Neutron Spin Echo Spectroscopy Viscoelasticity Rheology

252 Pages·1997·5.383 MB·English

by  B. Ewen, D. Richter (auth.)

134
Advances in Polymer Science
A. Abe. H.-J. Cantow • P. Corradini • K. Du~ek • S. Edwards
H. Fujita • G. Gl6ckner • H. H6cker • H.-H. H6rhold
H.-H. Kausch • J. P. Kennedy. J. L. Koenig • A. Ledwith
J. E. McGrath • L. Monnerie • S. Okamura • C. G. Overberger
H. Ringsdorf • T. Saegusa • J. C. Salamone • J. L. Schrag • G. Wegner
Springer
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Neutron Spin EchoS pectroscopy
Viscoelasticity
Rheology
With contributions by
B. Ewen, M. Mours, D. Richter, T. Shiga, H. H. Winter
~ Springer
This series presents critical reviews of the present and future trends in polymer
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Editors
Prof. Akihiro Abe Prof. Dr. Hartwig H/~cker
Department of Industrial Chemistry Lehrstuhl ftir Textilchemie
Tokyo Institute of Polytechnics und Makromolekulare Chemie
1583 Iiyama, Atsugi 243-o2, Japan RWTH Aachen
Veltmanplatz 8
D-52o62 Aachen, FRG
Prof. Hans-Joachim Cantow
Freiburger Materialforschungszentrum
Prof. Hans-Heinrich H6rhold
Stefan Meier-Str. 3xa
D-791o4 Freiburg i. Br., FRG Friedrich-Schfller-Universit~it Jena
Institut fiir Organische
und Makromolekulare Chemie
Prof. Paolo Corradini
Lehrstuhl Organische Polymerchemie
Universit~ di Napoli Humboldtstr. lo
Dipartimento di Chimica D-o7743 Jena, FRG
Via Mezzocannone 4
80134 Napoli, Italy
Prof. Hans-Henning Kausch
Laboratoire de Polym~res
Prof. Karel Du]ek
Ecole Polytechnique F6d~rale
Institute of Macromolecular Chemistry, Czech de Lausanne, MX-D
Academy of Sciences CH-lo15 Lausanne, Switzerland
162o6 Prague 616, Czech Republic
E-mail: [email protected]
E-mail: [email protected]
Prof. Joseph P. Kennedy
Prof. Sam Edwards
Institute of Polymer Science
University of Cambridge The University of Akron
Department of Physics Akron, Ohio 44 325, USA
Cavendish Laboratory
Madingley Road
Cambridge CB30HE, UK Prof. Jack L. Koenig
Department of Macromolecular Science
Case Western Reserve University
Prof. Hiroshi Fujita
School of Engineering
35 Shimotakedono-cho Cleveland, OH 44106, USA
Shichiku, Kita-ku
Kyoto 6o3, Japan
Prof. Anthony Ledwith
Pilkington Brothers plc. R & D
Prof. Gottfried G16ckner
Laboratories, Lathom Ormskirk
Technische Universitiit Dresden Lancashire L4o SUF, UK
Sektion Chemie
Mommsenstr. 13
D-oxo69 Dresden, FRG
VI Editors
Prof. I. E. McGrath Prof. Takeo Saegusa
Polymer Materials and Interfaces Lab. KRI International
Virginia Polytechnic and State University Inc. Kyoto Research Park 17
Blacksburg Chudoji Minamima-chi
Virginia 24o61, USA Shimogyo-ku Kyoto 600, Japan
Prof. Lucien Monnerie Prof. J. C. Salamone
Ecole Superieure de Physique et de Chimie University of Lowell
Industrielles Department of Chemistry
Laboratoire de Physico-Chimie College of Pure and Applied Science
Structurale et Macromol&tdaire One University Avenue
lo, rue Vauquelin Lowell, MA 0a854, USA
75231 Paris Cedex 05, France
Prof. John L. Schrag
Prof. Seizo Okamura
University of Wisconsin
No. 24, Minamigoshi-Machi Okazaki Department of Chemistry
Sakyo-Ku, Kyoto 606, Japan 11o: University Avenue
Madison, Wisconsin 537o6, USA
Prof. Charles G. Overberger
Department of Chemistry Prof. G. Wegner
The University of Michigan Max-Planck-Institut ffir Polymerforschung
Ann Arbor, Michigan 48109, USA Ackermannweg :o
Postfach 3148
D-55128 Mainz, FRG
Prof. Helmut Ringsdorf
Institut ftir Organische Chemie
J ohannes-Gutenberg-Universit~it
J.-J.-Becher Weg 1S-2o
D-55128 Mainz, FRG
E-mail: [email protected]
