Chain-Order Effects in Polymer Melts Probed byH1Double-Quantum NMR Spectroscopy

Whither tube theory: From believing to measuring

“…After speaking about these results at various conferences it was pointed out to me [14] that experimentally the coupling between segmental orientation of di¤erent chains has been known for long time ( [15], [16], [17] and references therein); it was attributed to nematic interactions between the backbones [18]. However, our current model has only excluded volume interactions, which produce all the coupling (in agreement with assumptions of ref.…”

Radiation-Induced Cross-Linking in a Silica-Filled Silicone Elastomer As Investigated by Multiple Quantum 1H NMR

“…Static 1 H Multiple Quantum NMR methods which measure the residual dipolar couplings, in specific, hold much promise for such efforts. [13][14][15][16][17][18][19][20]24 In elastomeric materials, the residual dipolar couplings have been shown to be the result of topological constraints interfering with fast reorientations on the NMR timescale that otherwise would be expected to average homonuclear dipolar couplings to zero. 9 The residual dipolar couplings, in fact, have been shown to be quite sensitive to network and morphological changes and have been used to test theories of polymer structure, ordering, and dynamics.…”

“…p. 4 More recently, it has been reported that the characterization of the growth of multiple quantum coherences can provide detailed insight into silicone network structure by increasing the selectivity of the NMR experiment to the structure and dynamics most connected to the topology of the polymer network, including chain ordering at the surface of inorganic filler particles. [13][14][15][16][17][18][19][20][21][22][23][24] In addition, it has been shown that echo based methods can over estimate the residual dipolar couplings due to the effects of magnetic susceptibilities and field gradients due to internal microscopic voids and the inorganic filler. 28 These effects have been observed to be large enough to reverse trends of <Ω d > vs crosslink density at different fields.…”

“…As a result, MQ-NMR has been shown to be more selective to local network structure and dynamics. [13][14][15][16][17][18][19][20] Typical curves for the various network models are shown in Figure 4. A network behaving as a single network with a single residual dipolar coupling shown in Figure 4A and described by equation {3}.…”

Inter-Chain Cross-Correlation in Multi-Chain Slip-Link Simulations without Force Balance at Entanglements

“…The effect of cross-correlation between different chains in entangled polymers has been reported [1][2][3] and its contribution to rheology is not negligible [4][5][6] . In the tube model 7) and its extensions 8,9) , the test chain is assumed to move independently and the cross-correlation is not considered, at least explicitly.…”