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Immobilization of Poly(N-Isopropylacrylamide) on Hydroxylated Surfaces Using Cross-linked Organosilane Networks

Alghunaim, Abdullah
http://rave.ohiolink.edu/etdc/view?acc_num=akron1467858917

Abstract Details

2016, Master of Science, University of Akron, Chemical Engineering.
Poly (N-isopropylacrylamide) (pNIPAAm), a thermo-responsive polymer that exhibits a lower critical solution temperature (LCST) of 32 °C in water has found an extensive use in tissue engineering and bioengineering applications in general. Since it is soluble in water, one of the main challenges that limit its applications in an aqueous environment is the tedious and expensive electron beam or plasma based procedures to retain it on a substrate. In this study, we report the use of various types of organosilanes to form siloxane networks for immobilizing pNIPAAm onto Si-wafer and silica glass substrates in a simple two-step approach: spin coating followed by thermal curing. Attempts are made to elucidate the entrapment mechanism and factors that affect such entrapment. It was found that the entrapment occurs via the segregation of high surface tension organosilanes towards the substrate at a temperature higher than the glass transition temperature (Tg) of pNIPAAm and simultaneous cross-linking of the segregated organosilane molecules that form siloxane networks. Organosilanes having low surface tension were found to segregate towards the air-film interface leading to poor entrapment. Factors such as polarity and hydrogen bonding were found to influence the retention of those organosilanes in the blend film during spin-coating and thermal annealing and subsequent film retention after 3 days of soaking in cold water. Additionally, organosilanes that are allowed to hydrolyze and oligomerize in the blend solution prior to spin-coating also resulted in higher organosilane retention and subsequently, thicker retained blend films compared to solutions that were spin-coated immediately after preparation. Substrates utilizing those organosilanes to entrap pNIPAAm resulted in stable films that exhibited thermo-responsive behaviors that were verified by wettability measurements. Rapid cell sheet detachment (<5 min) of embryonic mouse fibroblast cells were obtained on all substrates apart from pNIPAAm entrapped via a methyl-terminated organosilane due to poor cell adhesion. An epoxy based organosilane that is capable of chemically reacting with pNIPAAm was also used to chemically graft pNIPAAm. The resulting films were thicker than those obtained by the organosilane network entrapment approach; however these chemically grafted substrates showed poor cell adhesion and loss of thermo-responsiveness with the increase in its ratio to pNIPAAm. This study illustrates the simplicity and versatility of the entrapment approach utilizing network forming organosilanes, which could broaden the usage of pNIPAAm. The approach could possibly be used to entrap other functional polymers on hydroxylated substrates that might otherwise dissolve away in solution or when exposed to a particular solvent, or need laborious methods to be immobilized to the substrate.
Bi-min Zhang Newby, Dr. (Advisor)
Gang Cheng, Dr. (Committee Member)
Jie Zheng, Dr. (Committee Member)
Biomedical Research; Chemical Engineering; Chemistry; Materials Science; Polymers
Thermo-responsive; pNIPAAm; Organosilanes; APTES; tissue engineering; cell sheets

Recommended Citations

Citations

  • Alghunaim, A. (2016). Immobilization of Poly(N-Isopropylacrylamide) on Hydroxylated Surfaces Using Cross-linked Organosilane Networks [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467858917

    APA Style (7th edition)

  • Alghunaim, Abdullah. Immobilization of Poly(N-Isopropylacrylamide) on Hydroxylated Surfaces Using Cross-linked Organosilane Networks. 2016. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1467858917.

    MLA Style (8th edition)

  • Alghunaim, Abdullah. "Immobilization of Poly(N-Isopropylacrylamide) on Hydroxylated Surfaces Using Cross-linked Organosilane Networks." Master's thesis, University of Akron, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467858917

    Chicago Manual of Style (17th edition)

akron1467858917
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This open access ETD is published by University of Akron and OhioLINK.