Mesoporous Silicates Prepared Using Preorganized Templates in Supercritical Fluids

Pai, Rajaram A.; Humayun, Raashina; Schulberg, Michelle T.; Sengupta, Archita; Sun, Jianing; Watkins, James J.

doi:10.1126/science.1092627

Cited by 312 publications

(278 citation statements)

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“…1 Block copolymers can self-assemble into periodic domains via a process of microphase separation [2][3] and these systems, with controlled orientation and ordering have promise in a number of applications including nanolithography, membrane synthesis and nanofludics. [4][5][6][7] Solvent annealing of BCP films is an effective approach for obtaining ordered phase-separated thin films at low temperatures and in relatively short time periods since the solvent swells the polymer, creating free volume and providing the necessary chain mobility to the polymer blocks. [8][9] Generally, organic and halogenated solvents are preferred to swell one or more blocks within a polymer film, 10 even though they are toxic and have a negative environmental impact.…”

Section: Introductionmentioning

confidence: 99%

“…24 scCO2 can also be used to fabricate nanocellular structures and nanopores in block copolymer thin and thick films. 5,[25][26][27][28] Much attention has been paid to ordering and kinetics of BCP thick and thin films by scCO2, examined from both a theoretical and an experimental perspective. 23,25,[29][30] However, to-date surface periodic arrangements of two blocks has only been realized by annealing polymers above their melting points.…”

Section: Introductionmentioning

confidence: 99%

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Nanophase separation and structural evolution of block copolymer films: A “green” and “clean” supercritical fluid approach

et al. 2014

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Type of publicationArticle (peer-reviewed)Link to publisher's version http://dx.doi.org/10.1007/s12274-014-0616-7Access to the full text of the published version may require a subscription. Rights © Tsinghua University Press and Springer-Verlag Berlin Heidelberg2014. This is a pre-print of an article published in Nano Research. hexagonally ordered films were demonstrated using a supercritical fluid process at low temperatures and pressures. Predominant swelling of PEO domain in scCO2 induces nanophase separation. scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film.The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self-assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanophase separation and structural evolution of block copolymer films: A “green” and “clean” supercritical fluid approach

et al. 2014

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“…40 Pai achieved dielectric constants as low as 1.8 using the pre-organized supercritical fluid template approach with Pluronic F127 surfactant. 41 Jiang et al 42 44 reported a dielectric constant of 2.6 using a Pluronic P123 surfactant template while Yang and coworkers 45 measured dielectric constants as low as 1.5 and as high as 2.6 for the same template, but these authors were very careful to use carefully functionalized materials to control the properties of the films.…”

Section: Fig 5 Nanoindentation Studies Of Zeolite Films: Hardness Amentioning

confidence: 99%

Advances in Ultra Low Dielectric Constant Ordered Porous Materials

et al. 2011

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The development of ultra-low dielectric constant silicon-based materials was reviewed in this article. The dielectric constants of these kinds of mesoporous and microporous materials can be kept at less than 2 by controlling their pore size and pore density. Even though these materials show remarkable electrical breakdown characteristics and leakage currents, they have to surmount mechanistic issues, low resistance to electrical migration, and hydrophilicity. To further enhance material properties and make them compatible with current demands, research into other new synthesis methods is still required.

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“…[17] and pre-organised template/supercritical fluid inclusion techniques [18]. The later one represents an appealing avenue for tailoring mesoporous silica architectures since the organic structure directing agents (tri-block copolymer from the Pluronic family) are deposited in an initial first step before the inorganic component is infiltrated via supercritical inclusion/swelling.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

Farrell

Petkov²,

Morris

et al. 2010

Journal of Colloid and Interface Science

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Self-assembled nanoscale porous architectures, such as mesoporous silica films (MPS), block copolymer films (BCP) and porous anodic aluminas (PAAs), are ideal hosts for templating one dimension (1 D) nano-entities for a wide range of electronic, photonic, magnetic and environmental applications. All three templates offer dimensional scalability and tunability over a wide range, with critical pore sizes for each system well below the 20 nm threshold [1][2][3]. Recently, research has progressed towards controlling the pore direction, orientation and long range order of these nanostructures through so called directed self-assembly (DSA). Significantly, the introduction of a wide range of top-down chemically and physically pre-patterning substrates has facilitated the DSA of nanostructures into functional device arrays. The following review begins with an overview of the fundamental aspects of self-assembly and ordering processes during the formation of PAAs, BCPs and MPS films. Special attention is given to the different ways of directing self-assembly, concentrating on properties such as uni-directional alignment, precision placement and registry of the self-assembled structures to hierarchal or top down architectures. Finally, to distinguish this review from other articles we focus on research where nanostructures have been utilised in part to fabricate arrays of functioning devices below the sub 50 nm threshold, by subtractive transfer and additive methods. Where possible, we attempt to compare and contrast the different templating approaches and highlight the strengths and/or limitations that will be important for their potential integration into downstream processes. ACCEPTED MANUSCRIPT 3 SECTION 1.0: SELF ASSEMBLY AND NANO-ARCHITETCURESThe diversity of self-assembled nanostructures and more importantly, their precise orientation within a thin film (fixed to a substrate) ultimately determines their function and overall application. A large population of research reports to date have focused on identifying these orientations and related periodicities, using x-ray and microscopy tools, as well the development of methods for readily manipulating nanostructures, such as pre-patterning of silicon substrates for the alignment of block copolymers (BCPs) [4] and mesoporous thin films (MTFs) [5] and altering the growth direction of porous anodic alumina (PAA) templates [6]. In this section, a brief synopsis of the mechanisms behind the self-assembly/organisation of each system and highlight nanoscale architectures (and orientations), which are important from a device perspective. Templated mesoporous thin filmsOrdered mesoporous powders were first discovered by researchers at the Mobil Petrochemical Corporation in 1992 and shortly after, sol-gel derived mesoporous silica films were fabricated [1,7].The first series of ordered mesoporous films were reported by Yang et al. in 1996 [8], prepared using initial surfactant concentrations above their critical micelle concentration (CMC). However the films prepared fil...

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Mesoporous Silicates Prepared Using Preorganized Templates in Supercritical Fluids

Cited by 312 publications

References 29 publications

Nanophase separation and structural evolution of block copolymer films: A “green” and “clean” supercritical fluid approach

Nanophase separation and structural evolution of block copolymer films: A “green” and “clean” supercritical fluid approach

Advances in Ultra Low Dielectric Constant Ordered Porous Materials

Self-assembled templates for the generation of arrays of 1-dimensional nanostructures: From molecules to devices

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