Polymer Colloids: Current Challenges, Emerging Applications, and New Developments.

Polymer colloids are complex materials that have the potential to be used in a vast array of applications. One of the main reasons for their continued growth in commercial use is the water-based emulsion polymerization process through which they are generally synthesized. This technique is not only highly efficient from an industrial point of view but also extremely versatile and permits the large-scale production of colloidal particles with controllable properties.

Microwave-Assisted Ultrafast RAFT Miniemulsion Polymerization of Biobased Terpenoid Acrylates.

There is a growing preference to move away from traditional petrochemical-based polymers toward biobased alternatives. Here, we report the microwave-assisted RAFT polymerization of several terpenoid acrylates (tetrahydrogeraniol, cyclademol, nopol, and citronellol). These biobased monomers give polymers with a broad range of glass transition temperatures and are excellent candidates to substitute oil-based (meth)acrylates in applications such as coatings and adhesives.

Can We Push Rapid Reversible Deactivation Radical Polymerizations toward Immortality?

All reversible deactivation radical polymerization (RDRP) processes require a compromise between the rate of polymerization, which requires a high radical concentration, and retention of chain end functionality, which requires a low radical concentration. Here, we demonstrate that this compromise may be partially averted where fast deactivation of the propagating radical occurs. It is shown that, contrary to the predictions of classical reaction kinetics, when the probability density functions of the termination reactions are adjusted to take into account the time needed for radical diffusion, a reduction in the extent of termination can be expected if chain deactivation is rapid.

Linking Film Structure and Mechanical Properties in Nanocomposite Films Formed from Dispersions of Cellulose Nanocrystals and Acrylic Latexes.

Cellulose nanocrystals (CNCs) are unique, lightweight materials that possess high elastic modulus and tensile strength, making them of great interest in the formation of nanocomposite materials. However, efficient design of the composite material is essential in translating the mechanical properties of the individual CNCs into the nanocomposite film. In this work, we demonstrate the formation of structured CNC/acrylic dispersions by physical blending of the anionic CNCs with charged acrylic latex particles.

Dynamic Optimization and Non-linear Model Predictive Control to Achieve Targeted Particle Morphologies.

An event-driven approach based on dynamic optimization and nonlinear model predictive control (NMPC) is investigated together with inline Raman spectroscopy for process monitoring and control. The benefits and challenges in polymerization and morphology monitoring are presented, and an overview of the used mechanistic models and the details of the dynamic optimization and NMPC approach to achieve the relevant process objectives are provided. Finally, the implementation of the approach is discussed, and results from experiments in lab and pilot-plant reactors are presented.

Renewable Terpene Derivative as a Biosourced Elastomeric Building Block in the Design of Functional Acrylic Copolymers.

In order to move away from traditional petrochemical-based polymer materials, it is imperative that new monomer systems be sought out based on renewable resources. In this work, the synthesis of a functional terpene-containing acrylate monomer (tetrahydrogeraniol acrylate, THGA) is reported. This monomer was polymerized in toluene and bulk via free-radical polymerizations, achieving high conversion and molecular weights up to 278 kg·mol.

Phase Separation Driven On-Demand Debondable Waterborne Pressure-Sensitive Adhesives.

A waterborne pressure-sensitive adhesive (PSA) that shows high adhesive performance and easy debondability on demand without leaving residues on the substrate (adhesive failure) has been developed. A key component of the PSA is a semicrystalline phase that is beneficial for the adhesive properties and that becomes fluid when heated above the melting temperature. Migration of this liquid-like polymer to the substrate-adhesive interface and hardening upon cooling results in a hard non-tacky interface that facilitates debonding.

Mid-Chain Radical Migration in the Radical Polymerization of -Butyl Acrylate.

The occurrence of intramolecular transfer to polymer in the radical polymerization of acrylic monomers has been extensively documented in the literature. Whilst it has been largely assumed that intramolecular transfer to polymer leads to short chain branches, there has been some speculation over whether the mid-chain radical can migrate. Herein, by the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) of poly(-butyl acrylate) synthesized by solution polymerization under a range of conditions, it is shown that this mid-chain radical migration does occur in the radical polymerization of acrylates conducted at high temperatures, as is evident from the shape of the molecular weight distribution.

