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Structure Control of Functional Mesoporous Materials and Synthesis of Polydimethylsiloxane-Containing Block Copolymer

Wang, Siyang
http://rave.ohiolink.edu/etdc/view?acc_num=akron1463958304

Abstract Details

2016, Master of Science, University of Akron, Polymer Engineering.
Block copolymer templating is a versatile approach for the generation of well-defined porosity in a wide variety of framework chemistries. Here, we systematically investigate how the composition of a poly(methoxy poly[ethylene glycol] methacrylate)-block-poly(butyl acrylate) (PMPEG-PBA) template impacts the pore characteristics of mesoporous cobalt oxide films. Three templates with a constant PMPEG segment length and three different hydrophilic block volume fractions of 17%, 51% and, 68% for the PMPEG-PBA are cooperatively assembled with cobalt nitrate hexahydrate and citric acid. Irrespective of template composition, a spherical nanostructure is templated and elliptical mesostructures are obtained on calcination due to uniaxial contraction of the film. The average pore size increases from 11.4 ± 2.8 nm to 48.5 ± 4.3 nm as the length of the PBA segment increases as determined from AFM. For all three templates examined, a maximum in porosity (~35 % in all cases) and surface area is obtained when the precursor solids contain 35-45 wt % PMPEG-PBA. This invariance suggests that the total polymer content drives the structure through interfacial assembly. The composition for maximizing porosity and surface area with the micelle templating approach results from a general decrease in porosity with increasing cobalt nitrate hexahydrate content and the increasing mechanical integrity of the framework to resist collapse during template removal / crystallization as the cobalt nitrate hexahydrate content increases. Unlike typical evaporation induced self-assembly with sol gel chemistry, the hydrophilic/hydrophobic composition of the block copolymer template is not a critical component to the mesostructure developed with micelle-templating using metal nitrate-citric acid as the precursor. A series of PS-PDMS with narrow molecular weight distributions with aimed molecular weight was synthesized with PDMS-RAFT as a macro-chain transfer agent via reversible addition fragmentation chain transfer (RAFT) polymerization. The PDMS-RAFT agent is utilized to control the free radical polymerization of styrene monomer. Hydroxyl terminated polydimethylsiloxane (PDMS-OH) is end functionalized through esterification with a carboxylic acid functional RAFT agent. The thin films of the synthesized PS-PDMS block copolymers are fabricated with spin coating and subsequently annealed with solvent vapor annealing with soft shear (SVA-SS). Varied surface morphology can be obtained with different volume fraction of polystyrene block in PS-PDMS, however, long range ordered structures have not been obtained as expected. Moreover, tri-block copolymer polydimethylsiloxane-block-poly ethyl acrylate-block-poly styrene (PDMS-PS-PEA) with low polydispersity has been successful synthesized with low polydispersity (PDI) in order to investigate more interesting morphologies.
Bryan Vogt (Advisor)
Kevin Cavicchi (Advisor)
Mark Soucek (Committee Member)
114 p.
Polymer Chemistry
Soft templating SBA-16 nanoporous film

Recommended Citations

Citations

  • Wang, S. (2016). Structure Control of Functional Mesoporous Materials and Synthesis of Polydimethylsiloxane-Containing Block Copolymer [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1463958304

    APA Style (7th edition)

  • Wang, Siyang. Structure Control of Functional Mesoporous Materials and Synthesis of Polydimethylsiloxane-Containing Block Copolymer. 2016. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1463958304.

    MLA Style (8th edition)

  • Wang, Siyang. "Structure Control of Functional Mesoporous Materials and Synthesis of Polydimethylsiloxane-Containing Block Copolymer." Master's thesis, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1463958304

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.