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You searched for subject:(supercritical CO 60). Showing records 1 – 2 of 2 total matches.

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The Ohio State University

1. Ellis, Jeffrey LeClair. Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale.

Degree: PhD, Chemical Engineering, 2009, The Ohio State University

Nanotechnology is continually becoming more integrated into consumer products used by the general public on a daily basis. Consumers reap the benefits of enhanced properties for these commercial products, and yet they are still affordable. For biomedical products, that include nanofeatures, this is not yet a reality. The materials and methods used to fabricate these products are still far too expensive. There are many inexpensive and commercially available polymers that have potential to be used in these advanced biomedical products, but the fabrication techniques still lack the simplicity required to create an inexpensive end product.Supercritical CO2 has been used to overcome the polymeric nanofabrication barriers for high throughput production of biomedical devices. Novel CO2-assisted low temperature polymer nanoprocessing fabrication techniques have been implemented for use in biomedical product creation. Polymer nanofabrication techniques such as bonding, imprinting, and active biomolecule immobilization were demenonstrated. Due to being CO2-assisted techniques, these processes are intrinsically inexpensive and environmentally benign.In order to thoroughly investigate these nanofabrication techniques the interactions between CO2 and the polymer were examined on a thermodynamic level. Thermodynamic modeling results of high pressure CO2/polystyrene systems were used along with experimental bonding, imprinting, and immobilization results. It was found that the solubility of CO2 in a polymer matrix and the resulting reduction of the polymer glass transition temperature (Tg) largely dictate the polymer chain mobility and therefore the polymer's processability. For instance, it was shown that the polymer bond strength of polystyrene, bonded via a CO2-assisted technique, depended largely on the proximity of the processing conditions to the reduced Tg curve. It was also found that low aspect ratio nanofeatures could be patterned by CO2-assisted nanoimprint lithography in polystyrene at conditions near the reduced Tg curve.These CO2-assisted low temperature polymer processing techniques are now better understood in terms of the CO2/polymer thermodynamic properties, thus making these, and other similar, techniques easier to control. This fundamental information can be applied to scaling-up these technologies so that inexpensive polymer biomedical products with nanofeatures can soon be commercially produced, thus benefiting the health of society. Advisors/Committee Members: Tomasko, David (Advisor).

Subjects/Keywords: Chemical Engineering; polymer processing; polystyrene; supercritical CO<; sub>; 2<; /sub>;

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Ellis, J. L. (2009). Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1244033142

Chicago Manual of Style (16th Edition):

Ellis, Jeffrey LeClair. “Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale.” 2009. Doctoral Dissertation, The Ohio State University. Accessed May 07, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244033142.

MLA Handbook (7th Edition):

Ellis, Jeffrey LeClair. “Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale.” 2009. Web. 07 May 2021.

Vancouver:

Ellis JL. Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale. [Internet] [Doctoral dissertation]. The Ohio State University; 2009. [cited 2021 May 07]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1244033142.

Council of Science Editors:

Ellis JL. Dense Carbon Dioxide Assisted Polymer Processing at the Nanoscale. [Doctoral Dissertation]. The Ohio State University; 2009. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1244033142


The Ohio State University

2. Talreja, Manish. Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems.

Degree: PhD, Chemical Engineering, 2010, The Ohio State University

Supercritical (high pressure) CO2, owing to its ability to make polymers pliable at temperatures much lower than the glass transition temperature (Tg), has been established as a very promising solvent for numerous macro scale polymer processing applications. In this work, we have tried to expand the scope of supercritical CO2 assisted polymer processing to nano length scales with particular focus on manufacturing biomedical devices from polymer thin films. At such small length scales, however, the properties of the polymer become size dependent since the interfacial effects start dominating the bulk effects. As a result, adapting the macro and micro level fabrication technologies to nano level is not straightforward and requires integration of both theoretical and experimental tools. We have used CO2 assisted Nano-Imprint Lithography (CO2-NIL) for fabricating nanochannels on polystyrene thin films. CO2-NIL is a novel technique in which the features from a rigid mold are transferred on to a CO2 pressurized polymer thin film by application of compressive force. We have explored efficiency of pattern transfer, resolution, and effects of molecular weight on transferability of patterns, and have thus established CO2-NIL as a highly efficient and cost effective fabrication technique capable of transferring patterns as small as 20 nm in step height. To understand the surface characteristics and the molecular level effects of CO2 on polymer thin films, which are essential for optimizing the nanoscale experiments, we have used Polymer Density Functional Theory (PDFT) as our primary tool since it provides an adequate balance between the amount of details extracted and the computational costs involved. PDFT is a statistical mechanics based approach in which we express the free energy of the system as a functional of spatially varying density distributions of CO2 and polymer segments. Equilibrium density distributions, free energy at equilibrium, and hence the equilibrium properties are then obtained by minimizing this functional. We have studied CO2 solubility in polymer, surface adsorption of CO2 on polymer surface, interfacial tension, and interfacial width for both polyethylene and polystyrene thin films. In addition, we have shown how the molecular level structural changes induced by CO2 facilitate the nanoscale polymer processing, and that the causal mechanism of these changes is the enthalpic interactions between the polymeric segments and the CO2 molecules. This work is the first instance of application of PDFT to polymer films pressurized by CO2. We have also significantly enhanced the capability of PDFT by handling polymer chains much longer than previously reported using this theory, similar to the ones used commercially. PDFT is a very powerful tool that can be used to study the thermodynamic behavior in several important… Advisors/Committee Members: Kusaka, Isamu (Advisor).

Subjects/Keywords: Chemical Engineering; PDFT; CO<; sub>; 2<; /sub>; -NIL; Supercritical CO<; sub>; 2<; /sub>;

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Talreja, M. (2010). Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1275007561

Chicago Manual of Style (16th Edition):

Talreja, Manish. “Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems.” 2010. Doctoral Dissertation, The Ohio State University. Accessed May 07, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275007561.

MLA Handbook (7th Edition):

Talreja, Manish. “Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems.” 2010. Web. 07 May 2021.

Vancouver:

Talreja M. Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems. [Internet] [Doctoral dissertation]. The Ohio State University; 2010. [cited 2021 May 07]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1275007561.

Council of Science Editors:

Talreja M. Towards Understanding Interfacial Phenomena in Polymer-CO2 Systems. [Doctoral Dissertation]. The Ohio State University; 2010. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1275007561

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