Chain Order and Cross-Link Density of Elastomers As Investigated by Proton Multiple-Quantum NMR

We present a quantitative study of local segmental order in vulcanized natural and butadiene rubber far above the glass transition. Network chain order is dependent on the density of cross-links and is here derived from proton homonuclear residual dipolar couplings measured by static multiple-quantum NMR spectroscopy at low field. On the basis of a reasonable model of local chain structure and fast, uniaxially symmetric local motions, spin dynamics simulations are used to investigate the relationship between the experimentally determined residual coupling and the order parameter of the polymer backbone. The model is verified by site-resolved determinations of inter- and intraresonance residual couplings at high field. For both types of rubber, it is found that the distributions of the chain order parameter are rather narrow and in all cases well explained by the local coupling topology, thus excluding distributions of end-to-end separations or network chains lengths as important sources of broadening. Thi...

[1]  M. Brereton.  NMR transverse relaxation function calculated for constrained polymer chains: application to entanglements and networks , 1990 .

[2]  Local Dynamics of cis-1,4-Polybutadiene and cis-1,4-Polyisoprene. A Comparative Study Based on Cooperative Kinematics Theory and NMR Experiments , 1999 .

[3]  D. Theodorou,et al.  Atomistic Monte Carlo simulation of cis-1,4 polyisoprene melts. II. Parallel tempering end-bridging Monte Carlo simulations , 2001 .

[4]  D. Demco,et al.  Selective residual dipolar couplings in cross-linked elastomers by 1H double-quantum NMR spectroscopy. , 1998, Solid state nuclear magnetic resonance.

[5]  B. Blümich,et al.  Residual dipolar couplings by 1H dipolar-encoded longitudinal magnetization, double- and triple-quantum nuclear magnetic resonance in cross-linked elastomers , 1999 .

[6]  P. Callaghan,et al.  A simplified approach to the interpretation of nuclear spin correlations in entangled polymeric liquids , 1997 .

[7]  A. Heuer,et al.  Chain-Order Effects in Polymer Melts Probed by 1H Double-Quantum NMR Spectroscopy , 1998 .

[8]  Grant D. Smith,et al.  United Atom Force Field for Molecular Dynamics Simulations of 1,4-Polybutadiene Based on Quantum Chemistry Calculations on Model Molecules , 1998 .

[9]  G. Simon,et al.  Network characterisation of end-linked poly(dimethylsiloxane) by 1H-NMR-spin-spin relaxation , 1989 .

[10]  M. Volkenstein,et al.  Statistical mechanics of chain molecules , 1969 .

[11]  W. Kuhn,et al.  Beziehungen zwischen elastischen Konstanten und Dehnungsdoppelbrechung hochelastischer Stoffe , 1942 .

[12]  K. Saalwächter.  Detection of heterogeneities in dry and swollen polymer networks by proton low-field NMR spectroscopy. , 2003, Journal of the American Chemical Society.

[13]  H. Montes,et al.  Evidence for a Linear NMR−Elasticity Interrelationship in Polymeric Gels , 1997 .

[14]  M. Abdel-Goad,et al.  Rheological Properties of 1,4-Polyisoprene over a Large Molecular Weight Range , 2004 .

[15]  P. Callaghan,et al.  Molecular Ordering and the Direct Measurement of Weak Proton−Proton Dipolar Interactions in a Rubber Network , 1997 .

[16]  R. Kimmich.  NMR: Tomography, Diffusometry, Relaxometry , 2001 .

[17]  D. Demco,et al.  TWO-DIMENSIONAL PROTON MAGNETIZATION-EXCHANGE NMR SPECTROSCOPY IN CROSS-LINKED ELASTOMERS , 1996 .

[18]  W. Stockmayer.  Theory of Molecular Size Distribution and Gel Formation in Branched Polymers II. General Cross Linking , 1944 .

[19]  P. Flory.  Statistical Mechanics of Swelling of Network Structures , 1950 .

[20]  P. Flory.  Principles of polymer chemistry , 1953 .

[21]  A. Tonelli,et al.  Crystal Structure and Melting Entropy of Natural Rubber , 2005 .

[22]  Walter H. Stockmayer,et al.  Theory of Molecular Size Distribution and Gel Formation in Branched‐Chain Polymers , 1943 .

[23]  M. Arroyo,et al.  Vulcanization kinetics of natural rubber–organoclay nanocomposites , 2003 .

[24]  M Bak,et al.  SIMPSON: a general simulation program for solid-state NMR spectroscopy. , 2000, Journal of magnetic resonance.

[25]  Wolfgang Paul,et al.  The role of internal rotational barriers in polymer melt chain dynamics , 2002 .

[26]  M. Arroyo,et al.  Preparation and characterization of organoclay nanocomposites based on natural rubber , 2003 .

[27]  R. Maxwell,et al.  Residual dipolar coupling for the assessment of cross-link density changes in γ-irradiated silica-PDMS composite materials , 2002 .

[28]  J. Sommer,et al.  Swelling Heterogeneities in End-Linked Model Networks: A Combined Proton Multiple-Quantum NMR and Computer Simulation Study , 2004 .

[29]  B. Blümich,et al.  Chain orientation and slow dynamics in elastomers by mixed magic-Hahn echo decays , 2003 .

[30]  J. Cohen-Addad,et al.  Molecular Motion Anisotropy as Reflected by a "Pseudosolid" Nuclear Spin Echo: Observation of Chain Constraints in Molten cis-1, 4-Polybutadiene , 1974 .

[31]  B. Blümich,et al.  Segmental and Local Chain Mobilities in Elastomers by 13C−1H Residual Heteronuclear Dipolar Couplings , 2004 .

[32]  B. Wolf,et al.  Solvent quality as reflected in concentration‐ and temperature‐dependent Flory–Huggins interaction parameters , 2001 .

[33]  M. Brereton.  NMR study of the molecular anisotropy induced in a strained rubber network , 1993 .

[34]  F. Grinberg,et al.  Influence of the cross-link density and the filler content on segment dynamics in dry and swollen natural rubber studied by the NMR dipolar-correlation effect , 1999 .

[35]  M. Klüppel,et al.  Chain order in filled SBR elastomers: a proton multiple-quantum NMR study , 2004 .

[36]  B. Haidar,et al.  1H multiple-quantum nuclear magnetic resonance investigations of molecular order distributions in poly(dimethylsiloxane) networks: Evidence for a linear mixing law in bimodal systems , 2003 .

[37]  J. Karger‐Kocsis,et al.  Melt compounded epoxidized natural rubber/layered silicate nanocomposites: structure-properties relationships , 2003 .

[38]  K. Saalwächter.  Artifacts in Transverse Proton NMR Relaxation Studies of Elastomers , 2005 .

[39]  J. E. Mark.  Random Coil Configurations of cis-l,4-Poly-Butadiene and cis-1,4-Polyisoprene. Theoretical Interpretation , 1966 .

[40]  E. Samulski,et al.  Nuclear Magnetic Resonance Line Shape from Strained Gaussian Networks , 1997 .

[41]  C. G. Fry,et al.  Determination of crosslink density in thermoset polymers by use of solid-state proton NMR techniques , 1988 .

[42]  M. Ries,et al.  Relationship between the transverse NMR decay and the dipolar interaction in elastomers: a comparison of two models , 2002 .