Molecular weight distribution design with living polimerisation reactions

Abstract

The physico-chemical properties of polymers are highly affected by the lengths and relative amounts of chains, hence the importance of the prediction of the molecular weight distribution (MWD) is evident. In this work a living anionic polymerisation reaction has been modeled with the method of monodisperse growth. An ideal living anionic polymerisation is made up of an instantaneous initiation and a propagation reaction step. The method applied (monodisperse growth) has been specifically developed for the calculation and design of MWD in ideal living polymerisation. The method is based on the convolution method, but neglecting the dispersion caused by chain growth, consequently, the resulting MWD is only an approximate one. In this work also the assumption of instantaneous initiation has been used in order to simplify calculations. The calculated approximate MWDs have been tested against the precise ones calculated with slow methods for the sake of the tests. In addition, a design algorithm has been derived from the calculation method applied, and it has been applied to predict reactor conditions for polymerisation in a continuous stirred tank reactor (CSTR).