Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks’ glass transition temperatures

doi:10.1007/s11705-017-1626-2

Front. Chem. Sci. Eng.

2017, Vol. 11

Issue (3) : 440-447 https://doi.org/10.1007/s11705-017-1626-2

RESEARCH ARTICLE

Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks’ glass transition temperatures

Yang Zhou, Phillip Choi(

)

Department of Chemical and Materials Engineering, University of Alberta Edmonton, Edmonton, AB, T6G 1H9, Canada

Download: PDF(367 KB) HTML
Export: BibTeX | EndNote | Reference Manager | ProCite | RefWorks

Abstract

Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane-block-poly(N-isopropyl acrylamide) (PU-block-PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature (T_g) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU-block-PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU-block-PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU-block-PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2–0.4 nm in PU-block-PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

Keywords molecular dynamics simulation amphiphilic block copolymer free volume water diffusivity fujita model

Corresponding Author(s): Phillip Choi

Just Accepted Date: 23 January 2017 Online First Date: 17 March 2017 Issue Date: 23 August 2017

Cite this article:

Yang Zhou,Phillip Choi. Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks’ glass transition temperatures[J]. Front. Chem. Sci. Eng., 2017, 11(3): 440-447.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-017-1626-2
https://academic.hep.com.cn/fcse/EN/Y2017/V11/I3/440

Fig.1 Scheme 1Chemical structure of PU-block-PNIPAm

Fig.2 A cubic simulation cell containing 15 PU-block-PNIPAm and 10 water molecules (i.e., 0.5 wt-% water) upon a 200 ns MD annealing at 298 K

Fig.3 Temperature dependence of the specific volume of PU-block-PNIPAm, averaged over different initial configurations and the last 10 ns of each MD simulation at 1 atm. The best fit lines were used to determine the T_gs of the PU and PNIPAm blocks

Fig.4 Radial distribution functions of PNIPAm-PNIPAm and PU-PNIPAm at 300 K, radial distribution functions of PU-PNIPAm and PNIPAm-PNIPAm at 200, 300 and 400 K

Fig.5 A log-log plot of the mean square displacement of water molecules versus simulation time (averaged over 10 water molecules in PU-block-PNIPAm). The dashed line is the reference line with a slope of 1 (i.e., Einstein diffusion regime)

Fig.6 Self-diffusion coefficients of water in PU-block-PNIPAm calculated at various water concentrations over the range of 0.55-15 vol-% and at 298 and 450 K

Fig.7 The logarithm of self-diffusion coefficient versus the inverse of the square of free volume (5.2 wt-% at different temperatures)

Fig.8 Radial distribution functions of (a) water-PNIPAm segment, (b) water-PU segment and (c) water-water at different water concentrations at 298 K and 1 atm

Fig.9 Numbers of hydrogen bonds of water with polymer, water with PU segment, water with PNIPAm segment and polymer with polymer in the range of water concentration

Fig.10 Numbers of water-PU, water-PNIPAm and copolymer-copolymer hydrogen bonds of PU-block-PNIPAm at a water concentration of 5.2 wt-% over the temperature range of 280 to 460 K

