 So, now briefly I will tell you why this is so interesting because when you talk about soft condense matter, I mean it covers the wide range from plastics to paints to cosmetics, detergents to pharmaceutical to food stuff, almost a huge chunk of things that we use in our daily life and understanding their structure is important. Possibly the first time soft condense matter word was used or came into prominence was the work by DJNs and in his 1990 Nobel Prize, Nobel Prize, he mentioned about soft condense matters are also known as the complex fluid so in this first instrument that I talked to you about which is a slip based system, a large number of soft condense matter in 1 to 50 nanometer scale was studied by small angle neutron scattering and I will try to demonstrate some of the examples. The work done is huge and even what is being done is huge so far as the materials being studied but just to give you a test I have chosen a few examples because soft condense matters have an interesting thing that for example a polymer chain, a polymer chain it can bend, it can twist and in a medium it can either roll up or it can open up and make become either a coil or can move like a snake inside a medium and all these have to do with its utility in a particular application and people are interested to know how they coil up, what is the radius of gyration, do they coil up, do they open up and all these questions are asked and these can be answered by using small angle neutron scattering just I just take one example I take an example of surfactants. Surfactants are very interesting amphiphilic molecules they have got a hydrophobic tail group and the hydrophilic head group so basically if I may give a simplistic picture so it has got a tail by showing it like this I mean the tail is not really a rigid tail not like inorganic chemistry not a rigid tail but it's a flexible tail and it has got a hydrophilic head group so typically they comprise of heads and tails when you put the surfactants in a solution initiate or in water knack was media generally try to sit on the surface because the tails won't like to go inside the water but the fact is that when you keep increasing the concentration of surfactants on the surface then surfactant to surfactant interaction will not allow them to go beyond a certain concentration so above a certain critical concentration they do an interesting thing they start forming this kind of blue glues where the head groups are on the surface and the tail groups are inside so that is how they hide their tails from the water and this is a very very interesting thing I can just mention one thing that the detergents we use routinely they are the darts are oily so all our detergent all the I mean the dirt that you have there are oily darts and the detergents will have the surfactants so when the surfactants have this oily dirt and the water medium they form the surface this kind of structure on the dirt and removes it from the cloth and throws it out so this is one very simple example that I am telling you but this is a million dollar industry for that matter so this is the nature of micelles and I have just given you some of the micelles like there's a sit-up micelle which is cationic means it has got a head group which is having a charge anionic positively charged non-ionic surfactants and zuteron there are double charges so there are various kinds of surfactants and as I told you just now the micelles are the clusters of the surfactant molecules in aqua solution so the hydrophobic part goes inside the hydrophilic part remains outside and these are 50 ans now so this shape and size of these micelles are very important for various applications so micelle formation is a basically here it is known as a self-association process so they look like tiny microbes possibly they are chemical microbes but they associate with each other because they want to minimize the energy most of the self-assemblies always come from the fact that every assembly tries to minimize its energy here the interaction between the tail and water must be giving positive energy so it is better to hide the tails from the water and that's why this surfactant is formed so that the energy is minimal and these are large objects soft objects by soft timing a micelle is unlike a hard let us say cannon ball this is a soft squishy ball you can squeeze it you can change the shape of it and the dynamics of micelles in the solution will be slow typically time scales are milliseconds two fractions of a minute seconds and not the atomic and molecular dynamics which happens in femtosecond so here just this schematic shows how the micelles will form when you increase the density and these are the various kinds of micelles that can form they can form a sphere switch assured the simplest thing when you keep increasing the density of surfactants more and more then spheres no more a possibility because then sphere head groups will start repelling especially with the charge they will keep repelling then they like to go to this kind of confirmation which is cylindrical or they can form bilayers or they can form vesicles which are multi-layers vesicles are basically these micelles let me draw I'm very bad in drawing so these micelles might form vesicles like this where one head group looks inside so it is like it's like tokamak or like a meduvada you can say so this has got a geometry like this the vesicle or you can even have spherical vesicles where your multi-layer structures you can see the micelles are drawn here and there is one inside another inside another so there are multi layers so they can be like this or they can be vesicles like this and so and they are applied in various cases in detergents in emulsification in solubilization waiting in foaming applications micelles are used so I will just give a short example and I'll stop for the time being I'll come back with more examples on other systems so this is a micelle structure I am showing you so the tail group and the head group I have taken