PH-responsive polymeric materials for encapsulation and triggered release

Wang, Hsuan-Chin

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https://hdl.handle.net/2142/105111 Copy

Description

Title

PH-responsive polymeric materials for encapsulation and triggered release

Author(s)

Wang, Hsuan-Chin

Issue Date

2017-10-23

Director of Research (if dissertation) or Advisor (if thesis)

Zimmerman, Steven C.

Doctoral Committee Chair(s)

Zimmerman, Steven C.

Committee Member(s)

• Braun, Paul V.
• Cheng, Jianjun
• Sottos, Nancy R.

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• pH-responsive
• acid degradable
• microcapsules
• interfacial polymerization
• depolymerization

Abstract

The strong research interest in encapsulation chemistry for functional chemical species (commonly referred to as active ingredients or actives) arises from the need to devise tailored strategies to protect precious actives from premature degradation or leakage. Furthermore, to maximize the performance of the encapsulated actives, a controllable method is needed to release the materials at the desired time, location, and rate. To address these challenges, scientists look to stimuli-responsive polymers as a solution because polymers can be designed with tailored properties thanks to advancement in polymer chemistry and engineering. This dissertation discloses a collaborative effort between the Zimmerman group and Dow Chemical to develop novel pH-responsive polymeric materials for encapsulation and triggered-release. As a release trigger, pH is attractive because of the prevalence of environments with specific pH levels. In the first part of the dissertation, a diester diacid chloride monomer, PDDC, was utilized in the preparation of a novel pH-responsive polyamide microcapsule. PDDC was selected for its susceptibility to hydrolysis as well as simplicity in structure and synthesis. A mixture of polyamine monomers, which includes a triazine trisamine crosslinker and the commercially available DETA, reacted with PDDC to afford toluene-loaded (ca. 95% by weight), free-flowing microcapsules through interfacial polymerization. Through dye release experiments, the triazine-DETA-PDDC microcapsules exhibited a unique pH-dependent release behavior: similarly fast, first order like release profiles at pH 5 and pH 10 and a steady, linear release profile at pH 7.4. In a dry or hydrophobic environment, the microcapsules remained stable without UV-Vis detectable dye release or rapid loss of the volatile core solvent. In summary, the PDDC polyamide chemistry utilizes a single set of synthetically scalable monomers to prepare multi-pH responsive microcapsules that could see applications in different pH environments. The second portion of the dissertation concerns a novel polyacetal that utilizes a new mechanism to facilitate degradation. A small molecule model compound containing the novel acetal moiety was synthesized and confirmed by NMR to show the expected degradation products under an acidic environment. Linear polymers bearing the novel acetal repeat unit were synthesized, with molecular weight up to 50 kDa as calibrated by PS standards. Crosslinked microcapsules bearing the novel acetal repeat unit were fabricated by interfacial polymerization. Encapsulation of a hydrophobic photoacid generator (PAG) in the core of the microcapsules demonstrated UV-triggered degradation.

Graduation Semester

2017-12

Type of Resource

text

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http://hdl.handle.net/2142/105111

Copyright and License Information

Copyright 2017 Hsuan-Chin Wang

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