1	Mathews A S, Narine S. Poly[N-isopropyl acrylamide]-co-polyurethane copolymers for controlled release of urea. Journal of Polymer Science. Part A, Polymer Chemistry, 2010, 48(15): 3236–3243 https://doi.org/10.1002/pola.24090
2	Seo Y, Brown J R, Hall L M. Effect of tapering on morphology and interfacial behavior of diblock copolymers from molecular dynamics simulations. Macromolecules, 2015, 48(14): 4974–4982 https://doi.org/10.1021/ma502309h
3	Srinivas G, Discher D E, Klein M L. Self-assembly and properties of diblock copolymers by coarse-grain molecular dynamics. Nature Materials, 2004, 3(9): 638–644 https://doi.org/10.1038/nmat1185
4	Fujita H, Kishimoto A, Matsumoto K. Concentration and temperature dependence of diffusion coefficients for systems polymethyl acrylate and n-alkyl acetates. Transactions of the Faraday Society, 1960, 56: 424–437 https://doi.org/10.1039/tf9605600424
5	Fujita H. Free-volume model of diffusion in polymer solutions. Advances in Polymer Science, 1961, 3: 1–47 https://doi.org/10.1007/BFb0050514
6	Fujita H. Notes on free volume theories. Polymer Journal, 1991, 23(12): 1499–1506 https://doi.org/10.1295/polymj.23.1499
7	Fujita H. Comments on free volume theories for plymer-solvent systems. Chemical Engineering Science, 1993, 48(17): 3037–3042 https://doi.org/10.1016/0009-2509(93)80169-Q
8	Williams M L, Landel R F, Ferry J D. The temperature dependence of relaxation mechanisms in amorphous polymers and other glass-forming liquids. Journal of the American Chemical Society, 1955, 77(14): 3701–3707 https://doi.org/10.1021/ja01619a008
9	Hess B, Kutzner C, van der Spoel D, Lindahl E. GROMACS 4: Algorithms for highly efficient, load-balanced, and scalable molecular simulation. Journal of Chemical Theory and Computation, 2008, 4(3): 435–447 https://doi.org/10.1021/ct700301q
10	van der Spoel D, Lindahl E, Hess B, Groenhof G, Mark A E, Berendsen H J C. GROMACS: Fast, flexible, and free. Journal of Computational Chemistry, 2005, 26(16): 1701–1718 https://doi.org/10.1002/jcc.20291
11	Lindahl E, Hess B, van der Spoel D. GROMACS 3.0: A package for molecular simulation and trajectory analysis. Journal of Molecular Modeling, 2001, 7(8): 306–317 https://doi.org/10.1007/s008940100045
12	Berendsen H J, van der Spoel D, van Drunen R. GROMACS: A message-passing parallel molecular dynamics implementation. Computer Physics Communications, 1995, 91(1-3): 43–56 https://doi.org/10.1016/0010-4655(95)00042-E
13	Ostenbrink C, Villa A, Mark A E, van Gunsteren W F. A biomolecular force field based on the free enthalpy of hydration and solvation: The GROMOS force-field parameter sets 53A5 and 53A6. Journal of Computational Chemistry, 2004, 25(13): 1656–1676 https://doi.org/10.1002/jcc.20090
14	Daura X, Mark A E, van Gunsteren W F. Parametrization of aliphatic CHn united atoms of GROMOS96 force field. Journal of Computational Chemistry, 1998, 19(5): 535–547 https://doi.org/10.1002/(SICI)1096-987X(19980415)19:5<535::AID-JCC6>3.0.CO;2-N
15	Berendsen H J, Postma J P, van Gunsteren W F, Hermans J. Interaction models for water in relation to protein hydration. Intermolecular Forces, 1981, 331–342
16	Theodorou D N, Suter U W. Detailed molecular structure of a vinyl polymer glass. Macromolecules, 1985, 18(7): 1467–1478 https://doi.org/10.1021/ma00149a018
17	Hoover W G. Canonical dynamics: Equilibrium phase-space distributions. Physical Review A., 1985, 31(3): 1695–1697 https://doi.org/10.1103/PhysRevA.31.1695
18	Parrinello M, Rahman A. Polymorphic transitions in single crystals: A new molecular dynamics method. Journal of Applied Physics, 1981, 52(12): 7182–7190 https://doi.org/10.1063/1.328693
