CRC handbook of thermodynamic data of aqueous polymer solutions

515 Pages·2004·1.77 MB·English

by  C Wohlfarth

C R C H A N D B O O K O F
T
HERMODYNAMIC
D
of
ATA
A
QUEOUS
P
OLYMER
S
OLUTIONS
Christian Wohlfarth
CRC Press
Boca Raton London New York Washington, D.C.
© 2004 by CRC Press LLC
Library of Congress Cataloging-in-Publication Data
Wohlfarth, C.
CRC handbook of thermodynamic data of aqueous polymer solutions / by
Christian Wohlfarth.
p. cm.
Includes bibliographical references and index.
ISBN 0-8493-2174-3 (alk. paper)
1. Polymer solutions--Thermal properties--Handbooks, manuals, etc. 2.
Copolymers--Thermal properties--Handbooks, manuals, etc. 3. I. Title
QD381.9.S65W633 2003
547(cid:145).70454(cid:151)dc22 2003055693
This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with
permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish
reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials
or for the consequences of their use.
Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, micro(cid:222)lming, and recording, or by any information storage or retrieval system, without prior
permission in writing from the publisher.
The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works,
or for resale. Speci(cid:222)c permission must be obtained in writing from CRC Press LLC for such copying.
Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431.
Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for
identi(cid:222)cation and explanation, without intent to infringe.
Visit the CRC Press Web site at www.crcpress.com
' 2004 by CRC Press LLC
No claim to original U.S. Government works
International Standard Book Number 0-8493-2174-3
Library of Congress Card Number 2003055693
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper
© 2004 by CRC Press LLC
Foreword
The knowledge of thermodynamic data of aqueous polymer solutions is important for basic and
applied chemistry and chemical engineering, computational modelling and thermodynamic research. It has
many applications in the fields of biotechnology, membrane science and membrane technology,
environmental and green chemistry, food chemistry and food industry.
Among the existing publications in this field are C. Wohlfarth’s own book Vapor-Liquid
Equilibria of Binary Polymer Solutions (Elsevier, 1994) and his recent CRC Handbook of Thermo-
dynamic Data of Copolymer Solutions (CRC Press, 2001). Liquid-liquid equilibrium data can be found in
Albertson’s book Partition of Cell Particles and Macromolecules (Wiley, 1986), and more recently in
Zaslavsky’s book Aqueous Two-Phase Partitioning. Physical Chemistry and Bioanalytical Applications
(Dekker, 1995). All these data are fairly old and cover a limited number of properties and chemical
systems that represent only a minor portion in comparison with this new book. Commercial electronic
databases do not provide such data. This Handbook offers a new and complete collection on
thermodynamic data of aqueous polymer solutions.
This new book contains low- and high-pressure equilibrium data, vapor-liquid equilibria, liquid-
liquid equilibria, enthalpic and volumetric data, as well as second virial coefficients. This covers all the
necessary areas for researchers and engineers who work in this field. It will help users to retrieve quickly
all the relevant information from the original literature and also help researchers to plan new
measurements where data are missing.
The structure and the contents of this book are organized in a similar way as in the CRC
Handbook of Thermodynamic Data of Copolymer Solutions and this will facilitate the extraction of the
desired new data.
Last but not least, author C. Wohlfarth has been known for his experience in thermodynamics of
polymer solutions for more than 20 years.
I am sure that readers interested in the field of thermodynamic properties of polymer solutions
will benefit from this Handbook and will identify the work that has to be done in the future.
Dr. Henry V. Kehiaian
IUPAC Representative on ICSU Committee on
Data for Science and Technology (CODATA)
© 2004 by CRC Press LLC
PREFACE
Knowledge of thermodynamic data of polymer solutions is a necessity for industrial and
laboratory processes. Such data serve as essential tools for understanding the physical behavior of
polymer solutions, for studying intermolecular interactions, and for gaining insights into the molecular
nature of mixtures. They also provide the necessary basis for any developments of theoretical
thermodynamic models. Scientists and engineers in academic and industrial research need such data and
will benefit from a careful collection of existing data. The CRC Handbook of Thermodynamic Data of
Aqueous Polymer Solutions provides a reliable collection of such data for such polymer solutions from the
original literature.
