Publications by authors named "Laurent Billon"

30 Publications

  • Page 1 of 1

CO-Triggered ON/OFF Wettability Switching on Bioinspired Polylactic Acid Porous Films for Controllable Bioadhesion.

Biomacromolecules 2021 04 5;22(4):1721-1729. Epub 2021 Mar 5.

Université de Pau & des Pays de l'Adour, E2S UPPA, CNRS, IPREM-UMR 5254, Pau 64000, France.

Bioinspired honeycomb-like porous films with switchable properties have drawn much attention recently owing to their potential application in scenarios in which the conversion between two opposite properties is required. Herein, the CO-gas-triggered ON/OFF switching wettability of biocompatible polylactic acid (PLA) honeycomb porous films is fabricated. Highly ordered porous films with diameters between 2.0 and 2.8 μm are separately prepared from complexes of nonresponsive PLA and a CO-sensitive melamine derivative [,,-(3-(dimethylamino)propyl)-1,3,5-triazine-2,4,6-triamine, MET] the breath figure method. The hydrophilic CO-sensitive groups can be precisely arranged in the pore's inner surface and/or top surface of the films by simply changing the PLA/MET ratio. The sensitive groups in the pore's inner surface act as a switch triggered by CO gas controlling water to enter the pores or not, thus resulting in ON/OFF switching wettability. The largest response of the water contact angle of honeycomb films reaches 35°, from 100 to 65°, leading to an obvious hydrophobic-hydrophilic conversion. The improved surface wettability enhances the interaction between the cell and honeycomb film surface, thus resulting in a better cell attachment. Such smart properties accompanying the biocompatible polymer and biological gas trigger facilitate possible biomedical and bioengineering applications in the future for these films.
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http://dx.doi.org/10.1021/acs.biomac.1c00134DOI Listing
April 2021

Microgels self-assembly at liquid/liquid interface as stabilizers of emulsion: Past, present & future.

Adv Colloid Interface Sci 2021 Jan 30;287:102333. Epub 2020 Nov 30.

Universite de Pau et Pays de l'Adour, E2S UPPA, CNRS, Institut des Sciences Analytiques & de PhysicoChimie pour l'Environnement & les Matériaux, UMR5254, 2 avenue du Président Angot, Pau F-64053, France; Bio-inspired Materials Group: Functionalities & Self-assembly, Université de Pau & Pays Adour, 2 avenue du Président Angot, Pau F-64053, France. Electronic address:

The most recent developments on Pickering emulsions deal with the design of responsive emulsions able to undergo fast destabilization under the effect of an external stimulus. In this scenario, soft colloidal particles like microgels are considered novel class suitable emulsifiers. Microgels particles self-assemblies are highly deformable at interfaces covering higher surfaces than hard particles and their interfacial behavior strongly depends on external-stimuli. Microgels are very diverse owing to the large variety of them from the point of view of possible combinations of stimuli-responsiveness and different microstructures (crosslinking density and distribution). Herein, we illustrate the use of different types of responsive microgels not only from a structural point of view but also even from physical one. For that, the effect of different microgels parameters such as internal structure and charge density on mechanical properties of the interface will be discussed.
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http://dx.doi.org/10.1016/j.cis.2020.102333DOI Listing
January 2021

Bio-Inspired Silica Films Combining Block Copolymers Self-Assembly and Soft Chemistry: Paving the Way toward Artificial Exosqueleton of Seawater Diatoms.

Macromol Rapid Commun 2021 Feb 4;42(4):e2000582. Epub 2020 Dec 4.

Universite de Pau et Pays de l'Adour, E2S UPPA, CNRS, Institut des Sciences Analytiques & de PhysicoChimie pour l'Environnement & les Matériaux, UMR5254, 2 avenue du Président Angot, Pau, F-64053, France.

This review is in line with the principles of bio-inspiration and biomimicry in order to envisage a softer and more environmentally friendly chemistry. Here, the source of inspiration is a microalga from the oceans with the ability to build an exoskeleton of silica under ambient conditions. Following this model, this review is interested in different ways of creating porous silica films with a hierarchical porosity similar to diatoms. For this purpose, polymeric/hybrid/inorganic films structured in honeycomb using the breath figure method are reported. This versatile and easy to implement method based on the principle of rapid evaporation of a solvent in a humid atmosphere is widely used in the formation of structured films with micron-sized pores. In addition to this, the self-assembly of copolymer at the nanoscale can be addressed to obtain a hierarchically structured film. Following this structuration step, the degradation of a sacrificial block is then described from the most energy-intensive to soft process, allowing an added nanoporosity to the micron porosity of the BF method. Finally, hierarchical porous silica films are described using the sol-gel process, which is known as a soft chemistry process.
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http://dx.doi.org/10.1002/marc.202000582DOI Listing
February 2021

Immobilization of a Molecular Re Complex on MOF-derived Hierarchical Porous Carbon for CO Electroreduction in Water/Ionic Liquid Electrolyte.

ChemSusChem 2020 Dec 30;13(23):6418-6425. Epub 2020 Sep 30.

Laboratoire de Chimie des Processus Biologiques, UMR CNRS 8229, Collège de France-CNRS-Sorbonne Université, PSL Research University, 11 Place Marcelin Berthelot, 75005, Paris, France.

