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Cross-examining Polyurethane Nanodomain Formation and Internal Structure.

ABSTRACT: Structural and morphological interplay between hard and soft phases determine the bulk properties of thermoplastic polyurethanes. Commonly employed techniques rely on different physical or chemical phenomena for characterizing the organization of domains, but detailed structural information can be difficult to derive. Here, total scattering pair distribution function (PDF) analysis is used to determine atomic-scale insights into the connectivity and molecular ordering and compared to the domain size and morphological characteristics measured by AFM, TEM, SAXS, WAXS, and solid-state NMR 1H-1H spin-diffusion. In particular, density distribution functions are highlighted as a means to bridging the gap from the domain morphology to intradomain structural ordering. High real-space resolution PDFs are shown to provide a sensitive fingerprint for indexing aromatic, aliphatic, and polymerization-induced bonding characteristics, as well as the hard phase structure, and indicate that hard phases coexist in both ordered and disordered states.

SUBMITTER: Terban MW

PROVIDER: S-EPMC7594411 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Cross-examining Polyurethane Nanodomain Formation and Internal Structure.

Terban Maxwell W MW Seidel Karsten K Pöselt Elmar E Malfois Marc M Baumann Roelf-Peter RP Sander Ralf R Paulus Dirk D Hinrichsen Bernd B Dinnebier Robert E RE

Macromolecules 20201016 20

Structural and morphological interplay between hard and soft phases determine the bulk properties of thermoplastic polyurethanes. Commonly employed techniques rely on different physical or chemical phenomena for characterizing the organization of domains, but detailed structural information can be difficult to derive. Here, total scattering pair distribution function (PDF) analysis is used to determine atomic-scale insights into the connectivity and molecular ordering and compared to the domain ...[more]

PMID: 33132420

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Project description:Sphingomyelin is an abundant lipid in some cellular membrane domains, such as lipid rafts. Hydrogen bonding and hydrophobic interactions of the lipid with surrounding components such as neighboring sphingomyelin and cholesterol (Cho) are widely considered to stabilize the raft-like liquid-ordered (Lo) domains in membrane bilayers. However, details of their interactions responsible for the formation of Lo domains remain largely unknown. In this study, the enantiomer of stearoyl sphingomyelin (ent-SSM) was prepared, and its physicochemical properties were compared with the natural SSM and the diastereomer of SSM to examine possible stereoselective lipid-lipid interactions. Interestingly, differential scanning calorimetry experiments demonstrated that palmitoyl sphingomyelin, with natural stereochemistry, exhibited higher miscibility with SSM bilayers than with ent-SSM bilayers, indicating that the homophilic sphingomyelin interactions occurred in a stereoselective manner. Solid-state 2H NMR revealed that Cho elicited its ordering effect very similarly on SSM and ent-SSM (and even on the diastereomer of SSM), suggesting that SSM-Cho interactions are not significantly affected by stereospecific hydrogen bonding. SSM and ent-SSM formed gel-like domains with very similar lateral packing in SSM/Cho/palmitoyloleoyl phosphatidylcholine membranes, as shown by fluorescence lifetime experiments. This observation can be explained by a homophilic hydrogen-bond network, which was largely responsible for the formation of gel-like nanodomains of SSMs (or ent-SSM). Our previous study revealed that Cho-poor gel-like domains contributed significantly to the formation of an Lo phase in sphingomyelin/Cho membranes. The results of the study presented here further show that SSM-SSM interactions occur near the headgroup region, whereas hydrophobic SSM-Cho interactions appeared important in the bilayer interior for Lo domain formation. The homophilic interactions of sphingomyelins could be mainly responsible for the formation of the domains of nanometer size, which may correspond to the small sphingomyelin/Cho-based rafts that temporally occur in biological membranes.

Dataset Information

Cross-examining Polyurethane Nanodomain Formation and Internal Structure.

Publications

Cross-examining Polyurethane Nanodomain Formation and Internal Structure.

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