Scaling of glycine nucleation kinetics with shear rate and glass-liquid interfacial area

The scaling of the nucleation kinetics of glycine was investigated in supersaturated aqueous solutions under isothermal conditions. Induction times were measured in a Couette cell with a wide range of average shear rates γ_avg (25-250 s^-1) and a range of glass-liquid interfacial areas A (2.5-10 cm^2 per ml solution). The probability distributions of induction times were found to scale with shear rate and glass-liquid interfacial area, with the characteristic timescale (γ_avg.A)^-1. Primary nucleation rates and growth times to reach detection (estimated from the probability distributions) were both dependent on this timescale. In-situ dynamic light scattering revealed mesoscale clusters in the solutions that increased in size over time at rates which also depended on this timescale. The increase in size was thought to be due to the shear-enhanced aggregation or coalescence of mesoscale clusters leading to a higher number of larger mesoscale clusters, resulting in higher rates of primary nucleation.