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Structural and Chemical Contributions to Poly (N-alkyl acrylamide) Responsiveness

Lang, Xiaolong
http://rave.ohiolink.edu/etdc/view?acc_num=case1548428317696918

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Poly (alkyl acrylamide)s, most notably poly(N-isopropylacrylamide) (PNIPAM), are widely studied thermoresponsive polymers. Many undergo a coil to globule transition when heated above their lower critical solution temperature (LCST), and several exhibit cononsolvency behavior in mixtures of water and alcohol. Cononsolvency is a phenomenon in which a mixture of two solvents, each of which can individually dissolve a polymer, results in a poor solvent for that polymer. PNIPAM, and other thermoresponsive polymers, are attractive due to the ability to tune thermoresponsive properties, such as the critical temperature and polymer conformation, by controlling the polymer architecture. In order to study the structure-property relationships of PNIPAM and other similar poly(N-alkylacrylamide)s, low dispersity star PNIPAM and linear poly(N-alkylacrylamide)s with various terminal groups -- including bromine, phenyl, dodecyl, ethyl, and hydroxyl -- were synthesized via RAFT and ATRP polymerization. One pot aminolysis/thiolene chemistry was used for post-polymerization modification of terminal groups. The influence of terminal group, polymer architecture, monomer structure and alcohol structure on cononsolvency, assembly, and thermoresponsive behavior of poly (N-alkylacrylamide)s in solution was determined with a combination of small angle neutron scattering (SANS), turbidimetry measurements, dynamic light scattering, and dissipative particle dynamics (DPD) simulations. SANS measurements show that both the number of arms (f) and terminal group play a dominant role in the solution behavior of PNIPAM in relation to the interaction parameters, conformation of the arms of the polymer, and clustering/association of the polymers below the LCST. Large scale, fractal assemblies (larger than 1 μm) are observed below the critical temperature for polymers terminated with short hydrophobic groups, but for long hydrophobic terminal groups, polymers formed small micelles (ca. 15 nm). The size and shape of the non-polar, hydrophobic region of both the solvent molecules and the substitute group of poly(N-alkylacrylamides) influence hydrophobic hydration, which affects critical solution temperature (TC) and the phase transition behavior. These results indicate that, despite making up only a small fraction of the polymer, the terminal groups play a large role in both the conformation and assembly of PNIPAM and its analogs below the critical temperature, and hint at the possibility of new design strategies for thermoresponsive materials.
Michael Hore (Advisor)
Gary Wnek (Committee Member)
Emily Pentzer (Committee Member)
David Schiraldi (Committee Member)
194 p.
Polymers
LCST, Thermoresponsive; PNIPAM

Recommended Citations

Citations

  • Lang, X. (2019). Structural and Chemical Contributions to Poly (N-alkyl acrylamide) Responsiveness [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1548428317696918

    APA Style (7th edition)

  • Lang, Xiaolong. Structural and Chemical Contributions to Poly (N-alkyl acrylamide) Responsiveness. 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1548428317696918.

    MLA Style (8th edition)

  • Lang, Xiaolong. "Structural and Chemical Contributions to Poly (N-alkyl acrylamide) Responsiveness." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1548428317696918

    Chicago Manual of Style (17th edition)

case1548428317696918
323
© 2019, some rights reserved.Creative Commons License Structural and Chemical Contributions to Poly (N-alkyl acrylamide) Responsiveness by Xiaolong Lang is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.