Ian Maxwell

Emulsion polymerization of butyl acrylate. Kinetics of particle growth

The kinetics of the seeded emulsion polymerization of butyl acrylate have been studied dilatometrically at 50 °C, using both persulphate and γ-radiolysis for initiation. Kinetic data obtained for steady state polymerization and for the approach to (and, for γ-radiolysis, relaxation from) a steady state, gave rate coefficients for entry, exit, termination and propagation, using data-fitting techniques which have been shown to yield unambiguous rate parameters from such results. The system is found to have a high average number of free radicals per article (ranging from 3 to 9). The rate coefficient for exit (desorption) of free radicals from the particles is in accord with transfer/diffusion theory; exited free radicals tend to undergo subsequent re-entry. The entry rate shows that the free-radical capture efficiency is high but significantly less than 100% at the higher initiator concentrations studied; this is quantitatively interpreted by considering competing aqueousphase events. Values for the propagation and termination rate coefficients at 60% weight fraction polymer are reported, the latter being an order of magnitude less than predicted by current theory.

Parallel Evolution: Performance Studies at the University of Sydney

Performance studies at the University of Sydney has developed in relative isolation from the main-stream of performance studies in both North America and Europe, gathering itself around and in the context of a range of local constraints, concerns, and possibilities, with theatre at its center.

Radical Capture Efficiencies in Emulsion Polymerization Kinetics

Experimental data and models are presented for initiator efficiency in emulsion polymerization systems in the absence of particle formation. The data show that a number of models are inapplicable, viz., those assuming that the rate-determining step for free radical entry into a particle is either diffusional capture, surfactant displacement, or colloidal entry. The data however support the model (first suggested by Priest) of aqueous phase propagation to a critical degree of polymerization, whereupon capture of the resulting oligomeric free radical by a particle is instantaneous. Mutual aqueous phase termination of smaller species also occurs; one must take account of the fact that the rate coefficient for this is some two orders of magnitude greater than that for low molecular weight species in polymeric systems. This model is in quantitative and qualitative accord with the experimental dependences of the entry rate coefficient on the concentrations of initiator, of surfactant, of aqueous phase monomer, and of latex particles, as well as on particle size, on ionic strength and on temperature.

12 Hours before the Mast

‘12 Hours Before the Mast’ takes on the phenomenon—and the phenomenology—of being (all) at sea. Flowing from and around the illynxial experience of open-water yachting off the coast of Sydney, Australia, the essay proposes that sailing can be understood in terms of a triadic relationship between embodiment, technology and environment, any of those terms at any moment mediating the other two. In sailing in such circumstances, being-in-the-world emerges from a thick, chiasmatic co-extensivity with the fluid materiality of sea and air, from and through horizons encountered in their ineffability and blurredness. All this is undergirded by the physical, emotional and technical limits (and possibilities) of embodiment under duress, engaged in a mood of anxious playfulness, of playful anxiety.

My Big Fat Greek Baptism

Pavel Florensky, in Iconostasis, his great theological work of 1922, describes the screen, covered in representations — icons — of Christ, the Holy Mother and the Saints, separating the nave from the sanctuary in an Orthodox church, as a boundary between the visible and invisible worlds. In the Orthodox Church, the altar — where, Florensky writes, ‘God is, the sphere where heavenly glory dwells’ (my emphasis) — is that which is hidden by the iconostasis. Were we, Florensky explains, ‘wholly spiritualized’, there would be ‘no iconostasis other than standing before God Himself’. That which cleaves, of course, both brings together and places apart; the wall of saints mediates two worlds, and as such is a window, ‘proclaiming the Mystery’ through the ‘cloud of witnesses’ to that which ‘is from the other side of mortal flesh’ (1996, p. 62). The iconostasis, then, does not so much hide as it mediates, enables, empowers.

Controlled release kinetics from a spherical particle into a fluid of arbitrary density

Abstract A simple formula for the steady-state rate of release of molecules from a spherical particle is evaluated in terms of the particle size (Knudsen number), molecular diffusion coefficients within the particle and in the fluid phase, and the equilibrium distribution within the particle. The model accounts for depletion near the surface and the role of the fluid. The inputs required are the particle size, chemical potentials, diffusion coefficients, and fluid density.