4(%3)3 - Ecole nationale supérieure de chimie de Montpellier

The 1 HNMR spectrum obtained for the esterification product of RAFT agent showed persistantimpurities despite purifying over silica gel chromatography. With the obtained spectrum, it is difficult toascertain the peak signal for two methylene proton groups as well as lone proton of alkyne group.Nevertheless, we carried on with the same product to be reacted with the azide derivative ofpentaerythritol. For this, around 4.5 eq. moles of ethynyl 4-(phenylcarbonothioylthio)-4-cyanopentanoatewas reacted with 1 eq. moles of 2-(2-azidoacetyl)oxyethyl 2-azidoacetate in the presence ofcopper sulfate pentahydrate and sodium ascorbate. DMF was used as a solvent (Figure – 5.14). Thereaction was spontaneous as the color of the vial changed to deep red. After 1 hour, the reactioncontents were passed through a short alumina column, followed by the work up process, giving deepbrownish red color viscous product.Figure – 5.14: Click chemistry reaction for the coupling of ester derivative of RAFT with tetra azide derivative ofpentaerythritol. For clarity, the rest of the three groups have been omitted and represented by R.The analysis of 1 HNMR of the product indicates the presence of unreacted azide derivative in theproduct which resulted to presence of large number of peaks. At this moment it seems that betterpurification procedure is required to obtain the core molecule in the good yield and purity.5.4 CONCLUSIONVery preliminary results have been presented about the concept of nano-gel based self-healingsystem. Based on the finding of an earlier work, we established the fact that as the size of the nano-gelincreases, its rate of swelling increases rapidly with time. Although with miniemulsion, we were able to134