Synthesis of high molecular weight poly(n-butyl acrylate) macromolecules via seATRP: From polymer stars to molecular bottlebrushes

Electrochemically Mediated Surface-Initiated Atom Transfer Radical Polymerization by ppm of CuII/Tris(2-pyridylmethyl)amine

Atom transfer radical polymerization (ATRP) is one of the most widely used methods for modifying surfaces with functional polymer films and has received considerable attention in recent years. Here, we report an electrochemically mediated surface-initiated ATRP to graft polymer brushes onto solid substrates catalyzed by ppm amounts of CuII/TPMA in water/MeOH solution. We systematically investigated the type and concentrations of copper/ligand and applied potentials correlated to the polymerization kinetics and polymer brush thickness. Gradient polymer brushes and various types of polymer brushes are prepared. Block copolymerization of 2-hydroxyethyl methacrylate (HEMA) and 3-sulfopropyl methacrylate potassium salt (PSPMA) (poly(HEMA-b-SPMA)) with ultralow ppm eATRP indicates the remarkable preservation of chain end functionality and a pronounced "living" characteristic feature of ppm-level eATRP in aqueous solution for surface polymerization.

Synthetic Pressure Sensitive Adhesives for Biomedical Applications

Pressure sensitive adhesives are components of everyday products found in homes, offices, industries, and hospitals. Serving the general purpose of fissure repair and object fixation, pressure sensitive adhesives indiscriminately bind surfaces, as long as contact pressure is administered at application. With that being said, the chemical and material properties of the adhesive formulation define the strength of a pressure sensitive adhesive to a particular surface. Given our increased understanding of the viscoelastic material requirements as well as the intermolecular interactions at the binding interface required for functional adhesives, pressure sensitive adhesives are now being explored for greater use. New polymer formulations impart functionality and degradability for both internal and external applications. This review highlights the structure-property relationships between polymer architecture and pressure sensitive adhesion, specifically for medicine. We discuss the rational, molecular-level design of synthetic polymers for durable, removable, and biocompatible adhesion to wet surfaces like tissue. Finally, we examine prevalent challenges in biomedical wound closure and the new, innovative strategies being employed to address them. We conclude by summarizing the progress of current research, identifying additional clinical opportunities, and discussing future prospects.

Temperature-Responsive Bottlebrush Polymers Deliver a Stress-Regulating Agent In Vivo for Prolonged Plant Heat Stress Mitigation

Anticipated increases in the frequency and intensity of extreme temperatures will damage crops. Methods that efficiently deliver stress-regulating agents to crops can mitigate these effects. Here, we describe high aspect ratio polymer bottlebrushes for temperature-controlled agent delivery in plants. The foliar-applied bottlebrush polymers had near complete uptake into the leaf and resided in both the apoplastic regions of the leaf mesophyll and in cells surrounding the vasculature. Elevated temperature enhanced the in vivo release of spermidine (a stress-regulating agent) from the bottlebrushes, promoting tomato plant (Solanum lycopersicum) photosynthesis under heat and light stress. The bottlebrushes continued to provide protection against heat stress for at least 15 days after foliar application, whereas free spermidine did not. About 30% of the ∼80 nm short and ∼300 nm long bottlebrushes entered the phloem and moved to other plant organs, enabling heat-activated release of plant protection agents in phloem. These results indicate the ability of the polymer bottlebrushes to release encapsulated stress relief agents when triggered by heat to provide long-term protection to plants and the potential to manage plant phloem pathogens. Overall, this temperature-responsive delivery platform provides a new tool for protecting plants against climate-induced damage and yield loss.

From macromonomers to bottlebrush copolymers with sequence control: synthesis, properties, and applications

Bottlebrush polymers (BBPs) are a type of comb-like macromolecules with densely grafted polymeric sidechains attached to the polymer backbones, and many intriguing properties and applications have been demonstrated due to...

Exploring Electrochemically Mediated ATRP of Styrene

Electrochemically mediated atom transfer radical polymerization (eATRP) of styrene was studied in detail by using CuBr2/TPMA (TPMA = tris(2-pyridylmethyl)amine) as a catalyst. Redox properties of various Cu(II) species were investigated in CH3CN, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) both in the absence and presence of 50% (v/v) styrene. This investigation together with preliminary eATRP experiments at 80 °C indicated DMF as the best solvent. The effects of catalyst, monomer, and initiator concentrations were also examined. The livingness of the polymerization was studied by chain extension and electrochemical temporal control of polymerization.