The development of molecular catalysts for CO electroreduction within electrolyzers requests their immobilization on the electrodes. While a variety of methods have been explored for the heterogenization of homogeneous complexes, a novel approach using a hierarchical porous carbon material, derived from a metal-organic framework, is reported as a support for the well-known molecular catalyst [Re(bpy)(CO) Cl] (bpy=2,2'-bipyridine). This cathodic hybrid material, named [email protected] (HPC=hierarchical porous carbon), has been tested for CO electroreduction using a mixture of an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIM) and water as the electrolyte. Interestingly, it catalyzes the conversion of CO into a mixture of carbon monoxide and formic acid, with a selectivity that depends on the applied potential. The present study thus reveals that [email protected] is a remarkable catalyst, enjoying excellent activity (turnover numbers for CO reduction of 7835 after 2 h at -1.95 V vs. Fc/Fc with a current density of 6 mA cm ) and good stability. These results emphasize the advantages of integrating molecular catalysts onto such porous carbon materials for developing novel, stable and efficient, catalysts for CO reduction.
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http://dx.doi.org/10.1002/cssc.202002014DOI Listing
December 2020

Microstructure-driven self-assembly and rheological properties of multi-responsive soft microgel suspensions.

J Colloid Interface Sci 2021 Jan 31;581(Pt B):806-815. Epub 2020 Jul 31.

Universite de Pau et Pays de l'Adour, E2S UPPA, CNRS, Institut des Sciences Analytiques & de PhysicoChimie pour l'Environnement & les Matériaux, UMR5254, 64000 Pau, France; LERAM, LabCom UPPA/URGO, Hélioparc, 2 avenue Angot, 64053 Pau, France. Electronic address:

Hypotheses: The deformation and swelling ability of microgels is influenced by the crosslinking distribution. Varying microgels microstructure is expected to obtain suspensions with different flow behavior and thereby, different rheological properties.

Experiments: Different multi-responsive microgels were synthesized using two different crosslinkers and varying their amounts: N,N-methylene bis-acrylamide (MBA) and oligo(ethylene glycol) diacrylate (OEGDA). The rheological results were obtained by zero-shear viscosity and long-time creep measurements on concentrated microgel suspensions Microgel microstructure was analyzed by H nuclear magnetic resonance transverse relaxation measurements.

Findings: At a constant crosslinking rate, we show that the viscosity of OEGDA-crosslinked microgels diverges at a higher concentration than MBA ones, suggesting a looser shell and less restricted dangling chains at the periphery for the later. By scaling with the effective volume fraction, the viscosity curves of the different microgel suspensions reduce into a single curve and closely follow hard sphere models up to ϕ < 0.45. The results from creep tests revealed a much higher yield stress for MBA-crosslinked microgels, strengthening the hypothesis of a looser shell for the later. Finally, transverse relaxation (T) NMR measurements demonstrated that, although all microgels exhibit a core-shell microstructure, MBA samples present a less crosslinked shell corroborating with the rheological results.
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http://dx.doi.org/10.1016/j.jcis.2020.07.137DOI Listing
January 2021

Microwave-Assisted Ultrafast RAFT Miniemulsion Polymerization of Biobased Terpenoid Acrylates.

Biomacromolecules 2020 11 25;21(11):4559-4568. Epub 2020 Sep 25.

POLYMAT, University of the Basque Country UPV/EHU, Kimika Aplikatua Saila, Kimika Zientzien Fakultatea, Joxe Mari Korta Zentroa, Tolosa Hiribidea 72, 20018 Donostia-San Sebastián, Spain.

There is a growing preference to move away from traditional petrochemical-based polymers toward biobased alternatives. Here, we report the microwave-assisted RAFT polymerization of several terpenoid acrylates (tetrahydrogeraniol, cyclademol, nopol, and citronellol). These biobased monomers give polymers with a broad range of glass transition temperatures and are excellent candidates to substitute oil-based (meth)acrylates in applications such as coatings and adhesives. First, the process was studied in miniemulsion, finding that all terpenoid acrylates showed a substantial increase in both polymerization rate and reaction control when microwave irradiation was applied. These observations were attributed to nonthermal microwave effects, namely, to changes in the kinetic coefficients under irradiation. The reactions were also carried out in solution, where an amplified nonthermal microwave effect was observed. The results indicate that nonthermal microwave effects allow RAFT polymerization of these terpenoid acrylates to proceed with both improved control and at higher polymerization rates compared to using conventional heating.
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http://dx.doi.org/10.1021/acs.biomac.0c00662DOI Listing
November 2020

When a pH-triggered nanopatterned shape transition drives the wettability of a hierarchically self-organized film: A bio-inspired effect of "sea Anemone".

J Colloid Interface Sci 2021 Jan 29;581(Pt A):96-101. Epub 2020 Jul 29.

Universite de Pau et Pays Adour, E2S UPPA, CNRS, IPREM UMR 5254, 2 avenue du Président Angot, Pau F-64053, France; Bio-inspired Materials Group: Functionalities & Self-assembly, Universite de Pau et Pays Adour, 2 avenue du Président Angot, Pau F-64053, France. Electronic address:

Hypothesis: Hierarchically structured surfaces including sensitive materials presents the advantage to exalt wettability variation due to the combination of micro structure effect directed by Cassie Baxter and/or Wenzel behaviour which is tuned by the surface energy variation of sensitive polymer films.

Experiments: Herein is reported the synthesis and the hierarchical structuration of a pH sensitive diblock copolymer P(S-stat-MMA)-b-P4VP with a pH-sensitive Poly 4-vinylpyridine P4VP block. Applying the Breath Figure method casting (minute time scale process), this diblock copolymer allows to obtain a micro porous honeycomb film while a wall nano-structuration due to self-assembly of diblock copolymer is observed.

