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Bacterial biofilm formation on implant surfaces is a frequent reason for the failure of many biomedical devices. Polymer brushes, thin nanolayers constituted of densely grafted macromolecules, are promising candidates to use in many biomedical applications to control attachment of bacteria to a surface. In this work five different polymer brushes were synthesized and tested with respect to their ability to regulate Staphylococcus aureus adhesion. Namely, two mixed brushes [consisting of poly(ethylene glycol) and a positively charged polymers, poly(2-vynil pyridine) or quartenized poly(2-vynil pyridine)] are investigated along with one-component brushes of the respective polymers. Bacterial adhesion was regulated over two orders of magnitude via altering the polymer brush composition.

Hydrophobic, transparent organic–inorganic hybrid coatings were synthesized by the incorporation of SiO 2 nanoparticles in a matrix of 3-glycidoxypropyltrimethoxysilane (GPTS) and tetramethyl orthosilicate (TMOS) followed by overlaying isobutyltrimethoxysilane (IBTMS) film for enhanced hydrophobicity. Scanning probe microscopy, ellipsometry and contact angle measurements were used to study their morphology, thickness and surface properties. GPTS and TMOS sol with SiO 2 nanoparticles resulted in rough but transparent surface of homogeneous monolayer of ∼40 nm. The rough surface mimicking lotus leaf was chemically modified with a layer of IBTMS resulting in the contact angle of nearly 130°. Morphology as well as contact angles were dependent on the thickness of IBTMS hydrophobic coating layer. Process of creating rough but transparent and durable layer loaded with SiO 2 particles demonstrates the feasibility of meeting all three desired characteristics of transparency, durability and superhydrophobicity.

A method for the synthesis of fluorescent core–shell nanoparticles with reactive epoxide functional groups on the surface has been developed as a platform for the generation of functional and labeled nanoparticles for diverse applications. Namely, poly(glycidyl methacrylate), PGMA, was used to form a reactive and fluorescent shell on the nanoparticle surface. Prior to deposition on the silica nanoparticle, the PGMA was fluorescently labeled with Rhodamine B via a reaction between the epoxy groups of the polymer and carboxyl groups of the dye. A strong fluorescence emission was observed for the colloidal suspension of the modified nanoparticles. Atomic force microscopy, dynamic light scattering, and thermogravimetric and elemental analysis were used to characterize the nanoparticles. The reactive nanoparticles are a convenient and straightforward platform to generate fluorescent particles with various molecules attached to their exterior, because epoxy groups (located on the particle exterior) are highly a...

Hydrophobic grafted polymer layers were permanently anchored from the melt onto poly(ethylene terephthalate) (PET) and nylon substrates modified with air plasma and poly(glycidyl methacrylate) (PGMA) anchoring layer. Polypentafluorostyrene (PPFS) of different molecular weights with an end carboxyl group was used for the grafting. Atomic force microscopy imaging revealed that, in general, the grafted chains evenly covered all substrates. Thickness of the grafted layer increased with temperature and time of grafting. To reach a significant level of grafting and consequently high hydrophobicity temperature above 140°C, 5 min of grafting had to be used. For longer grafting time (1 h) the hydrophobicity could be reached at 120°C. The thickness of the grafted layer should be at least 2–3 nm to attain the high water‐contact angle. The polymer grafting technique developed could be readily applied to surface modification of fibers and textiles leading to generation of hydrophobic fibrous materials. In Commemoratio...

A novel approach was developed for the synthesis of tethered polymer layers with thickness and grafting density gradients. Poly(glycidyl methacrylate) (PGMA) was employed as a primary anchoring layer to attach the polymer chains to the surface of a silicon wafer. A linear temperature gradient heated stage was used for the generation of a gradual variation in the thickness of the anchoring PGMA film along the substrate. The obtained gradient was translated into the polymerization initiator gradient via the reaction between the epoxy groups of PGMA and the carboxyl functionality of 2-bromo-2-methylpropionic acid (BPA). The attachment of BPA to the surface modified with the monolayer of PGMA was confirmed by X-ray photoelectron spectroscopy experiments. To complete the experimental procedures, surface-initiated atom transfer radical polymerization was performed to synthesize the grafted polymer layers with thickness and surface densities that were varied along the substrate. The grafting density of the samples created in this three-step process ranged from 0.75 +/- 0.05 to 1.5 +/- 0.25 chains/nm(2). It was estimated, from a comparison of the surface densities of the initiator and the attached polymer, that the efficiency of the initiation from the surface was on the order of 5-10% and was dependent upon the surface concentration of the initiator and the time of polymerization.

