I am currently working on an article that involves practical research with polymers, specifically focusing on PVA (polyvinyl alcohol) and PEG (polyethylene glycol). Despite thorough preparation and experimentation, I am encountering significant challenges in achieving a consistent and uniform solution without gelation with these materials. These difficulties are impacting the progress of my research and the completion of my article. If anyone with experience in polymer chemistry, particularly in PVA/PEG systems, could offer their insights or advice, I would greatly appreciate your assistance. Please feel free to contact me.
To achieve a consistent PVA/PEG solution without gelation, keep PEG loading below 20 wt% and ensure thorough mixing at elevated temperatures (around 80°C). Maintain optimal stirring conditions and consider using additives like plasticizers to improve compatibility. Additionally, explore the incorporation of nanofillers to enhance stability and mechanical properties.
Vortex the PVA solution and add the PEG slowly. Mix in a magnetic mixer for half an hour, leave in the hot air oven for 2-3 minutes and repeat this dong several times. Do not exceed 125 degrees while waiting in the oven, and you can close the top of the beaker to prevent evaporating.
The observed gelation phenomenon is due to phase separation in a system containing 2 unlike polymers. Incompatibility in such systems is the rule rather than the exception. This is due to the fact that the entropy of mixing of polymers is severely reduced as compared to a mixture of monomers. This is because monomers in polymers are not free but connected. As a consequence phase separation is enhanced at higher polymer molar mass.
Phase diagrams of PVA-PEG-water mixtures have been published by Inamura (attached). This paper shows that 3 morphologies are encountered in such systems: homogeneous solutions, phase-separated solutions, and gels (Fig 1). You are certainly working in the latter regime. The paper also shows that the phase boundaries are strongly dependent on molar mass (Fig 2).
These results are displayed as triangular phase diagrams for three-component systems. Concentration of each component (PVA, PEG, H2O) is 100 % at the vertex. Systems at constant water content are represented by lines parallel to the basis of the triangle, i.e. the side of the triangle opposite to the H2O vertex. In a similar way lines for constant PVA and PEG content can be constructed. In doing so, the composition at the intersection of these lines can be evaluated. See for example the red lines in the second attachment. This example shows that at higher total polymer concentration (ca 20 %) homogeneous single phase solutions can be only obtained at low PEG content. Higher PEG contents can be only accommodated at higher dilution. Fig 2 in this attachment demonstrates that miscibility is enhanced at lower molar mass of PEG (compare (- - -) curves b and c).
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