prof. dr.-ing. h. hasse molecular simulation study of the

Laboratory of EngineeringThermodynamicsProf. Dr.-Ing. H. Hasse

Molecular Simulation Study of the V l T i i f H d lVolume Transition of Hydrogels

Jonathan Walter1, Thorsten Merker1, Viktor Ermatchkov1, Jadran Vrabec2, Hans Hasse1,

1Laboratory of Engineering Thermodynamics,TU Kaiserslautern, Germany

2Thermodynamics and Energy Technology,University of Paderborn GermanyUniversity of Paderborn, Germany


H d lHydrogelsWhat is a Hydrogel?• Three dimensional hydrophilic polymer network• Most important property: Swelling in aqueous solutions

Examples for Applications:• Super absorber• Contact lenses

D d li t• Drug delivery systems• Sensors• Actors (e g micro valves)

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Actors (e.g. micro valves)• Biocatalysis


P l (N i l l id ) (PNiPAM)Poly(N-isopropylacrylamide) (PNiPAM)Cross Linking of PNiPAM

Single Chaing

• Hydrophilic monomers

Cross Linker

• Chemical• MBA

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E i t l tExperimental setup

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D f lli i l tiDegree of swelling in aqueous solutions

Influence of the TemperatureDegree of Swelling Influence of the TemperatureDegree of Swelling depends on:• MonomerMonomer• Co-monomer(s)• Cross linker amount• Solvent• pH-value

Salt concentration• Salt concentration• Temperature• … PNiPAM MBA water

exp. data, this work… PNiPAM, MBA, water

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M l l M d li d Si l tiModeling:

Molecular Modeling and Simulationg

• Force fields from literature

PNiPAM water: SPC/E water: TIP4P

Gromos87 UA

Gromos96 53a6 UA

Simulation:

OPLS AA

• Molecular dynamics (MD) • NpT-ensemble

Program:• Gromacs 4.0.x

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MD Si l ti H d l N t kMD-Simulation Hydrogel Network

PNiPAM ith MBA iPNiPAM with MBA in Water, 360 K• 240 PNiPAM monomers• 240 PNiPAM monomers• 15 monomers per chain

(6 mol% cross linker)• 60 000 water molecules• Force field: OPLS-AA +

SPC/ESPC/E• Computational time

1 week on 256 CPUs

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MD Si l ti Si l Ch iMD-Simulation Single Chain

280 K

360 K

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PNiPAM, water, OPLS-AA + SPC/E, 75 monomers


P li i St d Ch i L thPreliminary Study: Chain Length

PNiPAM, water, 360 K

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T t D d fTemperature Dependence ofSingle Chain Radius of Gyration

PNiPAM tPNiPAM, water, OPLS-AA + SPC/E

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T t D d fTemperature Dependence ofSingle Chain Radius of Gyration


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T t D d fTemperature Dependence of Single Chain Radius of Gyration


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F Fi ld C i R ltForce Field Comparison - Results

PNiPAM water: SPC/E water: TIP4PGromos87 UA - -Gromos87 UA - -Gromos96 53a6 UA - +OPLS AA + +

Legend- Force field does not predict effect+ Force field predicts effecto ce e d p ed c s e ec

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T t D d f th S lliTemperature Dependence of the Swelling of PNiPAM in Water

Simulation Single Chain Experiment Hydrogel

OPLS-AA + SPC/E PNiPAM, MBAOPLS AA SPC/E PNiPAM, MBA

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J. Walter, V. Ermatchkov, J.Vrabec, H. Hasse, Fluid Phase Equilibria, 296: 164-172 (2010)


S lli f PNiPAM i W t M th lSwelling of PNiPAM in Water-Methanol Mixtures

Experiment Hydrogel Simulation Single Chain298 K

Experiment Hydrogel Simulation Single Chain298 K

PNiPAM, MBA OPLS-AA + SPC/E 298 K

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Summary S lli f h d l PNiPAM Swelling of hydrogels: PNiPAM Molecular modeling and simulation f Temperature dependence of swelling Hydrogel swelling simulations:

N k Networks Single chains

Qualitative predictions with force fields from the literature Qualitative predictions with force fields from the literature

Outlook Development of force fields for quantitative predictions

Outlook

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Acknowledgements:

German Research Foundation forfinancial Support

prof. dr.-ing. h. hasse molecular simulation study of the

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