Findings: The pH-triggered wettability is studied and correlated with the morphology evolution of P4VP nano-domains investigated by AFM in a liquid cell. Indeed, a nano-dots to nano-rings/donuts transition is highlighted when decreasing the pH below the pKa of the P4VP. This nano "sea Anemone" shape transition induces the macroscopic changes of the wettability of a hierarchically self-organized honeycomb film, explained by the protonation of P4VP chains inducing electrostatic repulsion and then hydrophilic surface.
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http://dx.doi.org/10.1016/j.jcis.2020.07.130DOI Listing
January 2021

A nanopatterned dual reactive surface driven by block copolymer self-assembly.

Nanoscale 2020 Apr 27;12(14):7532-7537. Epub 2020 Mar 27.

Universite de Pau et Pays de l'Adour, E2S UPPA, CNRS, Institut des Sciences Analytiques & de Physico-Chimie pour l'Environnement & les Matériaux, UMR5254, 64000, Pau, France.

Herein, we report the selective functionalization of nano-domains obtained by the self-assembly of a polystyrene-block-poly(vinyl benzyl azide) PS-b-PVBN copolymer synthesized in three steps. First, a polystyrene macro-initiator was synthesized, and then extended with vinyl benzyl chloride by nitroxide mediated polymerization to form polystyrene-block-poly(vinyl benzyl chloride) PS-b-PVBC. Nucleophilic substitution of vinyl benzyl chloride into a vinyl benzyl azide moiety is finally performed to obtain PS-b-PVBN which self-assembled into nano-domains of vinyl benzyl azide PVBN. Click chemistry was then used to bind functional gold nanoparticles and poly(N-isopropylacrylamide) (PNIPAM) on PVBN domains due to the specific anchoring at the surface of the nanopatterned film. Atomic force microscopy (AFM) was used to observe the block copolymer self-assembly and the alignment of the gold nanoparticles at the surface of the PVBN nanodomains. Thorough X-ray photoelectron spectroscopy (XPS) analysis of the functional film showed evidence of the sequential grafting of nanoparticles and PNIPAM. The hybrid surface expresses thermo-responsive properties and serves as a pattern to perfectly align and control the assembly of inorganic particles at the nanoscale.
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http://dx.doi.org/10.1039/c9nr10740aDOI Listing
April 2020

[email protected] Functional Nanoparticle-Driven Rod-Coil Diblock Copolymer Self-Assembly.

Langmuir 2019 Dec 10;35(51):16925-16934. Epub 2019 Dec 10.

CNRS/Université de Pau et des Pays de l'Adour/E2S UPPA , IPREM CNRS-UMR 5254 Hélioparc , 2 Avenue Président Angot , 64053 Pau Cedex 9, France.

Herein, a novel strategy to overcome the influence of π-π stacking on the rod-coil copolymer organization is reported. A diblock copolymer poly(3-hexylthiophene)--poly(ethylene glycol methyl ether methacrylate) (P3HT--PEGMA) was synthesized by the Huisgen cycloaddition, so-called "click chemistry", combining the PEGMA and P3HT blocks synthesized by atom transfer radical polymerization and Kumada catalyst transfer polymerization, respectively. Using a dip-coating process, we controlled the original film organization of the diblock copolymer by the crystallization of the P3HT block via π-π stacking. The morphology of the P3HT--PEGMA films was influenced by the incorporation of gold nanoparticles (GNPs) coated by poly(ethylene glycol) ligands. Indeed, the crystalline structuration of the P3HT sequence was counterbalanced by the addition in the film of gold nanoparticles finely localized within the copolymer PEGMA matrix. Transmission electron microscopy and time-of-flight secondary ion mass spectrometry analysis validated the GNP homogeneous localization into the compatible PEGMA phase. Differential scanning calorimetry showed the rod block crystallization disruption. A morphological transition of the self-assembly is observed by atomic force microscopy from P3HT fibrils into out-of-plane cylinders driven by the nanophase segregation.
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http://dx.doi.org/10.1021/acs.langmuir.9b02744DOI Listing
December 2019

Direct formation of hydrophilic honeycomb film by self-assembly in breath figure templating of hydrophobic polylacticacid/ionic surfactant complexes.

Soft Matter 2019 Jun;15(25):5052-5059

Polymer Research Institute, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, P. R. China.

Honeycomb-patterned porous films with good surface wettability have great potential applications in various areas. However, hydrophilic honeycomb films are difficult to obtain using the direct self-assembly of pure (co)polymers. Thus, additional and special treatments are required to improve film wettability, which makes the procedure complicated and difficult to access. In this study, a facile way to prepare hydrophilic honeycomb-structured porous films is proposed that uses the direct self-assembly of complexes of biocompatible hydrophobic poly(l-lactic acid) and dodecyltrimethylammonium chloride by breath figure templating. The addition of ionic surfactant not only improves film quality but also confers good wettability. The obtained hydrophilic pore arrays were found to effectively promote cell attachment. Such a hydrophilic honeycomb-patterned porous film could find potential applications where pore wetting is required, including tissue engineering, lithography, and nanoparticle embedding.
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http://dx.doi.org/10.1039/c9sm00845dDOI Listing
June 2019

Renewable Terpene Derivative as a Biosourced Elastomeric Building Block in the Design of Functional Acrylic Copolymers.

Biomacromolecules 2019 06 15;20(6):2241-2251. Epub 2019 May 15.

CNRS, Université de Pau et des Pays de l'Adour, E2S UPPA, IPREM-UMR 5254, Hélioparc , 2 Avenue Président Angot , 64053 Pau Cedex 9 , France.