Toward a Green Synthesis of Polyurethane/(Meth)acrylic Dispersions through Control of Colloidal Characteristics.

Polyurethane (PU)/acrylic waterborne hybrids are an attractive class of materials with wide application possibilities, but their synthesis typically requires significant quantities of solvent which has negative economic and environmental consequences. In this work, solvent-free and surfactant-free polyurethane (PU)/acrylic waterborne hybrids were obtained by synthesizing the PU prepolymer containing carboxylic groups directly in (meth)acrylic monomers that act as solvent. Then, the mixture is dispersed in water; the PU is chain-extended with diamines, and the (meth)acrylic monomers are polymerized.

Shedding light on the different behavior of ionic and nonionic surfactants in emulsion polymerization: from atomistic simulations to experimental observations.

Although surfactants are known to play a vital role in polymerization reactions carried out in dispersed media, many aspects of their use are poorly understood, perhaps none more so than the vastly different action of ionic and nonionic surfactants in emulsion polymerization. In this work, we combine experimental measurements of emulsion polymerization of styrene with atomistic molecular dynamics simulations to better understand the behavior of surfactants at monomer/polymer-water interfaces. In a batch emulsion polymerization of styrene, the nonionic surfactant Disponil AFX 1080 leads to two nucleation periods, in contrast to the behavior observed for the ionic surfactant SDS.

Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications.

Film forming, stable hybrid latexes made of methyl metacrylate (MMA), butyl acrylate (BA) and 2-hydroxyethyl methacrylate (HEMA) copolymer reinforced with modified multiwalled carbon nanotubes (MWCNTs) were synthesized by in situ miniemulsion polymerization. The MWCNTs were pretreated by an air sonication process and stabilized by polyvinylpyrrolidone. The presence of the MWCNTs had no significant effect on the polymerization kinetics, but strongly affected the polymer characteristics ( and insoluble polymer fraction).

The role of non-covalent interactions in the self-healing mechanism of disulfide-based polymers.

In this work, a theoretical protocol based on classical molecular dynamics has been defined, in order to study weak non-covalent interactions in diphenyl disulfide based compounds. This protocol is then used to study the influence of hydrogen bonds and π-π stacking in four selected cases, namely, monosubstituted and amine ortho trisubstituted urea and urethane-based diphenyl disulfides. In all cases, it has been observed that hydrogen bonds are much more relevant than π-π stacking, which has little influence.

Telemonitoring in-home complex chronic patients from primary care in routine clinical practice: Impact on healthcare resources use.

Background: Recent evidence indicates that home telemonitoring of chronic patients reduces the use of healthcare resources. However, further studies exploring this issue are needed in primary care.

Objectives: To assess the impact of a primary care-based home telemonitoring intervention for highly unstable chronic patients on the use of healthcare resources.

Direct Synthesis of Fractal Polymer Dispersions by Miniemulsion Polymerization.

Fractal colloids, which find applications in the preparation of advanced materials, are currently synthesized by means of a multistep procedure that yields a low solids content dispersion. This is not well suited for certain applications such as superhydrophobic coatings. In this work, a one-step method for the synthesis of higher solids content waterborne fractal polymer dispersions is presented and it is shown that the surfaces obtained from the fractal dispersions are superhydrophobic (contact angle, θ > 150°) which is beyond the current waterborne coating technology (θ = 130°-137°).

Adsorption and desorption behavior of ionic and nonionic surfactants on polymer surfaces.

We report combined experimental and computational studies aiming to elucidate the adsorption properties of ionic and nonionic surfactants on hydrophobic polymer surface such as poly(styrene). To represent these two types of surfactants, we choose sodium dodecyl sulfate and poly(ethylene glycol)-poly(ethylene) block copolymers, both commonly utilized in emulsion polymerization. By applying quartz crystal microbalance with dissipation monitoring we find that the non-ionic surfactants are desorbed from the poly(styrene) surface slower, and at low surfactant concentrations they adsorb with stronger energy, than the ionic surfactant.