Smart, Naturally-Derived Macromolecules for Controlled Drug Release

A series of troxerutin-based macromolecules with ten poly(acrylic acid) (PAA) or poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) homopolymer side chains were synthesized by a supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) approach. The prepared precisely-defined structures with low dispersity (M_w/M_n < 1.09 for PAA-based, and M_w/M_n < 1.71 for PDMAEMA-based macromolecules) exhibited pH-responsive behavior depending on the length of the polymer grafts. The properties of the received polyelectrolytes were investigated by dynamic light scattering (DLS) measurement to determine the hydrodynamic diameter and zeta potential upon pH changes. Additionally, PDMAEMA-based polymers showed thermoresponsive properties and exhibited phase transfer at a lower critical solution temperature (LCST). Thanks to polyelectrolyte characteristics, the prepared polymers were investigated as smart materials for controlled release of quercetin. The influence of the length of the polymer grafts for the quercetin release profile was examined by UV–VIS spectroscopy. The results suggest the strong correlation between the length of the polymer chains and the efficiency of active substance release, thus, the adjustment of the composition of the macromolecules characterized by branched architecture can precisely control the properties of smart delivery systems.

Systematic Review on the Effects, Roles and Methods of Magnetic Particle Coatings in Magnetorheological Materials

Magnetorheological (MR) material is a type of magneto-sensitive smart materials which consists of magnetizable particles dispersed in a carrier medium. Throughout the years, coating on the surface of the magnetic particles has been developed by researchers to enhance the performance of MR materials, which include the improvement of sedimentation stability, enhancement of the interaction between the particles and matrix mediums, and improving rheological properties as well as providing extra protection against oxidative environments. There are a few coating methods that have been employed to graft the coating layer on the surface of the magnetic particles, such as atomic transfer radical polymerization (ATRP), chemical oxidative polymerization, and dispersion polymerization. This paper investigates the role of particle coating in MR materials with the effects gained from grafting the magnetic particles. This paper also discusses the coating methods employed in some of the works that have been established by researchers in the particle coating of MR materials.

Surface-Initiated Photoinduced Iron-Catalyzed Atom Transfer Radical Polymerization with ppm Concentration of FeBr3 under Visible Light

Reversible deactivation radical polymerizations with reduced amount of organometallic catalyst are currently a field of interest of many applications. One of the very promising techniques is photoinduced atom transfer radical polymerization (photo-ATRP) that is mainly studied for copper catalysts in the solution. Recently, advantageous iron-catalyzed photo-ATRP (photo-Fe-ATRP) compatible with high demanding biological applications was presented. In response to that, we developed surface-initiated photo-Fe-ATRP (SI-photo-Fe-ATRP) that was used for facile synthesis of poly(methyl methacrylate) brushes with the presence of only 200 ppm of FeBr3/tetrabutylammonium bromide catalyst (FeBr3/TBABr) under visible light irradiation (wavelength: 450 nm). The kinetics of both SI-photo-Fe-ATRP and photo-Fe-ATRP in solution were compared and followed by 1H NMR, atomic force microscopy (AFM) and gel permeation chromatography (GPC). Brush grafting densities were determined using two methodologies. The influence of the sacrificial initiator on the kinetics of brush growth was studied. It was found that SI-photo-Fe-ATRP could be effectively controlled even without any sacrificial initiators thanks to in situ production of ATRP initiator in solution as a result of reaction between the monomer and Br radicals generated in photoreduction of FeBr3/TBABr. The optimized and simplified reaction setup allowed synthesis of very thick (up to 110 nm) PMMA brushes at room temperature, under visible light with only 200 ppm of iron-based catalyst. The same reaction conditions, but with the presence of sacrificial initiator, enabled formation of much thinner layers (18 nm).

Polymer Brushes via Surface-Initiated Electrochemically Mediated ATRP: Role of a Sacrificial Initiator in Polymerization of Acrylates on Silicon Substrates

Silicon wafers as semiconductors are essential components of integrated circuits in electronic devices. For this reason, modification of the silicon surface is an important factor in the manufacturing of new hybrid materials applied in micro- and nanoelectronics. Herein, copolymer brushes of hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) and hydrophobic poly(tert-butyl acrylate) (PtBA) were grafted from silicon wafers via simplified electrochemically mediated atom transfer radical polymerization (seATRP) according to a surface-initiated approach. The syntheses of PHEA-b-PtBA copolymers were carried out with diminished catalytic complex concentration (successively 25 and 6 ppm of Cu). In order to optimize the reaction condition, the effect of the addition of a supporting electrolyte was investigated. A controlled increase in PHEA brush thickness was confirmed by atomic force microscopy (AFM). Various other parameters including contact angles and free surface energy (FSE) for the modified silicon wafer were presented. Furthermore, the effect of the presence of a sacrificial initiator in solution on the thickness of the grafted brushes was reported. Successfully fabricated inorganic–organic hybrid nanomaterials show potential application in biomedicine and microelectronics devices, e.g., biosensors.

Low Ppm Atom Transfer Radical Polymerization in (Mini)Emulsion Systems

In the last decade, unceasing interest in atom transfer radical polymerization (ATRP) has been noted, especially in aqueous dispersion systems. Emulsion or miniemulsion is a preferred environment for industrial polymerization due to easier heat dissipation and lower production costs associated with the use of water as a dispersant. The main purpose of this review is to summarize ATRP methods used in emulsion media with different variants of initiating systems. A comparison of a dual over single catalytic approache by interfacial and ion pair catalysis is presented. In addition, future development directions for these methods are suggested for better use in biomedical and electronics industries.