Abstract:

The fractal dimensions (df) of aggregates of latex paticles coated by poly(ethylene oxide)(PEO) have been measured in worse than θ-solvents for different concentrations MgSO4 and temperatures by means of dynamic light scattering. For the lowest molar mass PEO studied (20kg•mol-1) the measurement df of about 2.1 was almost independent of temperature over the range studied. The value corresponds to partially reversible cluster aggregation, which leads to relatively compact aggregates. For the highest molar mass PEO studied (600kg•mol-1), the df decreased significantly ( from 2.4 to 1.7) with temperature, singnifying the generation of more ramified aggregates. The results obtained for this hydrophilic the generation of more ramified aggregates. The results obtained for this hydrophilic polymer contrast makedly with the aggregation of latexes stabilized by the hydrophobic polymer poly(N-isopropylacrylamide)(PNIPAM) which undergoes a coil-to-globule transition.

Key words: Fractal dimension, Poly(ethylene oxide)-polystyrene