Morphological transformations of diblock copolymers in binary solvents: A simulation study
Zheng Wang, Yuhua Yin, Run Jiang, Baohui Li()
School of Physics, Key Laboratory of Functional Polymer Materials of Ministry of Education, Nankai University, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, China
Morphological transformations of amphiphilic AB diblock copolymers in mixtures of a common solvent (S1) and a selective solvent (S2) for the B block are studied using the simulated annealing method. We focus on the morphological transformation depending on the fraction of the selective solvent CS2, the concentration of the polymer Cp, and the polymer–solvent interactions εij (i = A, B; j = S1, S2). Morphology diagrams are constructed as functions of Cp, CS2, and/or εAS2. The copolymer morphological sequence from dissolved→sphere→rod→ring/cage→vesicle is obtained upon increasing CS2 at a fixed Cp. This morphology sequence is consistent with previous experimental observations. It is found that the selectivity of the selective solvent affects the self-assembled microstructure significantly. In particular, when the interaction εBS2 is negative, aggregates of stacked lamellae dominate the diagram. The mechanisms of aggregate transformation and the formation of stacked lamellar aggregates are discussed by analyzing variations of the average contact numbers of the A or B monomers with monomers and with molecules of the two types of solvent, as well as the mean square end-to-end distances of chains. It is found that the basic morphological sequence of spheres to rods to vesicles and the stacked lamellar aggregates result from competition between the interfacial energy and the chain conformational entropy. Analysis of the vesicle structure reveals that the vesicle size increases with increasing Cp or with decreasing CS2, but remains almost unchanged with variations in εAS2.
S. A.Jenekhe and X. L.Chen, Self-assembled aggregates of rod-coil block copolymers and their solubilization and encapsulation of fullerenes, Science279(5358), 1903 (1998) https://doi.org/10.1126/science.279.5358.1903
2
R.Stoenescu, A.Graff, and W.Meier, Asymmetric ABC-triblock copolymer membranes induce a directed insertion of membrane protein, Macromol. Biosci.4(10), 930 (2004) https://doi.org/10.1002/mabi.200400065
3
R.Stoenescu and W.Meier, Vesicles with asymmetric membranes from amphiphilic ABC triblock copolymers, Chem. Commun.24(24), 3016 (2002) https://doi.org/10.1039/b209352a
4
Y. F.Zhou and D. Y.Yan, Real-time membrane fusion of giant polymer vesicles, J. Am. Chem. Soc.127(30), 10468 (2005) https://doi.org/10.1021/ja0505696
5
Y. F.Zhou and D. Y.Yan, Real-time membrane fission of giant polymer vesicles, Angew. Chem. Int. Ed.44(21), 3223 (2005) https://doi.org/10.1002/anie.200462622
6
R.Savic, L. B.Luo, A.Eisenberg, and D.Maysinger, Micellar nanocontainers distribute to defined cytoplasmic organelles, Science300(5619), 615 (2003) https://doi.org/10.1126/science.1078192
7
C.Allen, D.Maysinger, and A.Eisenberg, Nanoengineering block copolymer aggregates for drug delivery,Colloids Surf. B Biointerfaces16(1–4), 3 (1999) https://doi.org/10.1016/S0927-7765(99)00058-2
8
L. F.Zhang and A.Eisenberg, Multiple morphologies of “crew-cut” aggregates of polystyrene-b-poly(acrylic acid) block copolymers, Science268(5218), 1728 (1995) https://doi.org/10.1126/science.268.5218.1728
9
