Um novo mÃtodo para investigar cinÃticas de polimerizaÃÃo baseado em RMN

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Nowadays, research and development of polymer synthesis procedures are part of a technological branch which is quit intensive. This development depends, partially, on the ability of following and understanding the polymerization kinetics of these materials. For instance, mechanic stiffness of a polymer depends on size of its chains. On the other hand, for chain-growth polymerizations, sizes of the chains depend on how the auto-acceleration stage occurs during the polymerization. Thus, the development of techniques and methods which allow one to follow polymerization kinetics is of great interest for science and technology. In this work, it was developed a new method of following polymerization kinetics, essentially based on spin-lattice relaxation time measurements, T1, of hydrogen nuclei. Using a multi-exponential data inversion of the magnetization evolution in inversion-recovery experiments, this method is capable of producing polymeric and monomeric sites concentration values. The method was tested by following polymerization kinetics of two types of polymers as follow. Resapol 10-249, a commercial resin polyester-based, and poli(metyl methacrylate) (PMMA). Besides, experiments were made under various initial concentrations of the reagents. In order to assure the legitimacy of our results obtained by this method, we carried out infrared spectroscopy experiments with PMMA samples prepared as for NMR experiments. One of the advantages of this method is that one may follow the monomer conversion and also formation of the polymer itself. Finally, measurements on MMA suggest that method can be sensitive to the formation of one or more types of polymer, which would be desirable, as it would bring more information to polymerization kinetics of copolymers, for instance

ASSUNTO(S)

resina nmr nmr relaxation polymers ciencias exatas e da terra polÃmeros mma resin relaxaÃÃo rmn cinÃtica de polimerizaÃÃo mma kinetics of polymerization

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