17R4 is a tri-block copolymer that forms micelles when placed inwater or D2O. Both samples, at different concentrations, go through three stages. At low temperatures, the 17R4 does not start to form micelles but forms a large unimer network. After passing the temperature at which micelles start to form, the sample becomes clear. Both of these stages are in a one-phase state. At higher temperatures, the sample enterss a two phase state,where there is a polymer-rich and polymer-poor state. Both phases contain 17R4, just at different concentrations. By measuring the refractive index at various concentrations and temperatures, we are able to obtain a series of graphs, known as coexistence curves, which helps us understand the trend of 17R4 concentrations in both water and D2O. By using dynamic light scattering (DLS), we are able to determine the sizes of micelles and possibley 17R4 in water at varying concentrations and temperatures. Both these experiments help us analyze and understand the characteristics of 17R4.