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SMALL ANGLE X-RAY SCATTERING AND RHEOLOGY STUDIES OF POLYISOBUTYLENE WITH OLIGO(ß-ALANINE) GRAFTS

Zhao, Wenhan, ZHAO
http://orcid.org/0000-0003-1461-2385
http://rave.ohiolink.edu/etdc/view?acc_num=akron1528983070278315

Abstract Details

2018, Master of Science, University of Akron, Polymer Science.
Thermoplastic elastomers are used in various applications due to their outstanding mechanical performance. Here we consider three different polymers which have the same polyisobutylene main chain with side chains of oligo ß-alanine (PIB-g- ßA3). The ß-alanine units self-associate via hydrogen bonds into nanocrystals containing a ß-sheet secondary structure. In previous studies, the contributions of hydrogen bonding and a chain stretching entropy penalty have been studied. Based on that, here three different graft structures are considered for controlling the nanocrystal sizes: one with an eleven-carbon spacer between the backbone and oligo ß-alanine, one with an eleven-carbon spacer and a phenyl group and one with no spacer and a seventeen-carbon tail on the other end of the oligo ß-alanine. We investigate the structure of the microphase separation and crystallization with combined Small Angle X-ray Scattering and Wide Angle X-ray Scattering which are sensitive to size of the structure. All three polymers have quite small crystalline nanodomains in a matrix at room temperature. When increasing temperature, the nanocrystals melt and the well-defined microphase separation is lost. Rheology studies run upon cooling show that the storage modulus of the polymer with graft tails but no phenyl group increases quite gradually with decreasing temperature, because the ability of the ß-alanine units to order is hampered by the need for both the graft tail and parts of the PIB backbones to stretch for ordering to occur. The polymer with a spacer separating the ß-alanine units from the main chain, but no phenyl group or tails on the graft, shows the sharpest transition, highest transition temperature and the highest modulus in the ordered state, because the spacer means less constraint of the chain movement needed for ordering. The third polymer with a spacer, but also a phenyl group between the ß-alanine units and the spacer, orders similarly, but slightly less readily and has an ordered structure with slightly larger domains.
Mark Foster (Advisor)
Li Jia (Committee Member)
81 p.
Materials Science; Morphology; Polymers

Recommended Citations

Citations

  • Zhao, ZHAO, W. (2018). SMALL ANGLE X-RAY SCATTERING AND RHEOLOGY STUDIES OF POLYISOBUTYLENE WITH OLIGO(ß-ALANINE) GRAFTS [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1528983070278315

    APA Style (7th edition)

  • Zhao, ZHAO, Wenhan. SMALL ANGLE X-RAY SCATTERING AND RHEOLOGY STUDIES OF POLYISOBUTYLENE WITH OLIGO(ß-ALANINE) GRAFTS. 2018. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1528983070278315.

    MLA Style (8th edition)

  • Zhao, ZHAO, Wenhan. "SMALL ANGLE X-RAY SCATTERING AND RHEOLOGY STUDIES OF POLYISOBUTYLENE WITH OLIGO(ß-ALANINE) GRAFTS." Master's thesis, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1528983070278315

    Chicago Manual of Style (17th edition)

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