In order to move away from traditional petrochemical-based polymer materials, it is imperative that new monomer systems be sought out based on renewable resources. In this work, the synthesis of a functional terpene-containing acrylate monomer (tetrahydrogeraniol acrylate, THGA) is reported. This monomer was polymerized in toluene and bulk via free-radical polymerizations, achieving high conversion and molecular weights up to 278 kg·mol. The synthesized poly(THGA) shows a relatively low T (-46 °C), making it useful as a replacement for low T acrylic monomers, such as the widely used n-butyl acrylate. RAFT polymerization in toluene ([M] = 3.6 mol·L) allowed for the well-controlled polymerization of THGA with degrees of polymerization (DP ) from 25 to 500, achieving narrow molecular weight distributions ( D̵ ≈ 1.2) even up to high conversions. At lower monomer concentrations ([M] = 1.8 mol·L), some evidence of intramolecular chain transfer to polymer was seen by the detection of branching (arising from propagation of midchain radicals) and terminal double bonds (arising from β-scission of midchain radicals). Poly(THGA) was subsequently utilized for the synthesis of poly(THGA)- b-poly(styrene)- b-poly(THGA) and poly(styrene)- b-poly(THGA)- b-poly(styrene) triblock copolymers, demonstrating its potential as a component of thermoplastic elastomers. The phase separation and mechanical properties of the resulting triblock copolymer were studied by atomic force microscopy and rheology.
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http://dx.doi.org/10.1021/acs.biomac.9b00185DOI Listing
June 2019

Versatile oligo(ethylene glycol)-based biocompatible microgels for loading/release of active bio(macro)molecules.

Colloids Surf B Biointerfaces 2019 Mar 11;175:445-453. Epub 2018 Dec 11.

Université de Pau & Pays Adour, CNRS, IPREM UMR 5254, Equipe de Physique et Chimie des Polymères, 2 avenue du Président Angot, Pau F-64053, France; Bio-inspired Materials Group: Functionality & Self-assembly, Université de Pau & Pays Adour, 2 avenue du Président Angot, Pau F-64053, France. Electronic address:

The present study aims in the understanding of the effect of oligo(ethylene glycol)-based biocompatible microgels inner structure on the encapsulation/release mechanisms of different types of cosmetic active molecules. For that, multi-responsive microgels were synthesized using three types of cross-linkers: ethylene glycol dimethacrylate (EGDMA), oligo(ethylene glycol) diacrylate (OEGDA) and N,N-methylenebisacrylamide (MBA). The inner morphology of the microgels synthesized was studied by H-nuclear magnetic resonance (H NMR) and small-angle neutron scattering (SANS) techniques and no effect of cross-linker type on microgel microstructure was observed in the case of analysing purified microgel dispersions. Moreover, all the microgels synthesized presented conventional swelling/de-swelling behavior as a function of temperature and pH. Two hydrophobic, one hydrophilic, and one macromolecule as cosmetic active molecules were effectively loaded into different microgel particles via hydrophobic interactions and hydrogen-bonding interactions between -OH groups of active molecules and ether oxygens of different microgel particles. Their release profiles as a function of cross-linker type used and encapsulated amounts were studied by Peppas-Sahlin model. No effect of the cross-linker type was observed due to the similar inner structure of all the microgels synthesized.
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http://dx.doi.org/10.1016/j.colsurfb.2018.12.019DOI Listing
March 2019

Reactive nano-patterns in triple structured bio-inspired honeycomb films as a clickable platform.

Chem Commun (Camb) 2018 Nov;54(93):13068-13071

Université de Pau & Pays Adour, CNRS, IPREM UMR 5254, 2 Avenue du Président Angot, Pau F-64053, France.

A hierarchically structured platform was obtained from directed self-assembly of a poly(styrene)-b-poly(4-vinylbenzylchloride) (PS-b-PVBC) block copolymer (BCP) during breath figure (BF) templating. The BF process using a water/ethanol atmosphere gave a unique double porosity in which hexagonally arranged micron-sized pores were encircled by a secondary population of smaller, nano-sized pores. A third level of structuration was simultaneously introduced between the pores by BCP self-assembly to form out-of-the-plane nano-cylinders, offering a film with an unprecedented triple structure, which could be used as a reactive platform. Indeed the surface nano-domains of VBC were exploited as reactive nano-patterns for site-specific chemical functionalization.
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http://dx.doi.org/10.1039/c8cc05333bDOI Listing
November 2018

Hierarchically organized honeycomb films through block copolymer directed self-assembly in "breath figure" templating and soft microwave-triggered annealing.

Soft Matter 2018 Jun;14(23):4874-4880

Univ Pau & Pays Adour, CNRS UMR 5254, IPREM, Equipe Physique & Chimie des Polymères, 2 avenue Angot, 64053, Pau, France.

Hierarchically organized polymer films are produced with a high level of order from the combination of block copolymer nanophase segregation, "breath figure" methodology and microwave irradiation. A block copolymer based on poly(methyl methacrylate) and poly(n-butylacrylate) featuring cylindrical nanopatterns is involved in the "breath figure" process to create a microporous honeycomb structure. These films are submitted to microwave annealing to enhance the degree of ordering of the nano-segregation without the destruction of the honeycomb microstructure, which is not possible by classical thermal or solvent annealing. Ellipsometry, optical and atomic force microscopy are used to study three key parameters; the substrate nature, the film thickness and the microwave irradiation power. The silicon wafer is the substrate of choice to efficiently act as the heating transfer element and 60 seconds at 10 watts are enough to nicely order the 1 μm thick copolymer films. These conditions are eventually applied on hierarchically organized polymer films to obtain a hexagonal array of 100 nm deep holes within a matrix of perpendicularly aligned nano-cylinders.
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http://dx.doi.org/10.1039/c8sm00137eDOI Listing
June 2018

Directed Self-Assembly in "Breath Figure" Templating of Melamine-Based Amphiphilic Copolymers: Effect of Hydrophilic End-Chain on Honeycomb Film Formation and Wetting.

