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pH-responsive, shape changing amphiphilic Janus particles


Stimuli-responsive colloid surfactants for thermodynamically stable emulsions and phase inversion emulsification



Janus particles are biphasic colloids that have distinct chemistries and contrasting properties on each side. Because of their amphiphilicity, Janus particles have the unique ability to stabilize multiphasic fluid mixtures, such as emulsions. Janus particles also have a strong tendency to segregate to and remain at fluid interfaces, leading to highly stable emulsions.  However, current synthesis techniques generate only one type of emulsion, so a method where the chemical environment can be tuned on demand to generate different types of emulsions is desirable.



Researchers in the Lee lab have designed a new approach to synthesize a new class of colloidal materials, highly uniform, pH-responsive Janus particles in emulsions, via seeded emulsion polymerization and acid hydrolysis.  The hydrolysis of the composite particles leads to a drastic change in particle morphology. 


Janus particles with varying surface properties can be controlled by manipulating the chemical environment. The pH-dependent aggregation/dispersion behavior of the Janus particles generates both attractive and repulsive emulsions at low and high pH conditions, respectively. The ability to enable phase inversion allows for the generation of novel emulsions that cannot be achieved by traditional emulsion bulk synthesis methods. 



Daeyeon Lee, Professor of Chemical & Biomolecular Engineering



 Caption: Schematic illustration for synthesis of amphiphilic Janus particles and scanning electron microscopy images.  From Tu et al, JACS, 2014.



  • Generate highly uniform, pH-responsive Janus particles
  • Completely reverse amphiphilicity in response to changes in solution pH
  • Dynamically tunable
  • Easier separation than amphiphilic surfactants to remove particles from products



  • Solid surfactants
  • Stable, industrial emulsions; water-in-oil and oil-in-water
  • Paints, coatings
  • Oil recovery
  • Emulsion-based reactions



Stage of Development:

Proof-of-principle testing


Intellectual Property:

US pending (14/687,266)</rss.ip>


Reference Media:


Desired Partnerships:

  • License
  • Co-development

 Docket #  14-7092



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Patent Information:
For Information, Contact:
Joshua Jeanson
Associate Director, SEAS/SAS Licensing Group
University of Pennsylvania
Daeyeon Lee