Table of Contents
Neutron Spin Echo Investigations on the Segmental Dynamics
of Polymers in Melts, Networks and Solutions
B. Ewen, D. Richter ............................................
Deformation and Viscoelastic Behavior of Polymer Gels
in Electric Fields
T. Shiga ...................................................... 131
Rheology of Polymers Near Liquid-Solid Transitions
H. H. Winter, M. Mours ......................................... 165
Author Index Volumes 101 - 134 ................................. 235
Subject Index ................................................. 245
(cid:54) (cid:55)
Neutron Spin Echo Investigations on the
Segmental Dynamics of Polymers in Melts,
Networks and Solutions
B. Ewen(cid:49), D. Richter(cid:50)
(cid:49)MPI fu¨r Polymerforschung, Postfach 3148, 55021 Mainz, Germany
(cid:50)Institut fu¨r Festko¨rperforschung, Forschungszentrum Ju¨lich,
Postfach 1913, 52425 Ju¨lich, Germany
Neutronspinecho(NSE)spectroscopy,anadvancedhigh-resolutionquasi-elasticneutronscatter-
ingtechnique,providesthe unique opportunityto investigatelong-rangerelaxationprocessesof
macromoleculessimultaneouslyinspaceandtimeonnano-scales.Inparticular,informationonthe
single-chainbehaviorisnotrestrictedtodilutesolutions,butmayalsobeobtainedfromconcen-
tratedsolutionsandmelts,iflabellingbyprotondeuteriumexchangeisused.Thus,this method
facilitatesa directmicroscopic studyof molecularmodels developedto explainthemacroscopic
dynamicpropertiesofpolymers,e.g.transportandviscoelasticphenomena.
This article gives a short outline of the method and reviews the relevant experimental results
obtained from polymer melts and networks and from dilute and semi-dilute solutions of chain
moleculeswithdifferentarchitecturessincethefirstsuccessfulNSEworkonpolymerswaspublished
in1978.Theexperimentalobservationsarecomparedwiththepredictionsoftherelatedmicroscopic
modelsandothertheoreticalapproaches,whicharebrieflyintroducedandadaptedaccordingly.
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Quasi-ElasticNeutron Scattering . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Principles of the Method . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Neutron Spin Echo Technique. . . . . . . . . . . . . . . . . . . . . 6
2.2.1 Neutron Spin Manipulations with Magnetic Fields . . . . . 7
2.2.2 The Spin Echo Spectrometer . . . . . . . . . . . . . . . . . . 8
3 Polymer Motion in Dense Environments . . . . . . . . . . . . . . . . . 11
3.1 Rouse Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1 Theoretical Outline — The Rouse Model. . . . . . . . . . . . 12
3.1.2 NSE Observations on Rouse Dynamics . . . . . . . . . . . . 17
3.2 Transition from Rouse to Entanglement Controlled Dynamics. . 22
3.2.1 Mode Analysis and Generalized Rouse Model . . . . . . . . 24
3.2.2 NSE Results from the Transition Regime . . . . . . . . . . . 29
3.3 Entanglement Constraints in Long-Chain Polymer Melts. . . . . 36
3.3.1 Theoretical Outline — The Reptation or Tube Concept . . . 36
3.3.2 NSE Studies on Entangled Polymer Melts . . . . . . . . . . 43
3.4 On the Origin of EntanglementFormation . . . . . . . . . . . . . 52
3.4.1 Models for Entanglement Formation. . . . . . . . . . . . . . 52
3.4.2 NSE Experiments on EntanglementFormation . . . . . . . 55
Advancesin PolymerScience,Vol.134
(cid:40)Springer-VerlagBerlinHeidelberg1997
2 B.EwenandD.Richter
4 Polymer Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.1 Theoretical Outline — Dynamics of Junctions and Trapped Linear
Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.2 NSE Results from Polymer Networks . . . . . . . . . . . . . . . . 60
5 Polymer Dynamics in the Presence of a Solvent . . . . . . . . . . . . . 64
5.1 Dilute Solution of Linear Polymers. . . . . . . . . . . . . . . . . . 65
5.1.1 Theoretical Outline — The Zimm Model. . . . . . . . . . . . 65
5.1.2 NSE Results from Dilute Solutions of Linear Polymers. . . 78
5.2 Dilute Solutions of Cyclic Polymers. . . . . . . . . . . . . . . . . . 89
