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Siegel der Universität
Department für Chemie - Arbeitsgruppe Prof. Strey

Einfluss hydrophober Additive auf Mikroemulsionen mit sc-CO2 und deren Einfluss auf die Schaumbildung

Yvonne Pütz, 2012

 

The  preparation  of  nano-porous  materials  is  of  broad  interest  for a  wide  variety  of applications  such  as  heat  insulation,  sound  absorption  or  the
preparation  of  novel optoelectronic devices like organic light emitting diodes (OLEDs). However, the production of  these  materials  remains  a  challenge.  A  promising  idea  for  the preparation  of  low-cost, polymeric  nano-porous  materials  is  the  “Principle  of  Supercritical Microemulsions Expansion”  (POSME).  This  procedure  consists  of  preparing  nano-porous materials  via  the expansion and fixation of microemulsions containing a supercritical  (sc) fluid as  non-polar component. The first foaming experiments revealed that aging processes coarsen the pore size during the expansion considerably, leading to pore sizes in the range of micrometres rather than  nanometres.  Therefore,  a  low-molecular  additive  (co-oil)  is added  to  the  supercritical fluid,  which  is  intended  to  function  as  an  anti-aging  agent  and prevent  the  aging  of  the micelles  or  pores,  respectively.  In  this  work,  the influence  of different  low-molecular additives on microemulsions of the type H2O – CO2 /co-oil – non-ionic fluorinated surfactant was studied. It was found that the surfactant mass fraction needed to prepare a microemulsion is  considerably  decreased  by  adding  an  appropriate  co-oil.  However, exceeding  a  certain threshold leads to a strong increase of the surfactant mass fraction. Hence, an optimum co-oil content exists that allows the formulation of sc-CO 2 -microemulsions with a minimum amount of  surfactant.  The  phase  behaviour  of  the  microemulsion  depends systematically  on  the polarity of the co-oil. Furthermore, fluoro-surfactants which are commonly used to formulate sc-CO2  microemulsions were partially replaced by polyglycolalkyl-ether surfactants, which is of some importance for environmental reasons.