Philippe Degée

Preparation and characterisation of silicone-based coatings filled with carbon nanotubes and natural sepiolite and their application as marine fouling-release coatings

This article reports on the preparation and partial characterisation of silicone-based coatings filled with low levels of either synthetic multiwall carbon nanotubes (MWCNTs) or natural sepiolite (NS). The antifouling and fouling-release properties of these coatings were explored through laboratory assays involving representative soft-fouling (Ulva) and hard-fouling (Balanus) organisms. The bulk mechanical properties of the coatings appeared unchanged by the addition of low amounts of filler, in contrast to the surface properties, which were modified on exposure to water. The release of Ulva sporelings (young plants) was improved by the addition of low amounts of both NS and MWCNTs. The most profound effect recorded was the significant reduction of adhesion strength of adult barnacles growing on a silicone elastomer containing a small amount (0.05%) of MWCNTs. All the data indicate that independent of the bulk properties, the surface properties affect settlement, and more particularly, the fouling-release behaviour, of the filled materials.

New developments on the ring opening polymerisation of polylactide

Abstract Polylactides (PLA), biodegradable aliphatic polyesters, produced solely from renewable resources may substitute petrochemically based polymers in a broad range of applications in the near future, if we manage to produce them at lower cost and higher efficiency as nowadays. Possible applications include food packaging for meat and soft drinks, films for agro-industry and non-wovens in hygienic products. The authors developed, based on a new catalytic system, a reactive extrusion polymerisation process, which can be used to produce PLA continuously in larger quantities and at lower costs than before. This extrusion polymerisation process has been developed and tested with laboratory scale machines and the possibilities to extend this polymerisation process to lactide based blockcopolymers have been investigated.

Enhancement of Transfection Efficiency Through Rapid and Noncovalent Post-PEGylation of Poly(Dimethylaminoethyl Methacrylate)/DNA Complexes

AbstractPurpose. The aim of this work was to develop a new strategy to intro- duce poly(ethylene glycol) (PEG) into methacrylate-based polymer/DNA complexes in order to produce hemocompatible particles able to transfect cells in the presence of serum. Methods. Atom transfer radical polymerization was used to synthesize a well-defined poly(2-(dimethylamino)ethyl methacrylate) homopolymer (PDMAEMA) and a poly(2-(dimethylamino)ethyl methacrylate-b-poly(ethylene glycol) α-methyl ether, ω-methacrylate) palm-tree-like copolymer (P(DMAEMA-b-MAPEG)). The complexes obtained by self assembly of the pCMVβ plasmid and the polymers were used to transfect Cos-7 cells. Their physical properties—particle size and zeta potential—were characterized respectively by dynamic light scattering and electrophoretic mobility measurements. Ex vivo hemocompatibility was also determined. Results. The PDMAEMA/pCMVβ complexes transfected Cos-7 cells exclusively in the absence of serum. Although the P(DMAEMA-b-MAPEG) copolymer had no transfection activity per se, the addition of the latter to pre-formed PDMAEMA/DNA complexes significantly enhanced the activity and allowed transfection even in the presence of serum. The presence of palm-tree-like copolymers also improved the hemocompatibility properties of the complexes. No effect on platelet counts was observed for P(DMAEMA-b-MAPEG)/pCMVβ complexes, whereas a decrease of platelets was clearly observed when blood cells were incubated with PDMAEMA/pCMVβ complexes. Conclusions. Such a synergistic effect of noncovalent PEGylation of poly(amino methacrylate)/DNA complexes allows a new and versatile approach to tune up transfection efficiency.

Coordination-insertion ring-opening polymerization of 1,4-dioxan-2-one and controlled synthesis of diblock copolymers with ε-caprolactone

This communication deals with the coordination-insertion ring-opening polymerization of 1,4-dioxan-2-one (DX) as initiated by aluminium triisopropoxide (Al(O i Pr) 3 ) either in bulk or in solution. First, polymerization of DX has been carried out in bulk at 100°C and compared to the ring-opening polymerization promoted by tin(II)octoate. Block copolymers of e-capro lactone (CL) and DX have been then selectively obtained by first initiating CL polymenzation with Al(O-Pr) 3 in toluene and then adding DX to the living PCL macroinihator solution at room temperature. In spite of the inherent poor solubility of poly(1,4-dioxan-2-one) in most organic solvents. DX polymerization has proven to proceed through a living mechanism. Interestingly enough, the semi-crystalline P[CL-b-DX] block copolymers dis played two well scparated melting endotherms at ca 55 and 102°C for PCL and PDX sequences, respectively.

