Hybrid Polymer/Lipid Vesicles: Influence of polymer architecture and molar mass on line tension

Hybrid polymer/lipid vesicles are self-assembled structures that have been the subject of an increasing number of studies in recent years. They are particularly promising tools in the development of cell membrane models as they offer the possibility to fine-tune their membrane structure by adjusting the distribution of components (presence or absence of “raft like” lipid domains) which is of prime importance to control their membrane properties. Line tension in multiphase membranes is known to be a key parameter on membrane structuration but remains unexplored, either experimentally or by computer modelling for hybrid polymer /lipid vesicles. In this study we were able to measure the line tension on different budded hybrid vesicles, using micropipette aspiration technique, and show the influence of the molar mass and the architecture of block copolymers on line tension and its consequences for membrane structuration

Sonification for 3D Printing Process Monitoring

In order to monitor a 3D printing industrial process in a context of sensory overload and potential inattentional deafness, we designed a sonification of the information sent in by the printer. This sonification focuses not only on proper communication of the system's state, but also on lowering the amount of stress usually induced by prolonged listening. To this end, we made use of a combination of synthetic and natural sounds whose perceptual properties were modulated according to the data influx using parameter mapping. Then an experiment was conducted on the recognition of various normal and abnormal behaviours, also allowing the participants to assess the amount of stress they experienced upon listening. The results are quite promising, but also highlight a confusing overlap in the natural sounds used, which will need to be fixed in future iterations. For now, tester opinion is mostly positive on the stressful aspect. However, listening times may need to be longer in further experimentation to better assess how stressful this sonification is

omega-Dimethyl ammonium tetrakis-pentafluorophenyl borate polyisoprene as an organic template for alkylated metallocenes toward the synthesis of polyethylene beads

In this work, we report the self-assembly in heptane of omega-dimethyl ammonium tetrakis-pentafluorophenyl borate polyisoprenes into micellar aggregates and the use of these nano-objects to support alkylated metallocenes toward ethylene polymerization. Dynamic light scattering was used to demonstrate the self-assembly and the formation of the micellar structures having a core of polar dimethyl ammonium tetrakis-pentafluorophenyl borate moieties, and a corona of polyisoprene (PI). The latter were then used as organic supports for alkylated metallocenes to produce unprecedented millimetric polyethylene beads without loss of catalytic activity

Nanostructured thermotropic PBLG-PDMS-PBLG block copolymers

We report on the nano-organization and the thermal behavior of a series of triblock copolymers composed of a central soft polydimethylsiloxane (PDMS) and two polypeptide (poly-gamma-benzyl-L-glutamate) blocks. Peptide blocks with varied lengths and therefore different secondary structures (beta-sheet or alpha-helical) were attached to the PDMS central block. These two blocks are incompatible and microphase separate into different morphologies elucidated by polarized optical microscopy (POM), small-angle light scattering (SALS), X-ray spectroscopy (SAXS, WAXS) and atomic force microscopy (AFM). We demonstrate that the relative ratio of PBLG to PDMS direct both the type of nanodomain morphologies formed and also modifies the transition temperature. Each of these block copolymers have shown a reversible transition associated to its thermotropic liquid crystal behavior. At temperatures above the transition, the self-assembled structures are disrupted and prevented the organization at larger scales. (C) 2007 Elsevier Ltd. All rights reserved

Surface segregation of polypeptide-based block copolymer micelles: An approach to engineer nanostructured and stimuli responsive surfaces

We describe the surface segregation of polypeptide-based block copolymer micelles to produce stimuli-responsive nanostructures at the polymer blend/air interface. Such structures were obtained by simultaneous surface migration and self assembly at the surface of diblock copolymer/homopolymer blends. We employed blends composed of homopolymer (PS) and an amphiphilic block copolymer polystyrene-b-poly(L-glutamic acid) (PS-b-PGA). The surface was functionalized based on the preferential segregation to the polymer blend/air interface of the hydrophilic PGA block of the diblock copolymer upon annealing to water vapor. The surface migration of the diblock copolymer to the interface was demonstrated both by XPS and contact angle measurements. As a consequence, the PGA interfacial attraction leads to a large surface excess on diblock copolymer which in turn, through macrophase and microphase separation, produced separated domains at the surface with regions composed either of homo or block copolymer. Herein we demonstrate that the use of asymmetric diblock copolymers with a higher content in PS lead to spherical micellar assemblies randomly distributed at the surface. As observed by AFM imaging the blend composition, i.e. the amount of block copolymer within the blend influences the density of micelles at the surface. Finally, when exposed to water, the pH affects the surface morphology. The PGA segments are collapsed at low pH values and extended at pH values above 4.8, thus inducing variations on the topography of the films at the nanometer scale

Obtention of Giant Unilamellar Hybrid Vesicles by Electroformation and Measurement of their Mechanical Properties by Micropipette Aspiration

Giant vesicles obtained from phospholipids and copolymers can be exploited in different applications: controlled and targeted drug delivery, biomolecular recognition within biosensors for diagnosis, functional membranes for artificial cells, and development of bioinspired micro/nano-reactors. In all of these applications, the characterization of their membrane properties is of fundamental importance. Among existing characterization techniques, micropipette aspiration, pioneered by E. Evans, allows the measurement of mechanical properties of the membrane such as area compressibility modulus, bending modulus and lysis stress and strain. Here, we present all the methodologies and detailed procedures to obtain giant vesicles from the thin film of a lipid or copolymer (or both), the manufacturing and surface treatment of micropipettes, and the aspiration procedure leading to the measurement of all the parameters previously mentioned

Introduction de la réalité augmentée pour une mise en œuvre plus flexible de la fabrication additive

International audienc

Thermotropic liquid crystal behavior on PBLG-PDMS-PBLG triblock copolymers

In this contribution, the preparation of rod-coil-rod triblock copolymers based on polydimethylsiloxane and polypeptide [poly(gamma-benzyl-L-glutamate)] is reported. Firstly, self-assembly in rod-like structures was demonstrated via polarized optical microscopy and small-angle light scattering. Further structuration details were obtained using X-ray scattering and AFM imaging to establish the formation of a double-hexagonal structure and to accurately define the morphological dimensions of the rodlike structures. The thermal behavior of these structures was investigated using dynamic mechanical analysis and differential scanning calorimetry. We conclude by addressing an unexpected reversible thermal transition within the 130-150 degrees C temperature range and the ensuing associated organizational modifications

Membrane reinforcement in Giant Hybrid Polymer Lipid Vesicle achieved by controlling the polymer architecture

The physical properties of membranes of hybrid polymer lipid vesicles are so far relatively unknown. Since their discovery a decade ago, many studies have aimed to show their great potential in many fields of application, but so far, few systematic studies have been carried out to decipher the relationship between the molecular characteristics of the components (molar mass, chemical nature, and architecture of the copolymer), the membrane structure and its properties. In this work, we study the association of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and poly(dimethylsiloxane)-b-poly(ethylene oxide) (PDMS-b-PEO) diblock copolymers of different molar masses in giant hybrid vesicles and establish a complete phase diagram of the membrane structure. We also measured the mechanical properties of the giant hybrid unilamellar vesicle (GHUV) through micropipette aspiration at different lipid/polymer compositions. Thanks to a previous work using triblock PEO-b-PDMS-b-PEO copolymers, we were able to reveal the effect of the architecture of the block copolymer on membrane structure and properties. Besides, the association of diblock copolymers PDMS-b-PEO and POPC leads to the formation of hybrid vesicles with unprecedented membrane toughness