Monodisperse polymer particles dispersion polymerization

Morphology of the enzymatically synthesized phenolic polymers was controlled under the selected reaction conditions. Monodisperse polymer particles in the sub-micron range were produced by HRP-catalyzed dispersion polymerization of phenol in 1,4-dioxane-phosphate buffer (3 2 v/v) using poly(vinyl methyl ether) as stabihzer. °° ° The particle size could be controlled by the stabilizer concentration and solvent composition. Thermal treatment of these particles afforded uniform carbon particles. The particles could be obtained from various phenol monomers such as m-cresol and p-phenylphenol. 

Several methodologies for preparation of monodisperse polymer particles are known [1]. Among them, dispersion polymerization in polar media has often been used because of the versatility and simplicity of the process. So far, the dispersion polymerizations and copolymerizations of hydrophobic classical monomers such as styrene (St), methyl methacrylate (MMA), etc., have been extensively investigated, in which the kinetic, molecular weight and colloidal parameters could be controlled by reaction conditions [6]. The preparation of monodisperse polymer particles in the range 1-20 pm is particularly challenging because it is just between the limits of particle size of conventional emulsion polymerization (100-700 nm) and suspension polymerization (20-1000 pm). 

The rate of dispersion (co)polymerization of PEO macromonomers passes through a maximum at a certain conversion. No constant rate interval was observed and it was attributed to the decreasing monomer concentration. At the beginning of polymerization, the abrupt increase in the rate was attributed to a certain compartmentalization of reaction loci, the diffusion controlled termination, gel effect, and pseudo-bulk kinetics. A dispersion copolymerization of PEO macromonomers in polar media is used to prepare monodisperse polymer particles in micron and submicron range as a result of the very short nucleation period, the high nucleation activity of macromonomer or its graft copolymer formed, and the location of surface active group of stabilizer at the particle surface (chemically bound at the particle surface). Under such conditions a small amount of stabilizer promotes the formation of stable and monodisperse polymer particles. 

The HRP-catalyzed polymerization of phenols can also be carried out as a dispersion polymerization in 1,4-dioxane/buffer mixtures with poly(ethyl-ene glycol), poly(vinyl alcohol), and poly(methyl vinyl ether) as stabilizers. The dispersion polymerization of phenol and its derivatives leads to the formation of relatively monodisperse polymer particles with a typical diameter... 

Dispersion polymerization in organic hydrocarbon media was first developed by Osmond and Wagstaff [133] as a way to reduce the viscosity of the solvent-based coatings. Almog et al. [134] showed that monodisperse polymer particles... 

During the dispersion polymerization, the polymer precipitates from an initially homogeneous reaction mixture containing monomer, initiator, steric stabilizer, and solvents. Under favorable conditions, monodisperse polymer particles stabilized by a steric barrier of dissolved polymer are formed. The early work, mainly done in nonaqueous media such as aliphatic hydrocarbons, was thoroughly reviewed by Barrett [90]. Most of the studies dealt with polymer particles in the 0.1- to 2- jun size range. 

A silicone macromonomer has also been used to stabilize the dispersion polymerization of PMMA (44). The PDMS macromonomer used in this study was a commercially available methacryloxy functional PDMS macromonomer (Fig. 9). The polymerizations were carried out at 340 bar and 65 C for 4 h. When no PDMS macromonomer was added to the polymerization, only low conversions could be achieved and the polymer precipitated. Addition of a small amount of PDMS macromonomer (0.05 wt %) to the polymerizations increased the molecular weight and the yield of the polymer, but at least 3.5 wt % was necessary to obtain monodispersed polymer particles at high yield. PDMS homopolymer, which lacks the reactive MMA functional group, was not effective in stabilizing the polymerization in that a much greater concentration of the... 

In the second chapter (Preparation of polymer-based nanomaterials), we summarize and discuss the literature data concerning of polymer and polymer particle preparations. This includes the description of mechanism of the radical polymerization of unsaturated monomers by which polymer (latexes) dispersions are generated. The mechanism of polymer particles (latexes) formation is both a science and an art. A science is expressed by the kinetic processes of the free radical-initiated polymerization of unsaturated monomers in the multiphase systems. It is an art in that way that the recipes containing monomer, water, emulsifier, initiator and additives give rise to the polymer particles with the different shapes, sizes and composition. The spherical shape of polymer particles and the uniformity of their size distribution are reviewed. The reaction mechanisms of polymer particle preparation in the micellar systems such as emulsion, miniemulsion and microemulsion polymerizations are described. The short section on radical polymerization mechanism is included. Furthermore, the formation of larger sized monodisperse polymer particles by the dispersion polymerization is reviewed as well as the assembling phenomena of polymer nanoparticles. 

A styryl-type macromonomer having a water-soluble ROZO segment (Scheme 47) or having an amphiphilic ROZO block copolymer (Scheme 51) was extensively used as surfactant for the emulsion or dispersion polymerization. Polymerization of St or MMA in the presence the macromonomer as stabilizer (less than 3 wt% for the total monomer) in water took place with a radical initiator to give stable monodisperse polymer particles with a micron-size diameter. The macromonomer acted as both comonomer and stabilizer actually the copolymerization occurred. Therefore, the system is micelle forming but soap-free. Hydrophilic PMeOZO segments are preferential on the particle surface. 

Dispersion polymerization is defined as a type of precipitation polymerization by which polymeric microspheres are formed in the presence of a suitable steric stabilizer from an initially homogeneous reaction mixture. Under favorable circumstances, this polymerization can yield, in a batch process, monodisperse, or nearly monodisperse, latex particles with a relatively large diameter (up to 15 pm) [103]. The solvent selected as the reaction medium is a good solvent for both the monomer and the steric stabilizer, but a non-solvent for the polymer being formed and therefore a selective solvent for the graft copolymer. This restriction on the choice of solvent means that these reactions can be carried out... 

The occurrence of a secondary phase separation inside dispersed phase particles, associated with the low conversion level of the p-phase when compared to the overall conversion, explains the experimental observation that phase separation is still going on in the system even after gelation or vitrification of the a-phase [26-31]. A similar thermodynamic analysis was performed by Clarke et al. [105], who analyzed the phase behaviour of a linear monodisperse polymer with a branched polydisperse polymer, within the framework of the Flory-Huggins lattice model. The polydispersity of the branched polymer was treated with a power law statistics, cut off at some upper degree of polymerization dependent on conversion and functionality of the starting monomer. Cloud-point and coexistence curves were calculated numerically for various conversions. Spinodal curves were calculated analytically up to the gel point. It was shown that secondary phase separation was not only possible but highly probable, as previously discussed. 

A. J. C. Kuehne, M. C. Gather, J. Sprakel, Monodisperse Conjugated Polymer Particles by Suzuki-Miyaura Dispersion Polymerization. Nat. Commun. 2012, 3, 1088. 

Coating PANI onto various matrixes has been studied for a long time [38,39]. In particular, monodispersed particles with a perfect spherical shape are generally preferred as model ER materials to investigate ER effect since the morphology of the dispersed phase is one of the critical parameters. However, PANI particles synthesized by conventional oxidization polymerization are often of irregular shape. Therefore, to obtain monodispersed PANI ER particles, researchers have used monodispersed polymer spheres as core to develop various PANI-coated ER particles. For example, Jun et al. [40,41] have used monodisperse micron-sized porous... 

---