Shapes of Amphiphilic Codendrimers by Monte Carlo Simulation

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Shapes of Amphiphilic Co-dendrimers by Monte
Carlo Simulation
Edward G. Timoshenko (), Ronan Connolly and Yuri
A. Kuznetsov Theory and Computation Group,
Department of Chemistry, University College
Dublin
Web page http//darkstar.ucd.ie E-mail
Edward.Timoshenko_at_ucd.ie
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Statistical Mechanical approach
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Techniques adopted
Metropolis Monte Carlo simulation in continuous
space
Gaussian self-consistent (GSC) method
Equilibrium
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GSC for kinetics
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Self-consistent equation
Advantages fairly simple, fast, qualitatively
good for a wide range of systems across varied
solvent conditions. Disadvantages restricts the
radial distribution functions to a Gaussian
shape. This leads to overestimation of swelling
in a good solvent and underestimation of energy
in a poor one. More recently non-Gaussian (SGSC)
generalisation obtained.
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Branched polymers
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Tomalias poly(amidoamine) PAMAM
All of these syntheses have been divergent,
i.e., they involve the attachment of monomers to
increasingly large dendrimers
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Fréchets convergent synthesis of poly(aryl
ether) dendrimers
A number of more advanced (accelerated) synthesis
techniques have been also proposed recently.
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Applications of dendrimers and stars
Useful properties 1. Monodispersity 2. Large
number of end-groups that can be
functionalised 3. Relatively well-defined
structures 4. Reduced viscosity and hydrodynamic
radius.
Examples of applications 1. Catalysis 2.
Supramolecular chemistry 3. Medicine (e.g. drug
delivery) 4. Coatings and rheology modifiers 5.
Nanotechnology
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Model
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Nomenclature used for dendrimers
D number of monomers before a branch
point
G number of generations of branching
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Homo-dendrimers in good solvent

• D3G7 is more spherical than D3G3
• D3G7 has a hollow region near its centre

D3G3
D3G7
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Scaling results for homo-dendrimers
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Asphericity Eigenvalues of shape tensor

G
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Coil to globule transition
Gaussian Self-Consistent (GSC) results

• Low U(0) - good solvent
• High U(0)- poor solvent
• Collapse transition is more pronounced for
  larger dendrimers
• Poor Solvent
• compact globules
• Connectivity is not as important
• Uniform density and no cavity

D4G5
D6G5
D3G5
D2G5
D1G5
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Amphiphilic co-dendrimers
Inner-H D3G4
Outer-H D3G4
Both Inner- and Outer-H dendrimers form micellar
structures
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Inner-H co-dendrimers
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Outer-H co-dendrimers
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Binary core co-dendrimers
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Our computing facilities
Web http//darkstar.ucd.ie/cluster,
http//chemistry.ucd.ie/cscb/cluster
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Acknowledgements
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Screensaver