Microscopic State of Polymer Network Chains upon Swelling and Deformation

Abstract

We use low-resolution proton NMR to probe the chain deformation in swollen and nonlinearly deformed vulcanized rubber and end-linked PDMS networks on a microscopic level, extending earlier work focusing on uniaxial stretching and isotropic dilation upon swelling toward biaxial deformation and deformation of swollen samples. Previous studies have revealed that chain deformation in bulk samples is best described by tube models, and that chains in swollen samples deform affinely after an initial desinterspersion stage, upon which entanglement-related packing effects are relieved. We test whether a subsequent deformation may also be closer to affine, and find that this is not the case. Unexpectedly, nonisotropic deformation of swollen samples also follows tube-model predictions, which is explained by a dominance of structural inhomogeneities and significant reorganization of the topological constraints active in the swollen and possibly even the bulk state.

Simulating Stress–Strain Behavior by Using Individual Chains: Uniaxial Deformation of Amorphous Cis- and Trans-1,4-Polybutadiene

“…The measurements show smaller shape changes for the PDMS chains, though the chains of lowest molecular weight (squares) are less far from exhibiting affine deformation. A similar deviation from affine deformation along an average polybutadiene chain during uniaxial deformation was reported by Naumova et al [ 30 ] via NMR measurements. Alternate approaches for simulating changes in conformation probability density would be necessary to achieve closer agreement with these shape changes that have been measured experimentally.…”

“…Instead, they suggested constraints of the tubes imposed by surrounding chains [ 3 , 27 , 28 , 29 ]. Similar results that favor the relatively smaller deformations of the tube model, compared to affine deformation, were shown for shear and compression of lightly cross-linked elastomers [ 30 ]. Alternate explanations were mentioned in support of heterogeneous distributions of local forces that rely on deforming only a small fraction of elastically active chains [ 30 ].…”

“…Similar results that favor the relatively smaller deformations of the tube model, compared to affine deformation, were shown for shear and compression of lightly cross-linked elastomers [ 30 ]. Alternate explanations were mentioned in support of heterogeneous distributions of local forces that rely on deforming only a small fraction of elastically active chains [ 30 ]. In summary, some NMR methods support local chain orientation changes in response to deformation.…”

Recent Progress in Double Network Elastomers: One Plus One is Greater Than Two

“…Since the discovery of natural rubber in the 18th century, elastomers have been widely applied in industry. [1][2][3][4] The explosive development of elastomers makes them ubiquitous in human life. [5][6][7][8] Nowadays, elastomers are manufactured into products with a high level of diversity and can be utilized almost everywhere, in the ocean or even in space.…”

Sulfobetaine Hydrogels with a Complex Multilength-Scale Hierarchical Structure

“…D res is directly proportional to the order parameter of the backbone S b , which in turn relates to the number of segments N of the network chains (thus their length) and to a possible local stretching of the network chains, for example, in a swollen network , …”