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Supramolecular Reinforcement of Thermoset Elastomers by Oligo(ß-Alanine)

Tan, Xin
http://rave.ohiolink.edu/etdc/view?acc_num=akron1506083394683621

Abstract Details

2017, Doctor of Philosophy, University of Akron, Polymer Science.
A strategy of supramolecular reinforcement of thermoset elastomers is conceptualized and demonstrated. As an initial attempt, simple amphiphile PA1 consisting of a single ß-alanine oleophobic motif and a pentadecyl oleophilic motif was designed to self-assemble in a continuous styrene-butadiene rubber (SBR) phase to form discrete micelle-type structures during melt compounding and vulcanization and crystallize upon cooling to form supramolecular reinforcing particles dispersed in the rubber phase. The hierarchical structure and morphology of the PA1 assemblies in vulcanized SBR composites were studied by Fourier-transform infrared spectroscopy, differential scanning calorimetry, wide-angle X-ray diffraction and transmission electron microscopy. In the SBR continuous phase, PA1 formed ß-sheets, and the ß-sheets stacked to form crystals. The ß-sheet crystalline domains of PA1 were whisker-like nanocrystals at a filler loading of 5 phr, which aggregated to form globules at high filler loadings (10-20 phr). Consequently, the best tensile properties were achieved at 5 phr PA1 loading, where the toughness was increased to 2.6 times as high as that of the vulcanized gum SBR. To improve the dispersion and interaction with the rubber of supramolecular fillers, a reactive amphiphile (SA1) capped with a mercapto group was introduced. Two compounding techniques including melt compounding and solution mixing were used to disperse SA1 in SBR. At least a fraction of SA1 reacted in situ with SBR via thiol-ene reaction. SA1 was uniformly dispersed in SBR as short fibrous crystalline domains with widths less than ten nanometers even at high filler loadings (30 phr). The improved filler dispersion and filler-rubber interaction allowed effective energy dissipation and resulted in significantly improved mechanical properties. The best reinforcement was achieved by the solution-mixed SBR/30SA1 composite, which displays a 4-fold increase on tensile strength and a 5-fold increase in modulus at 300% strain, in comparison to the vulcanized gum SBR. The reinforcing performances of oligomeric congeners of SA1 with increased ß-alanine segment lengths (SA2 and SA3, having a ß-alanine dimer and trimer moiety, respectively) were further investigated. SBR/SA2 and SBR/SA3 composites were prepared by solution mixing. Short fibrous crystalline domains of SA2 and SA3 less than ten nanometers in width were uniformly dispersed in SBR. The tensile strength and stiffness increased with increased ß-alanine segment length, while the extensibility decreased. SBR/15SA2 showed the best overall tensile properties among all SBR composites reinforced by SA1, SA2, and SA3.
Li Jia, Dr. (Advisor)
Gary Hamed, Dr. (Committee Chair)
Matthew Becker, Dr. (Committee Member)
Abraham Joy, Dr. (Committee Member)
Kevin Cavicchi, Dr. (Committee Member)
228 p.
Polymer Chemistry; Polymers
supramolecular filler; rubber reinforcement; beta-alanine

Recommended Citations

Citations

  • Tan, X. (2017). Supramolecular Reinforcement of Thermoset Elastomers by Oligo(ß-Alanine) [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1506083394683621

    APA Style (7th edition)

  • Tan, Xin. Supramolecular Reinforcement of Thermoset Elastomers by Oligo(ß-Alanine). 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1506083394683621.

    MLA Style (8th edition)

  • Tan, Xin. "Supramolecular Reinforcement of Thermoset Elastomers by Oligo(ß-Alanine)." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1506083394683621

    Chicago Manual of Style (17th edition)

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