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TRR 102:  Polymers under Multiple Constraints: Restricted and Controlled Molecular Order and Mobility

Subject Area Chemistry
Biology
Materials Science and Engineering
Physics
Term from 2011 to 2023
Website Homepage
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 189853844
 
Final Report Year 2023

Final Report Abstract

The rich versatility and the variable properties and functions of macromolecules are based on the one hand on a large variety of chemically different monomers but on the other hand, on the fact that polymers are able to order and assemble in organized structures, encoded in the chemical sequence of the polymer chains. In this context the title of the CRC TRR 102 “Polymers under multiple constraints: restricted and controlled molecular order and mobility”, reflects the fact that in macromolecular systems the formation of structural order on the monomer scale is a complex process as it is often constrained by its environment due to the connectivity of the polymer chain. In the CRC, such processes of structure formation and selfassembly were investigated, where molecular structures and dynamics are affected either by chain connectivity alone or additionally by constraints such as specific interactions, external forces, geometrical confinement, crowding, or topological restrictions. Two outstanding examples of such ordering processes and central topics of the CRC are crystallization in the field of synthetic polymers and the formation of amyloids in the field of proteins. Polymer crystallization is a well-established field, yet consensus on crucial aspects has not yet been achieved, particularly regarding the mechanisms leading to the formation of semicrystalline morphologies that ultimately determine the mechanical properties. Our work has led to new insights into thermodynamic and kinetic aspects of this process, specifically by considering the effects of chain motion through the crystallites and the effects of entanglements on the morphology. On the theoretical side we analyzed the driving forces for crystallization of chain molecules. The results shed new light on the complex interplay of conformational and positional ordering taking place during polymer crystallization. Amyloid fibrils, as linear protein aggregates, are known to be associated with neurodegenerative disorders but also exist as functional aggregates. They consist of (mis)folded protein aggregates that share the partial order on the local scale, the nucleation and growth of larger scale structures during ordering with semicrystalline polymers. In this area we performed extended studies on amyloid β1-40 concerned with the effects of local variations/mutations on structure, fibrillation kinetics and toxicity assays. The results show the universality of fibrillation while aggregation kinetics and toxicity effects can vary largely. An overarching key aspect in our experimental and theoretical investigations were the initial stages of both ordering processes, crystallization and amyloid formation, either by homogeneous nucleation or induced at interfaces. The latter studies include the effects of different exemplary surfaces on amyloid formation, the complex reconstruction involving substrate and polymers on metal surfaces, crystallization at liquid interfaces, and the occurrence of a wetting transition at the interface substrate-liquid in the vicinity of the liquidsolid phase transition. Finally, new experimental and theoretical methods were developed and applied to specific problems in the field of the CRC. Application of advanced Monte Carlo simulations allowed the full analysis of the equilibrium thermodynamics of single and multiple chain systems. This approach enabled us to work out similarities and differences in thermodynamic transitions between synthetic polymers with van-der-Waals like interactions and protein systems with specific interactions. A new optical technique, Thermoplasmonic Manipulation, provides a new way of trapping and manipulation of large macromolecules and aggregates in solution. It was developed and applied to initial studies of protein aggregates within the CRC. In addition to these highlighted results and investigations, a number of special studies addressing specific problems and effects in the field of the CRC were pursued.

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