NMR Spectroscopy of Polymers

Transcription

1 r NMR Spectroscopy of Polymers Edited by ROGER N. IBBETT Courtaulds Research and Technology Coventry BLACKIE ACADEMIC & PROFESSIONAL An Imprint of Chapman & Hall London Glasgow New York Tokyo Melbourne Madras

2 Contents Editorial introduction R.N. IBBETT xiii 1 Introduction to NMR and its use in the study of polymer stereochemistry 1 F. HEATLEY 1.1 Introduction Basic principles of NMR The form of a liquid-state NMR spectrum Chemical shifts Spin-spin (scalar) coupling Intensities in NMR spectra Spin-decoupling s Nuclear magnetic relaxation Basic principles Practical implications of relaxation The nuclear Overhauser effect in 13 C NMR Experimental practice in high-resolution solution-state NMR of polymers The spectrometer The sample Advanced Fourier transform techniques One-dimensional techniques Two-dimensional NMR spectroscopy A survey of applications of high-resolution solution-state NMR to polymers Determination of functional groups and composition of composite systems Determination of end-groups Statistical characterisation of the structure of irregular chains The observation of polymer stereochemistry (tacticity) by NMR Stereochemistry of vinyl polymers Application of 2-D techniques for the assignment of tacticity-related peaks Tacticity sequence statistics in vinyl polymers Stereochemistry of poly(epoxides) Geometrical isomerism in polydienes Summary 47 References 48 Statistical analysis of copolymer sequence distribution 50 I.R. HERBERT 2.1 Introduction 2.2 Copolymerisation statistics and models 50 51

3 Vlll CONTENTS Copolymer number-average sequence lengths and necessary relationships Statistical models Statistical models and polymer propagation Examples of the use of copolymer statistics Copolymers with Bernoullian sequence distributions Copolymers with first-order Markov sequence distributions Penultimate model polymers and complex participation Other copolymers In situ methods and simulation techniques Polymer modification Summary 77 References 78 Solution-state NMR determination of polymer end-groups, substituents and minor structures 80 J.C. BEVINGTON, J.R. EBDON and T.N. HUCKERBY 3.1 Introduction General remarks Comments on experimental procedures End-groups Introductory remarks Azo initiators Peroxides Other initiators Transfer agents and retarders Main-chain scission In-chain units Regioselectivity in growth reactions Abnormal units Branching General remarks Low density polyethylene Polymers from other vinyl monomers Amino and phenolic resins Polysiloxanes Chemical modification of polymers Synthetic polymers Natural polymers Concluding comments 121 References 121 Liquid state NMR studies of polymer dynamics and conformation 125 O.W. HOWARTH 4.1 Introduction NMR relaxation theory The flow of spin populations Microscopic relaxation theory Relaxation mechanisms jjfe> The dynamics of flexible molecules and macromolecules Applications The conformational states of polymers Relation of conformation to NMR properties 152

4 CONTENTS 4.5 Application of conformational theory to relaxation and NOE Experimental methods 158 References 159 IX High-resolution solid-state NMR studies of polymer chemical and physical structures 161 A.E. TONELLI 5.1 Introduction High-resolution NMR spectroscopy of solids Dipolar coupling Chemical shift anisotropy Cross-polarization Acquisition and analyses of solid-state 13 C NMR spectra Applications of high-resolution CPMAS/DD NMR to polymer solids NMR determination of crystalline polymer conformation Solid-state NMR observations of copolymer sequences and their distribution between crystalline and amorphous phases NMR observations of solid-state polymer reactions Solid-state NMR observation of polymer blends and interphases NMR observations of orientation in solid polymers Summary 195 References 195 High-resolution solid-state l3 CNMR studies of local motions and spin dynamics in bulk polymers 198 F. LAUPRETRE 6.1 Introduction "CNMR investigation of local dynamics in bulk polymers at temperatures well above the glass-transition temperature Models for local dynamics Experimental studies Temperature dependence Factors controlling the local dynamics Conclusion l3 CNMR investigation of local dynamics in bulk polymers at temperatures below the glass-transition temperature Chemical shift anisotropy Spectrum lineshape Relaxation times and linewidths C-'H dipolar interaction Conclusion CNMR study of the molecular organization of some solid heterogeneous polymer systems Conclusion 228 References 228 Solid-state proton NMR studies of polymers 231 A.M. KENWRIGHT and B.J. SAY 7.1 Introduction 7.2 Heterogeneity in solid polymers

5 X CONTENTS 7.3 Underlying theory: the dipolar interaction The static part Suppressing the dipolar interaction The non-static part Relaxation in heterogeneous systems Heteronuclear effects Experimental methods FID/lineshape measurement Longitudinal relaxation, 7\ Relaxation in the rotating frame, T l Experimental details Treatment of results Lineshape/FID analysis of polymers Semi-crystalline homopolymers Filled elastomers and block copolymers Glassy systems Highly mobile systems: melts Relaxation time analysis of polymers Spin diffusion in relaxation methods for polymers Attempts to observe spin diffusion directly Attempts to suppress spin diffusion in relaxation measurements High-resolution proton methods for polymers, MAS and CRAMPS Carbon detection of proton magnetisation Oriented polymers Conclusions 270 References 271 Deuterium NMR of synthetic polymers 275 D.M. RICE 8.1 Introduction Experimental theory Basic pulse sequences A vector model for spin 1 dynamics Experimental methods Polymer orientation Stretched films of poly(p-phenylene vinylene) Planar orientation of polyethylene terephthajate Polymer motion Ring-flip motion of poly(p-phenylene vinylene) Chain motion of poly(p-phenylene vinylene) Segmental dynamics of Nylon Multi-dimensional experiments Exchange spectra of isotactic polypropylene Chain motion of poly(vinylidene fluoride) Diffusive motion of atactic polypropylene near T g Conclusions 303 Acknowledgements 304 References 304 NMR in polymers using magnetic field gradients: ф imaging, diffusion and flow 308 P.T. CALLAGHAN 9.1 Introduction 9.2 Theory

6 CONTENTS Magnetic field gradients and NMR imaging Pulsed gradient spin echo NMR Dynamic NMR imaging Applications of NMR imaging in polymers Solid-state imaging Elastomer imaging and solvent imaging Monomer and solvent imaging Pulsed gradient spin echo diffusion studies in polymers Centre of mass diffusion in polymer liquids Internal motions in high polymers Diffusion of small molecules in polymer systems Flow studies using dynamic NMR imaging <j-space imaging of morphology in colloidal and polymeric systems Conclusions 339 References 339 XI 343