The Handbook is divided into seven chapters: (1) Introduction, (2) Vapor-Liquid Equilibrium
(VLE) Data of Aqueous Polymer Solutions, (3) Liquid-Liquid Equilibrium (LLE) Data of Aqueous
Polymer Solutions, (4) High-Pressure Phase Equilibrium (HPPE) Data of Aqueous Polymer Solutions, (5)
Enthalpy Changes for Aqueous Polymer Solutions, (6) PVT Data of Polymers and Solutions, and (7)
Second Virial Coefficients (A ) of Aqueous Polymer Solutions. Finally, appendices quickly route the user
2
to the desired data sets. Thus, the book covers all the necessary areas for researchers and engineers who
work in this field.
In comparison with low-molecular systems, the amount of data for aqueous polymer solutions is
still rather small. About 800 literature sources were perused for the purpose of this handbook, including
some dissertations and diploma papers. About 1000 data sets, i.e., 165 vapor-pressure isotherms, a
number of Henry’s constants, 500 LLE and a small number of HPPE data sets, a number of volumetric
and enthalpic data and some second osmotic virial coefficients, are reported. Additionally, tables of
systems are provided where results were published only in graphical form in the original literature to lead
the reader to further sources. Data are included only if numerical values were published or authors
provided their numerical results by personal communication (and I wish to thank all those who did so). No
digitized data have been included in this data collection. The Handbook is the first complete overview
about this subject in the world’s literature. The closing day for the data collection was May 31, 2003. The
Handbook results from parts of a more general database, Thermodynamic Properties of Polymer Systems,
which is continuously updated by the author. Thus, the user who is in need of new additional data sets is
kindly invited to ask for new information beyond this book via e-mail at [email protected].
Additionally, the author will be grateful to users who call his attention to mistakes and make suggestions
for improvements.
The CRC Handbook of Thermodynamic Data of Aqueous Polymer Solutions will be useful to
researchers, specialists, and engineers working in the fields of polymer science, physical chemistry,
chemical engineering, material science, biological science and technology, and those developing
computerized predictive packages. The Handbook should also be of use as a data source to Ph.D. students
and faculty in Chemistry, Physics, Chemical Engineering, Biotechnology, and Materials Science
Departments at universities.
Christian Wohlfarth
Merseburg, August 2003
© 2004 by CRC Press LLC
About the Author
Christian Wohlfarth is Associate Professor for Physical Chemistry at Martin Luther University
Halle-Wittenberg, Germany. He earned his degree in Chemistry in 1974 and wrote his Ph.D. thesis on
investigations on the second dielectric virial coefficient and the intermolecular pair potential in 1977, both
at Carl Schorlemmer Technical University Merseburg. In 1985, he wrote his habilitation thesis, Phase
Equilibria in Systems with Polymers and Copolymers, at Technical University Merseburg.
Since then, Dr. Wohlfarth’s main research has been related to polymer systems. Currently, his
research topics are molecular thermodynamics, continuous thermodynamics, phase equilibria in polymer
mixtures and solutions, polymers in supercritical fluids, PVT-behavior and equations of state, and sorption
properties of polymers, about which he has published approximately 100 original papers. He has also built
a database, Thermodynamic Properties of Polymer Systems, and has written the books Vapor-Liquid
Equilibria of Binary Polymer Solutions and CRC Handbook of Thermodynamic Data of Copolymer
Solutions.
He is working on the evaluation, correlation, and calculation of thermophysical properties of pure
compounds and binary mixtures resulting in six volumes of the Landolt-Börnstein New Series. He is a
respected contributor to the CRC Handbook of Chemistry and Physics.
