Strasbourg, France
Strasbourg, France

Time filter

Source Type

Foy J.T.,Charles Sadron Institute
Nature Nanotechnology | Year: 2017

A current challenge in the field of artificial molecular machines is the synthesis and implementation of systems that can produce useful work when fuelled with a constant source of external energy. The first experimental achievements of this kind consisted of machines with continuous unidirectional rotations and translations that make use of ‘Brownian ratchets’ to bias random motions. An intrinsic limitation of such designs is that an inversion of directionality requires heavy chemical modifications in the structure of the actuating motor part. Here we show that by connecting subunits made of both unidirectional light-driven rotary motors and modulators, which respectively braid and unbraid polymer chains in crosslinked networks, it becomes possible to reverse their integrated motion at all scales. The photostationary state of the system can be tuned by modulation of frequencies using two irradiation wavelengths. Under this out-of-equilibrium condition, the global work output (measured as the contraction or expansion of the material) is controlled by the net flux of clockwise and anticlockwise rotations between the motors and the modulators. © 2017 Nature Publishing Group

Mutlu H.,Charles Sadron Institute | Lutz J.-F.,Charles Sadron Institute
Angewandte Chemie - International Edition | Year: 2014

The sequencing of biopolymers such as proteins and DNA is among the most significant scientific achievements of the 20th century. Indeed, modern chemical methods for sequence analysis allow reading and understanding the codes of life. Thus, sequencing methods currently play a major role in applications as diverse as genomics, gene therapy, biotechnology, and data storage. However, in terms of fundamental science, sequencing is not really a question of molecular biology but rather a more general topic in macromolecular chemistry. Broadly speaking, it can be defined as the analysis of comonomer sequences in copolymers. However, relatively different approaches have been used in the past to study monomer sequences in biological and manmade polymers. Yet, these "cultural" differences are slowly fading away with the recent development of synthetic sequence-controlled polymers. In this context, the aim of this Minireview is to present an overview of the tools that are currently available for sequence analysis in macromolecular science. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Krafft M.P.,Charles Sadron Institute
Accounts of Chemical Research | Year: 2012

For years, researchers had presumed that Langmuir monolayers of small CnF2n+1CmH2m+1 (FnHm) diblock molecules (such as F8H16) consisted of continuous, featureless films. Recently we have discovered that they instead form ordered arrays of unusually large (∼30-60 nm), discrete self-assembled surface domains or hemimicelles both at the surface of water and on solid substrates.These surface micelles differ in several essential ways from all previously reported or predicted molecular surface aggregates. They self-assemble spontaneously, even at zero surface pressure, depending solely on a critical surface concentration. They are very large (∼100 times the length of the diblock) and involve thousands of molecules (orders of magnitude more than classical micelles). At the same time, the surface micelles are highly monodisperse and self-organize in close-packed hexagonal patterns (two-dimensional crystals). Their size is essentially independent from pressure, and they do not coalesce and are unexpectedly sturdy for soft matter (persisting even beyond surface film collapse). We and other researchers have observed large surface micelles for numerous diblocks, using Langmuir-Blodgett (LB) transfer, spin-coating and dip-coating techniques, or expulsion from mixed monolayers, and on diverse supports, establishing that hemimicelle formation and ordering are intrinsic properties of (perfluoroalkyl)alkanes. Notably, they involve "incomplete" surfactants with limited amphiphilic character, which further illustrates the outstanding capacity for perfluoroalkyl chains to promote self-assembly and interfacial film structuring.Using X-ray reflectivity, we determined a perfluoroalkyl-chain-up orientation. Theoretical investigations assigned self-assembly and hemimicelle stability to electrostatic dipole-dipole interactions at the interface between Fn- and Hm-sublayers. Grazing-incidence small-angle X-ray scattering (GISAXS) data collected directly on the surface of water unambiguously demonstrated the presence of surface micelles in monolayers of diblocks prior to LB transfer for atomic force microscopy imaging. We characterized an almost perfect two-dimensional crystal, with 12 assignable diffraction peaks, which established that self-assembly and regular nanopatterning were not caused by transfer or induced by the solid support. These experiments also provide the first direct identification of surface micelles on water, and the first identification of such large-size domains using GISAXS.Revisiting Langmuir film compression behavior after we realized that it actually was a compression of nanometric objects led to further unanticipated observations. These films could be compressed far beyond the documented film "collapse", eventually leading to the buildup of two superimposed, less-organized bilayers of diblocks on top of the initially formed monolayer of hemimicelles. Remarkably, the latter withstood the final, irreversible collapse of the composite films."Gemini" tetrablocks, di(FnHm), with two Fn-chains and two Hm-chains, provided two superposed layers of discrete micelles, apparently the first example of thin films made of stacked discrete self-assembled nanoobjects.Decoration of solid surfaces with domains of predetermined size of these small "nonpolar" molecules is straightforward. Initial examples of applications include deposition of metal dots and catalytic oxidation of CO, and nanopatterning of SiO2 films. © 2011 American Chemical Society.

