Modeling the Mini-Emulsion Copolymerization of <i>N</i>‑Butyl Acrylate with a Water-Soluble Monomer: A Monte Carlo Approach

A Monte Carlo approach has been developed to simulate the miniemulsion polymerization of <i>n</i>-butyl acrylate with a water-soluble monomer, 2-hydroxyethyl methacrylate. The proposed simulation takes into account all the reactions in the aqueous and organic phases, as well as the entry of oligoradicals into the polymer particles by absorption and precipitation. The effect of the water-soluble monomer on the polymerization rate and on the molecular weight distribution of the polymer in the aqueous and organic phases has been studied. The addition of the water-soluble monomer retards the polymerization, though it had no significant effect on the molecular weight of the polymer produced in the particles; however, it increased the concentration of water-soluble polymer and its molecular weight. By this approach, it is possible to extract detailed information of polymer in the aqueous phase, such as the copolymer composition distribution

Branching at High Frequency Pulsed Laser Polymerizations of Acrylate Monomers

Branching at High Frequency Pulsed Laser Polymerizations of Acrylate Monomer

Macroinitiator and Macromonomer Modified Montmorillonite for the Synthesis of Acrylic/MMT Nanocomposite Latexes

A cationic macromonomer, 2-methacryloylethylhexadecyldimethylammonium bromide MA16, and a cationic macroinitiator, cationic acrylic/styrene oligomer end-capped with a nitroxide, were used to modify pristine Na−MMT, to enhance compatibility between the clay platelets and the host acrylic polymer matrix in waterborne nanocomposites. Both cationic species were successfully exchanged in the montmorillonite. The organically modified clays were used for the synthesis of acrylic (MMA/BA)/clay waterborne nanocomposites by miniemulsion polymerization. The 30% solids containing latexes were stable and coagulum free and presented better mechanical, thermal and barrier properties than the pristine acrylic copolymer

Encapsulation of Clay within Polymer Particles in a High-Solids Content Aqueous Dispersion

By using a two-step polymerization process, it was possible to encapsulate clay platelets within polymer particles dispersed in water. First, seed polymer particles with chemically bonded clay were obtained by batch miniemulsion polymerization. Then, the clay was buried within the particles by the addition of neat monomer in a second step. The final stable dispersions can have a solids content of up to 50 wt %. Transmission electron microscopy images clearly show the presence of clay platelets inside the polymer colloids, although they are not totally exfoliated. The obtained nanocomposites showed an increase in both the storage modulus in the rubbery state and the water resistance as the clay content increases. The approach presented here might be useful for encapsulating other high-aspect ratio nanofillers

UV-Tunable Biobased Pressure-Sensitive Adhesives Containing Piperonyl Methacrylate

Novel waterborne pressure-sensitive adhesives (PSAs) with biobased contents up to 71% and UV-light-tunable features have been developed using piperonyl methacrylate (PIPEMA) as a hard monomer. The biobased monomer was synthesized from piperonyl alcohol (derived from black pepper), and its homopolymer was fully characterized. Emulsion polymerization was chosen as a sustainable strategy to copolymerize piperonyl methacrylate together with biobased 2-octyl acrylate to produce high-solid-content latexes for pressure-sensitive adhesive applications. The UV light curing ability of the piperonyl methacrylate moieties in the copolymer backbone yielded PSAs with excellent shear resistance and reasonable adhesive properties (tack and peel)

Experimental Evidence Shedding Light on the Origin of the Reduction of Branching of Acrylates in ATRP

Intramolecular chain transfer to polymer and subsequent propagation of tertiary radicals cause extensive branching in radical polymerization of acrylic monomers. Studies in the literature have shown that under controlled radical polymerization conditions the extent of branching is significantly reduced. There are two competing theories to explain this effect. In one, the cause of reduced branching is attributed to a reduction in the number of backbiting events, and in the other that has been specifically applied to atom-transfer radical polymerization (ATRP), the cause is due to trapping of the tertiary radical by a fast deactivation step. In this article we show that trapping of the tertiary radical is not the cause for the reduction in branching fraction. This is shown by the absence of the corresponding patched midchain bromide structure as revealed by quantitative ¹³C NMR and by the ability to chain extend from a poly­(butyl acrylate-<i>co</i>-butyl 2-bromoacrylate) copolymer by ATRP. These results are complemented by quantum mechanical computations

From Polymer Latexes to Multifunctional Liquid Marbles

A simple method to prepare multifunctional liquid marbles and dry water with magnetic, color, and fluorescent properties is presented. Multifunctional liquid marbles were prepared by encapsulation of water droplets using flocculated polymer latexes. First, the emulsion polymerization reaction of polystyrene and poly­(benzyl methacrylate) was carried out using cheap and commercially available cationic surfactants. Subsequently, flocculation of the latex was provoked by an anion-exchange reaction of the cationic surfactant by the addition of lithium bis­(trifluoromethanesulfonyl)­imide salt. The flocculated polymer latex was filtered and dried, leading to very hydrophobic micronanoparticulated powders. These powders showed a great ability to stabilize the air/water interface. Stable liquid marbles were obtained by rolling water droplets onto the hydrophobic powders previously prepared. The use of very small polystyrene nanoparticles led us to the preparation of very stable and the biggest known liquid marbles up to 2.5 mL of water. Furthermore, the introduction of fluorescent comonomer dyes into the polymer powders allowed us to obtain new morphological images and new knowledge about the structure of liquid marbles by confocal microscopy. Furthermore, the introduction of magnetic nanoparticles into the polymer latex led to magnetic responsive liquid marbles, where the iron oxide nanoparticles are protected within a polymer. Altogether this method represents an accessible and general platform for the preparation of multifunctional liquid marbles and dry water, which may contribute to extending of their actual range of applications

Morphology of Three-Phase PS/PBA Composite Latex Particles Containing in Situ Produced Block Copolymers

Three-phase styrene−butyl acrylate composite polymer particles were synthesized by combining free radical polymerization, which yielded PS and PBA-co-PS, and controlled free radical polymerization, which yielded a large amount of PS-block-(PBA-co-PS)). Particle morphology evolves from core−shell when the particles did not contain block copolymer to hemispherical when a large amount of block copolymers was produced. The existing models could not predict this change in morphology. A general approach for the calculation of the equilibrium morphology of multiphase particles was developed using a Monte Carlo method

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. The versatility of the alkoxyamines is further exemplified by the ability to control the homopolymerization of styrene and by synthesis of a block copolymer of a second methacrylate in an efficient chain extension process