Chemistry 2018 Jan 4;24(2):425-433. Epub 2017 Dec 4.

Institut des Sciences Analytiques et de Physico-Chimie pour, l'Environnement et les Matériaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA), CNRS UMR 5254, Hélioparc, 2 avenue Angot, 64053, Pau Cedex 9, France.

Amphiphilic copolymers are widely used in the fabrication of hierarchically honeycomb-structured films through a "breath figure" (BF) process because the hydrophilic block plays a key role in stabilising water templating. However, the hydrophilic monomers reported are mainly confined to acrylic acid and its derivatives, which largely limits understanding of the formation of BF arrays and the introduction of additional functions on porous films. The relationship between polymer composition, film microstructure and surface properties are also less documented. Herein, a novel melamine-based hydrophilic moiety, N-[3-({3-[(4,6-bis{[3-(dimethylamino)propyl]amino}-1,3,5-triazin-2yl)amino]propyl}(methyl)amino)propyl]methacrylamide (ANME), was incorporated into polystyrene (PS) chains by combining atom-transfer radical polymerisation and post-modification to afford three well-defined end-functionalised PS-PANME derivatives. These polymers were used to fabricate honeycomb films through the BF technique. Both inner and outer microstructures of the films were characterised by optical microscopy, AFM and SEM. Polymer hydrophilicity is enhanced upon increasing the PANME content, which results in variation of the film microstructure and porosity, and provokes a transition from Cassie-Baxter to Wenzel behaviour. Furthermore, the surface wettability of as-prepared honeycomb films and corresponding pillared films is mainly governed by film morphology, rather than by the properties of the polymers. Knowledge of the relationships between polymer composition and film structure, as well as surface wettability, is beneficial to design and prepare hierarchically porous films with desirable structures and properties.
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http://dx.doi.org/10.1002/chem.201704369DOI Listing
January 2018

Hierarchical honeycomb-structured films by directed self-assembly in "breath figure" templating of ionizable "clicked" PH3T-b-PMMA diblock copolymers: an ionic group/counter-ion effect on porous polymer film morphology.

Chem Commun (Camb) 2017 Feb;53(11):1876-1879

IPREM CNRS-UMR 5254, Equipe de Physique et Chimie des Polymères, Université de Pau et des Pays de l'Adour, Hélioparc, 2 avenue Président Angot, 64053 Pau Cedex 9, France.

The self-assembly of 1,2,3-triazole and ionic 1,2,3-triazolium "clicked" poly(3-hexylthiophene)-b-poly(methylmethacrylate) (P3HT-b-PMMA) rod-coil diblock copolymers was used to fabricate honeycomb-patterned porous films via "breath figure" templating. The surface and inner morphologies of the honeycomb films can be both controlled by either ionizing the 1,2,3-triazole linker or changing the counter-ion nature.
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http://dx.doi.org/10.1039/c6cc09898cDOI Listing
February 2017

Thermodynamics of the multi-stage self-assembly of pH-sensitive gradient copolymers in aqueous solutions.

Soft Matter 2016 Aug;12(32):6788-98

Institute of Macromolecular Chemistry AS CR, v.v.i., Heyrovského nám. 2, CZ-162 06 Praha 6, Czech Republic.

The self-assembly thermodynamics of pH-sensitive di-block and tri-block gradient copolymers of acrylic acid and styrene was studied for the first time using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) performed at varying pH. We were able to monitor each step of micellization as a function of decreasing pH. The growth of micelles is a multi-stage process that is pH dependent with several exothermic and endothermic components. The first step of protonation of the acrylic acid monomer units was accompanied mainly by conformational changes and the beginning of self-assembly. In the second stage of self-assembly, the micelles become larger and the number of micelles becomes smaller. While solution acidity increases, the isothermal calorimetry data show a broad deep minimum corresponding to an exothermic process attributed to an increase in the size of hydrophobic domains and an increase in the structure's hydrophobicity. The minor change in heat capacity (ΔCp) confirms the structural changes during this exothermic process. The exothermic process terminates deionization of acrylic acid. The pH-dependence of the ζ-potential of the block gradient copolymer micelles exhibits a plateau in the regime corresponding to the pH-controlled variation of the micellar dimensions. The onset of micelle formation and the solubility of the gradient copolymers were found to be dependent on the length of the gradient block.
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http://dx.doi.org/10.1039/c6sm01105eDOI Listing
August 2016

Hierarchically porous bio-inspired films prepared by combining "breath figure" templating and selectively degradable block copolymer directed self-assembly.

Chem Commun (Camb) 2016 Jul;52(61):9562-5

Université de Pau & Pays Adour, IPREM (CNRS, UMR 5254)-Equipe de Physique & Chimie des Polymères (EPCP) - Hélioparc, 2 Avenue Président Angot, 64053, Pau, France.

Polymer films with hierarchical micro- and nano-porosities were prepared by combining the fast solvent evaporation "Breath Figure" (BF) method, exhibiting a highly regular honeycomb micro-porous texture, with the additional nanoscale self-assembly of polylactide-block-polystyrene (PLA-b-PS) diblock copolymers, PLA being used thereafter as a sacrificial component for nano-porosity.
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http://dx.doi.org/10.1039/c6cc04760bDOI Listing
July 2016

When block copolymer self-assembly in hierarchically ordered honeycomb films depicts the breath figure process.

Soft Matter 2016 Jan 3;12(3):790-7. Epub 2015 Nov 3.

Université de Pau et des Pays de l'Adour, Hélioparc, IPREM Equipe de Physique et Chimie des Polymères, UMR 5254 CNRS, 2 Avenue du Président Angot, 64053 Pau, France.