Poly(e-caprolactone) layered silicate nanocomposites: effect of clay surface modifiers on the melt intercalation process

Abstract Nanocomposites based on biodegradable poly(e-caprolactone) (PCL) and layered silicates (montmorillonite) modified by various alkylammonium cations were prepared by melt intercalation. Depending on whether the ammonium cations contain non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions, microcomposites or nanocomposites were recovered as shown by X-ray diffraction and transmission electron microscopy. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. The layered silicate PCL nanocomposites exhibited some improvement of the mechanical properties (higher Young’s modulus) and increased thermal stability as well as enhanced flame retardant characteristics as result of a charring effect. This communication aims at reporting that the formation of PCL-based nanocomposites strictly depends on the nature of the ammonium cation and its functionality, but also on the selected synthetic route, i.e. melt intercalation vs. in situ intercalative polymerization. Typically, protonated w-aminododecanoic acid exchanged montmorillonite allowed to intercalate ε -caprolactone monomer and yielded nanocomposites upon in situ polymerization, whereas they exclusively formed microcomposites when blended with preformed PCL chains. In other words, it is shown that the formation of polymer layered silicate nanocomposites is not straightforward and cannot be predicted since it strongly depends on parameters such as ammonium cation type and functionality together with the production procedure, i.e., melt intercalation, solvent evaporation or in situ polymerization.

Novel biodegradable adaptive hydrogels: controlled synthesis and full characterization of the amphiphilic co-networks.

Adaptive and amphiphilic poly(N,N-dimethylamino-2-ethyl methacrylate-graft-poly[epsilon-caprolactone]) co-networks (netP(DMAEMA-g-PCL)) were synthesized from a combination of controlled polymerization techniques. Firstly, PCL cross-linkers were produced by ring-opening polymerization (ROP) of epsilon-CL initiated by 1,4-butane-diol and catalyzed by tin(II) 2-ethylhexanoate ([Sn(Oct)2]), followed by the quantitative esterification reaction of terminal hydroxyl end-groups with methacrylic anhydride. Then, PCL cross-linkers were copolymerized to DMAEMA monomers by atom-transfer radical polymerization (ATRP) in THF at 60 degrees C using CuBr complexed by 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) and 2-ethyl isobutyrylbromide (EiBBr) as catalytic complex and initiator, respectively. A comprehensive study of gel formation was carried out by employing dynamic light scattering (DLS) to determine the gel point as a function of several parameters and to characterize the viscous solutions obtained before the gel point was reached. The evolution of the mean diameters was compared to a model previously developed by Fukuda and these attest to the living formation of the polymer co-network. Furthermore, we also demonstrated the reliability of ATRP for producing well-defined and homogeneous polymer co-networks by the smaller deviation from Florys theory in terms of cross-linking density. For sake of clarity, the impact of polymerization techniques over the final structure and, therefore, properties was highlighted by comparing two samples of similar composition, but that were produced by either ATRP or thermal-initiated free-radical polymerization (FRP).

Preparation of Well‐Defined Poly[(ethylene oxide)‐block‐(sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate)] Diblock Copolymers by Water‐Based Atom Transfer Radical Polymerization

Sodium2-acrylamido-2-methyl-1-propane sulfonate (AMPS) based (co)polymers are used in awide range of applications such as detergents, thickeners, paper-coatings, and dental adhesives but they have also gained interest due to their anticoagulant properties and their ability to improve the compatibility of polymers with blood. Similarly, poly(ethylene oxide) (PEO) segments are well-known to highly reduce non-specific interactions with blood proteins by a steric repulsion mechanism and might increase further blood compatibility of AMPS-based copolymers. In 2001, the preparation of well-defined PAMPS homopolymer and block copolymers with sodium 3-acrylamido-3methylbutanoate has been achieved by reversible additionfragmentation chain transfer (RAFT) polymerization using 4,40-azobis(4-cyanopentanoic acid) and 4-cyanopentanoic acid dithiobenzoate as initiator and chain transfer agent, respectively, at 70 8C in water. The solution pH was adjusted at 9.6. As far as water-based atom transfer radical Summary:Well-defined poly[(ethylene oxide)-block-(sodium 2-acrylamido-2-methyl-1-propane sulfonate)] diblock copolymers [P(EOm-b-AMPSn)], have been obtained by water-based ATRP using a-methoxy-o-(2-methylbromoisobutyrate) poly(ethylene oxide)s (MeO-P[EO]m-Br Bwithm ranging from 12 to 113) and CuBr 2Bpy (Bpy for 2,20-bipyridyl) as macroinitiator and catalytic complex, respectively.Compared to direct polymerization inwater, it has beendemonstrated that thewater/ methanol (3:1, v/v) mixture is better suited for predicting the final number-average molar mass from the initial monomer-tomacroinitiator molar ratio and achieving a quite narrow polydispersity, even at high monomer conversion (Mw=Mn 1.4 at 80% conversion). The effect of temperature, solvent mixture composition and addition of NaCl salt on the polymerization rate and extent of control over the copolymer molecular parameters have been highlighted as well.

