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Guiding and confining light at interfaces is crucial for applications involving light-matter interactions such as surface spectroscopy, nonlinear optics, and quantum information technology. While dielectric surface waves offer promising perspectives for strong light confinement at non-absorbing interfaces, their capacity has not yet been widely explored. Here, we focus on the propagation properties of optical modes supported at the free surface of a one-dimensional photonic crystal. The contributions of intrinsic and extrinsic loss mechanisms are investigated. Structures optimized to support long propagating optical surface waves are designed and fabricated. We experimentally demonstrate, for the first time, the existence of optical surface waves capable of propagating over centimeter-scale distances in the visible spectral range. Our results open new perspectives for the use of optical surface waves in integrated optics and enhanced light-matter interactions., Comment: 11 pages, 4 figures

We propose a versatile approach to the production of hyperbranched polymers with high degrees of branching and low dispersity values (Ä?), involving slow monomer addition of a thiol/yne monomer to multifunctional core molecules in the presence of photoinitiator and under UV irradiation. The small thiol/yne monomer was synthesized via 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide hydrochloride (EDC·HCl) esterification, and batch polymerizations were performed at varying concentrations. The batch thiol-yne polymerizations had fast reaction kinetics and large dispersity values that increased with increasing concentration. Introduction of monomer by slow addition to a multifunctional alkyne core (tri(prop-2-yn-1-yl) 1,3,5-benzenetricarboxylate) or alkene core (triallyl 1,3,5-benzenetricarboxylate) was found to lower dispersity at monomer concentrations of 0.5-2.0 M. Degrees of branching were determined by 1H NMR spectroscopy to be greater than 0.8 in most cases. Increasing the fraction of core molecule was found to decrease dispersity to values as low as 1.26 and 1.38 for the alkene core and alkyne core, respectively, for monomer concentrations of 0.5 M with 10 mol % core molecule. Molecular weights of the hyperbranched structures were also determined by light scattering size exclusion chromatography (SEC) detection, and intrinsic viscosities were determined by viscometry SEC detection. The Kuhn-Mark-Houwink-Sakurada α parameter decreased from 0.35 for the batch process to values as low as 0.21 (10 mol % alkene core) or 0.16 (10 mol % alkyne core), indicating that the thiol-yne structures became more globular and dense with the slow monomer addition strategy. This simple and versatile approach is a promising new development for the design of hyperbranched polymers of well-controlled molecular weight and molecular weight distributions, with very high degrees of branching.

We study the propagation length of Bloch surface waves in the visible spectrum. We show that a millimeter-range Bloch surface wave propagation may take place by improving the surface quality of the multilayer substrate.

Nanomedicine is an emerging field with great potential in disease theranostics. We generated sterically stabilized superparamagnetic iron oxide nanoparticles (s-SPIONs) with average core diameters of 10 and 25 nm and determined the in vivo biodistribution and clearance profiles. Healthy nude mice underwent an intraperitoneal injection of these s-SPIONs at a dose of 90 mg Fe/kg body weight. Tissue iron biodistribution was monitored by atomic absorption spectroscopy and Prussian blue staining. Histopathological examination was performed to assess tissue toxicity. The 10 nm s-SPIONs resulted in higher tissue-iron levels, whereas the 25 nm s-SPIONs peaked earlier and cleared faster. Increased iron levels were detected in all organs and body fluids tested except for the brain, with notable increases in the liver, spleen, and the omentum. The tissue-iron returned to control or near control levels within 7 days post-injection, except in the omentum, which had the largest and most variable accumulation of s-SPIONs. No obvious tissue changes were noted although an influx of macrophages was observed in several tissues suggesting their involvement in s-SPION sequestration and clearance. These results demonstrate that the s-SPIONs do not degrade or aggregate in vivo and intraperitoneal administration is well tolerated, with a broad and transient biodistribution. In an ovarian tumor model, s-SPIONs were shown to accumulate in the tumors, highlighting their potential use as a chemotherapy delivery agent.

The synthesis of multiblock copolymers is often considered to be synthetically challenging and time consuming. In this contribution, the development of a remarkably efficient and versatile procedure to access multiblock copolymers via reversible addition–fragmentation chain transfer (RAFT) polymerization is reported. The robustness and versatility of the RAFT process are demonstrated in this report by preparing multiblock copolymers using uncommon experimental conditions. The synthesis of each block was performed in the presence of air and only required 3 minutes to reach near full monomer conversion. This approach removes the necessity to deoxygenate the solution and allows access to complex copolymer structures in very short time periods. For example, this process allowed the preparation of a heptablock homopolymer with a well-defined architecture in just 21 minutes. We also discuss the limitations inherent to this approach. This strategy is shown to be particularly efficient when blocks with low degrees of polymerization (DP 50), the procedure is typically limited to the preparation of di- or triblock copolymers.

