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Investigation of a Side-Chain Crystalline Shape Memory Block Copolymer and Maximum Bubble Pressure Rheology of Organogels

Fei, Pengzhan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1384286113

Abstract Details

2013, Doctor of Philosophy, University of Akron, Polymer Engineering.
Shape memory polymers attracted many attentions recently for it is a smart material with applications in many fields. The objective of the first part of research was to investigate a new physically crosslinked shape memory triblock copolymer. Compared to the chemically crosslinked shape memory polymer an outstanding advantage of this shape memory material is that it can be very easily shaped and remolded by elevating the temperature to 140oC, and after remolding the initial shape memory properties are totally recovered by eliminating the defects introduced by the previous deformation cycling. For this investigation, a poly(styrene-block-(methylacrylate-random-octadecylacrylate)-block-styrene) (PS-b-(PMA-r-PODA)-b-PS) was synthesized by reversible addition fragmentation chain transfer polymerization. A three-dimensional, physically crosslinked network was generated by the self-assembly of the triblock copolymer, where the bridging of the midblocks across the glassy PS domains generates “permanent” network of the shape memory polymer. The side chain crystallization of the polyoctadecylacrylate side chains generates a second reversible network enabling shape memory properties. Shape memory tests by uniaxial deformation and recovery of molded dog-bone shape samples demonstrate that shape fixities above 96% and shape recoveries above 98% were obtained for extensional strains up to 300% when using rapid temperature jumps during strain fixing and recovery. Dynamic mechanical tests show the combination of creep and stress relaxation occurs during long-term annealing which is detrimental to the shape fixity and shape recovery of this SMP. The crystallinity of P(MA-r-ODA) samples, which had been heated, stretched, quenched and annealed at room temperature for different time, was measured by differential scanning calorimetry. The degree of crystallinity was found to increase with time where densification of the sample influences the creep and recovery behavior. For the second part of research maximum bubble pressure rheology measurement was demonstrated as a facile method to characterize gel properties, including gel transition temperature. A gel made from 12-hydroxystearic acid (12-HSA) and mineral oil was used for measurements. The difference between unpurified and purified gels of 12-HSA were identified by maximum bubble pressure rheology measurement. The rate of gel formation and the long-term gel stability gel-transition temperature were characterized by maximum bubble pressure rheology as well. The gel transition temperature of the 12-HSA gel was measurement by three methods: maximum bubble pressure rheology measurement, inversion test and dynamic oscillatory shear rheometer. The results showed consistency with each other, demonstrating the validity of this approach of gel transition temperature measurements.
Kevin Cavicchi, Dr. (Advisor)
Nicole Zacharia, Dr. (Committee Member)
Robert Weiss, Dr. (Committee Member)
Abraham Joy, Dr. (Committee Member)
Bi-min Newby, Dr. (Committee Member)
172 p.
Polymers

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Citations

  • Fei, P. (2013). Investigation of a Side-Chain Crystalline Shape Memory Block Copolymer and Maximum Bubble Pressure Rheology of Organogels [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1384286113

    APA Style (7th edition)

  • Fei, Pengzhan. Investigation of a Side-Chain Crystalline Shape Memory Block Copolymer and Maximum Bubble Pressure Rheology of Organogels . 2013. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1384286113.

    MLA Style (8th edition)

  • Fei, Pengzhan. "Investigation of a Side-Chain Crystalline Shape Memory Block Copolymer and Maximum Bubble Pressure Rheology of Organogels ." Doctoral dissertation, University of Akron, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1384286113

    Chicago Manual of Style (17th edition)

akron1384286113
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This open access ETD is published by University of Akron and OhioLINK.