Pyrolysis kinetics of [4-(hydroxymethyl)phenoxymethyl]polystyrene (Wang) resin using master-plot method and distributed reactivity model

Abstract

The pyrolysis of [4-(hydroxymethyl)phenoxymethyl]polystyrene (Wang) resin was studied by dynamic simultaneous thermogravimetric analysis (TGA) and derivative thermogravimetry techniques. The studied resin is used as the most commonly polymer supports in the peptide synthesis. A developed experimental master plots (exp-MP) model is presented that can be used to describe in more detail the pyrolysis of the resin established upon 4-hydroxybenzyl alcohol (PHB) on polystyrene, occurring throughout TGA experiments. This model assumes that the Wang resin is pyrolyzed through three parallel independent reaction steps, whereby their separation was performed through deconvolution procedure of the complex conversion rate curves. The mechanistic nature of each stage of Wang resin pyrolysis was explained by applying a combination of kinetic models such as diffusion mechanism, random nucleation and subsequent growth and chemical reactions mechanisms. The kinetic triplet parameters obtained in the present paper were then compared with those available in the literature. Within this kinetic study, the fraction distribution analysis (via distributed reactivity model) was performed, enabling reliable prediction of liquid products produced during the pyrolysis of the solid support of the Wang resin.