Nowadays, a challenge in the preparation of hierarchically ordered materials is the control of concomitant and interacting self-organization processes occurring in time at different length scales. In the present paper, the breath figure process is combined with block copolymer nano-phase segregation to elaborate hierarchically structured honeycomb porous films. Copolymer ordering, at the nanometer length scale, is observed and described in detail with respect to the array of pores of micrometer dimension, hence pointing out the structural interplays between both length-scales. The study is focused on two diblock copolymers made of polystyrene and poly(tert-butyl acrylate) (PS-b-PtBA) with compositions producing lamellae or hexagonal packing of cylinders at thermodynamical equilibrium. Transmission Electron Microscopy completed with Small and Ultra-Small Angle Scattering are performed to evidence the inner morphologies of the honeycomb. The structural data are discussed in the light of the honeycomb film formation process establishing the interest in using kinetically trapped block copolymer self-organization as an imprint to elucidate the complex breath figure process.
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http://dx.doi.org/10.1039/c5sm01774bDOI Listing
January 2016

Biomimetic Mussel Adhesive Inspired Anchor to Design [email protected](3-Hexylthiophene) Hybrid [email protected] Nanoparticles.

Macromol Rapid Commun 2015 Aug 1;36(16):1486-91. Epub 2015 Jun 1.

Université de Pau et des Pays de l'Adour, Equipe de Physique et Chimie des Polymere, Hélioparc 2 avenue Président Angot, 64053, Pau Cedex 9, France.

The functionalization of zinc oxide (ZnO) nanoparticles by poly(3-hexylthiophene) (P3HT) brush is completed by the combination of a mussel inspired biomimetic anchoring group and Huisgen cyclo-addition "click chemistry." Herein, the direct coupling of an azide modified catechol derivative with an alkyne end-functionalized P3HT is described. This macromolecular binding agent is used to access [email protected] [email protected] with a stable and homogeneous conjugated organic corona. Preliminary photoluminescence measurement proves an efficient electron transfer from the donor P3HT to the acceptor ZnO nanoparticles upon grafting, thus demonstrating the potential of such a combination in organic electronics.
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http://dx.doi.org/10.1002/marc.201500184DOI Listing
August 2015

Design of smart oligo(ethylene glycol)-based biocompatible hybrid microgels loaded with magnetic nanoparticles.

Macromol Rapid Commun 2015 Jan 25;36(1):79-83. Epub 2014 Nov 25.

CNRS, Université de Pau & Pays Adour, UMR 5254, IPREM, Equipe de Physique et Chimie des Polymères, 2 avenue du Président Angot, Pau, F-64053, France.

This article reports a rational strategy for preparing smart oligo(ethylene glycol)-based hybrid microgels loaded with high content of homogeneously distributed preformed magnetic nanoparticles (NPs) (up to 33 wt%). The strategy is based on the synthesis of biocompatible multiresponsive microgels by precipitation copolymerization of di(ethylene glycol) methyl ether methacrylate, oligo(ethylene glycol) methyl ether methacrylate, methacrylic acid, and oligo(ethylene glycol)diac-rylate. An aqueous dispersion of preformed magnetic NPs is straightforwardly loaded into the microgels. Robust monodisperse thermoresponsive magnetic microgels are produced, exhibiting a constant value of the volume phase transition temperature whatever the NPs content. The homogeneous microstructure of the initial stimuli-responsive biocompatible microgels plays a crucial role for the design of unique well-defined ethylene glycol-based thermoresponsive hybrid microgels.
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http://dx.doi.org/10.1002/marc.201400578DOI Listing
January 2015

Terpene and dextran renewable resources for the synthesis of amphiphilic biopolymers.

Biomacromolecules 2014 Jan 3;15(1):242-51. Epub 2013 Dec 3.

CNRS, University of Pau and Pays Adour, UMR 5254, IPREM, Equipe de Physique et Chimie des Polymères, 2 avenue du Président Angot, Pau, F-64053, France.

The present work shows the synthesis of amphiphilic polymers based on the hydrophilic dextran and the hydrophobic terpenes as renewable resources. The first step concerns the synthesis of functional terpene molecules by thiol-ene addition chemistry involving amino or carboxylic acid thiols and dihydromyrcenol terpene. The terpene-modified polysaccharides were subsequently synthesized by coupling the functional terpenes with dextran. A reductive amination step produced terpene end-modified dextran with 94% of functionalization, while the esterification step produced three terpene-grafted dextrans with a number of terpene units per dextran of 1, 5, and 10. The amphiphilic renewable grafted polymers were tested as emulsifiers for the stabilization of liquid miniemulsion of terpene droplets dispersed in an aqueous phase. The average hydrodynamic diameter of the stable droplets was observed at about 330 nm.
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http://dx.doi.org/10.1021/bm401521fDOI Listing
January 2014

Photoactive, porous honeycomb films prepared from Rose Bengal-grafted polystyrene.

Langmuir 2013 Aug 30;29(32):10264-71. Epub 2013 Jul 30.

CNRS, University of Pau and Pays de l'Adour, UMR 5254, IPREM, Equipe de Physique et Chimie des Polymères, 2 avenue du Président Angot, Pau, F-64053, France.

