Surfactant-free emulsion polymerization by “Grafting from” polyvinylamine stabilizer

• Autor(a) principal: Gomes, Catarina
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10198/11514
• topic: Surfactant free emulsion polymerization; Poly (N-vinylformamide); Poly (vinyl amine); Poly (methylmetacrylate); Graft copolymerization

Emulsion polymerization technique is one of the most common techniques employed in industry to synthesize a wide range of polymers due to its versatility, the possibility to control the properties of the final product and because it is an environmentally friendly technique. Nevertheless, large amounts of surfactant are usually required to stabilize the system which can have deleterious effects on water resistance and on the mechanical properties of the polymer. Among the different techniques employed to circumvent this problem, recently, graft copolymerization of a monomer from water-soluble polymers containing amino groups has been employed to synthesize polymer particles with amphiphilic core-shell nanostructures. Applications of these particles include controlled release drugs, water-borne coatings and diagnostic testing. In this project, water-soluble poly (N-vinylformamide) (PNVF) of different molecular weights was synthesized and characterized. Subsequently, the basic hydrolysis of these polymers was accomplished to obtain poly (vinyl amine) (PVAm) in an easy and controlled way. The synthesized poly (vinyl amines) were then employed as stabilizers in the surfactant-free emulsion polymerization of methyl methacrylate (MMA). The MMA monomer polymerizes via two different ways, grafting from polyvinylamine and homopolymerization, leading to a core-shell type particles with polyvinylamine-based shells. The effect of different variables such as initiator type and concentration, the pH of the reaction and the molecular weight of PVAm’s on the conversion, grafting efficiency and morphology of the polymer particles were investigated. Throughout all the work, an extensive characterization of the polymers obtained in each step was performed in order to clarify possible mechanisms involved in this polymerization process. For the characterization of the polymeric particles obtained during this work were used some characterization techniques such as AF4, NMR, DLS, TEM, SEC/GPC and FT-IR.