Abstract I Contents III List of Tables V List of Figures VI Chapter 1 Introduction 1 1.1 Self-assembly 1 1.1.1 Block Copolymer Self-assembly 4 1.2 Gyroid Phase from BCP Self-assembly 5 1.3 Phase Transition in BCPs 10 1.3.1 Thermal Induced Phase Transition 11 1.3.2 Shear Field Induced Phase Transition 12 1.3.3 Electric Field Induced Phase Transition 13 1.3.4 Solvent Evaporation Induced Phase Transition 14 1.3.5 Solvent selectivity Induced Phase Transition 17 1.4 Electron Tomography in Identification of Complex Structures 20 1.5 Silicon-containing BCPs 24 Chapter 2 Objectives 30 Chapter 3 Experimental 32 3.1 Materials 32 3.2 Sample Preparation 35 3.2.1 Sample Preparation for PS-PDMS BCP Bulk Samples 35 3.3 Instruments 36 3.3.1 Differential Scanning Calorimetry (DSC) 36 3.3.2 Transmission Electron Microscopy (TEM) 36 3.3.3 Electron Tomography(3D TEM) 36 3.3.4 Small-angle X-ray Scattering (SAXS) 37 3.3.5 Reactive Ion Etching (RIE) 38 3.3.6 Field-Emission Scanning Electron Microscopy (FESEM) 38 Chapter 4 Results and Discussion 39 4.1 Thermal Behavior of PS-PDMS BCP 39 4.2 PS-PDMS BCP Self-assembly 40 4.2.1 Intrinsic Phase of Self-assembled PS-PDMS 41 4.2.2 Effect of Evaporation Rate on PS-PMDS Self-assembly. 42 4.2.3 Effect of Solvent Selectivity on BCP Self-assembly 45 4.3 Order-order Phase Transitions Induced by Thermal Annealing 54 4.4 Examination of G→L through Electron Tomography 58 4.5 Transition Mechanism of PS-PDMS. 61 4.6 Inorganic Oxide Gyroid Template. 65 Chapter 5 Conclusions 67 Chapter 6 References 69 List of Tables Table 3-1. Characterization of PS-PDMS BCPs. 35 Table 4-1. Solubility parameters of solvents and corresponding morphologies from casting.. List of Figures Figure 1-1. Example of static self-assembly. (a) Crystal structure of a ribosome. (b) Self-assembled peptideamphiphile nanofibers. (c) An array of millimeter sized polymeric plates assembled at a water/perfluorodecalin interface by capillary interactions. (d) Thin film of a nematic liquid crystal on an isotropic substrate. (e) Micro meter sized metallic polyhedral folded from planar substrates. (f) A three-dimensional aggregate of micrometer plates assembled by capillary forces. 2 Figure 1-2. Example of dynamic self-assembly. (a)An optical micrograph of a cell with fluorescently labeled cytoskeleton and nucleus; (microtubules ~ 24nm in diameter) are colored red (b) Reaction-diffusion waves in a Belousov-Zabatinski reaction in a 3.5-inchptri dish (c) A simple aggregate of three millimeter-sized, rotating, magnetized disks interacting with one another viavortex-vortex interactions. (d) A school of fish. (e) Concentric rings formed by charged metallic beads 1mm in diameter rolling in circular paths on a dielectric support. (f) Convection cells formed above a micropatterned metallic support. The distance between the centers of the cells is~2mm. 3 Figure 1-3. Schematic phase diagrams showing the various “classical” BCP morphologies adopted by non-crystalline linear diblock copolymer. The blue component represents the minority phase and the matrix, majority phase surrounds it. 5 Figure 1-4. TEM micrographs obtained from a starblock copolymer material comprised of PS-PI arms with 30 wt % PS. The majority PI appears black because it was stained with OsO4. Tilting the specimen in the TEM converted the square projection in (a) into the wagon-wheel arrangement in (b) 7 Figure 1-5. TEM micrograph of the tetrapod-network structure in PS-PI BCP toluene-casting film, the inset shows the enlarged area 8 Figure 1-6. A constant-thickness structure, based on the G surface, proposed as a possible model for the gyroid morphology at a minority component volume fraction of 0.33. The regime illustrated in this figure is the matrix; the two independent networks are depicted as the white/void regions. 10 Figure 1-7. (a) 2D scattering pattern and experimental setup with respect to the geometry of the electric field and the X-ray beam. (b) Scattering profiles in dependence of the applied electric field strength. The characteristic reflection for a gyroid structure (0kv/mm) and a cylindrical structure (9kv/mm) re indexed. The arrow indicates a new reflection at 0.8q* arising from an intermediate morphology.. 