[Blueboard] Invitation to the MS Chemistry Thesis Defense of Ms. Maria Leah Rubio

Gina B. Mamauag gmamauag at ateneo.edu
Fri Nov 27 08:48:53 PHT 2015

​The Department of Chemistry

School of Science and Engineering

Invites you to the MS Thesis Defense of

*Ms. Maria Leah Rubio*

*MS Chemistry*



1.       Gilbert Yu, PhD

2.       Nestor Villarante, PhD

3.       Jose Mario Diaz, PhD


1.       Ronaldo Quezon M. Fabicon, PhD

*Date:*  03 December 2015

*Time:*  1:00 Pm

*Venue*: C205, Schmitt Hall

*Thesis Abstract:*

*The interaction between polyelectrolytes and oppositely charged
surfactants has been known since long but they continue to be the subject
of extensive fundamental and applied investigations due to their vast
number of applications. In particular, the combination of anionic
biopolymers and cationic surfactant is one field of research. In this
study, the interaction between cationic surfactant,
tetradecyltrimethylammonium bromide (TTAB) and different anionic
polysaccharides, alginate, carboxymethylcellulose (carboxyMC) and
iota-carrageenan were investigated by conductivity, surface tension, zeta
potential and viscosity measurements and the resulting complexes from their
interactions were characterized by FTIR spectroscopy, differential scanning
calorimetry and thermogravimetric analysis. Partial coagulation diagram
showed that the increase in polyelectrolyte charge density and
concentration broaden and shift the precipitation region towards higher
concentration of surfactant.  Critical concentrations of TTAB in presence
of different biopolymers revealed that while iota-carrageenan forms
aggregate with TTAB at lower surfactant’s concentration, the extent of
interaction was not as cooperative as in alginate-TTAB and carboxyMC-TTAB
sytems. The observed trend was explained in terms of the difference in
polyelectrolyte’s charge density and conformation. Electrostatic
contribution to the complexation was supported by charge neutralization at
the precipitation region and charge reversal with excess of surfactant
concentration. Viscometric results, which supported partial collapse theory
as a consequence of surfactant binding, suggested that
polyelectrolyte-surfactant interaction actually arises from cumulative
hydrophobic and electrostatic effects. FTIR and thermal analysis of the
isolated complexes indicated that each biopolymer was well incorporated
into what is most likely a network of polymer-surfactant complexes. Though
with varying extent of interactions, all investigated systems demonstrated
successful interaction with TTAB, thus, the possibility of forming
nanocapsules based on these systems was also explored. A two-step
nanoencapsulation method of solvent displacement and complex coacervation
was employed in generating nanocapsules encapsulationg citronella oil (CO).
Particle size, PDI and zeta potential measurements for a 1:1 volume ratio
of polyelectrolyte to nanoemulsion revealed that formed particles are
uniformly nanosized with neutral surface charge. Increasing the amount of
polymer yielded particles of relatively larger hydrodynamic diameter, more
polydisperse and of highly negative surface charge.  FTIR and TGA analysis
of freeze dried nanocapsules confirmed encapsulation of CO with a loading
capacity of 37%. Headspace GC-FID employed to monitor the release of
citronellal from the nanocapsules revealed sustained release of the active
ingredient making it a good candidate system for encapsulating not only CO
but other lipophilic compounds of similar properties.*

*Gina Mamauag-Buan*

*Chemistry Department*
*Ateneo de Manila University*
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