Solvent-free synthesis and purification of poly[2-(dimethylamino)ethyl methacrylate] by atom transfer radical polymerization

Solvent-free synthesis of well-defined poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) (co)polymers was performed by atom transfer radical polymerization conducted under very mild conditions (in bulk at 25 degrees C). The pH-dependence and the thermo-responsive behaviour of PDMAEMA in aqueous solution were operated to isolate and purify the (co)polymers without using any organic solvent or further catalyst extraction. The viscosity in aqueous solution of so-purified PDMAEMA homopolymers and their block copolymers with poly(ethylene glycol) (PEG) was studied as a function of molar mass and concentration and a typical polyelectrolyte behaviour was observed, these catalyst-deprived polycations are able to form stable and non toxic complexes with DNA, showing good transfection efficacies in gene therapy.

Self-nucleation and crystallization kinetics of double crystalline poly(p-dioxanone)-b-poly(epsilon-caprolactone) diblock copolymers.

The crystallization kinetics of each constituent of poly(p-dioxanone)-b-poly(epsilon-caprolactone) diblock copolymers (PPDX-b-PCL) has been determined in a wide composition range by differential scanning calorimetry and compared to that of the equivalent homopolymers. Spherulitic growth rates were also measured by polarized optical microscopy while atomic force microscopy was employed to reveal the morphology of one selected diblock copolymer. It was found that crystallization drives structure formation and both components form lamellae within mixed spherulitic superstructures. The overall isothermal crystallization kinetics of the PPDX block at high temperatures, where the PCL is molten, was determined by accelerating the kinetics through a previous self-nucleation procedure. The application of the Lauritzen and Hoffman theory to overall growth rate data yielded successful results for PPDX and the diblock copolymers. The theory was applied to isothermal overall crystallization of previously self-nucleated PPDX (where growth should be the dominant factor if self-nucleation was effective) and the energetic parameters obtained were perfectly matched with those obtained from spherulitic growth rate data of neat PPDX. A quantitative estimate of the increase in the energy barrier for crystallization of the PPDX block, caused by the covalently bonded molten PCL as compared to homo-PPDX, was thus determined. This energy increase can dramatically reduce the crystallization rate of the PPDX block as compared to homo-PPDX. In the case of the PCL block, both the crystallization kinetics and the self-nucleation results indicate that the PPDX is able to nucleate the PCL within the copolymers and heterogeneous nucleation is always present regardless of composition. Finally, preliminary results on hydrolytic degradation showed that the presence of relatively small amounts of PCL within PPDX-b-PCL copolymers substantially retards hydrolytic degradation of the material in comparison to homo-PPDX. This increased resistance to hydrolysis is a complex function of composition and its knowledge may allow future prediction of the lifetime of the material for biomedical applications.

Tensioactive Properties of Poly([R,S]-β-malic acid-b-ε-caprolactone) Diblock Copolymers in Aqueous Solution

Well-defined amphiphilic poly(β-malic acid-b-∈-caprolactone) diblock copolymers with tunable hydrophobic content have been synthesized. For the sake of comparison, amphiphilic α-lauryl, ω-methyl poly(β-malic acid) has been synthesized as well. The stability of the block copolymers in aqueous solutions against hydrolysis has been demonstrated, at least within a period of time long enough to rely on tensioactive measurements by the pendant drop method. The critical micellar concentration of such amphiphilic (co)-polymers has been determined by dynamic light scattering. The effect of pH, temperature, salt (NaCl) addition, and copolymer composition has been investigated. Whatever the copolymer composition, it has been shown that increasing pH from 2.2 to 8.5 increases surface tension in water. In contrast, reducing the length of the hydrophobic block lowers the surface tension in water but also the mean diameter of micellar structures.