X. T.Shuai, H.Ai, N.Nasongkla, S.Kim, and J. M.Gao, Micellar carriers based on block copolymers of poly(e-caprolactone) and poly(ethylene glycol) for doxorubicin delivery, J. Control. Release98(3), 415 (2004) https://doi.org/10.1016/j.jconrel.2004.06.003
10
H.Lomas, I.Canton, S.MacNeil, J.Du, S. P.Armes, A. J.Ryan, A. L.Lewis, and G.Battaglia, Biomimetic pH sensitive polymersomes for efficient DNA encapsulation and delivery, Adv. Mater.19(23), 4238 (2007) https://doi.org/10.1002/adma.200700941
11
X. B.Xiong, H.Uludag, and A.Lavasanifar, Biodegradable amphiphilic poly(ethylene oxide)-block-polyesters with grafted polyamines as supramolecular nanocarriers for efficient siRNA delivery, Biomaterials30(2), 242 (2009) https://doi.org/10.1016/j.biomaterials.2008.09.025
12
A.Blanazs, S. P.Armes, and A. J.Ryan, Self-assembled block copolymer aggregates: From micelles to vesicles and their biological applications, Macromol. Rapid Commun.30(4–5), 267 (2009) https://doi.org/10.1002/marc.200800713
13
K. J.Hanley, T. P.Lodge, and C. I.Huang, Phase behavior of a block copolymer in solvents of varying selectivity, Macromolecules33(16), 5918 (2000) https://doi.org/10.1021/ma000318b
14
C.Lai, W. B.Russel, and R. A.Register, Phase behavior of Styrene–Isoprene diblock copolymers in strongly selective solvents, Macromolecules35(3), 841 (2002) https://doi.org/10.1021/ma011696z
15
T. P.Lodge, B.Pudil, and K. J.Hanley, The full phase behavior for block copolymers in solvents of varying selectivity, Macromolecules35(12), 4707 (2002) https://doi.org/10.1021/ma0200975
16
B.Yu, B.Li, P.Sun, T.Chen, Q.Jin, D.Ding, and A. C.Shi, Cylinder-gyroid-lamella transitions in diblock copolymer solutions: A simulated annealing study, J. Chem. Phys.123(23), 234902 (2005) https://doi.org/10.1063/1.2137711
17
T.Suo, D.Yan, S.Yang, and A. C.Shi, A theoretical study of phase behaviors for diblock copolymers in selective solvents, Macromolecules42(17), 6791 (2009) https://doi.org/10.1021/ma900939u
18
M.Antonietti and S.Forster, Vesicles and liposomes: A self-assembly principle beyond lipids, Adv. Mater.15(16), 1323 (2003) https://doi.org/10.1002/adma.200300010
X. S.Wang, G.Guerin, H.Wang, Y. S.Wang, I.Manners, and M. A.Winnik, Cylindrical block copolymer micelles and co-micelles of controlled length and architecture, Science317(5838), 644 (2007) https://doi.org/10.1126/science.1141382
H. W.Shen and A.Eisenberg, Morphological phase diagram for a ternary system of block copolymer PS310-b- PAA52/Dioxane/H2O, J. Phys. Chem. B103(44), 9473 (1999) https://doi.org/10.1021/jp991365c
23
B.Du, A.Mei, K.Yin, Q.Zhang, J.Xu, and Z.Fan, Vesicle formation of PLAx–PEG44 diblock copolymers, Macromolecules42(21), 8477 (2009) https://doi.org/10.1021/ma9016339
24
H.Huang, B.Chung, J.Jung, H. W.Park, and T.Chang, Toroidal micelles of uniform size from diblock copolymers, Angew. Chem. Int. Ed.48(25), 4594 (2009) https://doi.org/10.1002/anie.200900533
25
A. G.Denkova, P. H. H.Bomans, M.O.Coppens, N. A. J. M.Sommerdijk, and E.Mendes, Complex morphologies of self-assembled block copolymer micelles in binary solvent mixtures: The role of solvent–solvent correlations, Soft Matter7(14), 6622 (2011) https://doi.org/10.1039/c1sm05461a
26
S.Zhong, H.Cui, Z.Chen, K. L.Wooley, and D. J.Pochan, Helix self-assembly through the coiling of cylindrical micelles, Soft Matter4(1), 90 (2008) https://doi.org/10.1039/B715459C
