Methyl Methacrylate Polymerization in Nanoporous Matrix: Reactivity and Resulting Properties

摘要

Nanoconfinement is well known to affect the reactivity and properties of polymers. In this work, the influence of nanoconfinement on free radical polymerization reaction kinetics and the properties of the polymer is investigated and discussed. Controlled pore glass (CPG) is used as a nanoconfining matrix for methyl methacrylate (MMA) polymerization with pore diameters ranging from 13 nm to 110 nm. Differential scanning calorimetry (DSC) was employed to measure the isothermal polymerization as a function of reaction time for reaction temperatures from 60 °C to 95 °C. Gel permeation chromatograph (GPC) and nuclear magnetic resonance spectroscopy (NMR) were used to obtain the molecular weight and tacticity of the polymer product. Nanoconfiment is found to result in the earlier onset of autoacceleration, presumablely due to a decrease in the rate of termination arising from decreases in chain diffusivity in the confined state. In addition, molecular weight, and isotacticity of the resulting PMMA are found to increase in 13 nm hydrophilic pores. A model of the nanoconfined reaction is able to quantitatively describe the reaction kinetics by accounting for changes in chain diffusivity, and qualitatively describe the enhancement in molecular weights without adjustable parameters.