Polymer dynamics and relaxation / Richard H. Boyd, Grant D. Smith.

Format:

Book

Author/Creator:

Boyd, Richard H. (Richard Hays), 1929-

Contributor:

Smith, Grant D., 1967-

Language:

English

Subjects (All):

Polymers.

Polymers--Structure.

Molecular dynamics.

Physical Description:

x, 255 pages : illustrations ; 26 cm

Place of Publication:

Cambridge ; New York : Cambridge University Press, 2007.

Summary:

Polymers exhibit a range of physical characteristics, from rubber-like elasticity to the glassy state. These particular properties are controlled at the molecular level by the mobility of the structural constituents. Remarkable changes in mobility can be witnessed with temperature, over narrow, well-defined regions, termed relaxation processes. This is an important, unique phenomenon controlling polymer transition behavior and is described here at an introductory level. The important types of relaxation processes from amorphous to crystalline polymers and polymeric miscible blends are covered, in conjunction with the broad spectrum of experimental methods used to study them. In-depth discussions of molecular level interpretation, including recent advances in atomistic level computer simulations and applications to molecular mechanism elucidation, are provided. The result is a self-contained, up-to-date approach to polymeric interpretation, suitable for researchers and graduate students in materials science, physics, and chemistry, interested in the relaxation processes of polymeric systems.

Contents:

Part I Methodology 1

1 Mechanical relaxation 3

1.1 Regimes of behavior 3

1.2 Superposition principle 5

1.3 Relaxation modulus 5

1.4 Simple stress relaxation 6

1.5 Dynamic modulus 7

1.6 Interconversion of stress relaxation and dynamic modulus 9

1.7 Representation of the relaxation function: single relaxation time (SRT) 11

1.8 Relaxations in polymeric materials tend to be "broad" 13

1.9 Distribution of relaxation times 14

1.10 Relaxation spectrum from E[subscript R](t) 15

1.11 Creep compliance 18

1.12 Dynamic compliance 19

1.13 Representation of the retardation function 21

1.14 Summary of the data transformations illustrated 22

Appendix A1 A brief summary of elasticity 23

2 Dielectric relaxation 27

2.1 Dielectric permittivity 27

2.2 Measurement of dielectric permittivity 30

2.3 Time dependence of polarization: reorientation of permanent dipoles 31

2.4 Polarization and permittivity in time dependent electric fields 33

2.5 Empirical representations of the dielectric permittivity 35

3 NMR spectroscopy 44

3.1 NMR basics 45

3.2 The pulsed NMR method 47

3.3 NMR relaxation measurements 49

3.4 NMR exchange spectroscopy 54

4 Dynamic neutron scattering 57

4.1 Neutron scattering basics 57

4.2 Time-of-flight (TOF) and backscattering QENS 63

4.3 Neutron spin echo (NSE) spectroscopy 66

5 Molecular dynamics (MD) simulations of amorphous polymers 70

5.1 A brief history of atomistic MD simulations of amorphous polymers 70

5.2 The mechanics of MD simulations 71

5.3 Studying relaxation processes using atomistic MD simulations 75

5.4 Classical atomistic force fields 76

Part II Amorphous polymers 81

6 The primary transition region 83

6.1 Mechanical relaxation 83

6.2 Dielectric relaxation 90

6.3 Mechanical vs. dielectric relaxation 96

6.4 NMR relaxation 104

6.5 Neutron scattering 110

7 Secondary (subglass) relaxations 120

7.1 Occurrence of mechanical and dielectric secondary processes 120

7.2 Complexity and multiplicity of secondary processes 121

7.3 Flexible side group motion as a source of secondary relaxation 129

7.4 NMR spectroscopy studies of flexible side group motion 138

8 The transition from melt to glass and its molecular basis 142

8.1 Experimental description 142

8.2 Molecular basis 157

Part III Complex systems 197

9 Semi-crystalline polymers 199

9.1 Phase assignment 200

9.2 Effect of crystal phase presence on amorphous fraction relaxation 209

9.3 Relaxations in semi-crystalline polymers with a crystal phase relaxation 214

9.4 NMR insights 223

10 Miscible polymer blends 227

10.1 Poly(isoprene)/poly(vinyl ethylene) (PI/PVE) blends 228

10.2 Models for miscible blend dynamics 229

10.3 MD simulations of model miscible blends 233

10.4 PI/PVE blends revisited 239

Appendix AI The Rouse model 244

AI.1 Formulation and normal modes 244

AI.2 Establishment of Rouse parameters for a real polymer 245

AI.3 The viscoelastic response of a Rouse chain 245

AI.4 Bead displacements and the coherent single-chain structure factor 246

Appendix AII Site models for localized relaxation 248

AII.1 Dipolar relaxation in terms of site models 248

AII.2 Mechanical relaxation in terms of site models 251.

Notes:

Includes bibliographical references and index.

ISBN:

9780521814195

0521814197

OCLC:

144226144