Macroporous Thermosets by Chemically Induced Phase Separation

Kiefer, J.; Hedrick, James L.; Hilborn, Jöns

doi:10.1007/3-540-49196-1_4

Cited by 34 publications

(42 citation statements)

References 135 publications

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“…To solve this problem, we have relied on a combination of kinetics and thermodynamics. The interaction between two polymers depends both on the interaction parameter and the degree of polymerization of the thermosetting material [29]. In the case of thermosetting systems, the situation is particularly complex since vitrification changes both the interaction parameter and the degree of polymerization.…”

Section: Porogensmentioning

confidence: 99%

Porous Organosilicates for On-Chip Applications: Dielectric Generational Extendibility by the Introduction of Porosity

Volksen¹,

Hawker²,

Hedrick³

et al. 2003

Springer Series in Advanced Microelectronics

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Dense alkyl-functionalized organosilicates have dielectric constants that are 25-30% lower than silica, which allows ultralow dielectric targets (k < 2.2) to be achieved at reduced porosity levels relative to those required for silica. Partially condensed silsesquioxane derivatives (RSiO 1.5 ) n generate highly crosslinked organosilicate films upon thermal and/or radiation curing. We have demonstrated that porous methyl silsesquioxane (MSSQ) thin films can be generated utilizing a sacrificial macromolecular porogen approach and a number of effective porogen classes have been identified. A key feature in this process is the compatibility of the porogen and the matrix polymer at low levels of vitrification. This allows the formation of nanoscopic domains of porogen in the vitrifying matrix prior to the removal of the porogen to generate the porosity. This is achieved through judicious selection of porogen and matrix prepolymer molecular weights as well as by control of porogen functionality, end groups, and macromolecular architecture. Optimization of structural and processing parameters allow the film dielectric constant to be varied continuously from 2.8-1.4 simply by changing the porosity level of the matrix. Although closed-cell structures are achieved for loading levels below 30%, subsequent percolation and interconnection at higher loading levels still result in nanoscopic pore diameters (< 500Å).Given the integration difficulties associated with any change in the onchip insulator material, dielectric generational extendibility has become an important manufacturing issue. The level of dielectric constant tunability in porous organosilicates provided by the sacrificial porogen approach may allow the dielectric generational extendibility needed for future generation semiconductor products. IntroductionThe unrelenting drive toward decreasing device dimensions and increasing on-chip densities will result in increasing signal delays due to capacitive coupling and crosstalk in the back-end-of-line (BEOL) interconnect wiring [1]. The RC delays depend on the resistivity of the wiring metal, the metal dimensions, and the dielectric constant of the insulating media. While the switch P.S. Ho et al. (eds.), Low Dielectric Constant Materials for IC Applications

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Section: Porogensmentioning

confidence: 99%

Porous Organosilicates for On-Chip Applications: Dielectric Generational Extendibility by the Introduction of Porosity

Volksen¹,

Hawker²,

Hedrick³

et al. 2003

Springer Series in Advanced Microelectronics

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“…10 Several general methods for creating porous polymers have been described. These methods include conventional foaming techniques involving a nonreactive gas, 11 emulsion-templating, 12,13 thermally induced phase separation, 14 chemically induced phase separation (CIPS), 15 selective degradation of block copolymers, 16 and molecular imprinting. 17 Relative to the other methods for producing porous polymer materials, CIPS probably provides the greatest versatility with respect to the range of materials that can be generated.…”

Section: Introductionmentioning

confidence: 99%

“…15,18,19 Due to the increase in the free energy of mixing that occurs as reaction takes place between the reactive precursors, the poragen phase separates from the mixture during the process of cross-linking. Porosity is generated by removal of the poragen from the cross-linked material using an extraction or evaporation process.…”

Section: Introductionmentioning

confidence: 99%

“…Phase separation in CIPS is the result of the decrease in entropy created by the increase in polymer molecular weight that occurs as a result of cross-linking reactions. Kiefer and coworkers 15 modified the Flory-Huggins equation so that it can be applied to reactive solutions. The modified equation is ∆G V = (∆G/V T ) = RT/V 0 {(1-4/3q) ø pol ln ø pol + (ø sol /Z sol ) ln ø sol } + | d → (q)| 2 ø pol ø sol , where ∆G V is the change in free energy of the system per unit volume, ∆G is the change in free energy of the system, V T is the total free volume, R is the gas constant, T is temperature, V 0 is the molar volume of precursor monomers, q is the extent of reaction or conversion, ø pol is the volume fraction of polymer, ø sol is the volume fraction of solvent, Z sol is the ratio of the molar volume of solvent to the molar volume of precursor monomers, and d → (q) is the change in the solubility parameter of the polymer during cross-linking.…”

Section: Introductionmentioning

confidence: 99%

“…The transformation of a two-phase liquid blend to a miscible blend upon heating is consistent with the upper critical solution temperature behavior expected for the liquid blends. 15 Monolithic discs of the samples were extracted with supercritical CO 2 and the extraction process monitored by periodically weighing the discs using a robotic weighing instrument. Extraction time was adjusted based on results obtained from sample weighing to ensure full extraction of the poragen.…”

mentioning

confidence: 99%

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The development of a high-throughput/ combinatorial workflow for the study of porous polymer networks

Majumdar¹,

Bahr²,

Crowley³

et al. 2012

IJHTS

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A high-throughput workflow was developed for the study of porous polymers generated using the process of chemically induced phase separation. The workflow includes automated, parallel preparation of liquid blends containing reactive, polymer network-forming precursors and a poragen, as well as a high-throughput poragen extraction process using supercritical CO 2 . A structure-process-property relationship study was conducted using epoxy-amine cross-linked networks. The experimental design involved variations in polymer network cross-link density, poragen composition, poragen level, and cure temperature. A total of 216 unique compositions were prepared. Changes in opacity of the blends as they cured were monitored visually. Morphology was characterized using a scanning electron microscope on a subset of the 216 samples. The results obtained allowed for the identification of compositional variables and process variables that enabled the production of porous networks.

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Templating of Silsesquioxane Cross‐Linking Using Unimolecular Self‐Organizing Polymers

et al. 2003

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Macroporous Thermosets by Chemically Induced Phase Separation

Cited by 34 publications

References 135 publications

Porous Organosilicates for On-Chip Applications: Dielectric Generational Extendibility by the Introduction of Porosity

Porous Organosilicates for On-Chip Applications: Dielectric Generational Extendibility by the Introduction of Porosity

The development of a high-throughput/ combinatorial workflow for the study of porous polymer networks

Templating of Silsesquioxane Cross‐Linking Using Unimolecular Self‐Organizing Polymers

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