Publications

This page lists most of our publications starting from 2014.

Total: ca. 150 Publications

Please refer to Google Scholar for a complete list.

Search By Tags
RSS Feed

Effect of Molecular Architecture of PDMAEMA–POEGMA Random and Block Copolymers on Their Adsorption o

Get the full paper here: J. Phys. Chem. B. 119, 15275 (2015). Block copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) with varying block sizes were synthesized by consecutive reversible addition–fragmentation chain transfer (RAFT) polymerization and then exposed to cellulose substrates with different anionic charge density. The extent and dynamics of quaternized PDMAEMA-b-POEGMA adsorption on regenerated cellulose, cellulose nanofibrils (CNF), and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNF) was determined by using electromechanical and optical techniques, namely, qua

Bioactive Gyroid Scaffolds Formed by Sacrificial Templating of Nanocellulose and Nanochitin Hydrogel

Get the full paper here: Adv. Mater. 27, 2989 (2015). A sacrificial templating process using lithographically printed minimal surface structures allows complex de novo geo­metries of delicate hydrogel materials. The hydrogel scaffolds based on cellulose and chitin nanofibrils show differences in terms of attachment of human mesenchymal stem cells, and allow their differentiation into osteogenic outcomes. The approach here serves as a first example toward designer hydrogel scaffolds viable for biomimetic tissue engineering.

Self-Assembled, Iridescent, Crustacean-Mimetic Nanocomposites with Tailored Periodicity and Layered

Get the full paper here: ACS Nano, 9, 10637 (2015). Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced molecular interactions. Herein, we develop a facile, waterborne self-assembly pathway to mimic the multiscale cuticle structure of the crustacean armor by combining hard reinforcing cellulose nanocrystals (CNCs) with soft poly(vinyl alcohol) (PVA). We show iridescent CNC nanocomposites with cholesteric liquid-crystal structure, in which different helical pitches and photonic band gaps can be realized by varying the CNC/PVA ratio. We further show that multilayered crustacean-mimetic materi

Approaches to Program the Time Domain of Self-Assemblies

Get the full paper here: Soft Matter, 11, 7857 (2015). Self-regulating reconfigurable soft matter systems are of great interest for creating adaptive and active material properties. Such complex functionalities emerge from non-linear and interactive behavior in space and time as demonstrated by a plethora of dynamic, self-organizing biological structures (e.g., the cytoskeleton). In man-made self-assemblies, patterning of the spatial domain has advanced to creating hierarchical structures via precise molecular programming. However, orchestration of the time domain of self-assemblies is still in its infancy and lacks universal design principles. In this Emerging Area article we outline major

Biocatalytic Feedback-Driven Temporal Programming of Self-Regulating Non-Equilibrium Peptide Hydroge

Get the full paper here: Angew. Chem. Int. Ed, 54, 13258 (2015). Switchable self-assemblies respond to external stimuli with a transition between near-equilibrium states. Although being a key to present-day advanced materials, these systems respond rather passively, and do not display autonomous dynamics. For autonomous behavior, approaches must be found to orchestrate the time domain of self-assemblies, which would lead to new generations of dynamic and self-regulating materials. Herein, we demonstrate catalytic control of the time domain of pH-responsive peptide hydrogelators in a closed system. We program transient acidic pH states by combining a fast acidic activator with the slow, enzym

Polyacid Microgels with Adaptive Hydrophobic Pockets and Ampholytic Character: Synthesis, Solution P

Get the full article here: Soft Matter, 11, 8342 (2015). Microgels with internal and reconfigurable complex nanostructure are emerging as possible adaptive particles, yet they remain challenging to design synthetically. Here, we report the synthesis of highly charged poly(methacrylic acid) (PMAA) microgels incorporating permanent (poly(methyl methacrylate) (PMMA)) and switchable hydrophobic pockets (poly(N,N′-diethylaminoethyl methacrylate) (PDEAEMA)) via emulsion polymerization. We demonstrate detailed tuning of the size, crosslinking density and tailored incorporation of functional comonomers into the polyacid microgels. Analysis via cryo-TEM and pyrene probe measurements reveal switchable

Conducting, Self-Assembled, Nacre-Mimetic Polymer/Clay Nanocomposites

Get the full paper here: ACS Appl. Mat. Inter. 7, 15681 (2015) We demonstrate electrically and ionically conducting nacre-mimetic nanocomposites prepared using self-assembly of synthetic nanoclay in combination with PEDOT:PSS and a poly(ionic liquid) polymer from aqueous dispersions. The resulting nacre-mimetics show high degrees of mesoscale order and combine high stiffness and high strength. In terms of conductivities, the resulting hybrids exceed simple additive behavior and display synergetic conductivities due to high levels of interfaces and anisotropic conductivity pathways. The approach highlights the integration of relevant functionalities into stiff and strong bioinspired materials

Hierarchical Nacre-Mimetics with Synergistic Mechanical Properties by Control of Molecular Interacti

Get the full article here: Angew. Chem. Int. Ed. 54, 8653 (2015). Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass-transition temperature Tgand bonded by quadruple hydrogen-bonding motifs, and subsequently assembled with high-aspect-ratio synthetic nanoclays to generate nacre-mimetic films. The high dynamics and self-healing of the polymers render transparent films with a near-perfectly

