Equilibrium free-radical polymerization of methyl methacrylate under nanoconfinement

• Published in: Polymer (Guilford) Vol. 66; pp. 173 - 178
• Main Authors: Zhao, H.Y., Simon, Sindee L.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2015
• Subjects: Confinement; Entropy; Entropy effect; MMA equilibrium polymerization; Molecular weight; Nanoconfinement; Nanostructure; Polymerization; Polymethyl methacrylates; Porosity; Propagation (polymerization); Nanoconfinement; MMA equilibrium polymerization; Entropy effect
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2015.04.017

The effect of nanoconfinement on the equilibrium free radical polymerization of methyl methacrylate (MMA) is investigated using differential scanning calorimetry. The ceiling temperature is shifted to lower temperatures in 13 nm diameter pores, with pore surface chemistry showing no significant effect. The results indicate that the change in the entropy of propagation decreases in nanopores due to confinement effects (i.e. ΔSp,conf is a more negative value than ΔSp,bulk). The change in the entropy of propagation is independent of temperature for the bulk equilibrium polymerization, whereas the change in the entropy of propagation in nanopores becomes less negative and more bulk-like with increasing polymerization temperature presumably due to the lower molecular weight chains produced at high temperature. The data suggest that our system is one of weak confinement with chain entropy scaling with molecular weight to the 1.1 power (i.e. ∼ N1.1). [Display omitted] •The thermodynamics of nanoconfined free radical polymerization is studied using DSC.•The change in entropy for chain propagation becomes more negative in nanopores.•The equilibrium conversion and ceiling temperature decrease due to nanoconfinement.•Surface chemistry does not appear to have an effect at high reaction temperatures.•Chain entropy in the 13-nm pores scales with N1.1 indicating weak confinement.