Orientation Behavior of Thermoplastic Elastomers Studied by ²H-NMR Spectroscopy

Abstract

In functionalized polybutadienes extended supramolecular junction zones are formed by self-aggregation of functional units via directed hydrogen bonds. The unusual 2 H-NMR lineshapes as well as the large quadrupolar splittings indicate highly oriented network chains in the stretched samples. Angular dependent measurements and inversion--recovery experiments prove the uniaxiality of the deformation and the homogeneity of the polymer backbone dynamics. A quantitative analysis of the lineshapes according to present theories is not possible but the spectra can be understood assuming a gradient of orientation alone individual network chains. For the highest strain ratios of λ>10 the 2H-NMR spectra give evidence of completely stretched chain segments which are located near the supramolecular clusters.The orientation behavior of elastomers has been studied extensively by means of a wide variety of different methods, e.g. FT-IR dichroism and strain birefringence. As a very powerful tool, 2 H-solid-state NMR was used to monitor dynamics and orientation on a molecular level simultaneously. Not only rigid (7 ) or liquid crystal (2 ) systems but also highly mobile materials such as elastomers (3 ) or even polymer melts (4 ) can be investigated. Mainly covalently endlinked PDMS networks were studied as models for 'ideal' networks. In order to understand the results of the NMR experiments different approaches have been developed based on short-range nematiclike orientational couplings (5), deformation behavior of single chains (6\ anisotropic junction fluctuations (7 ) or the effect of a screened potential (8 ). Turning towards more complex systems, the orientation behavior of statistically crosslinked polybutadienes and thermoplastic elastomers, such as poly(styrene-£-butadiene-ostyrene) block copolymers and segmented polyurethanes has also been investigated by means of 2 H-NMR (9 ).An unusual type of thermoreversible network was realized in flexible polydienes such as polybutadiene, which are attached by polar functional units (70 ).

Molecular Ordering and the Direct Measurement of Weak Proton−Proton Dipolar Interactions in a Rubber Network

“…In our second set of experiments, we have carried out a series of measurements of the residual dipolar interactions in a rubber sample at fixed orientation (θ o = 90°) but stretched over a range of extension ratios up to λ = 4. The experiments were performed using a specially constructed jig similar to that diagrammed in Figure of ref . The jig was used to controllably extend a rubber sample running through a solenoidal rf coil oriented normal to the magnetic field.…”

In Honor of Reimund Stadler

“…He finished his habilitation in Macromolecular Chemistry in 1988 and then moved, as an associate professor in Organic and Macromolecular Chemistry, to the Johannes Gutenberg-Universität Mainz, Institute of Organic Chemistry, in 1989, where he was later appointed to full professor in 1991 after declining an offer from Northwestern University in Chicago. During the years in Mainz his group continued to work on blends [16,17] and semi-interpenetrating networks, [18,19] polymers with hydrogen bonding groups, [17,[20][21][22][23][24][25][26][27][28][29][30][31][32][33] with strong influence on works of other teams at the same time and later on, [34][35][36][37] but also extended the chemistry on triazoline dions into the direction of Diels-Alder polymers, [38][39][40][41] developed a synthetic route to polydialkylaminoisoprenes, [42,43] block copolymers with This collection starts with a trend article by Nikos Hadjichristidis and Alejandro Müller and co-workers on the morphology, crystallization behavior and properties of multicrystalline polymer systems based on triple crystalline triblock terpolymers (1900292). This topic is very well aligned with Reimund Stadler's research interest in the field of block copolymers with at least one crystalizable block.…”

“…He finished his habilitation in Macromolecular Chemistry in 1988 and then moved, as an associate professor in Organic and Macromolecular Chemistry, to the Johannes Gutenberg‐Universität Mainz, Institute of Organic Chemistry, in 1989, where he was later appointed to full professor in 1991 after declining an offer from Northwestern University in Chicago. During the years in Mainz his group continued to work on blends and semi‐interpenetrating networks, polymers with hydrogen bonding groups, with strong influence on works of other teams at the same time and later on, but also extended the chemistry on triazoline dions into the direction of Diels–Alder polymers, developed a synthetic route to polydialkylaminoisoprenes, block copolymers with branched topologies, with a focus on linear ABC triblock copolymers, which actually started with their use as compatibilizers in a polymer blend …”