Molecular Dynamics Simulations of confined PEO Interlayed in GO

1. eman ta zabal zazu UPV/EHU Molecular DynamicsSimulationsofconfined PEO Interlayed in GO F. Alvarez Iñigo García-Yoldi Juan Colmenero

2. Outline • Background: • Bulk PEO homopolymerbehaviour. • Confined PEO within a blendwith PMMA. • Confined PEO interlayedwith GO. • Conclusions

3. Bulk PEO homopolymer 5 chainsof 43 monomers (1515 atoms) Forcefield: COMPASS Simulation time: 400 ns Temperatures: 350, 375, 400 and 500K Mn PEO: 2Kg/mol < Me

4. Bulk PEO homopolymerValidationof SELF motionobtainedfromsimulations by NeutronScattering [FOCUS(PSI)] measuremments

5. Bulk PEO homopolymerValidationof COLLECTIVE motionobtainedfromsimulations by NeutronScattering (TOFTOF) measuremments

6. Confined PEO within a blendwith PMMA 5 chainsof 43 monomersof PEO and 15 chainsof 100 monomersof PMMA (7200 atoms) 20% PEO and80% PMMA AsymmetricPolymerblend Forcefield: COMPASS Simulation time: 200 ns Temperatures: 300, 350, 400 and 500K

7. Confined PEO within a blendwith PMMA Validationof Single ChainDynamicStructure Factor obtainedfrom 10% protonated PEO,10% deuterated PEO and 80% deuterated PMMA

8. Molecular dynamicssimulations by meansofthe COMPASS forcefieldforBulkHomopolymer PEO andforanasymmetricblendwith PMMA display a verygoodagreementwithneutronscatteringexperiments. • However… will COMPASS be abletocopewithconfined PEO behaviourinterlayed in GO?

10. COMPASS results compatible withabinitio DFT calculations

12. COMPASS results compatible withabinitio DFT calculations

14. COMPASS results compatible withabinitio DFT calculations

15. Confined PEO interlayedwith GO 5 chainsof 43 monomersof PEO wereinterlayedwith GO in a 20 % weightproportion in PEO. The 2048 carbonatomslayerisfurnishedwith 256 hydroxyland 512 epoxyfunctionalgroups placed randomly. Molecular dynamicssimulationsof up to 50 nswhererun at T= 300, 350 and 400K.

16. Thestrongerconfinementof PEO in PEO/GO leadsto more reducedmobilitybutalsodevelopesanhetereogeneity (as manifested in thedoublepeakfeature) in the radial distributionfunction

17. Thisheterogeneity can be, more explicitly, observedwhenoneanalyzesseparatelythefastest 100 H in PEO andtheslowest 100 ones (out of a total of 870) Although in both sets there are traces ofboth, fasterandslowerhydrogenes, therelative ratios are clearlydifferentandget more distinctwith time.

18. Although, in principle, it looks as ifwemeet a newtypeofconfinement in GO withrespecttotheonefoundfortheassymetricblendwiththe, more rigidpolymer, PMMA, in thefollowingwewill show thecloseagreementforthedynamicsofthefaster H of PEO in PEO/GO andthedynamicsof H in PEO at a higher T in a blendwithfixedrigid PMMA.

19. H for PEO in PEO/fixedPMMAblend at T=350K Fast H for PEO in PEO/GO at T=400K TheIntermediateScatteringFunctionsforthefast H of PEO in PEO/GO at T=400K andforthe H in theblendwithfixedlyrigid PMMA matrix at T=350K are almostcoincident.

20. Thecloseresemblance can be betterappreciated in thedirectspatialdomainwherethelikelinessamongthe radial distributionfunctionsisquantitative at times at leastuntil 500 psandstillqualitativeabovethisvalue.

21. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

22. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

23. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

24. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

25. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

26. Moreover, above 500 psthequantitativeagreement can still be met by shiftingthe times: The radial distributionsfunctionsoflonger times for PEO in thefixed PMMA matrix at 350K coincide withthoseofthefast H in GO at faster times.

27. Conclusions • Thesameforcefield (COMPASS) thatwasvalidated by NS measuremnts in MD simulationsofbulk PEO andanasymmetricblendof PEO/PMMA has beenshowntoyieldresults compatible withthoseobtained by abinitio DFT calculations in thedescriptionoftheinteractionsbetween PEO and GO.

28. Conclusions • PEO in PEO/GO isunder a strongerconfinementthan in anasymmetricblendwith PMMA. • A heterogeneousscenarioismetwheresome H ofthepolymer are more hinderedwhereasothers are more mobilethanthe average. • Thefaster H subset observed in PEO interlayedwithin GO seemsto display a selfdynamicsveryclosetothatofthe H in PEO within a blendwith a fullyfrozen PMMA matrix at a lowertemperature (around 50 K lower). Only at longer times (andlower Q values) seems PEO in PEO/GO tobecome more mobile.

29. Conclusions • A tentativeproposablescenariocould be thefollowingone: Thepresenceofhydroxylandepoxygroupshighlyconstrain by meansofhydrogenbondingthedynamicsoftheinterlayed PEO. Nevertheless, somepartsof PEO are stillfastenoughto display thesameselfdynamicsthattheoneobtained in a rigid PMMA matrix at a lowertemperature. Thefactthat a smalldrift can be observed at longer times (same RDF at lower times for PEO in GO) andlow Q values (faster ISF for PEO in GO) might be dueto a creepofthe PEO chainsthatcould be possible in theinterlayed PEO in GO buthindered in thefixedrigidmatrix.