27
D. H.Han, X. Y.Li, S.Hong, H.Jinnai, and G. J.Liu, Morphological transition of triblock copolymer cylindrical micelles responding to solvent change, Soft Matter8(7), 2144 (2012) https://doi.org/10.1039/c2sm07020k
28
B. E.McKenzie, J. F.de Visser, H.Friedrich, M. J. M.Wirix, P. H. H.Bomans, G.de With, S. J.Holder, and N. A. J. M.Sommerdijk, Bicontinuous nanospheres from simple amorphous amphiphilic diblock copolymers, Macromolecules46(24), 9845 (2013) https://doi.org/10.1021/ma4019729
29
P.Sun, Y.Yin, B.Li, T.Chen, Q.Jin, D.Ding, and A.C.Shi, Simulated annealing study of morphological transitions of diblock copolymers in solution, J. Chem. Phys.122(20), 204905 (2005) https://doi.org/10.1063/1.1924452
30
R.Wang, Z.Jiang, and G.Xue, Excluded volume effect on the self-assembly of amphiphilic AB diblock copolymer in dilute solution, Polymer52(10), 2361 (2011) https://doi.org/10.1016/j.polymer.2011.03.010
31
J.Cui and W.Jiang, Vesicle formation and microphase behavior of amphiphilic ABC triblock copolymers in selective solvents: A Monte Carlo study, Langmuir26(16), 13672 (2010) https://doi.org/10.1021/la102211d
32
J.Cui and W.Jiang, Structure of ABCA tetrablock copolymer vesicles and their formation in selective solvents: A Monte Carlo study, Langmuir27(16), 10141 (2011) https://doi.org/10.1021/la202377t
33
J.Cui, Y. Y.Han, and W.Jiang, Asymmetric vesicle constructed by AB/CB diblock copolymer mixture and its behavior: A Monte Carlo study, Langmuir30(30), 9219 (2014) https://doi.org/10.1021/la501674a
34
P. T.He, X. J.Li, M. G.Deng, T.Chen, and H. J.Liang, Complex micelles from the self-assembly of coilrod- coil amphiphilic triblock copolymers in selective solvents, Soft Matter6(7), 1539 (2010) https://doi.org/10.1039/b926370e
35
W.Kong, B.Li, Q.Jin, D.Ding, and A. C.Shi, Helical vesicles, segmented semivesicles, and noncircular bilayer sheets from solution-state self-assembly of ABC Miktoarm star terpolymers, J. Am. Chem. Soc.131(24), 8503 (2009) https://doi.org/10.1021/ja900405r
36
C. I.Huang and Y. C.Hsu, Effects of solvent immiscibility on the phase behavior and microstructural length scales of a diblock copolymer in the presence of two solvents, Phys. Rev. E74(5), 051802 (2006) https://doi.org/10.1103/PhysRevE.74.051802
37
I.Carmesin and K.Kremer, The bond fluctuation method: A new effective algorithm for the dynamics of polymers in all spatial dimensions, Macromolecules21(9), 2819 (1988) https://doi.org/10.1021/ma00187a030
38
R. G.Larson, Self-assembly of surfactant liquid crystalline phases by Monte Carlo simulation, J. Chem. Phys.91(4), 2479 (1989) https://doi.org/10.1063/1.457007
39
R. G.Larson, Monte Carlo simulation of microstructural transitions in surfactant systems, J. Chem. Phys.96(11), 7904 (1992) https://doi.org/10.1063/1.462343
40
N.Metropolis, A. W.Rosenbluth, M. N.Rosenbluth, A. H.Teller, andE.Teller, Equation of state calculations by fast computing machines, J. Chem. Phys.21(6), 1087 (1953) https://doi.org/10.1063/1.1699114
B.Xia, W.Li, and F.Qiu, Self-assembling behaviors of symmetric diblock copolymers in C homopolymers, Acta Chimi. Sin. 72(1), 30 (2014) https://doi.org/10.6023/A13080892
43
H.Du, J.Zhu, and W.Jiang, Study of controllable aggregation morphology of ABA amphiphilic triblock copolymer in dilute solution by changing the solvent property, J. Phys. Chem. B111(8), 1938 (2007) https://doi.org/10.1021/jp067221x
