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.
CH5011-COLLOIDS AND SURFACES Jayadheer A (CH09B001) Sai Prashanth Reddy D (CH09B015) Nirup Kumar N (CH09B034) Krishna Teja R (CH09b050)
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
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.
Ref. Toki, TY Chow, T Ohnaka, H Samura, & T Saegusa, 1992)
Polyvinylpyrrolidone also commonly called Polyvidone or Povidone, Monomer: N-vinylpyrrolidone.
molecular weight of nearly 40,000 K value of 30 (Fikentschers formula) (Fikentschers Formula) 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) (Ref. Ashland_Inc)
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 LUDOX TM-50 colloidal silica, 50 wt. % suspension in water (Ref. Aldrich)
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
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
Material Density (g/ml) @ 25oC Silica 50% 1.4 PVP 02% 1.008 PVP 10% 1.02 PVP 30% 1.07Table 2: Colloidal Silica data from manufacturer(Aldrich)and PVP data from (Ashland_Inc)
By Volume By Weight Inference2 % PVP 50 %Silica 2 % PVP 50 %Silica 1 1 1.008 1.4 Very less viscous mixture10 % 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 viscous30 % 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
The structure of the gel formed can be studied using IR spectroscopy, SEM, DLS and other relevant techniques The rheological properties like Visco-elasticity of the gel can be studied with changing the polymer and silica proportions.
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.
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.
Belyakova, L. A., Anatoly M. Varvarin, Diana Y. Lyashenko, & Nadiya V. Roik. (2003). Study of interaction of poly(1-vinyl-2-pyrrolidone) with a surface. Colloid Interface Sci., 264, 2–6. Spinde, K., Konstantinos Pachis, Joanna Antonakaki, & 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