© 2004 by CRC Press LLC
CONTENTS
1. INTRODUCTION
1.1. Objectives of the handbook
1.2. Experimental methods involved
1.3. Guide to the data tables
1.4. List of symbols
1.5. References
2. VAPOR-LIQUID EQUILIBRIUM (VLE) DATA
OF AQUEOUS POLYMER SOLUTIONS
2.1. Partial water vapor pressures or water activities
for binary polymer solutions
2.2. Partial solvent vapor pressures or solvent activities
for ternary aqueous polymer solutions
2.3. Classical mass-fraction Henry’s constants of water vapor
in molten polymers
2.4. References
3. LIQUID-LIQUID EQUILIBRIUM (LLE) DATA
OF AQUEOUS POLYMER SOLUTIONS
3.1. Cloud-point and/or coexistence curves of quasibinary solutions
3.2. Table of systems where binary LLE data were published only in
graphical form as phase diagrams or related figures
3.3. Cloud-point and/or coexistence curves of quasiternary solutions
containing water and at least one polymer
3.3.1. Nonelectrolyte solutions
3.3.2. Electrolyte solutions
3.4. Table of systems where ternary LLE data were published only in
graphical form as phase diagrams or related figures
3.5. Cloud-point and/or coexistence curves of quasiquaternary solutions
containing water and at least one polymer
3.5.1. Nonelectrolyte solutions
3.5.2. Electrolyte solutions
3.6. Table of systems where quaternary LLE data were published only in
graphical form as phase diagrams or related figures
3.7. Lower critical (LCST) and/or upper critical (UCST) solution temperatures
of aqueous polymer solutions
3.8. References
© 2004 by CRC Press LLC
4. HIGH-PRESSURE PHASE EQUILIBRIUM (HPPE) DATA
OF AQUEOUS POLYMER SOLUTIONS
4.1. Experimental data of quasibinary polymer solutions
4.2. Table of systems where binary HPPE data were published only
in graphical form as phase diagrams or related figures
4.3. Experimental data of quasiternary solutions containing water
and at least one polymer
4.4. Table of systems where ternary HPPE data were published only
in graphical form as phase diagrams or related figures
4.5. References
5. ENTHALPY CHANGES FOR AQUEOUS POLYMER SOLUTIONS
5.1. Enthalpies of mixing or intermediary enthalpies of dilution,
and polymer partial enthalpies of mixing (at infinite dilution),
or polymer (first) integral enthalpies of solution
5.2. Partial molar enthalpies of mixing at infinite dilution of water
and enthalpies of solution of water vapor in molten polymers
from inverse gas-liquid chromatography (IGC)
5.3. Table of systems where additional information on enthalpy effects
in aqueous polymer solutions can be found
5.4. References
6. PVT DATA OF POLYMERS AND SOLUTIONS
6.1. PVT data of some polymers and their aqueous solutions
6.2. Excess volumes and/or densities of aqueous polymer solutions
6.3. Table of systems where additional information on volume effects
in aqueous polymer solutions can be found
6.4. References
7. SECOND VIRIAL COEFFICIENTS (A )
2
OF AQUEOUS POLYMER SOLUTIONS
7.1. Experimental A data
2
7.2. References
APPENDICES
Appendix 1 List of systems and properties in order of the polymers
Appendix 2 List of solvents in alphabetical order
Appendix 3 List of solvents in order of their molecular formulas
© 2004 by CRC Press LLC
1. INTRODUCTION
1.1. Objectives of the handbook
Knowledge of thermodynamic data of aqueous polymer solutions is a necessity for industrial and
laboratory processes. Furthermore, such data serve as essential tools for understanding the physical
behavior of polymer solutions, for studying intermolecular interactions, and for gaining insights into the
molecular nature of mixtures. They also provide the necessary basis for any developments of theoretical
thermodynamic models. Scientists and engineers in academic and industrial research need such data and
will benefit from a careful collection of existing data. However, the database for polymer solutions is still
modest in comparison with the enormous amount of data for low-molecular mixtures, and the specialized
database for aqueous polymer solutions is even smaller. On the other hand, aqueous polymer solutions are
gaining increasing commercial interest because of their unique physical properties, and thermodynamic
data are needed for optimizing applications, e.g., separations of complex mixtures of biomolecules,
recovery of antibiotics, precipitation and purification of proteins, separation of lignins from cellulose in
the paper pulping process, extraction of radioactive metal ions like strontium, cesium, actinides or
lanthanides from aqueous systems, formation of membranes, spinning fibers into aqueous media, or
thermoseparating polymers.
