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

The polymerization was conducted at 70 o C in dried toluene for a degree of polymerization (DP)value of 60 to obtain a PMMA macroinitiator with a molecular weight of 7700 g/mol, verified by 1 HNMR(Figure – 4.6) and PDI value of 1.15, calculated using size exclusion chromatography analysis. This palered color PMMA would serve as the RAFT macroinitiator for the polymerization of the octadecylmethyacrylate monomer, synthesized in the first stage.The copolymerization of octadecyl methacrylate was conducted at 80 o C with PMMA RAFTmacroinitiator in toluene, for various degree of polymerization (DP) values. The values of Ln([Mo]/[M])obtained for different DPs reveal a linear dependence (Figure – 4.7) over the time signifying a controlledcopolymerization persisted throughout the reaction time. It also means that the number of propagatingspecies remained almost constant during the polymerization duration.21,81,61,4DPth=15DPth=37DPth=60DPth= 295Ln ([Mo]/[M])1,210,80,60,40,200 25 50 75 100 125 150 175Time (min)Figure – 4.7: Variation of Ln([M o ]/[M]) as a function of time for different degree of polymerization valuesThe evolution of molecular weights also showed a linear evolution with respect to % conversion(Figure – 4.8). As it can be seen, a very high molecular weight was obtained for a given conversion valuefor DP = 295. As the DP value decreases, a significant decrease is observed in the increase of molecularweight. A higher DP (for example: 295) signifies higher amount of the monomer concentration thus moremonomer molecules are available to further react with the propagating chains.108