Christophe Pagnoulle

Design and qualification of a diffractive trifocal optical profile for intraocular lenses

PURPOSE: To theoretically and experimentally assess a new aspheric diffractive trifocal intraocular lens (IOL). SETTING: Centre Spatial de Liège, Liège, Belgium. DESIGN: Evaluation of diagnostic test or technology. METHODS: The theoretical profile of the IOL was designed using software simulation and validated by optical calculation software tools that enabled complete theoretical characterization. These data resulted in a new aspheric diffractive trifocal IOL. The IOL theoretically allows improved intermediate vision without impairing near and far vision and favors distance vision in mesopic conditions without increasing halos or glare perception under dim light or large pupil conditions. The theoretical findings were compared with those of in vitro testing on the optical bench. RESULTS: There was good agreement between the theoretical profile and achieved IOL profile. The simulated and achieved light distribution and focus distribution showed good concordance. The FineVision aspheric trifocal IOL provided intermediate addition at 1.75 diopters. CONCLUSION: The combination of 2 diffractive profiles to achieve far, intermediate, and near correction is validated. Further clinical investigations are required to validate these principles. Financial Disclosure: Dr. Houbrechts has no financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Ternary polymer blend with core–shell dispersed phases: effect of the core-forming polymer on phase morphology and mechanical properties

Abstract Phase morphology and mechanical properties of ternary blends consisting of PS (polystyrene), SBR (styrene butadiene rubber) and different polyolefins (POs) have been studied. PS, systematically forms the matrix, SBR and PO being combined in the dispersed phase. Although POs of various melt viscosity and stiffness are used, the binary (SBR/PO) dispersed phase is of a core–shell structure, in which PO forms the core. Upon increasing the viscosity of PO, the average size of the cores and the SBR domains including them increases. Comparison of the experimental shear storage modulus of the blends with theoretical predictions indicates that the stress transfer from the PS matrix to the PO core through the SBR shell depends on the modulus of the SBR envelope. The ultimate mechanical properties of the ternary blends are sensitive to the stiffness of the PO core.

Imparting antifouling properties of poly(2-hydroxyethyl methacrylate) hydrogels by grafting poly(oligoethylene glycol methyl ether acrylate)

The antifouling properties of poly(2-hydroxyethyl methacrylate- co-methyl methacrylate) hydrogels were improved by the surface grafting of a brush of poly(oligoethylene glycol methyl ether acrylate) [poly(OEGA)]. The atom-transfer radical polymerization (ATRP) of OEGA (degree of polymerization = 8) was initiated from the preactivated surface of the hydrogel under mild conditions, thus in water at 25 degrees C. The catalytic system was optimized on the basis of two ligands [1,1,4,7,10,10-hexamethyl-triethylenetetramine (HMTETA) or tris[2-(dimethylamino)ethyl]amine (Me6TREN)] and two copper salts (CuIBr or CuICl). Faster polymerization was observed for the Me 6TREN/CuIBr combination. The chemical composition and morphology of the coated surface were analyzed by X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy, contact angle measurements by the water droplet and captive bubble methods, scanning electron microscopy, and environmental scanning electron microscopy. The hydrophilicity of the surface increased with the molar mass of the grafted poly(OEGA) chains, and the surface modifications were reported in parallel. The antifouling properties of the coatings were tested by in vitro protein adsorption and cell adhesion tests, with green fluorescent protein, beta-lactamase, and lens epithelial cells, as model proteins and model cells, respectively. The grafted poly(OEGA) brush decreased the nonspecific protein adsorption and imparted high cell repellency to the hydrogel surface.

Carbon nanotube composites for broadband microwave absorbing materials

In this paper, we present a new shielding and absorbing composite based on carbon nanotubes (CNTs) dispersed inside a polymer dielectric material. The extremely high aspect ratio of CNTs and their remarkable conductive properties lead to good absorbing properties with very low concentrations. A broadband characterization technique is used to measure the microwave electrical properties of CNT composites. It is shown that a conduction level of 1 S/m is reached for only 0.35 wt % of a CNT, while, for a classical absorbing composite based on carbon black, 20% concentration is mandatory. The conductive properties are explained by a phenomenological electrical model and successfully correlated with rheological data aiming at monitoring the dispersion of conductive inclusions in polymer matrices

XPS analysis of the PC/PVDF interface modified by PMMA. Location of the PMMA at the interface

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be changed by the addition of polymethylmethacrylate (PMMA), which is miscible with PVDF and concentrates at the PVDF/PC interface. Location of PMMA at the PC/PVDF interface has been confirmed by XPS analysis, which shows that the interface enrichment in PMMA already takes place when only 10 wt% PMMA is premixed with PVDF.