Surface-initiated polymerization represents a versatile strategy to modify a diverse range of materials with thin, functional polymer coatings. While in many cases the desired functional groups can be directly incorporated via (co)polymerization of the appropriate monomer(s), other functional groups are incompatible with the polymerization strategies that are commonly used to grow polymer brushes and can only be introduced by postpolymerization modification. Determining the local concentration and spatial distribution of these functional groups in postmodified brushes is a challenging task but could help to optimize the design and properties of these polymer coatings. This article reports on the use of X-ray photoelectron spectroscopy (XPS) combined with C-60 cluster ion sputtering to address this challenge. Poly(glycidyl methacrylate) (PGMA) brushes prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) were used as a model platform and were postmodified with propylamine and bovine serum albumin (BSA). The XPS depth-profiling experiments showed that the small propylamine molecules were essentially homogeneously distributed throughout the brush, with the exception of the top few nanometers, which were enriched in propylamine moieties. It was also demonstrated that the amount of propylamine introduced within the polymer brush increased with increasing the postpolymerization reaction time, while no concentration gradients could be observed, indicative of a fast diffusion of the propylamine through the polymer brush layer. On the other hand, XPS depth-profiling experiments performed on polymer brushes that were postmodified with BSA revealed that this protein was only localized in the topmost layers of the polymer coating, which reflects the steric hindrance by the dense polymer brush that prevents efficient diffusion of these large molecules. Together, the results of these experiments demonstrate that XPS depth-profiling combined with C-60 cluster ion sputtering is an efficient and powerful means to study the distribution of functionalities incorporated within a polymer brush layer by postpolymerization modification reactions.

This contribution reports on the preparation of functional hyperbranched polystyrene-based materials via a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization, thiol-yne chemistry, and postpolymerization modification reactions. The thiol-yne approach allows the rapid preparation of hyperbranched polymers under mild reaction conditions from polymeric chains bearing a thiol group at one chain end and an alkyne moiety at the other. Postpolymerization modifications of the focal thiol and peripheral alkyne functionalities present within the hyperbranched structures were conducted using two highly efficient strategies, i.e., phosphine-catalyzed thiol-ene reaction and copper-catalyzed azide-alkyne cycloaddition (CuAAC), respectively. In addition to introducing functionalities by postpolymerization modification onto the periphery of the hyperbranched polymers, the interior of the globular structure could also be functionalized by taking advantage of the isocyanate chemical handle of a poly(styrene

Polymer brushes represent an interesting platform for the development of high-capacity protein binding surfaces. Whereas the protein binding properties of polymer brushes have been investigated before, this manuscript evaluates the feasibility of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA-co-PDEAEMA) (co)polymer brushes grown via surface-initiated atom transfer radical polymerization (SI-ATRP) as protein reactive substrates in a commercially available microarray system using tantalum-pentoxide-coated optical waveguide-based chips. The performance of the polymer-brush-based protein microarray chips is assessed using commercially available dodecylphosphate (DDP)-modified chips as the benchmark. In contrast to the 2D planar, DDP-coated chips, the polymer-brush-covered chips represent a 3D sampling volume. This was reflected in the results of protein immobilization studies, which indicated that the polymer-brush-based coatings had a higher protein binding capacity as compared to the reference substrates. The protein binding capacity of the polymer-brush-based coatings was found to increase with increasing brush thickness and could also be enhanced by copolymerization of 2-(diethylamino)ethyl methacrylate (DEAEMA), which catalyzes epoxide ring-opening of the glycidyl methacrylate (GMA) units. The performance of the polymer-brush-based microarray chips was evaluated in two proof-of-concept microarray experiments, which involved the detection of biotin-streptavidin binding as well as a model TNF alpha reverse assay. These experiments revealed that the use of polymer-brush-modified microarray chips resulted not only in the highest absolute fluorescence readouts, reflecting the 3D nature and enhanced sampling volume provided by the brush coating, but also in significantly enhanced signal-to-noise ratios. These characteristics make the proposed polymer brushes an attractive alternative to commercially available, 2D microarray surface coatings.

