Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session B42: Focus Session: Block Copolymer Thin Films I |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Gila Stein, University of Houston Room: 214B |
Monday, March 2, 2015 11:15AM - 11:51AM |
B42.00001: Morphology of Conjugated Block Copolymer Films: Self-Assembly, Crystallization, and Phase Separation Invited Speaker: Rafael Verduzco All-Conjugated Block Copolymers comprised of donor and acceptor polymer blocks are currently under development for use in organic photovoltaic devices. An attractive feature of these materials is their potential to self-assemble into well-defined donor and acceptor domains. However, achieving self-assembled film structures requires additional processing and annealing due to the high crystallization temperature of conjugated polymers and low Flory-Huggins chi interaction parameter between polymer blocks. This talk will present experimental studies into the processing-dependent morphology of all-conjugated block copolymer films relevant for organic photovoltaic devices. Conjugated block copolymer films that contain poly(3-hexyl thiophene) (P3HT) as the donor block exhibit crystallization as the predominant feature. Even at relatively low mass contents, the P3HT block crystallizes in solvent cast films. The orientation of P3HT crystallites is face-on for as-cast or low-temperature annealed films, but under annealing at elevated temperature, the crystallite orientation flips to an edge-on orientation. This behavior is observed for a wide-range of acceptor polymer blocks. Analysis of films by grazing-incidence X-ray scattering shows that conjugated block copolymers exhibit poor mesoscale ordering in solvent cast or thermally annealed films. Under solvent annealing, periodic lamellae with characteristic domain size of 4 nm are observed. The domain size is independent of block copolymer molecular weight and composition, and we hypothesize is driven by a combination of crystallization and micro-phase segregation. Finally, we investigate the morphology of PTB7 block copolymers as compatibilizers for PTB7-fullerene blends. Addition of PTB7 block copolymers can increase or decrease domain sizes, and morphology is stable to long-term thermal annealing. [Preview Abstract] |
Monday, March 2, 2015 11:51AM - 12:27PM |
B42.00002: Polypeptoids: A model system for exploring sequence and shape effects on block copolymer self-assembly Invited Speaker: Rachel Segalman While our ability to understand the detailed relationship between block copolymer chemistry and mesoscopic self-assembly has made remarkable progress over the last many years, yet we are still limited to a relatively small number of blocks in terms of structure-property understanding. Thus, there is a need to explore self-assembly phase space with sequence using a model system. Polypeptoids are non-natural, sequence specific polymers that offer the opportunity to probe the effect of sequence on self-assembly with much simpler molecular interactions and more scalable synthesis than traditional polypeptides. In this talk, I will discuss the use of this model system to understand the role of sequence on chain collapse and globule formation in solution, polymer crystallization, and block copolymer self-assembly. I will then discuss potential application as surface active agents for anti-fouling. [Preview Abstract] |
Monday, March 2, 2015 12:27PM - 12:39PM |
B42.00003: Morphology Development in Block Copolymer Thin Films via Direct Immersion Annealing Arvind Modi, Sarang Bhaway, Bryan Vogt, Ashutosh Sharma, Alamgir Karim Conventional methods of annealing thin block copolymer (BCP) films include Thermal Annealing and Solvent Vapor Annealing (SVA) processes. Both of the processes have demonstrated excellent control over morphologies and nanostructures. However, both have constraints including long annealing time duration and/or complicated setup requirement. We introduce Direct Immersion Annealing (DIA) of thin block copolymer (BCP) films involving immersion of polymer films directly into the solvent mixture composed of selective non-solvent and solvent for blocks. Non-solvent prevents the dissolution of films while the good solvent permeates the film and plasticizes the blocks. A fine control of swelling ratio can be achieved through an easy and robust control of solvent volume fractions. We studied cylindrical Poly(styrene-block-methyl methacrylate) system in detail and quantified the growth of correlation length ($\xi )$ with time(t) [$\xi =$At$^{n}$]. We observe a reduction in growth exponent (n) with several fold increase in pre-exponential factor (A) compared to isotropic thermal annealing. We further demonstrate the extension of this strategy to systems with diverse range of $\chi $-parameter, molecular weight and other morphologies. [Preview Abstract] |
Monday, March 2, 2015 12:39PM - 12:51PM |