Basic information on polymers can be found in the Polymer Handbook (1999BRA). Some data
books on polymer solutions appeared in the early 1990s (1990BAR, 1992WEN, 1993DAN, and
1994WOH), but most data for polymer solutions have been compiled during the last decade. Older liquid-
liquid equilibrium data for aqueous polymer systems were collected in some books dedicated to the
separation of biomolecules by aqueous two-phase systems (1985WAL, 1986ALB, and 1995ZAS). A data
book with information on copolymer solutions appeared in 2001 (2001WOH). No databooks or databases
dedicated specially to aqueous polymer solutions presently exist. Thus, the intention of the Handbook is to
fill this gap and to provide scientists and engineers with an up-to-date compilation from the literature of
the available thermodynamic data on aqueous polymer solutions. The Handbook does not present theories
and models for polymer solution thermodynamics. Other publications (1971YAM, 1990FUJ, 1990KAM,
1999KLE, 1999PRA, and 2001KON) can serve as starting points for investigating those issues. Theories
for aqueous two-phase systems are reviewed by Cabezas (1996CAB). The state of the art for surfactants
and polymers in aqueous solutions is summarized by Holmberg et al. (2003HOL).
The data within this book are divided into six chapters:
• Vapor-liquid equilibrium (VLE) data of binary or ternary aqueous polymer solutions
• Liquid-liquid equilibrium (LLE) data of (quasi) binary, ternary, or quaternary
aqueous polymer solutions
• High-pressure phase equilibrium (HPPE) data of aqueous polymer solutions
• Enthalpy changes for aqueous polymer solutions
• PVT data of polymers and their aqueous solutions as well as excess volumes and
densities
• Second virial coefficients (A ) of aqueous polymer solutions
2
Data from investigations applying to more than one chapter are divided and appear in the relevant
chapters. Data are included only if numerical values were published or authors provided their results by
personal communication (and I wish to thank all those who did so). No digitized data have been included
in this data collection, but some tables include systems data published in graphical form.
© 2004 by CRC Press LLC
____________________________________________________________________________________
1.2. Experimental methods involved
Vapor-liquid equilibrium (VLE) measurements
Investigations on vapor-liquid equilibrium of polymer solutions can be made by various methods:
1. Absolute vapor pressure measurement
2. Differential vapor pressure measurement
3. Isopiestic sorption/desorption methods, i.e., gravimetric sorption, piezoelectric sorption,
or isothermal distillation
4. Inverse gas-liquid chromatography (IGC) at infinite dilution, IGC at finite concentrations,
and headspace gas chromatography (HSGC)
5. Steady-state vapor-pressure osmometry (VPO)
Experimental techniques for vapor pressure measurements were reviewed in 1975BON and
2000WOH. Methods and results of the application of IGC to polymers and polymer solutions were
reviewed in 1976NES, 1988NES, 1989LLO, 1989VIL, and 1991MU1. Reviews on ebulliometry and/or
vapor-pressure osmometry can be found in 1974TOM, 1975GLO, 1987COO, 1991MAY, and 1999PET.
The measurement of vapor pressures for polymer solutions is generally more difficult and more
time-consuming than that of low-molecular mixtures. The main difficulties can be summarized as follows:
Polymer solutions exhibit strong negative deviations from Raoult’s law. These are mainly due to the large
entropic contributions caused by the difference between the molar volumes of solvents and polymers as
was explained by the classical Flory-Huggins theory about 60 years ago. However, because of this large
difference in molar mass, vapor pressures of dilute solutions do not differ markedly from the vapor
pressure of the pure solvent at the same temperature, even at polymer concentrations of 10-20 wt%. This
requires special techniques to measure very small differences in solvent activities. Concentrated polymer
solutions are characterized by rapidly increasing viscosities with increasing polymer concentration. This
leads to a strong increase in time required to obtain real thermodynamic equilibrium caused by slow
solvent diffusion effects (in or out of a non-equilibrium-state polymer solution). Furthermore, only the
solvent coexists in both phases because polymers do not evaporate. The experimental techniques used for
the measurement of vapor pressures of polymer solutions have to take into account all these effects.
Vapor pressures of polymer solutions are usually measured in the isothermal mode by static
methods. Dynamic methods are seldom applied, e.g., ebulliometry (1975GLO and 1987COO). At least,
one can consider measurements by VPO to be dynamic ones, where a dynamic (steady-state) balance is
obtained. Limits for the applicable ranges of polymer concentration and polymer molar mass, limits for
the solvent vapor pressure and the measuring temperature and some technical restrictions prevent its
broader application, however. Static techniques usually work at constant temperature. The three different
methods (1 through 3 above) were used to determine most of the vapor pressures of polymer solutions in
the literature. All three methods have to solve the problems of establishing real thermodynamic
equilibrium between liquid polymer solution and solvent vapor phase, long-time temperature constancy
during the experiment, determination of the final polymer concentration, and determination of pressure
and/or activity. Absolute vapor pressure measurement and differential vapor pressure methods were
mostly used by early workers. Most recent measurements were done with the isopiestic sorption methods.