Lutz J.-F.,Charles Sadron Institute
ACS Macro Letters | Year: 2014

Current polymer terminology only describes very simple copolymer structures such as block, graft, alternating periodic, or statistical copolymers. This restricted vocabulary implies that copolymers exhibit either segregated (i.e., block and graft), regular (i.e., alternating and periodic), or uncontrolled (i.e., statistical or random) comonomer sequence distributions. This standard classification does not include many new types of sequence-controlled copolymers that have been reported in recent years. In this context, the present viewpoint describes a new category of copolymers: aperiodic copolymers. Such structures can be defined as copolymers in which monomer sequence distribution is not regular but follows the same arrangement in all chains. The term aperiodic can be used to describe encoded comonomer sequences in monodisperse sequence-defined copolymers but also the block sequence of some multiblock copolymers. These new types of copolymers open up very interesting perspectives for the design of complex materials. Some recent relevant literature on the topic is discussed herein. (Figure Presented). © 2014 American Chemical Society.

Lutz J.-F.,Charles Sadron Institute
Accounts of Chemical Research | Year: 2013

Synthetic polymer materials are currently limited by their inability to store information in their chains, unlike some well-characterized biopolymers. Nucleic acids store and transmit genetic information, and amino acids encode the complex tridimensional structures and functions within proteins.To confer similar properties on synthetic materials, researchers must develop" writing" mechanisms, facile chemical pathways that allow control over the primary structure of synthetic polymer chains. The most obvious way to control the primary structure is to connect monomer units one-by-one in a given order using iterative chemistry. Although such synthesis strategies are commonly used to produce peptides and nucleic acids, they produce limited yields and are much slower than natural polymerization mechanisms. An alternative strategy would be to use multiblock copolymers with blocks that have specified sequences. In this case, however, the basic storage element is not a single molecular unit, but a longer block composed of several repeating units. However, the synthesis of multiblock copolymers is long and tedious. Therefore, researchers will need to develop other strategies for writing information onto polymer chains.In this Account, I describe our recent progress in the development of sequence controlled polymerization methods. Although our research focuses on different strategies, we have emphasized sequence-regulation in chain-growth polymerization processes. Chain-growth polymerizations, particularly radical polymerization, are very convenient methods for synthesizing polymers. However, in most cases, such approaches do not lead to controlled monomer sequences. During the last five years, we have shown that controlled/living chain-growth polymerization mechanisms offer interesting advantages for sequence regulation. In such mechanisms, the chains form gradually over time, and therefore the primary structure can be tuned by using time-controlled monomer additions. For example, the addition of small amounts of acceptor comonomers, such as N-substituted maleimides, during the controlled radical polymerization of a large excess of donor monomer, such as styrene, allows the writing of information onto polymer chains in a robust manner. Even with these advances, this strategy is not perfect and presents some of the drawbacks of chain-growth polymerizations, such as the formation of chain-to-chain sequence defects. On the other hand, this approach is experimentally easy, rapid, scalable, and very versatile. © 2013 American Chemical Society.

Lutz J.-F.,Charles Sadron Institute
Advanced Materials | Year: 2011

We describe here the advantages of oligo(ethylene glycol)-based (co)polymers for preparing thermoresponsive materials as diverse as polymer-enzyme bio-hybrids, injectable hydrogels, capsules for drug-release, modified magnetic particles for in vivo utilization, cell-culture substrates, antibacterial surfaces, or stationary phases for bioseparation. Oligo(ethylene glycol) methacrylates (OEGMAs) can be (co)polymerized using versatile and widely-applicable methods of polymerization such as atom transfer radical polymerization (ATRP) of reversible addition-fragmentation chain-transfer (RAFT) polymerization. Thus, the molecular structure and therefore the stimuli-responsive properties of these polymers can be precisely controlled. Moreover, these stimuli-responsive macromolecules can be easily attached to-or directly grown from-organic, inorganic or biological materials. As a consequence, the OEGMA synthetic platform is today a popular option for materials design. The present research news summaries the progress of the last two years. The (controlled) radical polymerization of oligo(ethylene glycol) methacrylates (OEGMAs) is a new construction platform in materials science. Indeed, thermoresponsive polymers constructed with OEGMAs allow design of a wide variety of smart materials such as polymer-enzyme bio-hybrids, injectable hydrogels, capsules for drug-release, modified magnetic particles for in vivo utilization, cell-culture substrates, antibacterial surfaces, or stationary phases for bioseparation. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhamnogalacturonans-I (RGs-I) are complex structural components of the (primary) cell wall. Their backbone, composed of the repeating diglycosyl [→2)-α- L-Rhap-(1→4)-α-D-GalpA-(1→], is believed to be branched at O-4/O-3 positions by 4 different side chain types, viz. (1→5)-α-L-arabinan, (1→4)-β- D-galactan, arabinogalactan-I, and sometimes with arabinogalactan-II. However, the fine structure of RGs-I remains somewhat enigmatic, as shown by various continuous findings, such as branches of galactoarabinan, arabinogalactan with a (1→6) - D-galactan core, and possibly (1→3)-rhamnan. This timely review is the first of its kind, highlighting the freak structural diversity and the functional versatility of RG-I, one of the two major structural domains of complex pectins. © 2011 Copyright Taylor and Francis Group, LLC.

