Chemical and Biomolecular Engineering Faculty Research


Poly (Methacrylic Acid) Grafted with Poly (Ethylene Glycol) and N-dodecane as Ph-sensitive Surfactants for Water-in-oil Fermentations

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Fall 2003


pH-sensitive surfactants are potentially beneficial to water-in-oil fermentations. Ideally, the surfactants promote emulsification at fermentation pH (typically ∼7) but, upon pH adjustment, lose surface activity to allow easy phase separation for product recovery. In this study, poly(methacrylic acid) (PMAA) grafted with poly(ethylene glycol) (PEG) and n-dodecane was synthesized with an initial MAA/EG molar ratio of 1:1 or 20:1 and a MAA/LMA (lauryl methacrylate) ratio of 1:0.16, 1:0.47, or 1:0.78. The polymers' pH sensitivity comes from the complexation between PMAA and PEG at low pH, which turns hydrophilic PMAA and PEG into a hydrophobic complex. The surface activity was confirmed to decrease markedly as pH dropped below ∼6.0. For polymers with 20:1 MAA/EG, the residual surface activity at low pH was still enough to inhibit the desired phase separation. However, the polymers with MAA/EG/LMA ratios of 1:1:0.47 and 1:1:0.78 showed good emulsification at neutral pH and fast phase separation at pH 4. The polymer with 78% LMA produced the finest droplets, desirable for supporting higher cell concentrations in the fermentation.





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