Search results for "Brush"

Performance analysis of photovoltaic powered dc motor — Propeller system

2015

The application of autonomous directly photovoltaic (PV) powered electro-mechanical has received increasing attention for different applications (e.g. PV water pumping, PV powered cooling of arid climate greenhouses, solar vehicles etc). The PV array output is a nonlinear and time-dependent power supply that varies with solar intensity and cell temperature, so the performance characteristics of the directly PV-powered DC motor — propeller system are very different than when powered by a constant DC voltage. The focus of this work is to do performance analysis of directly PV-powered DC motor — propeller system. Through performance evaluation, it has been observed that power transfer matching…

A randomized controlled trial of a power brush/irrigator/mouthrinse routine on plaque and gingivitis reduction in orthodontic patients

2018

ABSTRACT Objectives: To assess plaque and gingivitis reduction in orthodontic patients after 4 weeks' use of an oscillating-rotating power brush, irrigator, and mouthrinse. Materials and Methods: This was a randomized, examiner-blind, clinical trial comparing plaque and gingivitis outcomes for an experimental power brush/irrigator/mouthrinse oral hygiene routine vs a dental prophylaxis followed by regular manual brushing (positive control). Fifty-one participants with fixed orthodontic appliances in the upper and lower jaw and a minimum of 15 gingival bleeding sites were randomly assigned to experimental or positive control treatment. Both groups were instructed to use their products at lea…

Functionalization and patterning of reactive polymer brushes based on surface reversible addition and fragmentation chain transfer polymerization

2012

We present the synthesis of reactive polymer brushes prepared by surface reversible addition–fragmentation chain transfer polymerization of pentafluorophenyl acrylate. The reactive ester moieties can be used to functionalize the polymer brush film with virtually any functionality by simple post-polymerization modification with amines. Dithiobenzoic acid benzyl-(4-ethyltrimethoxylsilyl) ester was used as the surface chain transfer agent (S-CTA) and the anchoring group onto the silicon substrates. Reactive polymer brushes with adjustable molecular weight, high grafting density, and conformal coverage through the grafting-from approach were obtained. Subsequently, the reactive polymer brushes …

Precision Anisotropic Brush Polymers by Sequence Controlled Chemistry

2020

The programming of nanomaterials at molecular length-scales to control architecture and function represents a pinnacle in soft materials synthesis. Although elusive in synthetic materials, Nature has evolutionarily refined macromolecular synthesis with perfect atomic resolution across three-dimensional space that serves specific functions. We show that biomolecules, specifically proteins, provide an intrinsic macromolecular backbone for the construction of anisotropic brush polymers with monodisperse lengths via grafting-from strategy. Using human serum albumin as a model, its sequence was exploited to chemically transform a single cysteine, such that the expression of said functionality is…

Spherical and rod-like colloids with polymer-brush surfaces

2008

In this paper, we describe a strategy to overcome incompatibility of colloidal particles and polymer coils as well as immiscibility of spherical and rod-shaped nanoparticles. Two new types of model colloids are presented, colloidal nanospheres with hairy surfaces (spherical brushes) and polymacromonomers to represent cylindrical brushes. The spherical brushes are synthesized from polyorganosiloxane-μ-gels of diameter 20 nm by grafting onto anionically prepared polystyrene macromonomers of molecular weight M w=5000 g/mol. On average, each sphere has a surface layer of 200 polymer chains. Compatibility of spherical nanoparticles with polymer coils was probed by turbidity of as-cast films as w…

Solvent Determines Nature of Effective Interactions between Nanoparticles in Polymer Brushes

2015

We study the effective interaction between two parallel rod-like nanoparticles in swollen and collapsed polymer brushes as a function of penetration depth by 2D self-consistent field calculations. In vertical direction, the interaction is always attractive. In lateral direction, the behavior under good and poor solvent conditions is qualitatively different. In swollen brushes (good solvent), nanoparticles always repel each other. In collapsed brushes (poor solvent), we identify two different regimes: an immersed regime, where the nanoparticles are fully surrounded by the brush, and an interfacial regime, where they are located in the interface between brush and solvent. In the immersed regi…

Friction between Polymer Brushes in Good Solvent Conditions:  Steady-State Sliding versus Transient Behavior

2003

Previous molecular dynamics simulations of friction between polymer brushes in relative sliding motion [Kreer, T.; Muser, M. H.; Binder, K.; Klein, J. Langmuir 2001, 17, 7804] are extended beyond steady-state conditions. We study two different protocols:  (i) stop and return and (ii) stop and go. In protocol (i), the relative, lateral motion between the two surfaces is stopped abruptly and reimposed opposite to the initial direction after the system could relax for some time. Protocol (ii) is similar except that the sliding direction is maintained. In the constant-velocity steady state, the average lateral extension lc of the polymers is found to be a power law of the sliding velocity v, na…

Polymer Brushes on Flat and Curved Substrates: What Can be Learned from Molecular Dynamics Simulations

2017

Capillary Rise in Nanotubes Coated with Polymer Brushes

2009

The spontaneous rise of a fluid in a brush-coated nanocapillary is studied by molecular dynamics simulation of a coarse-grained model. The cases of changing wettability of both the capillary walls and the brush were examined. We also investigated the impact of polymer chain length on the transport of fluid along the nanotube. We found that capillary filling takes place in both lyophilic and lyophobic tubes, provided that the polymer brush coating is wetted by the fluid. In all the cases studied, capillary rise proceeds by a time-square law, but the mechanisms behind them (Lucas-Washburn or diffusive propagation) differ, depending on the chain length N. For a wettable wall, the speed of flui…

Structure of bottle brush polymers on surfaces: weak versus strong adsorption.

2011

Large-scale Monte Carlo simulations are presented for a coarse-grained model of cylindrical molecular brushes adsorbed on a flat structureless substrate, varying both the chain length N of the side chains and the backbone chain length N(b). For the case of good solvent conditions, both the cases of weak adsorption (only 10 to 15% of the monomers being bound to the surface) and strong adsorption (~40% of the monomers being bound to the surface, forcing the bottle brush into an almost 2D conformation) are studied. We focus on the scaling of the total linear dimensions of the cylindrical brush with both chain lengths N and N(b), demonstrating a crossover from rod-like behavior (for not very la…