenveto......................................................................................... 140 Acknowledgements............................................................................ 142 List of Publications............................................................................ 144 Curriculum Vitae............................................................................... 145

LIST OF ABBREVIATIONS

AFM ATR-IR DIP DMAc DP HMDS HMW LMW OCC PS SEM SR STM THF TMSC WRV XPS

atomic force microscopy attenuated total reflectance infrared spectroscopy deinked, recycled pulp (a pulp grade) dimethylacetamide degree of polymerization hexamethyldisilazane high molecular weight low molecular weight old corrugated container (a pulp grade) polystyrene scanning electron microscopy Schopper-Riegler method for determining drainage resistance scanning tunnelling microscopy tetrahydrofuran trimethylsilyl cellulose water retention value X-ray Photoelectron Spectroscopy

GENERAL INTRODUCTION1.1 General In short, cellulose is the most abundant polymer in nature. It is the principal ingredient of woody plants, which makes the diversity of its applications range from housing to paper and textiles. Arguably, it is one of the most influential chemical compounds in the history of human culture. Basing an entire doctoral thesis on one compound alone might seem a trivial undertaking. Even when regarding the ubiquity and the great industrial potential of cellulose, its scientific impetus has remained vague to a considerable number of modern scientists. Cellulose is, it is true, a linear polymer of repeating, painstakingly similar carbohydrate units with a molecular structure that was resolved nearly 80 years ago. For a casual observer, the challenges raised by, for example, papermaking appear primarily as engineering problems, not scientific dilemmas. This is, however, a gross generalisation. From purely a fundamental point of view, the supramolecular structure of cellulose in any form has been subject to debate for nearly a century, and despite the recent breakthroughs much is yet to be unravelled, such as the nature of amorphous cellulose. Although the bulk of cellulose research published is still very much of an applied nature, the more fundamental aspects have always been there and, at present, they are gathering more and more interest. Like with any line of production, the importance of basic research has been acknowledged even by the rather conservative pulp and paper industry. The industrial applications of cellulose constantly generate questions of scientific nature for organic, physical and macromolecular chemists. Organic chemists, for instance, examine cellulose as a molecule of potentially reactive functional groups. This approach can be applied to celluloses capabilities as a backbone for synthetic derivatives. It is also important when one investigates what kind of reactions are taking place during, for instance, bleaching of wood pulp. Physical chemistry of cellulose, on the other hand, is concentrated on the surface properties of cellulose: how the surface acts as an adsorbate for e.g. surfactants or polyelectrolytes, how does it interact with water, or how the cellulose surface behaves as a charged entity. There is an abundance of examples for

Chapter 1 applications of the physicochemical aspects, including bonding between fibres in papermaking or swelling of the amorphous cellulose matrix by water. Swelling, for one, is a phenomenon of fundamental importance in papermaking, synthetics, and textile industry. 1.2 Molecular structure Cellulose is a linear homopolymer composed of (14)--glucopyranose. The name cellulose was coined by Anselme Payen, a French chemist, physicist and mathematician. Already in 1838, he suggested that the cell walls of almost any plant are constructed of the same substance.[1] It was not until the 20th century, however, some five years after Haworths discovery of the structure of cellobiose, the dimer of cellulose,[2] that the molecular structure was proposed by Sponsler and Dore in 1926.[3] Actually, Freudenberg had already suggested cellobiose as one of the main units (>60%) of cellulose as early as 1921.[4] The existence of cellobiose as the sole building block of cellulose was finally proved in 1930 by Haworth et al.[5] The work by Sponsler and Dore neglected some of the essential points of discussion, such as the chain arrangement, but it has, nevertheless, been the basis for practically any cellulose model ever since. The basis of the cellulose structure is the chair-conformed anhydroglucose unit whose number determines the degree of polymerization. Furthermore, cellulose chain has a direction since the terminal groups on the chain ends are different: non-reducing end with closed ring structure and reducing end with aliphatic structure and a carbonyl group in equilibrium with cyclic hemiacetals (Figure 1).[6,7]

OHHO

AnhydroglucoseO O OH OH HO OHn O

OH

Reducing end groupO HO OOH

OHOH

O H

HO

O

HO

OH

CellobioseFigure 1. The structure of cellulose. Anhydroglucose is the monomer of cellulose, cellobiose is the dimer. The cellulose chain has a direction, the other end being a closed ring structure and the other being an aliphatic reducing end in equilibrium with cyclic hemiacetals. There is a decisive distinction between cellulose and the monomer glucose. Glucose is a water-soluble carbohydrate with mutarotation of the hydroxyl group on the anomeric carbon,[8] whereas cellulose is an insoluble polymer with a rigid hydrogen bonding network. Virtually any property of glucose differs from cellulose. Already cellohexaose, consisting of six monomers, does not dissolve in water and the 13C NMR spectrum is close to that of cellulose.[9] Thirty anhydroglucose units is enough to represent the polymer cellulose in its structure and properties.

2

General Introduction 1.3 Supramolecular structure Crystalline cellulose comes in four different polymorphs named cellulose I, II, III, and IV. Cellulose I is the form found in nature and it occurs in two allomorphs, I and I. Cellulose II is the crystalline form that emerges after re-crystallization or mercerisation with aqueous sodium hydroxide.[10-12] Cellulose II is thermodynamically the most stable crystalline form. Cellulose IIII and IIIII are obtained by a liquid ammonia treatment of cellulose I and II, respectively[13-15] and cellulose IV is a result from heating cellulose III,[13] the transformation being usually partial.[16] In addition, cellulose is found abundantly in amorphous form, usually incorporated with cellulose I.[17-19] Controversially, the first published accounts on the supramolecular structure of native cellulose (cellulose I)[20] predate the determination of the molecular structure, only a year after von Laues discovery of X-ray diffraction[21,22] and in the same year as Bragg performed its first applications,[23] i.e. in 1913. It soon became evident that the supramolecular architecture offered big challenges compared with the relatively simple molecular structure of repeating anhydroglucose units. The first proper model for cellulose I was proposed by Meyer and Mark in 1928[24] and updated by Meyer and Misch in 1937.[25] The unit cell to emerge out of those studies is still used today for educational and practical purposes. Slightly improved but contr