Macromolecular anchoring layer approach was used for preparation of an effective macroinitiator for the synthesis of grafted polymer layers by atom transfer radical polymerization (ATRP) initiated from the surface. For the initial surface modification, a thin layer of poly(glycidyl methacrylate) (PGMA) was deposited on the surface of a silicon wafer. The ATRP macroinitiator was synthesized on the substrate surface by the reaction between epoxy groups of PGMA and carboxy functionality of bromoacetic acid (BAA). Variation of the time and temperature of the BAA deposition as well as PGMA layer thickness allowed control over the amount of BAA attached to the surface. The PGMA anchoring layer allowed the achievement of initiator surface density significantly higher than that reported for a self-assembled monolayer of ATRP initiators. Polymer brushes were synthesized on the PGMA/BAA-modified substrates by ATRP. Different surface concentrations of BAA were used in our grafting experiments to acquire knowledge about the relationship between the amount of initiator anchored to the surface through PGMA and the rate of the grafted layer formation. The increase in the surface density of the initiating moieties led to the increase in the grafting rate. However, a cutoff initiator concentration beyond which no increase of the thickness of the grafted layer was observed. From comparison between the surface densities of the initiator and the attached polymer it was determined that the efficiency of the initiation from the surface was on the level of 5-15%.

A new method for the preparation of ultrathin tethered polymer layers with gradually changing thickness was developed utilizing the grafting to approach. The grafting procedure allowed translation of the tempermature gradient created in a heating stage into a gradient of polymer chain grafting density. The gradient tethered polymer layers demonstrated gradual changes in wetting properties and morphology transition from pinned micelles to a brush regime along the substrate.

The present study was focused on permanent grafting of poly(ethylene glycol) (PEG) layers (brushes) from the melt to adsorbed reactive macromolecules. A poly(glycidyl methacrylate) (PGMA) was used to form the reactive primary adsorbed layer. It was found that a thin (1.5 nm) PGMA layer had a high grafting efficiency, and elevated temperatures considerably accelerated the grafting process. The grafting extent was eventually limited by concentration and accessibility of functional reactive groups in the primary adsorbed layer. Several distinct types of brush morphologies were observed depending on the grafted layer height. Isolated crystals were detected for brushes possessing lower grafting density. At higher levels of PEG attachment, the crystalline formations uniformly covered the entire surface of the substrate. The development of highly extended crystalline formations on the surface and marked expansion of the PEG brushes in water indicated that an extremely high grafting density was attained. The deve...

Well-defined cleavable poly(styrene-block-ethylene oxide) polymers were prepared by living anioinc polymerization, using cumyl potassium as the initiator. These polymers contained an acid cleavable moiety, such as diphenyl methyl or anthracenyl methyl ether linkage, between polystyrene and poly ethylene oxide block. Atomic force microscopy (AFM) studies on the thin films illustrate the formation of nanoporous architecture due to acid cleavage of the polyethylene oxide fraction.

An effective approach is described for the synthesis of binary patterned polymer brushes using a combination of capillary force lithography and surface-initiated polymerization. First, the approach calls for an ultrathin polystyrene (PS) mask to be deposited, in a pattern, over a surface to which a layer of polymerization initiator has already been anchored. Next, surface-initiated atom transfer radical polymerization (ATRP) is performed. This can graft the initial polymer brush onto those areas of the surface unprotected by the PS mask. After grafting is complete, the PS mask is removed and a second brush is synthesized on the newly exposed areas.

Immersion lithography is a new promising approach capable of further increasing the resolution of semiconductor devices. This technology requires the development of new immersion media that satisfy the following conditions: the media should have high refractive index, be transparent and photochemically stable in DUV spectral range. They should also be inert towards photoresists and optics and be liquid to permit rapid scanning. Here we propose and explore a novel strategy in which high refractive index medium is made of small solid particles suspended in liquid phases (nanocomposite liquids). The dielectric particles have high refractive index and the refractive index of nanocomposite liquids becomes volume weighted average between refractive indices of nanoparticles and the liquid phase. We investigate aluminum oxide (alumina) nanoparticles suspended in water. Alumina is known to have high (1.95) refractive index and low absorption coefficient at 193 nm. Alumina nanoparticles were prepared by chemical methods followed by removal of organic molecules left after hydrolysis reactions. Measurements of optical and reological properties of the nanocomposite liquid demonstrated potential advantage of this approach for 193 nm immersion lithography.

Polyethylene terephthalate (PET, polyester) capillary-channeled polymer (C-CP) fibers were employed as the base structure for surface modification to provide a sorbent for solid phase extraction (SPE) of aqueous cations. Surface functionalization with polyacrylic acid (PAA) was achieved using a “grafting to” approach, yielding a stable sorbent that has the potential of being employed over a large range of pH values and a variety of sample matrices. PAA was chosen for surface modification because the repeating acrylic acid monomeric unit, which contains a carboxylic acid, has the ability to bind metal ions. In a micropipette-tip SPE format, these PAA-functionalized C-CP fibers showed the ability to efficiently bind several metals (Cu2+, Cu+, Ni2+, Fe3+, UO22+), while elution could be achieved with extremely low concentrations of hydrochloric acid (1 ml of 0.005%), resulting in overall recoveries of greater than 88%. A single tip was carried throughout the entire study as a control, and showed overall recoveries averaging 96% over the course of 19 extraction experiments and a 12-month period, demonstrating the chemical stability of the sorbent material, and suggesting the potential of the C-CP fiber SPE tips to be used multiple times.

By mimicking the hydrophobicity and miniature protrusions of the lotus leaves using a monolayer of non-fluorinated hydrophobic polymer and functionalized nanoparticles, respectively, we have developed a permanent nanocoating to create ultrahydrophobic fibers/textiles with excellent water repellency and self-cleaning ability.