14 Figure 1-8. Plan-view bright-field TEM images of the as-cast OsO4-stained SBS thin films(brighter region refer to PS domain and darker region refer to PB domain) with inset Fourier transforms: (a) fast (~200 nL/s); (b) intermediate (~5 nL/s); (c) slow (~1.5nL/s); (d) very slow (~0.2 nL/s)... 15 Figure 1-9. Tapping mode AFM phase image of SBS triblock copolymer (brighter region refer to PB domain and darker region refer to PS domain): (a) cast from CCl4 solution (very fast) and cast from toluene solution at evaporation rate (b) 0.1 ml/h; (c) 0.01 ml/h; (d) 0.001 ml/h; (e) 0.00005 ml/h (thin region) (f) 0.00005 ml/h (thick region)... 16 Figure 1-10. Phase diagram for SI(11-21) as a function of temperature (T) and polymer volume fraction (ϕ) for solutions in DOP, DBP, DEP, and C14. Filled and open circles identify ODTs and OOTs, respectively. The dilute solution critical micelle temperature (cmt) is indicated by a filled square... 19 Figure 1-11. TEM micrographs and corresponding SAXS profile of P2VP-b-PI(26/74) diblock copolymer films prepared by solvent casting from (a) n-BtCl, (b) CCl4, (c) toluene, (d) benzene (e) THF, (f) CH2Cl2 and (g) 1,4-dioxane solutions.... 20 Figure 1-12. Visualization of a gyroid/PL grain boundary showing conservation of the orientation: (a) original portion of the TEM micrograph; (b) 3D visualization of the volume after binarization, hS and S are transparent; (c) 3D visualization after segmentation of the binarized volume; (d) and (e) visualization of each gyroid network clearly connected to one out of two layers of the PL phase.... 22 Figure 1-13. Demonstration of the effect of geometrical relationship between direction of tilt axis and orientation of cylindrical nanodomains on 3D reconstruction. There are three types of geometrical relationship. Each column shows a model, three cross sections of 3D reconstruction, and a “missing wedge” in Fourier space (shown by gray volume), from top to the bottom. The cylindrical nanodomains rotate around the tilt axis from -60° to 60° with 1° increment. Tilt axis is always along the x-direction. Electron beam comes from top (from the z-direction). An x-z cross section is a tomogram where the filtered back projection (FBP) is carried out. In the bottommost raw, diffraction patterns from the infinitely long cylinders are shown together with the missing wedge. Since the missing wedge is the volume in Fourier space where no projections can be sampled, diffraction spots within this wedge cannot contribute to the resulting 3D reconstruction..... 23 Figure 1-14. Comparison of missing volume in Fourier space between (a) dual-axis tomography and (b) single-axis tomography. Directions of tilt axes in the dual-axis tomography are along qx and qy axes. In single-axis tomography, tilt axis is along qx axis. Hexagonally packed infinitely long cylindrical morphology aligned along y-axis as shown in Figure 1.64b gives diffraction pattern only in the qx-qz plane. Some of the diffraction spots are outside the “missing pyramid”, and hence the cylinders can be reconstructed in dual-axis tomography (a), while all diffraction spots are inside the “missing wedge” in single-axis tomography (b)..... 24 Figure 1-15. Possible Mechanism of the Oxygen Plasma Oxidation of PDMS....... 25 Figure 1-16. An AFM image of surface topography of P(PMDSS)-DG after ozonolysis and UV exposure. The PI networks have been removed, resulting in the formation of ordered tortuous pathways within a silicon oxycarbide matrix. Bright regions are highest. Dark regions are empty. The maximum height on the image is 10 nm. (Inset) [012] view at zero height of a volume-rendered surface of the double gyroid structure with empty strut networks, which appear dark........ 27 Figure 1-18. SEM images of as cast (a) PS-PMAPOSS and (b) PMMA-PMAPOSS; solvent annealed (c) PS-PMAPOSS, and (d) PMMA-PMAPOSS; Oxygen RIE treated (e) PS-PMAPOSS and (f) PMMA-PMAPOSS films........ 