Preparation of Highly Monodisperse Monopatch Particles with Orthogonal Click-type Functionalization

Get the full paper here: Small, 11, 4540 (2015). (Highlighted in SCIENCE; 349, 393, 2015). Patchy particles are next generation colloidal building blocks for self-assembly and find further use as (bio) sensors. Progress in this direction crucially depends on developing straightforward preparation pathways able to provide patchy particles with highest uniformity and integrating precise, orthogonal, and spatially localized functionalizations to mediate interaction patterns. This continues to be one of the great challenges in colloid science. Herein, a method is shown utilizing functionalized random and block copolymers as microcontact printing inks to prepare patchy particles with outstanding

Nanoscale Hybrid Silica/Polymer Janus Particles with a Double-Responsive Hemicorona

Get the full article here: Polymer, 79, 299 (2015). We report a versatile large-scale synthesis strategy for hybrid Janus nanoparticles with a silica core and a unilaterally attached polymer corona in a size range below 100 nm. The stimuli-responsive behavior of these nanoparticles with a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) hemicorona is investigated. The synthesis is based on a modified version of the Pickering emulsion polymerization technique in combination with surface-initiated atom transfer radical polymerization (ATRP) in a “grafting from” approach. In a first step, poly(vinyl acetate) (PVAc) latex particles are prepared via Pickering emulsion polymerization. Colloidal

Strong Anionic Polylectrolyte Microgels

Get the full article here: Polym. Chem. 6, 5550 (2015). We report a facile synthesis of highly uniform poly(styrene sulfonic acid) microgels, which carry a strong polyelectrolyte group at every repeating unit. We demonstrate tuning of particle size, as well as particle softness, and show first solution state characterization.

A Generic Concept to Program the Time Domain of Self-Assemblies with a Self-Regulation Mechanism

Get the full article here: Nano Lett., 15, 2213, (2015). Nature regulates complex structures in space and time via feedback loops, kinetically controlled transformations, and under energy dissipation to allow non-equilibrium processes. Although man-made static self-assemblies realize excellent control over hierarchical structures via molecular programming, managing their temporal destiny by self-regulation is a largely unsolved challenge. Herein, we introduce a generic concept to control the time domain by programming the lifetimes of switchable self-assemblies in closed systems. We conceive dormant deactivators that, in combination with fast promoters, enable a unique kinetic balance to est

Cleaning the Click: A Simple Electrochemical Avenue for Copper Removal from Strongly Coordinating Ma

Get the full article here: ACS Macro Lett. 4, 298 (2015). We introduce a novel electrochemical method for the purification of complex water-soluble functional polymers contaminated with copper salts originating from copper-catalyzed azide/alkyne ligation chemistry, for which no standard purification protocol is suitable. A triethylene glycol methyl ether methacrylate (TEGMA) star polymer with 2-ureido-4H-pyrimidone (UPy) end groups was prepared via an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) and copper-catalyzed azide/alkyne cycloaddition (CuAAc) and selected as a model system for electrolysis of an aqueous polymer solution. We systematically

Nacre-Mimetics with Synthetic Nanoclays up to Ultrahigh Aspect Ratio

Get the full paper here: Nat. Commun. 6, 5967 (2015). Nacre-mimetics hold great promise as mechanical high-performance and functional materials. Here we demonstrate large progress of mechanical and functional properties of self-assembled polymer/nanoclay nacre-mimetics by using synthetic nanoclays with aspect ratios covering three orders in magnitude (25–3,500). We establish comprehensive relationships among structure formation, nanostructuration, deformation mechanisms and mechanical properties as a function of nanoclay aspect ratio, and by tuning the viscoelastic properties of the soft phase via hydration. Highly ordered, large-scale nacre-mimetics are obtained even for low aspect ratio na

Aligned Bioinspired Cellulose Nanocrystal-Based Nanocomposites with Synergetic Mechanical Properties

Get the full paper here: ACS Appl. Mater. Interfaces, 7, 4595 (2015). Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced supramolecular interactions. Such biomimetic design principles remain difficult to realize for bulk nanocomposites. Herein, we establish an effective drawing procedure that induces a high orientation of crystalline cellulose nanocrystals (CNCs) in a matrix of carboxymethylcellulose (CMC) at high level of reinforcements (50 vol %). We show such alignment in rather thick bulk films and report synergetic improvement with a simultaneous increase of stiffness, strength, and w

Print your Membrane: Rapid Prototyping of Complex 3D-PDMS Membranes via a Sacrificial Resist

Get the full article here; J. Membr. Sci. 478, 12 (2015). Polydimethylsiloxane is a translucent silicone material present in most lab-on-a-chip devices. In membrane technology, polydimethylsiloxane provides a separation barrier for various applications such as oxygenation, vapor recovery and nanofiltration. The easy-to-use combination of silicon and crosslinker and its properties make it widely applicable for two-dimensional device geometries. Here we develop a new sacrificial lithography technique to produce three-dimensional membrane geometries using rapid prototyping. The three-dimensional PDMS membranes are applied for gas–liquid-contacting. The membrane geometries are based on triple-pe

Archive
  • Twitter Social Icon
  • Facebook - White Circle
  • LinkedIn Social Icon

© Andreas Walther - all rights reserved