Particles Size Analysis Essay

3.1 Particles size analysis

The microgels particles characterized by DLS were reported previously [43]. The hydrodynamic diameter was determined by Stokes-Einstein relations. Fig. 1 illustrates the temperature dependent particle size and size distribution of copolymer microgels with different AMPS content in water at 25oC and 50oC. The data shows that the hydrodynamic diameters of microgels increases from 343.4 nm to 538 nm at 25oC and 132.5 nm to 414.8 nm at 50oC with increasing AMPS concentration in the feed recipe but its diameters reduces with increasing temperature. At 25oC, the bimodal peak with broad size distribution was observed for the microgels sample with low mole% of AMPS i.e. MG-100, MG-102 and MG-106. Only monomodal peak with narrow size distribution observed for all microgels at 50oC, which means that the process of aggregation of microgel particles was already completed. At the temperature of 50oC, which is well above the LCST of PNIPAM, the PNIPAM chains shrink and all individual particles aggregate because of attractive forces i.e. intra/intermolecular and hydrophobic interaction, which dominate over interaction between polymers with water molecules. At low temperature, the aggregates will dissociate in individual swollen particles which show broad size distribution. The intensity of microgel particles is found to be

The circularity measures the shape of particle closeness to perfect circle and values are in the range of 0 to 1. The shape of particle is circular when the value of circularity ≅1 and irregular shape when circularity value close to 0. The calculated circularity value of microgel samples from 0.27 to 1.03 as shown in Fig.4. The lowest value observed 0.27 for sample MG-100 and has irregular shape, ≅1 for MG-102, MG-106, and MG-110 and has spherical shape. The circularity value depends on composition and surface roughness of