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SFB-Transregio 102

Polymere unter Zwangsbedingungen: eingeschränkte und kontrollierte molekulare Ordnung und Beweglichkeit


Der SFB Transregio 102 ist ein langfristiges Grundlagen-Forschungsprojekt, das von der als Sprecherhochschule fungierenden Martin-Luther-Universität Halle-Wittenberg gemeinsam mit der Universität Leipzig beantragt wurde und durchgeführt wird.

Der SFB-TRR 102 wird von der DFG gefördert.

1. Förderperiode: 01.07.2011 - 30.06.2015

2. Förderperiode: 01.07.2015 - 30.06.2019

Aktuelle Highlights aus der Forschung

One-Pot Synthesis of Thermoresponsive Amyloidogenic Peptide-Polymer Conjugates via Thio-Bromo “Click” Reaction of RAFT Polymers

Conjugation to fibrillating proteins and peptides represents a methodological challenge, as potential binding sites are blocked due to the ongoing fiber-formation, blocking the sites for attachments. A synthetic strategy to efficiently prepare main-chain peptide-polymer conjugates developing an in situ tandem reaction based on the aminolysis/thio-bromo “click” reaction. This method allows to tether an amyloidogenic peptide fragment Aβ17-20(LVFF) to the ω-chain end of poly(diethylene glycol methyl ether acrylate) (PDEGA), prepared via reversible addition fragmentation chain transfer polymerization (RAFT). Tuning of the lower critical solution temperature of the polymer allows a modulation of the aggregation into micellar structures.

Intracrystalline Jump Motion in Poly(ethylene oxide) Lamellae of Variable Thickness: A Comparison of NMR Methods

It has long been known that the degree of crystallinity of linear polymers depends on the presence or absence of chain motion within and through the crystalline lamellae. While this fact has not yet found widespread appreciation or even explicit consideration in theoretical accounts of polymer crystallization, recent results from project A01 demonstrate that even the morphology is qualitatively different in the two cases. That is, polymers with intracrystalline mobility display lamellar stacks with well-defined amorphous-phase thickness but a wider distribution of crystallite thickness, in some contradiction to conventional wisdom. It is thus of high interest to develop an understanding of the relation between the intra-crystalline chain motion and morphological parameters, such as the crystallite thickness. Here, we report on a comprehensive NMR study of intracrystalline chain dynamics in poly(ethylene oxide), and find that the weak but notable thickness dependence of the monomer jump correlation time within the crystalline stems is in agreement with a model based on the diffusive motion of defects that are likely generated within the fold surface.

Interface-Induced Crystallization of Polycaprolactone on Graphite via First-Order Prewetting of the Crystalline Phase

The crystallization of liquids is often initiated at the interface to a solid. Due to the difficult accessibility of a buried liquid-solid interface, direct experimental observations of interface induced crystallization have been scarce and only a recently crystallization induced by prefreezing, which had been theoretically predicted beforehand was observed in experiment. In prefreezing, a thin crystalline film forms on a solid substrate in a finite temperature interval above the bulk melting temperature of the liquid. The thickness of this prefrozen films increases on approaching the melting temperature and continues to grow into the bulk upon further cooling.
The phenomenon can be understood in the general framework of wetting theory, which generally describes the behavior of wetting layers forming on surfaces near phase transitions. Wetting transitions are theoretically well understood, and an important criterion for classification is the question if the transition is continuous or discontinuous. The corresponding experimental question here is, if the prefrozen film forms continuously or appears suddenly with a finite thickness. We here present an experiment on a polymeric model system, which allows a temperature dependent measurement of the prefreezing layer and shows that the transition is of first order.

In our experiment we use in-situ Atomic Force Microscopy measurements on an ultrathin film of a crystallizable polymer on graphite, which acts as a substrate inducing crystallization. Due to the general instability of the chosen sample system, it is possible for this case to directly measure the thickness of the prefrozen layer as a function of temperature.

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