## 3 Results and Discussion
Here it is important to notice that though the brushes seem not to be uniformly grafted from the surface, but such an effect arises from the microscopy analysis and depending on the staining of particles or placement of particles on the microscope grids, the same particles with more uniform grafting were also observed. It was also observed that the particles were partially aggregating after the polymer grafting. As mentioned earlier, the use of surfactant was avoided in the process owing to the poisoning of the ATRP catalyst with the surfactant, but the process then leads to the generation of larger particles. Smaller particles are important substrates owing to different applications and it is of interest to achieve the grafting of environmentally responsive polymer on the surface of these particles too. To avoid the  
Figure 1: (a,b) SEM and TEM micrographs of the latex particles functionalized with a copolymer layer carrying ATRP initiator and (c,d) the grafted brushes of poly(_N_-isopropylacrylamide) from the surface of the functionalized particles using ATRP [58,59]. negative interactions of ATRP catalyst and surfactant, the particles were extensively washed before the PNIPAAM grafting reaction. Figure 2a shows the crosslinked polystyrene particles synthesized with emulsified polymerization conditions. Figure 2b is the micrograph depicting the particles after surface functionalization with a thin layer of copolymer of styrene, BPOEA and divinylbenzene. The particles were smoother in morphology as compared to the particles generated without the use of surfactant (Figure 1). The particles were grafted with PNIPAAM and the grafted particles are shown in Figure 2c,d. The particles can be seen covered with thick layers on PNIPAAM, which are visibly lighter in color owing to non-compact nature as compared to polystyrene particles owing to their higher thickness as well as compact nature. The amount of grafted polymer could also be controlled by changing the initial amount of _N_-isopropylacrylamide added during grafting reaction. This confirms the successful generation of polymer grafts by using atom transfer radical polymerization on the surface of smaller particles also, thus expanding the applicability of ATRP on the substrates generated by two different polymerization methods. Similar to the case of grafted particles of Figure 1, the particles in the case of emulsified conditions were also observed to have some extent of aggregation after grafting. Figure 2: (a) Crosslinked polystyrene latex particles generated by the use of surfactant, (b) particles of Figure 2a surface modified with ATRP initiator and (c) and (d) are the particles of Figure 2b after grafting with poly(_N_-isopropylacrylamide) brushes. As observed in Figures 1 and 2, partial aggregation of the particles was observed after PNIPAAM grafting, probably owing to the sticky surface of the polymer particles. Further studies were also carried out to confirm this phenomenon. Figure 3a shows the cryo scanning electron micrograph of the grafted particles. Cryo SEM allows better investigation of the structural features of the grafted polymer layer as the instantaneous freezing of the system in this case eliminates any shrinkage of the grafted polymer brushes on the surface of the particles. It was observed in the micrograph that PNIPAAM brushes around the particles formed a homogenous layer and aggregated the particles together owing to long brushes of sticky nature. It should also be noted that the latex were thoroughly washed after PNIPAAM grafting, therefore, the observed layer in the micrograph is not free polymer but is bound to the polymer particles. Figure 3b also shows the behavior of the latex particles when pulled away from each other. The homogenous grafting of the polymer around the surface of the polymer particles does not allow quick separation owing to the entanglement of the grafted brushes as well because of their sticky nature.