Honeycomb-structured porous polymer films based on photosensitizer-grafted polystyrene are prepared through the breath figure process. Rose Bengal (RB) photosensitizer is first attached to a well-defined poly(styrene-stat-4-vinylbenzyl chloride) statistical copolymer, synthesized by nitroxide-mediated radical polymerization. The RB grafted poly(styrene-stat-4-vinylbenzyl chloride) (ca. 20,000 g mol(-1) molar mass, 1.2 dispersity) leads to porous polymer films, with a hexagonal pore pattern, while a simple mixture of poly(styrene-stat-4-vinylbenzyl chloride) and the insoluble RB photosensitizer produced unstructured, nonporous films. The RB-grafted honeycomb films, compared with the corresponding nonporous flat films, are more efficient for oxidation of organic molecules via singlet oxygen production at a liquid/solid interface. The oxidations of 1,5-dihydroxynaphthalene to juglone and α-terpinene to ascaridole are followed in ethanol in the presence of both types of films. Oxidation of the organic molecules is a factor 5 greater with honeycomb compared to the nonporous films. This gain is ascribed to two factors: the specific location of the polar photosensitizer at the film interface and the greater exchange surface, as revealed by fluorescence and scanning electron microscopies.
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http://dx.doi.org/10.1021/la402079zDOI Listing
August 2013

Polystyrene-coated micro-sized particles by "in situ" surface initiated polymerization in accord with Langmuir model adsorption.

J Colloid Interface Sci 2012 May 1;374(1):237-40. Epub 2012 Feb 1.

Laboratoire des Matériaux, Catalyse, Environnement et Analyses Analytiques, Université Libanaise, Beirut, Lebanon.

This study describes the mechanism of adsorption of polystyrene chains PS "in situ" growth from micro-sized commercial silicate particles, i.e. Feldspar. The main aim is to derive adsorption isotherms from thermal gravimetric analysis (TGA) and size exclusion chromatography (SEC) data obtained during the direct polymerization of PS initiated by a pre-adsorbed radical initiator onto the inorganic surface. The adsorption isotherm plot indicates that the PS adsorption is in accord with the Langmuir Model. The amount of PS monolayer coverage increases with polymerization time, and it is highly dependent on the monomer diffusion to the surface during the hybrid inorganic/organic synthesis. Such behavior depends on the concentration gradient between monomer concentration in solution and that adsorbed by polymerization onto the micro-sized particles surface of Feldspar.
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http://dx.doi.org/10.1016/j.jcis.2012.01.048DOI Listing
May 2012

pH sensitive hierarchically self-organized bioinspired films.

Macromol Rapid Commun 2011 Jul 17;32(14):1072-6. Epub 2011 Jun 17.

IPREM Equipe de Physique et Chimie des Polymères, UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex, France.

In the present manuscript, we have demonstrated that hierarchically structured smart porous polymer films based on honeycomb-patterned surface can be elaborated from PS-b-P4VP pH-responsive block copolymer using the breath figure process. Despite the fast film formation by a bottom-up process, the copolymer nanostructuration was observed inside the walls of the honeycomb porous film. Atomic force microscopy (AFM), small angle X-ray and neutron scattering (SAXS and SANS) measurements were used to reveal both the hexagonal arrays formed by the pores at the micrometer length scale and the hexagonal copolymer self-assembly at the nanometer length scale. Contact angle (CA) measurements were used to point out the reversible pH-responsive wettability character of the surface. The PS-b-P4VP honeycomb film shows a contact angle variation of 20° between pH 9 and pH 3. An increase of the roughness was obtained with the pincushions hexagonal array enhancing the pH responsiveness of the polymer film with a switching CA gap of 75° when pH tuned from pH 9 to pH 3. This work presents the first report on honeycomb porous and pincushion films exhibiting a reversible pH-responsive character.
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http://dx.doi.org/10.1002/marc.201100296DOI Listing
July 2011

A versatile route to functional biomimetic coatings: ionomers for honeycomb-like structures.

Soft Matter 2007 Nov;3(12):1492-1499

Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux, Equipe de Physico-chimie des Polymères IPREM/EPCP CNRS UMR 5254, Université de Pau et Pays de l'Adour, Hélioparc Pau Pyrénées 2 Avenue Angot, 64053 Pau Cedex 09, France.

Highly ordered films were prepared by spreading out carbon disulfide (CS) solutions of ionomers over inorganic surfaces and for the first time over an organic surface. These ionomers, hydrophobic homopolymers or copolymers end-capped by a cationic group, were easily synthesized in a one-step reaction by a control radical process called nitroxide-mediated polymerization. Optical and electronic microscopy observations of the films lead to the definition of new criteria for the formation of such structures. Firstly, the effect of a solid support on the honeycomb structure regularity was studied. By comparing two polar substrates, it was found that a more regular organization is obtained over mica than over glass. This phenomenon may be due to the electrostatic interactions between cationic ionomer ends and oxanions of the mica surface. Moreover, for the first time, highly ordered hexagonal patterns were also created on a flexible and soft polymeric surface, a poly(vinyl chloride) sheet. Secondly, it was found that the characteristics of the polymeric chain of the ionomer and mainly its glass transition temperature play an important role in the process of formation of ordered structures. The iridescent aspect of the films, due to light diffraction and optical interferences, was studied and quantified by spectrogoniometry. Finally, results of measurements of superficial tension are discussed; the presence of a honeycomb film at the surface of a material very significantly enhances its hydrophobicity. All these criteria of highly ordered structures correlated to a water repellency and iridescent behaviours lead to a functional biomimetic material.
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http://dx.doi.org/10.1039/b710282hDOI Listing
November 2007

In situ thermo-dependant trapping of carbon radicals: a versatile route to well-defined polymer-grafted silica nanoparticles.

Soft Matter 2007 Jul;3(8):1014-1024

Institut Pluridisciplinaire de Recherche sur l'Environnement et les matériaux Equipe de Physico-Chimie des Polymères, UMR 5254, Hélioparc, 2 avenue Angot, 64000 Pau, France.

