(309c) Examples of Multiscale Modelling in Chemical Product Design

One alternative in design of structured chemical products is to identify the desired end-use properties of the product and then to match this value by manipulation (design) of the product at the microstructure level. For development and/or manufacture of the same structured product, the end-use properties of the product are controlled by manipulating the microstructure formation of the final product. Typical examples are polymeric structure-based chemical products where the end-use of the polymer defines the product function (or performance) while the properties of its microstructure defines its design and manufacture. Clearly, any model-based design of these structured products will require models at micro-scale (related to properties of the microstructure) as well as macro-scale (related to the end-use properties of the final product). In this case, the macro-scale (end-use) property of the product could be regarded as an average property of its microstructure, calculated through an appropriate population balance model. The important parameters in the population balance model could be, for example, a combination of number of microstructures, their size and their distribution, or, a set of molecular (or atomic) descriptors. That is, the population balance model parameters are the links between the models at different scales of size. An interesting feature of the design of structured chemical products is that while the property of the product at the macro-scale and at micro-scale may be unique, the way to link them is not unique. That is, different macro-scale structures with the same end-use property maybe obtained through different arrangements of the same micro-scale. Alternatively, different microstructures arranged in different forms could be made to give the same end-use function. A large number of chemical products from the pharmaceutical, food, agro-chemicals, cosmetics, etc., sectors show the above ?micro-macro? relationship. While development of these products has been and continue to be experiment based trial and error, use of modelling tools, specially those with multiscale modelling features are finding increasing use. Multiscale modelling combined with experiments, has the potential to significantly reduce the time and cost to market for these structured chemical products. The presentation will highlight some of the important issues related to the use of multiscale modelling in structured chemical product design through illustrative examples. For each example, the representation of the structure at different scales, the definition of properties, the linking parameters, the multiscale model features, the simulation strategy, and, the chemical product design problem formulation and solution, will be highlighted.