Influence Of Solvent Properties On The Thermodynamics And Nucleation Kinetics Of HMBTAD

The solvent often has a significant influence on the crystal behavior of a substance.The research on the influence of solvent properties on the crystal thermodynamics and nucleation kinetics is of paramount importance to the control of crystal polymorph,shape and size distribution.In this work,with N,N’-Bis(2,2,6,6-etramethyl-4-piperidinyl)-1,6-hexanediamine(HMBTAD)as the model system,the impact of solvent properties on the crystal thermodynamics were investigated systematically.More specifically,this work aims at analyzing the influence of solvent properties and intermolecular action on the nucleation kinetics quantitatively,and correlating the thermodynamics with nucleation kinetics of solute.Finally,the effect of solution volume on the stochastic distribution of induction time was further evaluated,which could provide guidance for the design of nucleation experiments.Solubility data is the basic thermodynamic property of crystal nucleation process study.In this work,the solubility data of HMBTAD in seven organic solvents,including acetonitrile,acetone,methyl acetate,ethyl acetate,propyl acetate,isopropyl acetate,and isobutyl acetate,and two binary solvents,acetone + acetonitrile,and methyl acetate + acetonitrile,were determined by the dynamic method.The solubility data of solute HMBTAD in different solvents were fitted with a series of empirical and theoretical models.Furthermore,the mixing thermodynamic properties were calculated and discussed based on the model parameters.Finally,the solubility data were correlated versus the solvent dielectric constant to analyze the relationship between solvent properties and crystal thermodynamics.Based on the thermodynamic data,solute-solvent systems with appropriate solubility were chosen to conduct induction time measurements.Nucleation rate of HMBTAD in four ester solvents and acetonitrile + acetone binary solvents was determined using the stochastic induction time method at small solution volume,and its nucleation rate model was established by taking their uncertainty into consideration.Also,nucleation kinetic parameters were calculated with Poisson Distribution and Classical Nucleation Theory.In addition,the influence of intermolecular bonding between the solute and solvent on the nucleation difficulty was further evaluated and analyzed based on the Raman spectra of crystal and saturated solution of HMBTAD.Finally,a statistical model was established to estimate the effect of solution volume on the inherent stochastic distribution of nucleation induction time based on the nucleation kinetic parameters obtained previously.Induction time of HMBTAD in acetonitrile were determined at different supersaturations under different solution volume.By comparing the theoretical calculated value with the experimental ones,it can help to identify the transition volume at which the induction time becomes reproducible.The result also acts as a tool for the design of nucleation experiments and the selection of solution volume.