Controlled synthesis of anthracene-labeled ω-amine polystyrene to be used as a probe for interfacial reaction with mutually reactive PMMA

Anthracene-labeled polystyrene (PS) endcapped by a primary amine has been synthesized by atom transfer radical copolymerization of styrene with 3-isopropenyl-α,α-dimethylbenzyl isocyanata (m-TMI). The m-TMI co-monomer (5.7 mol-%) does not perturb the control of the radical polymerization of styrene. The pendan isocyanate groups of the copolymer chains of low polydispersity (M w /M n = 1.25) and controlled molecular weight (up to 35 000) have been derivatized into anthracene by a reaction with 9-methyl(aminomethyl)anthracene. The anthracene-labeled PS (ca. 2 mol-% label) has been conveniently analyzed by size-exclusion chromatography with a UV detector (SEC-UV). Moreover, the ω-bromide end-group of the copolymer chains has been derivatized into a primary amine, making the labeled PS chains reactive towards non-miscible poly(methyl methacrylate) (PMMA) chains endcapped by an anhydride. The interfacial coupling of the mutually reactive PS and PMMA chains has been studied under static conditions (i.e., at the interface between thin PS and PMMA films) and successfully analyzed by SEC-UV.

Biomechanical and optical properties of 2 new hydrophobic platforms for intraocular lenses.

Purpose To compare the biomechanical and optical properties of 2 new hydrophobic platforms and a series of commercially available foldable intraocular lenses (IOLs). Setting Center for Education and Research on Macromolecules, University of Liège, Liège, Belgium. Design Experimental study. Methods Eleven benchmark foldable IOLs (iPure, Podeye, Acrysof SN60WF, Envista MX60, Sensar AR40e, Tecnis ZCB00, Isert 251, AF‐1 YA‐60BB, Finevision, Acri.Tec 366D, and Ioflex) were tested by standard analytical methods for biomechanical, rheological, and optical investigations under identical conditions. Results With 1 exception, IOLs equilibrated in aqueous medium had a lower glass‐transition temperature, higher deformability, lower injection forces, and complete recovery of their initial optical properties after injection. Typical hydrophobic acrylic dry‐packaged IOLs required higher injection forces with high residual deformation and lost part of their initial optical quality after injection. Hydrophobic acrylic C‐loop, double C‐loop, and closed quadripod haptics applied optimum compression forces to the capsular bag with negligible optic axial displacement and tilt compared with plate haptics and poly(methyl methacrylate) haptics. Conclusions The combination of the C‐loop haptic and the bioadhesive glistening‐free material, which absorbs a predetermined amount of water, allowed for a biomechanically stable IOL. The same material used in association with a double C‐loop haptic design facilitated the perioperative manipulation and placement of the IOL in a smaller capsular bag without impairing the other biomechanical properties of a single C‐loop design. Financial Disclosure Dr. Pagnoulle has a proprietary interest in the GF material. Drs. Pagnoulle and Bozukova are employees of Physiol S.A. Dr. Jérôme has no financial or proprietary interest in any material or method mentioned.

Premade versus in situ formed compatibilizer at the PS/PMMA interface: contribution of the Raman confocal microscopy to the fracture analysis

The interface of a two-layer assembly of polystyrene (PS) and poly(methyl methacrylate) (PMMA) was modified by an intermediate layer of either a premade poly(styrene-g-methyl methacrylate) copolymer (P(S-g-MMA)) or a preblend of mutually reactive PS and PMMA synthesized by atom transfer radical polymerization (ATRP). No significant difference was found in the interfacial fracture toughness measured by the double cantilever beam test, although the morphology of the interfacial region was not the same when observed by transmission electron microscopy. The premade copolymer formed a distinct interphase, in contrast to the sharp interface that was observed in the case of the reactive system. The analysis of the fracture surfaces by Raman confocal microscopy showed that the fracture occurred alternatively in the PS phase and either at the PS/copolymer interface for the non reactive system or at the PS/PMMA interface for the reactive one.

Microwave absorbers based on foamed nanocomposites with graded concentration of carbon nanotubes

A multilayered foamed nanocomposite with graded concentration of carbon nanotubes is proposed as a novel microwave absorber. The dispersion and foaming process enables to control the gradation in conductivity of each layer. Absorption performances are demonstrated through measurements of reflectivity and shielding effectiveness over the frequency range [8-16 GHz]. An improvement of about 5 dB in reflectivity is observed with respect to a foamed composite having a similar uniform concentration, while in both cases the shielding effectiveness is kept higher than 15 dB.

Antimicrobial activity of polystyrene particles coated by photo-crosslinked block copolymers containing a biocidal polymethacrylate block

Abstract A commercially available poly(ethylene-co-butylene) copolymer, endcapped by a short polyisoprene block and a hydroxyl group (PI-b-PEB-OH), has been derivatized into a macroinitiator for atom transfer radical polymerization (ATRP) by esterification of the hydroxyl end-group by an activated bromidecontaining acyl bromide. Two types of triblock copolymers, PI-b-PEB-b-poly- (dimethylaminoethyl methacrylate) (PDMAEMA) and PI-b-PEB-b-poly[2-(tert-butylamino) ethyl methacrylate] (PTBAEMA), have been synthesized and used to coat polystyrene particles. These coatings have been permanently immobilized by UV cross-linking of the isoprene units. They exhibit a biocidal activity against Gramnegative bacteria either intrinsically in case of the PTBAEMA block or upon quaternization of the PDMAEMA block by octyl bromide. The antimicrobial activity is directly related to the concentration of coated PS particles in the medium.