B42.00004: Real-Time observation of PS-PDMS block copolymer self-assembly under solvent vapor annealing Wubin Bai, Kevin Yager, Caroline Ross Solvent annealing provides a convenient way to produce microphase separation in films of block copolymers, but the morphology transition of the film during the solvent absorption, equilibrium solvent-BCP concentration and solvent desorption process are not well known. An in situ study of solvent annealing of polystyrene-block-polydimethylsiloxane (PS-PDMS, 16 kg/mol, fPDMS $=$ 30{\%}, period 17 nm) diblock copolymer was carried by synchrotron grazing-incidence small-angle X-ray scattering (GISAXS). The swollen film morphology was found to be strongly dependent on swelling ratio. A transition from the disordered state to a highly ordered state which contained multiple layers of in-plane cylinders was observed at a swelling ratio around 1.45 from samples with 100nm to 1000nm as-cast thickness. The rate of solvent absorption was found to be less important to the dried morphology, while the time of equilibrium solvent-BCP concentration stage was found to influence the orientation of self-assembled microdomains and the drying rate was found to affect the degree of structure deformation. The implications of the results to pattern generation for block copolymer directed self-assembly will be discussed. [Preview Abstract] |
Monday, March 2, 2015 12:51PM - 1:03PM |
B42.00005: The kinetics of swelling in block copolymer thin films during ``solvo- microwave'' and solvo- thermal annealing: The effect of vapour pressure Parvanrh Mokarian-Tabari, Timothy Collins, Cian Cummins, Claudia Delgado Sim\~ao, Clivia Sotomayor, Michael A. Morris Long annealing time associated with high chi block copolymers is a major disadvantage for their integration in industrial applications. Microwave-assisted microphase separation appears to offer considerable benefits in reducing annealing times for BCPs. However, despite the promise of this technique, little is known about the mechanism of how microwave irradiation might sponsor the molecular motion that accompanies microphase separation. In our earlier work we carried out an \textit{in situ} temperature measurement during ``solvo-microwave'' annealing of poly(styrene-b-lactic acid) (PS-$b$-PLA) in presence of THF and also in the conventional oven. Comparing the results indicated that vapour pressure of THF might have a major role to achieve fast self- assembly (60 seconds) in PS-$b$-PLA film. Here, we study the kinetics of swelling by monitoring the pressure through \textit{in situ} pressure experiments during ``solvo-microwave'' and solvo-thermal annealing. The preliminary data suggest that the rate at which the THF pressure increases is the key factor. This suggests that kinetics, i.e., the rate of film swelling and diffusion, affects the order and the coherence length of the pattern. We estimated the defect density in the patterns by our recently developed defect analysis software. [Preview Abstract] |
Monday, March 2, 2015 1:03PM - 1:15PM |
B42.00006: Fluorine effects on morphology and surface energy of diblock copolymer thin films Umesh Shrestha, Dvora Perahia, Stephen Clarson The interfacial composition and structure formed by the segregation between the incompatible blocks in a diblock copolymer thin film influence the stability and response of the film to external stimuli. Introduction of fluorine enhances the interfacial energy as well as chemical and thermal stability of the polymer film. Here we follow the interfacial structure and response of Si containing diblock co-polymer polytrifluoro propyl methyl siloxane-polystyrene (PTEPMS-PS) with the SiF fraction ranging from 0.03 to 0.5 in surface of the films as a function of temperature and solvent, using atomic force microscopy and contact angle measurement. We found that the tendency of the fluorine to migrate towards surface affects the surface energy while Si in backbone enhances the flexibility of the chains. Thin films prepared from selective good solvent for one of the blocks and good solvent for both blocks formed different structures compared to their melts. Correlation between morphology and volume fraction is dominant above the Tg of the polystyrene whereas below Tg limited effect is observed. [Preview Abstract] |
Monday, March 2, 2015 1:15PM - 1:27PM |
B42.00007: Perpendicularly oriented nanostructures by using star-shaped poly(methyl methacrylate)-block-polystyrene thin film Sangshin Jang, Kyuseong Lee, Hong Chul Moon, Jicheol Park, Jongheon Kwak, Gumhye Jeon, Jin Kon Kim Thin films of star-shaped 18-arm poly(methyl methacrylate)-block-polystyrene copolymers ((PMMA-b-PS)$_{18}$) with two different volume fraction of PS block (f$_{PS}$) (0.60 and 0.75). Interestingly, perpendicularly oriented lamellar and cylindrical structures were confirmed by atomic force microscopy (AFM) and grazing-incidence small angle X-ray scattering (GISAXS), after thermal annealing without additional treatment such as random copolymer treatment or solvent annealing. Perpendicularly oriented nanostructures were also achieved for versatile substrates such as PS(or PMMA)-brushed substrate, flexible substrate (PEN) or gold-deposited substrate. [Preview Abstract] |
Monday, March 2, 2015 1:27PM - 1:39PM |
