This dissertation investigates the self assembly and automatic oscillation of intelligent
poly (N-isopropylacrylamide) [PNIPAM] microgel particles. The equilibrium phase
diagram as a function of temperature and concentration was constructed for the charged
PNIPAM spheres. The PNIPAM microgel particles display rhythmic size oscillations
when covalently coupled to a nonlinear chemical reaction, the Belousov-Zhabotinsky
(BZ) reaction. The nonequilibrium dynamics of PNIPAM microgels in the presence of
BZ reaction was studied by the systematic variation of substrate concentrations and
temperature. In addition, the BZ chemical reaction was modeled to reveal the existence
of upper temperature limits for nonlinear chemical systems.
The experiments employ environment sensitive PNIPAM particles that are sensitive to
temperature, pH, and ionic strength. The PNIPAM particles have been demonstrated
here to behave as hard spheres at low pH values and soft spheres at high pH. This is
done by measuring the freezing and melting boundary of fluid-crystal coexistence region
with a new technique which is simpler and quicker compared to the traditional
sedimentation method.
A novel method was developed to achieve size uniformity of PNIPAM gel particles with
covalently-bound tris(bipyridyl)ruthenium(II) via the coordination chemistry between a
ruthenium complex and the monodispersed PNIPAM gel particles bearing bipyridine
ligands. The correlation between the dynamic behavior of BZ reaction induced mechanical oscillations of PNIPAM particles and substrate concentrations was presented
in a ternary phase diagram. In particular, the dependence of oscillation frequency and
induction time on the substrate concentrations was studied. The temperature dependency
of the induction time and oscillatory frequency of the BZ reaction in this polymerimmobilized
catalyst system were compared to the bulk BZ reaction with the catalyst in
the solution phase. Prolonged induction times were observed for the immobilized
catalyst, compared with free catalyst, while little difference was observed on the
oscillation frequency.
A theoretical improvement has been achieved by incorporating the temperature
dependence in the BZ Oregonator model. Bifurcation has been calculated in the phase
space spanned by initial reagents concentration ratio, stoichiometric factor and
temperature. The existence of upper temperature limits has been demonstrated.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-464 |
| Date | 16 January 2010 |
| Creators | Pullela, Srinivasa |
| Contributors | Cheng, Zhengdong |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation |
| Format | application/pdf |
Page generated in 0.0018 seconds