title: Modeling of phase separation mechanism in polycaprolactone/dioxane binary systems.
abstract: OBJECTIVE
  Unidirectional freezing followed by freeze-drying is a way to produce microcellular material from a polymer solution for biomedical application. As a distinctive feature of this type of process, bundles of channels are observed with an average diameter of hundreds of microns. Variations in porous morphology, particularly in porosity, density, and degree of regularity of spatial organization of pores, have been observed when polymer concentrations and quenching temperature are changed. To examine these issues in more detail the thermally induced phase separation of a polycaprolactone/dioxane solution was studied as a function of polymer concentration and quenching temperature in connection with the ultimate morphology of the micro-cellular material.
  
  
  METHODS
  We prepared microcellular samples of polycaprolactone by freeze/freeze-drying technique. The microstructure of the material was observed by scanning electron microscopy. Moreover, a mathematical model for the prediction of the temperature profile and morphology was developed.
  
  
  CONCLUSIONS
  A microstructural disorder region inside the samples was sometimes observed in connection with process parameters. The developed model is able to capture the formation of such a microstructural disorder region as a direct consequence of the slowing down of the solid-liquid interface. Predictions of the model as a function of freezing rate and concentration are in excellent agreement with experimental observation.
authors.affiliation: Institute of Composite and Biomedical Materials, National Research Council of Italy, Naples, Italy. larobina@unina.it
authors.forename: Domenico
authors.initials: D
authors.lastname: Larobina
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Guarino
authors.forename: Luigi
authors.initials: L
authors.lastname: Ambrosio
mesh_terms: D004146:Dioxanes / Q000737:chemistry*; D005612:Freeze Drying; D008855:Microscopy, Electron, Scanning; D008962:Models, Theoretical; D011091:Polyesters / Q000737:chemistry*; D016062:Porosity; D013696:Temperature
chemical_list: D004146:Dioxanes; D011091:Polyesters; C016240:polycaprolactone; C025223:1,4-dioxane