19	Zhang Q G, Liu Q L, Chen Y, Wu J Y, Zhu A M. Microstructure dependent diffusion of water-ethanol in swollen poly (vinyl alcohol): A molecular dynamics simulation study. Chemical Engineering Science, 2009, 64(2): 334–340 https://doi.org/10.1016/j.ces.2008.10.028
20	Bondi A. van der Waals volumes and radii. Journal of Physical Chemistry, 1964, 68(3): 441–451 https://doi.org/10.1021/j100785a001
21	Raghu A V, Gadaginamath G S, Jawalkar S S, Halligudi S B, Aminabhavi T M. Synthesis, characterization, and molecular modeling studies of novel polyurethanes based on 2,2′-[ethane-1,2-diylbis (nitrilomethylylidene)] diphenol and 2,2′-[hexane-1,6-diylbis (nitrilomethylylidene)] diphenol hard segments. Journal of Polymer Science. Part A, Polymer Chemistry, 2006, 44(20): 6032–6046 https://doi.org/10.1002/pola.21686
22	Zhou D, Bayati F, Choi P. On the weak dependence of water diffusivity on the degree of hydrophobicity of acetylated hydroxypropyl xylan. Carbohydrate Polymers, 2013, 98(1): 644–649 https://doi.org/10.1016/j.carbpol.2013.06.025
23	Schild H G. Poly(N-isopropylacrylamide): Experiment, theory and application. Progress in Polymer Science, 1992, 17(2): 163–249 https://doi.org/10.1016/0079-6700(92)90023-R
24	Harmandaris V, Mavrantzas V, Theodorou D, Kröger M, Ramírez J, Öttinger H C, Vlassopoulos D. Crossover from the rouse to the entangled polymer melt regime: Signals from long, detailed atomistic molecular dynamics simulations, supported by rheological experiments. Macromolecules, 2003, 36(4): 1376–1387 https://doi.org/10.1021/ma020009g
25	Cohen M H, Turnbull D. Molecular transport in liquids and glasses. Journal of Chemical Physics, 1959, 31(5): 1164–1169 https://doi.org/10.1063/1.1730566
26	Sreenivasan K. Diffusion of water and alcohol in chemically modified polyurethane. Polymer International, 1993, 30(3): 363–365 https://doi.org/10.1002/pi.4990300314
27	Pulat M, Akdoğan A. The diffusion and bulk properties of polyurethane (PU)-based hydrophilic and hydrophobic membranes. Journal of Applied Polymer Science, 2002, 85: 193–198 https://doi.org/10.1002/app.10596
28	McNeill M E, Graham N B. Properties controlling the diffusion and release of water-soluble solutes from poly(ethylene oxide) hydrogels 1. Polymer composition. Journal of Biomaterials Science. Polymer Edition, 1993, 4(3): 305–322 https://doi.org/10.1163/156856293X00582
29	Costa L, Storti G. Self-diffusion of small molecules into rubbery polymers: A lattice free-volume theory. Journal of Polymer Science. Part B, Polymer Physics, 2010, 48(5): 529–540 https://doi.org/10.1002/polb.21918
30	Scholfield M R, Ford M C, van der Zanden C M, Billman M M, Ho P S, Rappé A K. Force field model of periodic trends in biomolecular halogen bonds. Journal of Physical Chemistry B, 2015, 119(29): 9140–9149 https://doi.org/10.1021/jp509003r
31	Tamai Y, Tanaka H, Nakanishi K. Molecular dynamics study of water in hydrogels. Molecular Simulation, 1996, 16(4-6): 359–374 https://doi.org/10.1080/08927029608024085

[1]	Bo Chen, Yan Dai, Xuehua Ruan, Yuan Xi, Gaohong He. Integration of molecular dynamic simulation and free volume theory for modeling membrane VOC/gas separation[J]. Front. Chem. Sci. Eng., 2018, 12(2): 296-305.
[2]	Fufeng LIU,Wenjie DU,Yan SUN,Jie ZHENG,Xiaoyan DONG. Atomistic characterization of binding modes and affinity of peptide inhibitors to amyloid-β protein[J]. Front. Chem. Sci. Eng., 2014, 8(4): 433-444.
[3]	Lin ZHANG, Yan SUN. Effect of ligand chain length on hydrophobic charge induction chromatography revealed by molecular dynamics simulations[J]. Front Chem Sci Eng, 2013, 7(4): 456-463.

Viewed

Full text

Abstract

Cited

Shared

Discussed