We report in this paper an original and simple method for the grafting of polymer chains on colloidal silica particles. We first synthesize an alkoxyamine bi-functional initiator, by coupling 2-methyl-2-[--butyl--(dimethoxyphosphoryl-2,2-dimethylpropyl)aminoxy]propionic acid (MAMA) and an acrylate coupling agent, 3-(trimethoxysilyl)propyl acrylate (TPMA). Based on the fact that MAMA dissociates at 25 °C, but activates polymerization of acrylates at only 110 °C, it is possible to stop the reaction after the insertion of only one C[double bond, length as m-dash]C acrylate double bond, in the temperature range 25-80 °C. This synthetic methodology is called " thermo-dependant trapping of carbon radicals". The "new" initiator obtained at that stage is then grafted on Stöber silica particles, by simple condensation of its alkoxysilane functions. We show that the initiator-grafting density is twice as high as the value obtained by our first approach of "trapping of carbon radicals". The last step of the synthesis process is the grafting from polymerization of polybutylacrylate (PBA). Transmission electron microscopy (TEM) images and small-angle neutron scattering (SANS) spectra show that the PBA-grafted silica particles are spherical, with a narrow size distribution, and do not form aggregates. Moreover, by this versatile route, the grafted polymer density, the molecular weight and therefore the polymer-layer morphology, can be easily controlled and tuned. It can also be extended to other monomers that work well with SG1 nitroxide.
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http://dx.doi.org/10.1039/b705249aDOI Listing
July 2007

Choose sides: differential polymer adhesion.

Langmuir 2007 Jun 10;23(12):6660-6. Epub 2007 May 10.

Lehrstuhl für Angewandte Physik and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstr. 54, 80799 München, Germany.

AFM-based single molecule desorption measurements were performed on surface end-grafted poly(acrylic acid) monolayers as a function of the pH of the aqueous buffer to study the adhesion properties of polymers that bridge two surfaces. These properties were found to depend on the adhesion forces of both surfaces in a differential manner, which is explained with a simple model in analogy to the Bell-Evans formalism used in dynamic force spectroscopy. The measured interaction forces between the poly(acrylic acid) chains and silicon nitride AFM tips depend on the grafting density of the polymer monolayers as well as on the contour length of the polymer chains. This study demonstrates that the stability of polymer bridges is determined by the adhesion strengths on both surfaces, which can be tuned by using pH-dependent polyelectrolyte monolayers.
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http://dx.doi.org/10.1021/la063682yDOI Listing
June 2007

Effect of the synthetic methodology on molecular architecture: from statistical to gradient copolymers.

Soft Matter 2006 Aug;2(9):770-778

Laboratoire de Physico-Chimie des Polymères, UMR 5067 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc 2 Avenue du Président Angot, 64053 Pau cedex, France.

Styrene-butyl acrylate (S-BuA) copolymers were synthesized by nitroxide-mediated controlled radical polymerization using an alkoxyamine as an initiator. Using different synthetic methodologies, statistical copolymers were be obtained by batch nitroxide mediated polymerization while the gradient composition was a forced gradient by continuous addition of S during BuA polymerization (semi-batch process). These gradient copolymers have been studied by H NMR and size exclusion chromatography to characterize the gradient composition molecular structure. The evolution of the composition was correlated with the glass transition temperature () of the copolymers. The gradient copolymers exhibit one with a value in between the of polystyrene and poly(butyl acrylate), indicating that the materials did not present well defined microphase separation. Specific organization at the air-polymer interface of such copolymers has also been demonstrated by comparison between classical and attenuated total reflection (ATR) Fourier transform infra-red spectra. This bulk soft matter assembly was confirmed by AFM analysis, which showed a different morphology at the surface and in the bulk following removal of the top layer. Moreover, for the most well defined gradient composition, a specific nano-structuring was demonstrated by small angle neutron scattering. The preliminary rheological properties of these gradient copolymers were studied and are discussed in relation with their molecular structure.
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http://dx.doi.org/10.1039/b607797hDOI Listing
August 2006

Nanostructure and mechanical properties of polybutylacrylate filled with grafted silica particles.

Langmuir 2006 Jul;22(15):6683-9

Laboratoire de Physico-Chimie des Polymères UMR 5067, Université de Pau et des Pays de l'Adour, Avenue de l'Université, 64000 Pau, France.

We investigate the nanostructure and the linear rheological properties of polybutylacrylate (PBA) filled with Stöber silica particles grafted with PBA chains. The silica volume fractions range from 1.8 to 4.7%. The nanostructure of these suspensions is investigated by small-angle neutron scattering (SANS), and we determine their spectromechanical behavior in the linear region. SANS measurements performed on low volume fraction composites show that the grafted silica particles are spherical, slightly polydisperse, and do not form aggregates during the synthesis process. These composites thus constitute model filled polymers. The rheological results show that introducing grafted silica particles in a polymer matrix results in the appearance of a secondary process at low frequency: for the lowest volume fractions, we observe a secondary relaxation that we attribute to the diffusion of the particles in the polymeric matrix. By increasing the silica volume fraction up to a critical value, we obtain gellike behavior at low frequency as well as the appearance of a structure factor on the scattering intensity curves obtained by SANS. Further increasing the silica particle concentration leads to composites exhibiting solidlike low-frequency behavior and to an enhanced structure peak on the SANS diagrams. This quantitative correlation between the progressive appearance of a solidlike rheological behavior, on one hand, and a structure factor, on the other hand, supports the idea that the viscoelastic behavior of filled polymers is governed by the spatial organization of the fillers in the matrix.
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http://dx.doi.org/10.1021/la0607003DOI Listing
July 2006
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