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Topics Publication 1: Controlled radical polymerization: industrial stakes, obstacles and applications. References : M. Destarac. Macromol. React. Eng. 2010, vol. 4, March issue. Cover picture. Abstract : The extraordinary scientific development of controlled radical polymerization (CRP) contrasts with the very limited number of commercially available products derived from these technologies. The present comprehensive survey takes up existing public knowledge on industrial features of CRP and gives a critical point of view on its global status, and on each CRP technique in particular. The main techniques, namely RAFT/MADIX, NMP, ATRP, OCRP, OHRP, (R)ITP, are introduced. The focus is put on their current status in industry, based on selected patent literature, conference proceedings, professional press releases and technical data sheets of commercial products. This includes the industrial availability of CRP agents, the types of polymers that have been commercialized or that are at an advanced stage of development, and the related applications and markets. The strengths and weaknesses are given for the different CRP techniques, and ways of improvement are suggested. As is often the case for strong technological breakthroughs, the CRP processes face a multitude of hurdles (at different degrees depending on the type of CRP), that must be overcome and which greatly increase the time-to-market for polymer products compared to mature technologies. In spite of its slow development, CRP is seen as a revolutionary method to produce precisely controlled, next generation specialty polymer additives and materials.  Publication 2 : MADIX Technology: from Innovative Concepts to Industrialization of Block Copolymers for Emulsion Stabilization. References : M. Destarac, S. Deroo, H. Lannibois-Dréan, A. Sénéchal, W. Bzducha. Abstract : It is well-established that amphiphilic diblock copolymers exhibit interesting interfacial properties in liquid formulations. We illustrate the potential of MADIX-derived diblock copolymers as emulsion stabilizers against coalescence for water-in-oil (w/o) emulsions. P(alkyl acrylate)-b-P(acrylic acid) copolymers of varying Mn, block ratio and nature of the acrylate monomer were evaluated either as single emulsifiers or in combination with conventional surfactants. It is shown that a well-chosen diblock copolymer of adapted Mn and hydrophilic-lipophilic balance presents specific features that makes it a nearly universal stabilizer for w/o emulsions, suitable for a very broad range of solvent polarity. This work led to the industrial development and commercialization of the Rhodibloc® RS copolymer as a powerful surfactant booster for inverse emulsions.  Publication 3 : Vinylogous thionothio compounds for RAFT polymerization. Références :M. Destarac, I. Gauthier-Gillaizeau, C-T. Vuong, S.Z. Zard. Macromolecules 2006, 39, 912. Résumé: Une nouvelle gamme de dithioesters vinylogues (A) est développée afin d’étudier leur réactivité en polymérisation radicalaire contrôlée par transfert de chaîne par addition-fragmentation réversible (procédé RAFT). Il est démontré que l’agent RAFT A est un excellent agent de contrôle pour polymériser le styrène et les acrylates. Mn croît linéairement avec la conversion en monomère et l’indice de polymolécularité Mw/Mn est inférieur à 1,2. Une famille d’agents RAFT originale –les thioether-thiones- est également proposée. Le thioether-thione B est extrêmement réactif lors de la polymérisation. Un ralentissement très marqué de la polymérisation en présence de B est expliqué par un mécanisme d’addition-fragmentation vinylogue entraînant la formation de radicaux intermédiaires très délocalisés.   Publication 4 : On the importance of xanthate substituents in the MADIX process References : M. Destarac, D. Taton, S.Z. Zard, T. Saleh, Y. Six. ACS Symposium Series 2003, 854 (Advances in Controlled / Living Radical Polymerization), 536. Abstract : We proposed a range of vinylogous dithioesters (A) to promote the controlled free-radical polymerization of styrene and acrylates according to a reversible addition-fragmentation chain transfer (RAFT) mechanism. It was demonstrated that the RAFT agent A is a highly reactive transfer agent which enables to control both Mn and Mw/Mn throughout polymerization. An original thioether-thione compound B was also considered to mediate RAFT polymerization of styrene and acrylates. It was shown that B was inserted into polymer chains in the early stages of polymerization through a peculiar vinylogous addition-fragmentation mechanism including highly delocalized intermediate radicals, responsible for a marked decrease of the overall rate of polymerization.  Publication 5 : Dithiocarbamates as universal reversible addition-fragmentation chain transfer agents. References : M. Destarac, D. Charmot, X. Franck, S.Z. Zard. Macromol. Rapid Commun. 2000, 21, 1035. Abstract : The structural effect of miscellaneous xanthates RS(C=S)OZ’ on the level of control of free radical polymerization was investigated. Such polymerizations referred to as the MADIX process involve the use of xanthates as reversible chain transfer agents. In the case of S-alkyl-O-ethyl xanthates RS(C=S)OEt, the process involves slow degenerative transfer of xanthate end-groups between polymer chains. This leads to styrene and acrylate-derived polymers with predetermined molar masses at high conversions and polydispersity index between 1.5 and 2. In this series, the more substituted and stabilized the R leaving group, the better the control over molar masses as a function of the monomer conversion. Excellent control can be achieved in the polymerization of vinyl esters, acrylic acid and acrylamide. The reactivity of the C=S bond of xanthates can be dramatically increased towards polystyryl and polyacrylyl radicals by incorporating electron-withdrawing substituents in the activating Z=OZ’ group of S-(1-ethoxycarbonyl)ethyl-O-alkyl xanthates, C2H5OCO(CH3)CH-S(C=S)OZ’. This allows the preparation of polymers with controlled molar masses and PDI close to unity.  |
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