5.3 Dilute Solutions of Star-Shaped Polymers. . . . . . . . . . . . . . 90
5.3.1 Theoretical Outline — Influence of the Static Structure
on the Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.3.2 NSE Results from Stars in Dilute Solution . . . . . . . . . . 96
5.4 Semi-Dilute Solutions of Linear Homopolymers . . . . . . . . . . 109
5.4.1 Theoretical Outline — Collective Diffusion and Screening
of Hydrodynamic Interactions. . . . . . . . . . . . . . . . . . 109
5.4.2 NSE Results from Semi-Dilute Solutions of Linear
Homopolymers. . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.5 Semi-dilute Solutions of Polymer Blends and Block Copolymers 120
5.5.1 Theoretical Outline — The Interdiffusion Mode. . . . . . . . 120
5.5.2 NSE Results from Polymer Blends and Block Copolymers. 122
5.6 Collective Diffusion of Tethered Chains . . . . . . . . . . . . . . . 123
6 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
2
NeutronSpinEchoInvestigationsontheSegmentalDynamics 3
1 Introduction
Viscoelasticandtransportpropertiesofpolymersintheliquid(solution,melt)or
liquid-like (rubber) state determine their processing and application to a large
extent and are of basic physical interest [1—3]. An understanding of these
dynamic properties at a molecular level, therefore, is of great importance.
However,thisunderstandingiscomplicatedbythefactsthatdifferentmotional
processes may occur on different length scales and that the dynamics are
governed by universal chain properties as well as by the special chemical
structure of the monomer units [4,5].
The earliest and simplest approach in this direction starts from Langevin
equations with solutions comprising a spectrum of relaxation modes [1—4].
Special features are the incorporation of entropic forces (Rouse model, [6])
whichrelaxfluctuationsofreducedentropy,andofhydrodynamicinteractions
(Zimm model, [7]) which couple segmental motions via long-range backflow
fields in polymer solutions, and the inclusion of topological constraints or
entanglements (reptation or tube model, [8—10]) which are mutually imposed
within a dense ensemble of chains.
Another approach, neglecting the details of the chemical structure and
concentratingontheuniversalelementsofchainrelaxation,isbasedondynamic
scalingconsiderations[4,11].Inparticularinpolymersolutions,thisapproach
offers an elegant tool to specify the general trends of polymer dynamics,
although it suffers from the lack of a molecular interpretation.
A real test of these theoretical approaches requires microscopic methods,
whichsimultaneously give direct access to the space and time evolutionof the
segmental diffusion. Here, quasi-elastic scattering methods play a crucial role
sincetheyallowthemeasurementofthecorrespondingcorrelationfunctions.In
particular,thehigh-resolutionneutronspinecho(NSE)spectroscopy[12—15]is
very suitable for such investigations since this method covers an appropriate
range in time (0.005)t/ns)40) and space (r/nm (cid:91)15). Furthermore, the
possibilityoflabellingbyhydrogen-deuteriumexchangeallowstheobservation
of single-chain behavior even in the melt.
ThispaperreviewsNSEmeasurements onpolymermelts,networksandsolu-
tions, published since the first successful NSE study on polymers [16] was per-
formedin1978.Theexperimentalobservationsarediscussedintheframeworkof
related microscopic models,scaling predictionsor other theoretical approaches.
Thepaper is organizedin the following way: In Section2, theprinciplesof
quasi-elastic neutron scattering are introduced, and the method of NSE is
shortly outlined. Section 3 deals with the polymer dynamics in dense environ-
ments, addressing in particular the influence and origin of entanglements. In
Section4, polymer networks are treated. Section5 reports on the dynamics of
linearhomo-andblockcopolymers,ofcyclicandstar-shapedpolymersindilute
and semi-dilute solutions, respectively. Finally, Section 6 summarizes the con-
clusions and gives an outlook.
3