Elastomer polymer brushes on flat surface by bimolecular surface-initiated nitroxide mediated polymerization

Recent Advances in Hybrid Biomimetic Polymer-Based Films: from Assembly to Applications

Biological membranes, in addition to being a cell boundary, can host a variety of proteins that are involved in different biological functions, including selective nutrient transport, signal transduction, inter- and intra-cellular communication, and cell-cell recognition. Due to their extreme complexity, there has been an increasing interest in developing model membrane systems of controlled properties based on combinations of polymers and different biomacromolecules, i.e., polymer-based hybrid films. In this review, we have highlighted recent advances in the development and applications of hybrid biomimetic planar systems based on different polymeric species. We have focused in particular on hybrid films based on (i) polyelectrolytes, (ii) polymer brushes, as well as (iii) tethers and cushions formed from synthetic polymers, and (iv) block copolymers and their combinations with biomacromolecules, such as lipids, proteins, enzymes, biopolymers, and chosen nanoparticles. In this respect, multiple approaches to the synthesis, characterization, and processing of such hybrid films have been presented. The review has further exemplified their bioengineering, biomedical, and environmental applications, in dependence on the composition and properties of the respective hybrids. We believed that this comprehensive review would be of interest to both the specialists in the field of biomimicry as well as persons entering the field.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Surface-initiated SET living radical polymerisation for the synthesis of silica–polymer core–shell nanoparticles

We report the use of surface-initiated single-electron transfer living radical polymerisation (SI SET-LRP) to prepare inorganic–organic core–shell nanoparticles with functional grafted chains of high molecular weight.

Nitroxides: applications in synthesis and in polymer chemistry

This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.

In situ thermo-dependant trapping of carbon radicals: a versatile route to well-defined polymer-grafted silica nanoparticles

We report in this paper an original and simple method for the grafting of polymer chains on colloidal silica particles. We first synthesize an alkoxyamine bi-functional initiator, by coupling 2-methyl-2-[--butyl--(dimethoxyphosphoryl-2,2-dimethylpropyl)aminoxy]propionic acid (MAMA) and an acrylate coupling agent, 3-(trimethoxysilyl)propyl acrylate (TPMA). Based on the fact that MAMA dissociates at 25 °C, but activates polymerization of acrylates at only 110 °C, it is possible to stop the reaction after the insertion of only one C[double bond, length as m-dash]C acrylate double bond, in the temperature range 25-80 °C. This synthetic methodology is called " thermo-dependant trapping of carbon radicals". The "new" initiator obtained at that stage is then grafted on Stöber silica particles, by simple condensation of its alkoxysilane functions. We show that the initiator-grafting density is twice as high as the value obtained by our first approach of "trapping of carbon radicals". The last step of the synthesis process is the grafting from polymerization of polybutylacrylate (PBA). Transmission electron microscopy (TEM) images and small-angle neutron scattering (SANS) spectra show that the PBA-grafted silica particles are spherical, with a narrow size distribution, and do not form aggregates. Moreover, by this versatile route, the grafted polymer density, the molecular weight and therefore the polymer-layer morphology, can be easily controlled and tuned. It can also be extended to other monomers that work well with SG1 nitroxide.

Choose sides: differential polymer adhesion

AFM-based single molecule desorption measurements were performed on surface end-grafted poly(acrylic acid) monolayers as a function of the pH of the aqueous buffer to study the adhesion properties of polymers that bridge two surfaces. These properties were found to depend on the adhesion forces of both surfaces in a differential manner, which is explained with a simple model in analogy to the Bell-Evans formalism used in dynamic force spectroscopy. The measured interaction forces between the poly(acrylic acid) chains and silicon nitride AFM tips depend on the grafting density of the polymer monolayers as well as on the contour length of the polymer chains. This study demonstrates that the stability of polymer bridges is determined by the adhesion strengths on both surfaces, which can be tuned by using pH-dependent polyelectrolyte monolayers.