2. To find the appropriate proportions of given
polymer and particle solutions that forms a
shake gel i.e., shears induced gelation.
To verify the reversible gelation mechanism
3. Interaction between PVP and the surface of silica
takes place mainly by means of hydrogen bonds.
Research has shown that PVP occurs in two forms
on the silica surface, reversibly adsorbed and
irreversibly grafted onto the surface of silica.
The irreversible adsorption can be attributed to
the formation of relatively strong –C=O….H-OSi
hydrogen bonds whereas the interactions
between Si and N.
8. molecular weight of nearly 40,000
K value of 30 (Fikentscher's formula)
(Ref. Ashland_Inc)
Where, c = concentration in g/100 ml;
c = viscosity of the solution;
0 = viscosity of the solvent;
k = value according to Fikentscher (K = 1000* k)
(Fikentscher's Formula)
9. Spherical silica particles are suspended in an
aqueous phase.
The colloidal suspension is stabilized by pH
adjustment and then concentrated, usually
by evaporation.
Brand Aldrich
Formula SiO2
Mol Wt. 60.08 g/mol
Density 1.4 g/ml @25 oC
Table: Data for LUDOXTM-50 colloidal silica, 50 wt. % suspension in water
(Ref. Aldrich)
10. Polymer solution
Colloidal Silica suspension
Take different proportions of the solutions
using micro-pipette
Mix them in a culture bottle
Shake the bottle to observe the formation of
gel
Repeat the experiment for various
concentrations
11. Glassware should be properly cleaned and
sterilized in ovens or using nitrogen vents
Store the micro pipette vertically to prevent
liquids from running inside the shaft of the
pipette.
Minimize the exposure time for PVP while
weighing, as it can gain weight by absorbing
atmospheric water
Should wear goggles and potentially lab aprons
12. Table 2: Colloidal Silica data from manufacturer
(Aldrich)and PVP data from (Ashland_Inc)
Material Density (g/ml)
@ 25oC
Silica 50% 1.4
PVP 02% 1.008
PVP 10% 1.02
PVP 30% 1.07
13. By Volume By Weight Inference
2 % PVP 50 %Silica 2 % PVP 50 %Silica
1 1 1.008 1.4 Very less viscous mixture
10 % PVP 50 %Silica 10 % PVP 50 %Silica
1 1 1.02 1.4 viscous liquid
1 3 1.02 4.2 more viscous
1 6 1.02 8.4 more viscous
30 % PVP 50 %Silica 30 % PVP 50 %Silica
2 1 2.14 1.4 very high viscous
4 3 4.28 4.2 Some gel is formed
1 1 1.07 1.4 Some gel is formed
1 3 1.07 4.2 Shake gel
1 7 1.07 9.8 Shake gel
17. The structure of the gel formed can be
studied using IR spectroscopy, SEM, DLS and
other relevant techniques
The rheological properties likeVisco-elasticity
of the gel can be studied with changing the
polymer and silica proportions.
18. The gelation that occurred upon shaking the
solution rigorously has contribution of both
reversibly and irreversibly adsorbed polymer
particles.
When left to settle, a part of polymer desorbs
and this can be attributed to reversible
gelation
A number of experiments were conducted
using different concentrations, and
proportions of PVP with 50% colloidal silica.
19. Experiments were also conducted using PVA as
polymer. Since, 20% PVA solution formed a very
viscous fluid, PVP was considered for further
experiments
Using 30% PVP and 50% Silica in 1:1 volume
proportions, a near gel was formed.
So, different proportions of these mixtures were
tried and a near shake gel is finally obtained.
Increasing the proportion of silica particles led to
the formation of better shake gels.This also
supports the mechanism of reversible gelation.
20. Belyakova, L.A., Anatoly M.Varvarin, DianaY. Lyashenko, & NadiyaV. Roik.
(2003). Study of interaction of poly(1-vinyl-2-pyrrolidone) with a surface.
Colloid Interface Sci., 264, 2–6.
Spinde, K., Konstantinos Pachis, JoannaAntonakaki, & Silvia. (2011). Influence
of Polyamines and Related Macromolecules on Silicic Acid
Polycondensation: Relevance to “Soluble Silicon Pools”? Chemistry of
Materials, 4676–4687.
Toki, M.,TY Chow,T Ohnaka, H Samura, &T Saegusa. (1992). Structure of
poly (vinylpyrrolidone)-silica hybrid. Polymer Bulletin, 36.
Aldrich, S. (n.d.). LUDOX®TM-50 colloidal silica. Retrieved Nov 10, 2012, from
http://www.sigmaaldrich.com/catalog/product/aldrich/420778?lang=en®io
n=IN
Ashland_Inc. (n.d.). IspCorp. Retrieved Nov 10, 2012, from
http://online1.ispcorp.com/Brochures/Performance%20Chemicals/PVP.pdf
It is soluble in water and other polar solvents.
Being a branched polymer, it is extensively used as a binder in many pharmaceutical, adhesive industries.