Brinkmann M.,Charles Sadron Institute
Journal of Polymer Science, Part B: Polymer Physics | Year: 2011

This review focuses on the structural control in thin films of regioregular poly(3-hexylthiophene) (P3HT), a workhorse among conjugated semiconducting polymers. It highlights the correlation existing between processing conditions and the resulting structures formed in thin films and in solution. Particular emphasis is put on the control of nucleation, crystallinity and orientation. P3HT can generate a large palette of morphologies in thin films including crystalline nanofibrils, spherulites, interconnected semicrystalline morphologies and nanostructured fibers, depending on the elaboration method and on the macromolecular parameters of the polymer. Effective means developed in the recent literature to control orientation of crystalline domains in thin films, especially by using epitaxial crystallization and controlled nucleation conditions are emphasized. © 2011 Wiley Periodicals, Inc.

Roy R.K.,Charles Sadron Institute | Lutz J.-F.,Charles Sadron Institute
Journal of the American Chemical Society | Year: 2014

We report the intramolecular double compaction of sequence-controlled linear macromolecules into "structured" random coils. These compartmentalized single-chain objects were prepared by performing successive cross-linking reactions in an orthogonal fashion. The foldable precursors were synthesized by sequence-controlled copolymerization of styrene with N-substituted maleimides (MIs), namely pentafluorophenyl 4-maleimidobenzoate (1) and TIPS-protected N-propargyl maleimide (2). These two functional MIs allow intramolecular cross-linking. The activated ester pentafluorophenyl moieties of 1 were reacted with ethylenediamine, whereas the deprotected alkyne functions of 2 were self-reacted by Eglinton coupling. The compaction of model copolymers containing only one cross-linkable zone (i.e., either 1 or 2) was first studied. (1)H NMR and SEC analysis indicated that these structures could be efficiently compacted into single-chain objects. Thus, more complex copolymers containing two individually addressable cross-linking zones were prepared and sequentially compacted. Detailed characterization of the folding process indicated that double-compaction occurred and that the formed single-chain particles contain distinct cross-linked subdomains.

Giuseppone N.,Charles Sadron Institute
Accounts of Chemical Research | Year: 2012

To design the next generation of so-called "smart" materials, researchers will need to develop chemical systems that respond, adapt, and multitask. Because many of these features occur in living systems, we expect that such advanced artificial systems will be inspired by nature. In particular, these new materials should ultimately combine three key properties of life: metabolism, mutation, and self-replication.In this Account, we discuss our endeavors toward the design of such advanced functional materials. First, we focus on dynamic molecular libraries. These molecular and supramolecular chemical systems are based on mixtures of reversibly interacting molecules that are coupled within networks of thermodynamic equilibria. We will explain how the superimposition of combinatorial networks at different length scales of structural organization can provide valuable hierarchical dynamics for producing complex functional systems. In particular, our experimental results highlight why these libraries are of interest for the design of responsive materials and how their functional properties can be modulated by various chemical and physical stimuli. Then, we introduce examples in which these dynamic combinatorial systems can be coupled to kinetic feedback loops to produce self-replicating pathways that amplify a selected component from the equilibrated libraries. Finally, we discuss the discovery of highly functional self-replicating supramolecular assemblies that can transfer an electric signal in space and time. We show how these wires can be directly incorporated within an electronic nanocircuit by self-organization and functional feedback loops.Because the network topologies act as complex algorithms to process information, we present these systems in this order to provide context for their potential for extending the current generation of responsive materials. We propose a general description for a potential autonomous (self-constructing) material. Such a system should self-assemble among several possible molecular combinations in response to external information (input) and possibly self-replicate to amplify its structure. Ultimately, its functional response (output) can drive the self-assembly of the system and also serve a mechanism to transfer this initial information. Far from equilibrium, such synergistic processes could give rise to evolving, "information gaining" systems which become increasingly complex because internal self-organization rapidly reduces the potential energy surrounding the system. © 2012 American Chemical Society.

Loading Charles Sadron Institute collaborators
Loading Charles Sadron Institute collaborators