Gas-liquid chromatography as IGC closes the gap at high polymer concentrations where vapor pressures
cannot be measured with sufficient accuracy. HSGC can be considered as some combination of absolute
vapor pressure measurement with GLC.
The following text (a short summary from the author’s own review, 2000WOH) explains briefly
the usual experimental equipment and the measuring procedures.
© 2004 by CRC Press LLC
____________________________________________________________________________________
1. Absolute vapor pressure measurement
Absolute vapor pressure measurement can be considered the classical technique for this purpose,
because one measures directly the vapor pressure above a solution of known polymer concentration. The
literature gives a variety of absolute vapor pressure apparatuses developed and used by different authors.
Vapor pressure measurement and solution equilibration were often made separately. A polymer sample is
prepared by weighing, the sample flask is evacuated, degassed solvent is introduced into a sample flask
that is sealed thereafter. Samples are equilibrated at elevated temperature in a thermostatted bath for some
weeks. The flask with the equilibrated polymer solution is then connected with the pressure-measuring
device at the measuring temperature. The vapor pressure is measured after reaching equilibrium and the
final polymer concentration is obtained after correcting for the amount of evaporated solvent. Modern
equipment applies electronic pressure sensors and digital technique to measure the vapor pressure. Data
processing can then be made online by computers. A number of problems have to be solved during the
experiment. The solution is usually of an amount of some cm3 and may contain about 1g of polymer or
even more. Degassing is absolutely necessary. All impurities in the pure solvent have to be eliminated.
Equilibration of all prepared solutions is very time consuming (liquid oligomers do not need so much
time, of course). Increasing viscosity makes the preparation of concentrated solutions more and more
difficult with further increasing the amount of polymer. Solutions above 50-60 wt% can hardly be
prepared (depending on the solvent/polymer pair under investigation).
The determination of the volume of solvent vaporized in the unoccupied space of the apparatus is
difficult and can cause serious errors in the determination of the final solvent concentration. To
circumvent the vapor phase correction, one can measure the concentration directly by means, for example,
of a differential refractometer. The contact of solvent vapor with the Hg surface in older equipment may
cause further errors. Complete thermostatting of the whole apparatus is necessary to avoid condensation of
solvent vapor at colder spots. Since it is disadvantageous to thermostat Hg manometers at higher
temperatures, null measurement instruments with pressure compensation were sometimes used. Modern
electronic pressure sensors can be thermostatted within certain temperature ranges. If pressure
measurement is made outside the thermostatted equilibrium cell, the connecting tubes must be heated
slightly above the equilibrium temperature to avoid condensation.
The measurement of polymer solutions with lower polymer concentrations requires very precise
pressure instruments, because the difference to the pure solvent vapor pressure becomes very small with
decreasing amount of polymer. A common consistency test on the basis of the integrated Gibbs-Duhem
equation does not work for vapor pressure data of binary polymer solutions because the vapor phase is
pure solvent vapor. Thus, absolute vapor pressure measurements need very careful handling, plenty of
time and an experienced experimentator. They are not the methods of choice for highly viscous polymer
solutions, and they were seldom applied to aqueous polymer solutions.
2. Differential vapor pressure measurement
The differential method can be compared under some aspects with the absolute method, but it has
some advantages. The measuring principle is to obtain the vapor pressure difference between the pure
solvent and the polymer solution at the measuring temperature. Again, the polymer sample is filled, after
weighing, into a sample flask, the apparatus is evacuated, a desired amount of degassed solvent is distilled
into the sample flask to build the solution and the samples have to be equilibrated for a necessary duration
of time. The complete apparatus is kept at constant measuring temperature and, after reaching equilibrium,
the pressure difference is read from the manometer difference and the concentration is calculated after
correcting the amount of vaporized solvent in the unoccupied space of the equipment. The pure solvent
vapor pressure is usually precisely known from independent experiments.
© 2004 by CRC Press LLC