The underlying mechanisms for self-healing of poly(disulfide)s.

Recently, self-healing polymers based on disulfide compounds have gained attention due to the versatile chemistry of disulfide bonds and easy implementation into polymeric materials. However, the underlying mechanisms of disulfide exchange which induce the self-healing effect in poly(disulfide)s remain unclear. In this work, we elucidate the process of disulfide exchange using a variety of spectroscopic techniques.

New Class of Alkoxyamines for Efficient Controlled Homopolymerization of Methacrylates.

Despite significant efforts, the design of alkoxyamines for polymerization of methacrylic monomers in a well-controlled fashion with good retention of the active chain ends remains a challenge. Herein, the facile synthesis of several alkoxyamines, which are capable of achieving this long sought-after goal, is reported. Controlled homopolymerization of methyl methacrylate is achieved as determined by a linear increase in molecular weight with conversion and first-order rate plots for various alkoxyamine concentrations.

Controlling film topography to form highly hydrophobic waterborne coatings.

Coatings have a tremendous impact on economy as they reduce corrosion that has an estimated cost of 3% of the world's GDP. Hydrophobic coatings are particularly efficient for this purpose and the challenge is to produce cost effective and environmentally friendly, highly hydrophobic, cohesive and non-porous coatings applicable to large and irregular surfaces. This work shows that this goal can be achieved by forming wrinkles on the surface of waterborne coatings through fine-tuning of the film forming conditions.

Highly Hydrophobic Coatings from Waterborne Latexes.

This work reports on the formation of highly hydrophobic coatings from waterborne latexes able to form films at ambient temperature. The contact angle of film forming copolymers of 2-ethylhexyl acrylate and perfluorodecyl acrylate (PFDA) was limited to 114° because flat surfaces were obtained. Attempts to increase the roughness of the film using blends of film-forming latexes with the latex of PFDA homopolymer (which is not film forming) were not successful under regular casting conditions because the PFDA particles accumulated at the film-substrate interface.

On the Termination Mechanism in the Radical Polymerization of Acrylates.

In a recent publication, Nakamura and co-workers studied the termination mechanism in the radical polymerization of acrylates. Contrary to conventional thinking, their conclusion is that termination is overwhelmingly by disproportionation. This finding impacts on a large body of the previous work in the polymerization of acrylic monomers which this work seeks to address.

Design of new disulfide-based organic compounds for the improvement of self-healing materials.

Self-healing materials are a very promising kind of materials due to their capacity to repair themselves. Among others, diphenyl disulfide-based compounds (Ph2S2) appear to be among the best candidates to develop materials with optimum self-healing properties. However, few is known regarding both the reaction mechanism and the electronic structure that make possible such properties.

Redox Active Compounds in Controlled Radical Polymerization and Dye-Sensitized Solar Cells: Mutual Solutions to Disparate Problems.

Controlled radical polymerization (CRP) and dye-sensitized solar cells (DSSCs) are two fields of research that at an initial glance appear to have little in common. However, despite their obvious differences, both in application and in scientific nature, a closer look reveals a striking similarity between many of the compounds widely used as control agents in radical polymerization and as redox couples in dye-sensitized solar cells. Herein, we review the various redox active compounds used and examine the characteristics that give them the ability to perform this dual function.

New evidence for hybrid acrylic/TiO2 films inducing bacterial inactivation under low intensity simulated sunlight.

This study addresses the preparation and characterization of hybrid films prepared from Titanium dioxide (TiO2) Pickering stabilized acrylic polymeric dispersion as well as their bacterial inactivation efficiency under sunlight irradiation. Complete bacterial inactivation under low intensity simulated solar light irradiation (55 mW/cm(2)) was observed within 240 min for the films containing 10 weight based on monomers (wbm) % of TiO2, whereas 360 min were needed for the films containing 20 wbm% of TiO2. The hybrid films showed repetitive Escherichia coli (E.