## 3 Results and Discussion  
Generation of environmentally reversible behavior on the surface can lead to a number of exciting applications of both spherical as well as flat substrates. In order to control the properties of the surfaces efficiently, it is important to control the surface functionalization processes, first with ATRP initiator and subsequently with PNIPAAM polymer brushes. In the case of functionalization of surfaces with ATRP initiator, it is important that a uniform distribution of the initiator is obtained on the surface of the particles. It was also reported earlier that a number of factors like presence of crosslinker, presence of surfactant, mode of addition of monomers, colloidal characteristics of the system _etc._ can influence the initiator distribution on the surface of the particles [58]. The functionalization of surfaces with PNIPAAM is directly proportional to the quality of the ATRP initiator distribution on the surface of the particles. In the case of grafting of PNIPAAM from the flat surface, it is also important to ensure that the particles adsorbed on the flat surface form a uniform layer so that the dead-spaces between them are minimized as such spaces do not contribute towards the environmentally responsive behavior. The use of ATRP for polymer grafting is advantageous as it allows an efficient control on the amount or molecular weight of the polymer grafted on the surface. The density of the initiator on the surface can also be varied by varying the molar ratio of monomers in the shell forming monomer batch, thus again allowing control on the extent of surface grafting according to the requirement. The particle synthesized without the use of surfactant were earlier reported and the grafting of PNIPAAM chains on the surface of these particles was also successful [58, 59]. The synthesis of the particles without the use of surfactant was achieved by homogenous nucleation where the micelles are absent in the absence of any additionally added surfactant and the negative charges on the surface of forming particles owing to the initiator residues provide partial colloidal stability. The non-emulsified polymerization conditions were used because the commonly used ionic surfactants in emulsified systems can poison the ATRP catalyst thus hindering control over the molecular characteristics of the grafted chains. The absence of surfactant thus allows better control on the grafted polymer properties, but on the other hand, also leads to much larger particles as compared to emulsified systems owing to lesser number of particles formed during polymerization. Also, the colloidal instability of the particles formed by emulsifier free conditions poses problems during the surface functionalization. Therefore, it was observed that the functionalization of such particles with ATRP initiator was significantly affected by minor changes in the polymerization system. The addition of small amount of divinylbenzene crosslinker to the system was observed to be beneficial as it destabilizes the particles forming due to secondary nucleation and as a result, these particles collapsed on the seed particles thus allowing the better functionalization of seed particles with the ATRP initiator as compared to the case where there is generation of secondary particles thus causing the division of ATRP initiator molecules in the latex and secondary particles. Figure 1a,b, respectively, shows the scanning and transmission electron micrographs of the crosslinked polystyrene particles functionalized with a thin copolymer layer of styrene, BPOEA and divinylbenzene. The surface of the particles was not completely smooth or spherical owing to the collapse of smaller secondary particles on the surface during the course of polymerization. Figure 1c,d represents the transmission electron micrographs of the particles after grafting with PNIPAAM. The polymer brushes can be clearly seen protruding out from the surface of the particles.