an example from a novel micelle what is one is that Konrad's Gemini surfactants where instead of one head group there are two micelles they're attached by a spacer group and this is a multi-headed surfactant where one tail group has got multiple head groups so how do they basically what we study here that when I put them in aqua solution how they form structures when the structures break so this is what of interest not only to the chemists and physicists but also to the industry because depending on how the micelles form how big the micelles are their applications become important so Gemini surfactant has very unusual properties the Gemini surfactants I am going to show us made in ISC Bangalore and I just want to share with you some empirical results you know you can see that micelle has got a head group which has got an area and the tail group has a length l and there's a packing parameter called v equal to a by l p equal to v by a l where basically the volume the head group area and the tail and the volume of the micelle is dictated by this ratio v by a l and spherical micelles when this packing parameter is less than one third it forms a spherical micelle which I have showed you earlier if it is between one third and half then it forms a cylindrical micelle when it is between half and one it from vesicles this can be shown even from calculations from simulations need not be experimental and there are bilates when p is equal to one and reverse micelles when p is greater than one so I just take one or two examples there's a flexible versus rigid spacer so the spacer which I showed here in this case this spacer this can be a rigid group it can be a benzoid group or it can be something it can be another polymer chain like which is flexible or a group which is rigid so here I am just using the example here you can see this is a flexible chain CH2M this is a long chain interestingly the experiment that we could do in the small angle machine here we find that the slope of the curve changes drastically depending on the length of this flexible chain group and it follows a one by q one by q square and zero one by q to the power zero slope for m equal to five three four and five as the slope becomes smaller and smaller and zero here but in case of rigid head groups we have a peak which shows as I told you I wrote to you just showed you earlier that the intensity is proportional to pq and s of q structure as well as form factor these are form factor part these are there's a structure also here multi lamellar vesicle it forms and vesicle to vesicle distance you can find out draw x by by q from the peak position is on 31 angstrom so we can find out the coordination numbers from small angle neutrons scattering we can also find out the geometry in solution of a millimolar micellar solution with different lengths of head groups and this is a very interesting experiment that was done on the slip based small angle neutrons scattering machine okay so before I complete today I wanted to discuss with a few more examples that this is about multiheaded surfactants now multi micelles are micelles are forming because the competition of two opposing forces that we know that the hydrophobic attraction between the tails and the aggression where the illustrative repulsion between the head groups limit the size of a micelle so basically the tails they're hydrophobic and they want to hide from the water I said they'll be going inside so when a form of micelle multi-headed one it has got more number of tails so they like to come together they will like to bunch together they will like to bunch together bunch together because there's a attraction hydrophobic attraction between them but at the same time because this is a multi-headed multi-headed micelle you can see there's a charge on the head group and then the charge on the head group will repel each other so there are two competing forces the tails they like to bunch together and the heads they want to move where together and then that will dictate the balance between these two forces that will dictate what is going to be the geometry of the micelle using multi-headed surfactants so this is just a schematic you can see that this is a job when the head group is one it's a very simplistic picture actually you form spheres and here when you have two head groups or three head groups then you can see these tails tend to tangle because the head groups like to maintain the distance between them the head groups like to maintain the distance between them the tails to form the micelle they tend to get tangled in this region there's lots of tangling but this will give very very different small angle neutron scattering signals and you can actually find out what is happening when you put such multi-headed surfactants inside NACWAS medium so I have just used one example very interesting example you see that the structure of micelles of multi-headed surfactants I have used this thing h equal to 1 2 and 3 this is data interestingly as you go to larger and larger number of head groups surely the repulsion takes place but you can see that the number the number of the combination combinatorial number goes down drastically from 240 photo 20 and this is basically they form a prolique ellipsoid in this case and you can see that the axis the axis is the semi-major axis drastically reduces when you go from one to three the number of head groups and the tails they really tangle and fold to such a large extent because their attraction between them there is no repulsion and the such that to increase in the number of head group the tails get more and more tangled that's what this experimental result dictates so this completes a part of my discussion on small angle neutron scattering I'll use few more examples on the slit-based geometry and at least few more examples on the double crystal based medium resolution science in the next lecture before I draw a curtain on small angle neutron scattering and move on to other mesoscopic techniques in my lecture thank you