B42.00008: Vertical Continuity and Alignment of Block Copolymer Domains by Kinetically Controlled Electrospray Deposition Hanqiong Hu, Youngwoo Woo, Xunda Feng, Chinedum Osuji We report the fabrication of vertically aligned cylindrical block copolymer (BCP) domains using continuous electrospray deposition (ESD) onto bare wafer surfaces. The out-of-plane orientation of hexagonally packed styrene cylinders was achieved in a ``fast-wet'' deposition regime where rapid evaporation of solvent in droplets of polymer solution drove the vertical alignment of SBS domains. The deposition conditions were optimized such that thermally activated crosslinking of the polybutadiene matrix provided kinetic control of the morphology, locking in the vertical alignment and preventing relaxation of the system to its preferred parallel orientation on the non-treated substrate. Physically continuous and vertically oriented domains is achieved over several microns of film thickness. We describe the effects of flow rate, collection distance and substrate temperature on thin film morphology and demonstrate selective etching capabilities. The ability of ESD to fabricate well-ordered and aligned BCP films on non-treated substrates, the low utilization of material relative to spin-coating and the continuous nature of the deposition may open up new opportunities for BCP thin films. We are exploring ESD as a new platform for sequential deposition of BCPs with different functionalities. [Preview Abstract] |
Monday, March 2, 2015 1:39PM - 1:51PM |
B42.00009: Edge effects and surface patterns in a quenched lamella forming block copolymer Andrew B. Croll, Peggy Willenbring, Alexander Wagner Thin lamellar systems are well known to form surface structures when cast in a thickness that is not commensurate with a lamellar spacing. The structures have often been considered an ideal two dimensional system and much has been learned of the patterns dynamics. This early work considered a uniform isotropic film in a region infinitely far from a boundary. Here we specifically consider the influence of a pre-existing boundary on the pattern formation process, and identify the emergence of a unique new lengthscale in the problem. Our work combines an idealized experimental system (polystyrene-poly2vinylpyridine diblock near the order-to-disorder transition point) with precise numerical computation (a Lattice-Boltzmann model) in order to develop an understanding of the relative importance of the key physical phenomena underlying the results. The new lengthscale is found to be inversely proportional to both total film thickness and quench depth and offers unique opportunities to engineer structures extending beyond the 2D layer into the 3$^{\mathrm{rd}}$ dimension. [Preview Abstract] |
Monday, March 2, 2015 1:51PM - 2:03PM |
B42.00010: A Stable Hexagonally Modulated Lamellar (HML) Structure of Asymmetric Polystyrene-b-Poly(2-vinylpyridine) in Film Geometry Sungmin Park, Hyungju Ahn, Byeongdu Lee, Du Yeol Ryu When a block copolymer (BCP) is confined in film geometry, the phase transitions would be different or shifted from those of the corresponding bulk. In this study, the phase transition of an asymmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) films in the presence of the strong interfacial interactions were investigated by grazing incidence small-Angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM). The order-to-order transition (OOT) and order-to-disorder transition (ODT) in film geometry were influenced by the strong favorable interactions between the P2VP block and substrate, resulting in the thickness-dependent phase diagram. The phase stability of a hexagonally modulated lamellar (HML) structure was identified in film geometry, and in the films below 10Lo it was extended over the entire temperature range even above the ODT temperature of the bulk. [Preview Abstract] |
Monday, March 2, 2015 2:03PM - 2:15PM |
B42.00011: Adsorbed block copolymer nanolayers on solids Jennifer Imbrogno, Mani Sen, Steven Kahn, Shotaro Nishitsuji, E. Bhoje Gowd, Maya K. Endoh, Tadanori Koga Directed self-assembly of block copolymers (BCP) has been used as an advanced lithography method. In this study, we aim to shed light onto the structures of BCP at the polymer melt-solid interface. Polystyrene-block-poly (4-vinylpyridine) (PS-b-P4VP) block copolymer was used. Spun-cast 32 nm PS-b-P4VP thick films on silicon substrates were (i) thermally annealed at high temperature above Tg of the polymers or (ii) solvent vapor annealing with chloroform (non-selective solvent) and subsequent 1-4, dioxane (selective solvent). Using atomic force microscopy (AFM), we found perpendicular hexagonally packed cylinders at the topmost surface of the resultant PS-b-P4VP films regardless of the annealing processing. In addition, to study the adsorbed layer structure, we rinsed the annealed films with toluene and characterized the morphologies and film structures using grazing incidence small-angle X-ray scattering, x-ray reflectivity and AFM. The details will be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700