Particle morphology control

Leontidis E, Kleitou K, Kyprianidou-Leodidou T, Bekiari V, Lianos P (2002) Gold colloids from cationic surfactant solutions. 1. Mechanisms that control particle morphology. Langmuir 18 3659-3668... 

Bimetallic DENs can be prepared using methodologies comparable to those for monometallic DENs. Important additional considerations are the interactions between metal salt precursors and the potential to control particle morphology... 

Organic templating or the molecular manipulation of microstructure [137-140] has been of great interest to those seeking controlled particle morphology especially for applications where a combination of molecular sieving and chemically active framework sites could be... 

Ethylene partial pressure within the gas-phase process is an important variable used to control particle morphology. For the manufacture of LLDPE, ethylene partial pressure is limited to a value that maintains acceptable particle morphology. This constraint lowers catalyst productivity. A commercial catalyst with a productivity of at least 1,500 to 2,000 g PE/g of catalyst is necessary for a commercial reactor. One important goal in polyethylene research is to provide a better catalyst system where catalyst productivity maybe increased, yet maintaining acceptable particle morphology. Catalysts with productivities of > 3,000 g PE/g catalyst are preferred. 

Further important features of emulsion polymerization are the good heat transfer, the relatively low viscosity of the product latexes at high polymer concentrations and the ability to control particle morphology (e.g. formation of core-shell particle structures by successive additions of different monomers). In addition, it is worth noting that the reaction mechanism usually is more complex than indicated here. Chain transfer agents are often used to reduce desorption of small radical species from the particles takes place, and other modes of particle nucleation can operate. 

There are six integrated steps that may be employed in the development of a particle system with tailored size and morphology. These are (i) know the material (ii) determine synthesis conditions to prepare the desired phase (iii) develop methods to control particle size within the context of the material system (iv) develop techniques to control particle morphology within the context of the material system (v) control the state of agglomeration using colloid chemical principles and (vi) control yield of the material by selection of the starting materials and their concentrations. 

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