Microemulsions polymerisation

Finally, very recently Shea et al. successfully employed inverse microemulsion polymerisation for the preparation of MIP beads in the tens of nanometers range using hydrophilic peptides as template molecules. In this case it was the template molecule which was prefunctionahsed with a hydrophobic chain to orient it towards the surface of the growing bead during polymerisation. The rebinding efficiency of the resulting nanoparticles was however found to depend markedly on the nature of the employed template and to be lower than that recorded with beads of similar... 

Microemulsion polymerisation has shown a great advantage over conventional polymerisation strategies such as emulsion polymerisation with respect to the end particle size, polydispersity and reproducibility of the product characteristics. Although we still face severe problems regarding the polymerisation of microemulsions (see Section 11.2 in Chapter 11), it has been employed for the synthesis of polymeric nanoparticles of pharmaceutical interest. Microemulsion polymerisation involves free-radical polymerisation in a large number of monomer-swollen microemulsion droplets and represents a thermodynamically stable, transparent one-phase reaction system. Generally, the microemulsion droplet is considered as initiation locus for the polymerisation. The type of microemulsion used for the polymerisation depends on the monomer properties [148]. 

It is very important to design a microemulsion polymerisation process that enables successful removal of nanoparticles formed and does not affect the drug efficacy and stability during the polymerisation process. Both these criteria are difficult to meet in the pharmaceutical arena and hence extensive investigations are required to establish the potential of microemulsion polymerisation [153, 154]. 

PS microspheres, produced by microemulsion polymerisation, generally contain only one or a few... 

In contrast, microemulsion polymerisation is a much more recent subject of study, as yet not greatly developed [6.5]. The considerable interest shown in this line of research is a direct consequence of the 1974 petrol crisis. This stimulated... 

Any study on microemulsion polymerisation must be preceded by an appropriate formulation and phase diagrams of systems in which the monomer is to be dispersed must be characterised. What is the formulator looking for The main constraint is cost. Systems should contain the highest possible monomer concentration for the smallest possible quantity of surfactants. This is indeed... 

Microemulsion polymerisation is a new area of research being developed at the present time. The mechanisms behind particle nucleation and growth have not been perfectly understood as yet. Nevertheless, from studies carried out recently [6.5], we can outline the general features common to all systems investigated. 

Microemulsion polymerisation is a new technique for the production of microlatexes made up of nanometric particles and polymers with specific properties. Let us summarise the main features of the process ... 

Very recently, polyacrylamide microlatexes prepared in the way described above have been used to microencapsulate certain types of rat cells [6.5]. These microcapsules are characterised by total absence of cell toxicity and the possibility of delaying antibody penetration in vitro. For these reasons, they may prove useful for encapsulating living cells. Also in the medical field of applications, water-in-oil microemulsion polymerisation has been used to synthesise functionalised nanoparticles with an enzyme immobilised inside them. These are used as a support in nucleotide probes [6.18]. 

Microemulsion processes may well find applications in areas which have traditionally used emulsion polymerisation. At the present stage of research, it is mainly water-in-oil microemulsion polymerisation which offers the most possibilities and several patents have been taken out [6.5]. This process minimises certain problems encountered in classic inverted emulsions, namely instability of the latexes they produce, large polydispersity of polymer particles, and the large quantity of coagulum which increases production costs. Water-soluble (co)polymers prepared in microemulsion polymerisation can be used in various ways ... 

As flocculants for a wide range of substrates (such as cellulose fibres) and in water treatment. Reverse latexes are destabilised and reversed by adding excess water or possibly another surface active agent. Microlatexes prepared in microemulsion polymerisation are self-reversing and therefore do not require addition of another surfactant to favour this transformation. Furthermore, the corresponding polymers, confined within such small particles, with such low polydispersity, should exhibit better characteristics in this respect. 

Colloid Polymer Science 279, No.9, Sept.2001, p.879-86 MICROEMULSION POLYMERISATION OF STYRENE USING A POLYMERISABLE NONIONIC SURFACTANT AND A CATIONIC SURFACTANT... 

Colloid Polymer Science 278, No.9, Sept. 2000, p.821-9 MICROEMULSION POLYMERISATION OF STYRENE STABILIZED BY SODIUM DODECYL SULPHATE AND DIETHYLENE GLYCOL MONOALKYL ETHER Chem C S Liu C W... 

Toronto, 27th April-2nd May 1997, p. 1733-7. 012 FUNCTIONALISED CORE-SHELL POLYMERS PREPARED BY MICROEMULSION POLYMERISATION... 

A novel process for the preparation of latex with high solid content, but maintaining the characteristics of microemulsion polymerisation latex, small particle size (less than 50 nm) and polymer with high molecular weight (more than 10 6) is presented. With the PS latex obtained by microemulsion polymerisation as seed, core shell, styrene-butyl acrylate polymers functionalised with itaconic acid are prepared. Materials were characterised by differential scanning calorimetry, dynamic mechanical thermal analysis and transmission electron microscopy. These polymers have better mechanical properties than the non functionalised or those prepared by emulsion polymerisation. 11 refs. 

No. 24,18th Nov. 1996, p.7678-82 NOVEL CHARACTERISTICS OF POLYSTYRENE MICROSPHERES PREPARED BY MICROEMULSION POLYMERISATION Weihua Ming Jun Zhao Xuliang Lu Changchun Wang Shoukuan Fu Fudan,University... 

Neyret and Vincent [30] have developed such an approach for the formation of microgel particles, named inverse microemulsion polymerisation. The oil phase consisted of anionic 2-acrylamido-2-methylpropanesulfonate (AMPS) and cationic (2-(methacryloyloxy)ethyl) trimethylammonium (MADQUAT) monomers in addition to a BA cross-linker. The co-polymerisation was initiated using UV irradiation and the product isolated and re-dispersed in aqueous electrolyte solution to yield polyampholyte microgel particles. The particles became swollen in the presence of high electrolyte concentrations as a result of screening of the attractive electrostatic interactions between neighbouring chains. 

Most of the ultrasonic polymerisation studies involve miniemulsion polymerisation process where both shear and radicals generated by acoustic cavitation at 20 kHz are important. However, Teo et al. [65] have also used high frequency (213 kHz) to successfully carry out microemulsion polymerisation. By manipulating the concentration of surfactant used to stabilise the emulsion droplets, shear forces needed to generate emulsion droplets could be avoided. 

B. Teo, M. Ashokkumar, F. Grieser, Microemulsion polymerisation via high frequency ultrasound irradiation. J. Phys. Chem. C 112, 5265-5267 (2008)... 

---