Hydrophilic regions inside colloidal polymer particles in water

Macromolecules

Volumn 39, Issue 6, 2006, Pages 2007-2009

  Tauer, Klaus ^a  

^a MAX PLANCK INSTITUTE OF COLLOIDS AND INTERFACES   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

FREE ENERGY; HYDROPHILICITY; INTERFACIAL ENERGY; MONOMERS; MORPHOLOGY; POLYETHYLENE GLYCOLS; POLYMERIZATION; POLYMERS; SURFACE ACTIVE AGENTS;

HYDROPHOBIC TAILS; MACROMONOMERS; POLYMER PARTICLES; SOLID SPHERE MORPHOLOGY;

COLLOIDS;

EID: 33645827519     PISSN: 00249297     EISSN: None     Source Type: Journal    
DOI: 10.1021/ma060221a     Document Type: Article

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9. The polymerizations were carried out as follows: 1930 mL of water, 91.1 g of styrene monomer, 0.021 g of sodium hydrogen carbonate buffer, and, if necessary, the thiomalic acid chain-transfer agent (either 1 or 0.2 mol % relative to styrene monomer) were charged in the reactor under stirring and purged with nitrogen gas. After at least 30 min the temperature was equilibrated (70 °C), and the reaction was started by injecting 1.872 g of KPS dissolved in 70 mL of degassed water. The reheating up to 70 °C after injecting the initiator solution occurred within less than 2 min. Samples of almost 100 mL volume were taken from the bottom valve of the reactor at different polymerization times.
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27. During a 2 week period two students jointly carried out their first emulsion polymerization (sample t4-1). They took 10 samples over the whole duration. On the TEM pictures of sample 1-7 taken between 30 and 273 min after the start anomalous particles appeared. Two attempts (samples t4-2 and t4-3) to reproduce these results failed. In comparison to the students' results, the repeated runs resulted in polymers with an up to a factor of 3 higher average molecular weight. The conclusion was that in the students' run some chain transfer agent (perhaps some lubricant from the stirrer dropped from the shaft into the reactions mixture) was accidentally present. Indeed, polymerizations in the presence of thiomalic acid as chain transfer agent resulted in anomalous particles.