28 Figure 1-19. SEM images of (a,b) parallel cylinders on trench substrates with narrow mesas (Wmesa ) 125 nm and Wtrench ) 875 nm) under a high vapor pressure of toluene (condition ER from Figure 3) and (c) perpendicular cylinders in a wide-mesa pattern (Wmesa ) 270 nm and Wtrench ) 730 nm) at a lower vapor pressure (condition Bâ). The annealing time was 15 h........ 29 Figure 3-1. Synthesis of the PS-b-PDMS copolymers 34 Figure 4-1. DSC thermograms of PS44-PDMS29 (fPDMSv = 0.4) BCPs in (a) high-temperature region and (b) low-temperature region.. 40 Figure 4-2. (a) TEM mass-thickness-contrast micrograph and (b) corresponding 1D SAXS profile of solution-cast PS-PDMS BCP after thermal annealing at 180oC for 12 hr. 42 Figure 4-3. TEM micrographs of PS-PDMS bulk sample casing from toluene solution with slow evaporation rate: (a) the (111) plane of double gyroid; (b) the (220) plane of double gyroid; (c) corresponding one-dimensional SAXS profile. 44 Figure 4-4. PS-PDMS bulk sample casing from toluene solution with fast-evaporation rate: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile. 45 Figure 4-5. PS-PDMS bulk sample casting from 1,2 dichloroethane solution: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile. 50 Figure 4-6. TEM micrograph of PS-PDMS bulk sample casting from 2 –chloropropane shows lamalle phase. 50 Figure 4-7. PS-PDMS bulk sample casting from chloroform solution: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile. 51 Figure 4-8. PS-PDMS bulk sample casting from chlorobenzene solution: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile 51 Figure 4-9. PS-PDMS bulk sample casting from 1,2-dichloroethane solution: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile 52 Figure 4-10. TEM micrograph of PS-PDMS bulk sample casting from: (a) dimethylaniliane solution and(b) 1,1,2-trichloroethane solution. 52 Figure 4-11. TEM micrograph of PS-PDMS bulk sample casting from methylcyclohexane solution 53 Figure 4-12. PS-PDMS bulk sample casting from hexane solution: (a) TEM micrograph; (b) corresponding one-dimensional SAXS profile 53 Figure 4-13. TEM micrographs of PS-PDMS bulk samples by using toluene as solvents for solution-casting: (a) before thermal annealing; (b) after thermal annealing at 180oC for 1min; (c) after thermal annealing at 180oC for 5min 56 Figure 4-14. SAXS profile of PS-PDMS bulk samples by using toluene as solvents for solution-casting: before thermal annealing (solid line); after thermal annealing at 180oC for 1min (dash line); after thermal annealing at 180oC for 5min (dash dot line). 57 Figure 4-15. (a) Time-resolved 1D SAXS profiles of PS-PDMS bulk samples by using toluene as solvent for solution casting (Annealing at 150oC for 40 minute collect data every 1 minute); (b) enlarged plot near the position of L(10); (c) enlarged plot near the position of L(30). 58 Figure 4-16. (a) Visualization of a gyroid/lamellae grain boundary: original portion of the TEM micrograph corresponding to the box area of (b) enlarged the red dashed line box area of 3D image in (a) for further study the mesh like nanostructure; (c) side view of the reconstructed mesh like nanostructure.. 59 Figure 4-17. The orthogonal digital slices of the reconstructed 3D images. (10 nm for the x-y section; 10 nm for the z-y section; 10 nm for the x-z section). 60 Figure 4-18. The orthogonal digital slices of reconstructed 3D images (10 nm for the x-y section). Blue one is the top layer of reconstructed 3D images; red one is the middle layer of reconstructed 3D images. Overlapping the two slices image, we will get an image which is similar to the 2D TEM image.. 61 Figure 4-19. Illustration of solvent and molecular chain model corresponding to the phase transition mechanism.. 64 Figure 4-20. Hypothesize of the phase transition mechanism.. 64 Figure 4-21. XPS spectra of (a) Si 2p; (b) O 1s and (c) C 1s of PS125-PDMS35 (fPDMSv = 0.25) and oxidized PS125-PDMS35 (fPDMSv = 0.25) thin films... 66 Figure 4-22. Top-view FESEM image of double gyroid SiOC, the (211) plane of gyroid phase with double-wave pattern can be clearly observed... 66