This manuscript reports on the post-polymerization modification of poly(glycidyl methacrylate) (PGMA) and PGMA-co-poly(2-(diethylamino)ethyl methacrylate) (PGMA(x)-co-PDEAEMA(y)) (co)polymer brushes prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). The aim of this study was to evaluate the ability of tertiary amine groups incorporated in the polymer brush to accelerate the ring-opening of the epoxide groups by primary amines and to facilitate the aqueous, room temperature post-polymerization modification of the brushes. Using Fourier transform infrared (FTIR) spectroscopy to monitor the ring-opening reaction of the epoxide groups, it was found that the incorporation of 2-(diethylamino)ethyl methacrylate (DEAEMA) groups in the PGMA brushes significantly accelerated the rate of the post-polymerization modification reaction with several model amines. The rate enhancement was dependent on the fraction of DEAEMA units incorporated in the copolymer brush. For example, whereas 24 h was necessary to obtain a conversion of approximately 40% for PGMA brushes immersed in a 1 M propylamine solution in water, the same conversion was reached, in identical reaction conditions, after 8 and 2 h with copolymer brushes containing 10 mol % and 25 mol % of DEAEMA along the copolymer chains, respectively. In a final series of proof-of-concept experiments, the feasibility of the glycidyl methacrylate containing brushes to act as substrates for protein immobilization was studied. Using FTIR spectroscopy and quartz crystal microbalance with dissipation (QCM-D) experiments, it could be demonstrated that the incorporation of DEAEMA units not only enhanced the rate of the protein immobilization reaction, but also resulted in higher protein binding capacities as compared to a PGMA homopolymer brush. These features make PGMA(x)-co-PDEAEMA(y) brushes very attractive candidates for the development of protein microarrays, among others.

We demonstrate the first cavity confinement of Bloch surface waves in the fundamental mode of a Fabry–Perot cavity. The cavity consists of two distributed Bragg mirrors separated by a spacer of dimensions smaller than the wavelength (633nm). The cavity mode exhibits quality factor of 400. This quality factor is the highest recorded thus far for a subwavelength optical surface waves cavity.

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

In this study, the application of reaction calorimetry, an efficient tool to obtain kinetic and safety data, is presented on the free radical dispersion polymn. of MMA in scCO2. The effect of three major parameters with respect to the reaction evolution are studied, namely of stirrer type and stirring speed, the monomer and CO2 concn. and the stabilizer concn. The effective formation of the dispersion as well as the balance between the polymer formed in the continuous phase or inside the particles are key features of this anal.

We review the use of thiol–yne reaction for the design of branched structures, dendrimers and hyperbranched polymers. In addition to its typical ‘click’ chemistry attributes, the advantages of this reaction include the ability to generate almost perfect branching patterns, the possibility to introduce many more functionalities at each generational step and its tolerance towards chemical functionality, allowing the introduction of a wide range of functional groups into the structures.

This contribution describes the preparation of nonfouling polypeptide brushes via surface-initiated ring-opening polymerization of oligo(ethylene glycol) modified L-lysine N-carboxyanhydrides. Circular dichroism experiments indicated that these surface-anchored polypeptide chains assume an α-helical conformation, which does not change between pH 4 and 9. Furthermore, nonspecific adsorption of fluorescent labeled bovine serum albumin and fibrinogen on glass slides modified with these brushes was greatly reduced compared to unmodified glass substrates.

This manuscript describes the synthesis of poly(methacrylic acid) (PMAA) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) of sodium methacrylate (NaMA) and their use as substrates for the mineralization of calcium carbonate. A CuBr/CuBr2/bipyridine catalyst system in aqueous solution at room temperature allowed the synthesis of brushes with thicknesses of up to 300 nm. Using substrates modified with mixtures of an ATRP-initiator modified trimethoxysilane and an "inert" pivaloyl-modified trimethoxysilane to initiate the ATRP of NaMA, a series of brushes with varying chain density could be prepared. Subsequent mineralization experiments revealed that, while low-density brushes promoted the formation of calcite crystals, high-density brushes were covered with a thin layer of amorphous CaCO3 (ACC). This is of interest because ACC can serve as a metastable precursor for different crystalline CaCO3 polymorphs and offers attractive perspectives for the bottom-up fabrication of well-defined CaCO3 crystal architectures. © 2007 American Chemical Society.

Keywords: Ion sensors ; Polymer brushes ; Protein microarray ; Surface-initiated polymerization ; Transfer Radical Polymerization Reference EPFL-ARTICLE-171424doi:10.2533/chimia.2011.276View record in Web of Science Record created on 2011-12-16, modified on 2017-05-10

We report the first experimental demonstration of high quality factor confinement of Bloch surface waves at visible wavelengths. The cavities consist of planar Fabry-Perot resonators that are fabricated on top of a Bloch surface supporting substrate. This work presents the design and fabrication methods used for the setting up of the experiment. Quality factors of the order of 2000 are measured. This work demonstrates that optical surface waves can be efficiently confined, and thus constitute a viable alternative to guided waves for on chip optical components and operations.