Confined Self-Assembly of Block Copolymers

Transcription

1 Confined Self-Assembly of Block Copolymes An-Chang Shi Depatment of Physics & Astonomy McMaste Univesity Hamilton, Ontaio Canada Collaboatos: Bin Yu and Baohui Li, Nankai Univesity Peng Chen and Haojun Liang, USTC

2 Diblock Copolymes: Bulk Stuctues Competition between entopy and enegy R G 1/ ~ N T 1/6 / 3 χ d ~ χ N Leads to micophase sepaation of diblock copolymes Cochan et al, 006 f

3 Self-Assembly of Block Copolymes Using block copolyme self-assembly to poduce and contol nanostuctues Phases and phase tansitions of block copolyme systems: multiblock, blends, solutions, od-coil Kinetics of ode-ode tansitions: theoy of spinodal decomposition and nucleation Effects of extenal degees of feedom: polydispesity, electic fields, confinements

4 Confined Self-Assembly of Block Copolymes 1 Enginee new stuctues though confinement. Undestand confined self-assembly of amphiphilic molecules. Suface inteactions Selective o neutal Stuctual fustation Confinement size and domain peiod Geometies Dimension and shape of confinement Confinements natually occu in nanomateials and biological systems

5 1D Confinement: Stuctual Fustation ΔF paallel selective Pependicula neutal D/L 0

6 Symmetic Diblock Copolyme in Cylindes

7 Motivation fom Expeiments PBD-PS f 0.64 H. Xiang, et al. J. Polym. Phy. B43, Silica/sufactant blend Y. Y. Wu et al., Natue Mateials. 3,

8 D Mophologies Cylindical poe SCMFT: Tanslational symmety along the poe -D f 0.5 f 0.68 f 0.34 D 17R g W. Li, R. A. Wickham, and R. A. Gabay, Macomolecules 39,

9 Model Block Copolymes Cylinde-foming asymmetic diblock copolymes Cochan, Gacia-Cevea, Fedickson, 006 DBCP 1: f0.18, χn ~ 80 - Close to C-S bounday -Robust cylindes 1 DBCP : f0.36, χn 14 -Close to C-L bounday - Defomable cylindes

10 Model System I: Lattice Model Bond-fluctuation model of polymes Camesin & Keme, Lason AN A -b-bn-n A ; N1 Equilibium stuctues obtained with a simulated annealing method Kikpatick et al Cylinde foming diblock copolymes confined in a cylindical poe Stuctue as a function of wallpolyme inteactions and poe diamete B. Yu, B. Li, and ACS

11 Model System II: Self-consistent Field Theoy [ ] 1.,,,, f N s f q s q ds Q B A f c φ φ η φ χ ω φ β β,,, 0 s q s q s q s ω σ +, 1 A A c f q d V Q,,0 1,,0 β β f q q q + }. { ln ω φ ω φ φ χ ρ c B A g Q N d V F R V N

12 Model System II: Self-consistent Field Theoy Mean-fields: Monome densities: Incompessibility: ωa χnφb H + η ω χnφ + H + η B 1 φ dsq s q s A Q 1 1 φ B dsq, s q, s Q f φ A + φ B 1 A f,, 0 inside the poe Suface field Suface field: H: Shot anged potential Split-step FT method is used to solve the modified diffusion equations W. LI and R. A. Wickham; P. Chen, H. Liang and ACS

13 Bulk Stuctues: DBCP I AN A -b-bn-n A ; N1 ε AB X3X4 L f A 1/4 3X30X4 f A 1/6 L N A 6,5: Lamellae N A 4: Gyoid N A 3,: Cylindes B. Yu, B. Li and ACS

14 Confinement Induced Stuctues: DBCP 1 Case 1: Wall attacts the majoity blocks f A 1/6, ε AB 1.0, ε WA 1.0, ε WB -1.0 Mophologies ae contolled by the atio D/L 0 B. Yu, B. Li and ACS

15 Packing of flexible linea objects in cylindes Why Helix? Stong segegation leads to fixed cylinde size d z A L d D f L R S S R L R C π π π tan + S R S L L S L L z z + π Geomety leads to a cylinde length L 4 4 sin 1 d D f L L D f d d D f S R A z A A π

16 Back of the envelop calculation leads to Popeties of Helix Good qualitative ageement 4 4 sin 1 d D f L L D f d d D f S R A z A A π B. Yu, P. Sun, T. Chen, Q. Jin, D. Ding, B. Li, and A. C. Shi, 007

17 Confinement Induced Stuctues: DBCP 1 Case : Wall attacts the minoity blocks f A 1/6, ε AB 1.0, ε WA -1.0, ε WB 1.0 Mophologies ae contolled by the atio D/L 0 Effective diamete: D-3L 0 / B. Yu, B. Li and ACS

18 Effective diamete: D-3L 0 / B. Yu, B. Li and ACS

19 Confinement Induced Stuctues: DBCP 1 Case 3: Neutal wall f A 1/4, ε AB 1.0, ε WA 0.0, ε WB 0.0 Mophologies ae contolled by the atio D/L 0 New mophologies induced by neutal wall B. Yu, B. Li and ACS

20 SCFT Results: f 0. χ N 40 Attacts majoity B Attacts minoity A Neutal wall Weihua Li and Rob Wickham, 006

21 Fee Enegy Compaison: 1 st Ode Tansitions f 0. χ N 40 Weihua Li and Rob Wickham, 006

22 Popeties of helices f 0. χ N 40 Weihua Li and Rob Wickham, 006

23 Confined Self-Assembly of Diblock Copolymes: DBCP One-dimensional confinement f A 0.36, χn14 The cylindes can defom! P. Chen, HJ Liang and ACS 007

24 Confined Self-Assembly of Diblock Copolymes: DBCP Defomation of cylindes leads to complex stuctues f A 0.36, χn14 P. Chen, HJ Liang and ACS 007

25 Effects of Confining Geomety The shape of the poes mattes! f 1/6 B. Yu, et al, JCP 007

26 Effects of Confining Geomety The shape of the poes mattes! f 1/6 B. Yu, et al, JCP 007

27 Effects of Confining Geomety One-dimensional and thee-dimensional confinements f 1/ ~ ~..4~ D/L 0 > D/L 0 B. Yu, et al 007

28 Summay and Discussion Confined self-assembly leads to ich vaiety of mophologies which ae not found in the bulk Stuctue fomation is coelated with the paamete D/L 0 stuctual fustation effect A geneic mophological tansition sequence, fom sting of sphees to cylinde to helix then tooids, is pedicted Mophologies ae consistent with known expeiments and theoy Moe challenges ahead: mechanisms, geometies, moe complex copolymes, etc.