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The majority of human-made materials are represented by  plastics and elastomers, polymeric solids synthesized from petrochemically obtained feedstock. When compared to materials that are constructed from the polymers produced in cells, human-made synthetics are substantially less adapted to function with or within living organisms. The adaptation of materials to fit a set of requirements can be described in terms of their character in the dimensions of hydrophilicity, viscoelasticity, and toughness. Polymers used by plants and animals, such as in tissues, are always built from water-soluble compounds, and are therefore predominantly hydrophilic, unlike most synthetic materials. The viscoelasticity, a property which encompasses both the time-dependent compliant (viscous) as well as the elastic (solid) response of a material, of natural materials is diverse and can be often described as solid with a dissipating component. Finally, natural materials present a toughness, the fracture resistance of a material to high deformations, that is adapted to their function in the organisms that the materials serves. While hydrophilicity, viscoelasticity, and toughness can be tuned in synthetic materials to some extent, the majority of available materials do not offer independent control of either.The adoption of synthetic materials for use in the human body is highly attractive for the medical field: novel materials will allow to better rehabilitate tissues or even take over their function. However, chemical platforms do not offer the repertoire that billions of years of evolution allowed to perfect in biology. In this thesis, I present complex coacervates as a material class that offers untapped possibilities to bridge the property gap between natural and synthetic materials.Complex coacervates, also termed polyelectrolyte complexes or saloplastics when high stiffnesses are reached, are phases that form on reversible association of oppositely charged polyelectrolytes in wa

The application of complex coacervates in promising areas such as coatings and surgical glues requires a tight control of their viscous and elastic behaviour, and a keen understanding of the corresponding microscopic mechanisms. While the viscous, or dissipative, aspect is crucial at pre-setting times and in preventing detachment, elasticity at long waiting times and low strain rates is crucial to sustain a load-bearing joints. The independent tailoring of dissipative and elastic properties proves to be a major challenge that can not be addressed adequately by the complex coacervate motif by itself. We propose a versatile model of complex coacervates with customizable rheological fates by functionalization of polyelectrolytes with terpyridines, which provide transient crosslinks through complexation with metals. We show that the rheology of the hybrid complexes shows distinct footprints of both metal-ligand and coacervate dynamics, the former as a contribution very close to pure Maxwell viscoelasticity, the latter approaching a sticky Rouse fluid. Strikingly, when the contribution of metal-ligand bonds is dominant at long times, the relaxation of the overall complex is much slower than either the "native"coacervate relaxation time or the dissociation time of a comparable non-coacervate polyelectrolyte-metal-ligand complex. We recognize this slowing-down of transient bonds as a synergistic effect that has important implications for the use of complementary transient bonding in coacervate complexes.

The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave tert-butyl groups from poly(tert-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA. We show the effect of complete tert-butyl cleavage on a ABA triblock copolymer, where poly(N-isopropylacrylamide) (pNIPAM) is A and pAA is B, by means of viscosimetry, DLS, and SAXS on solutions above overlap. The pNIPAM blocks dehydrate, and their increased self-affinity above the lower critical solution temperature (LCST) results in network formation by the triblocks. This manifests itself as an increase in viscosity and a slowing down of the first-order correlation function in light scattering. However, this stickering effect manifests itself exclusively when the pAA block is tert-butyl-free. Additionally, SAXS shows that the conformational properties of tert-butyl-free pAA copolymers are markedly different from those with residual esters. Thus, we illustrate a surprising effect of hydrophobic impurities that act across blocks and assert the usefulness of HCl/HFIP in pAA synthesis.

Nature has developed elegant and economical strategies to produce materials that are well-adapted to their purposes. As biology evolved to remarkable and complex designs, synthetic mimics are evolving toward new levels of complexity achieving larger combinations of properties within one material. The field of bioinspiration encompasses a wide range of advanced materials ranging from biooptics to energy materials, to biomaterials. In this paper an overview is given of selected recent developments in the field of bioinspired material design focusing on gecko-inspired adhesives, mussel-inspired coatings, and spider silk-inspired biomaterials.

H-Si(111)-terminated surfaces were alkenylated via two routes: Through a novel one-step gas-phase hydrosilylation reaction with short alkynes (C3 to C6) and for comparison via a two-step chlorination and Grignard alkenylation process. All modified surfaces were characterized by static water contact angles and X-ray photoelectron spectroscopy (XPS). Propenyl- A nd butenyl-coated Si(111) surfaces display a significantly higher packing density than conventional C10-C18 alkynederived monolayers, showing the potential of this approach. In addition, propyne chemisorption proceeds via either of two approaches: The standard hydrosilylation at the terminal carbon (lin) at temperatures above 90°C and an unprecedented reaction at the second carbon (iso) at temperatures below 90°C. Molecular modeling revealed that the packing energy of a monolayer bonded at the second carbon is significantly more favorable, which drives iso-attachment, with a dense packing of surface-bound iso-propenyl chains at 40% surface coverage, in line with the experiments at <90°C. The highest density monolayers are obtained at 130°C and show a linear attachment of 1-propenyl chains with 92% surface coverage.