Accession Number : ADA310171
Title : Controlled Radical Polymerization with Dendrimers Containing Stable Radicals.
Descriptive Note : Technical rept.,
Corporate Author : CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF CHEMISTRY
Personal Author(s) : Shigemoto, T. ; Matyjaszewski, K. ; Leduc, M. ; Frechet, J. M.
PDF Url : ADA310171
Report Date : 12 JUN 1996
Pagination or Media Count : 22
Abstract : TEMPO-based stable radicals were attached to dendrimers of variable size and used to control radical polymerization of styrene, vinyl acetate and (meth)acrylates. Thermal polymerization of styrene with (G-2)-TEMPO proceeded in a similar but not better controlled manner than with TEMPO alone. In the polymerization of styrene initiated with BPO, the kinetics and the molecular weigh/conversion relations showed the same tendency as with TEMPO, though the polydispersity was higher than in the absence of dendrimers. This indicates that homolytic cleavage occurs at the reaction temperature, monomer can diffuse inside the cavity of dendrimer, and polymer is at least partially compatible with dendrimer. Model reactions indicate that the higher observed polydispersities could not be ascribed to transfer to benzyl hydrogen atoms. Therefore, the higher polydispersities could originate from the self-initiated polymerization of styrene outside of the dendrimers as well as the slow exchange of these chains with chains attached to dendrimers. To evaluate the effect of self-initiation, vinyl acetate, methyl methacrylate, and n-butyl acrylate were used, however, the resulting polymers were incompatible with the dendrimers. The growing chains are easily released from the cavity of the dendrimers into solution, and their return into the cavities of the dendrimers was not fast enough to control the polymerization. The results of the polymerization in decalin solution indicate that polymerization of these monomers is better controlled but only at the early stages of the polymerizations. The subsequent precipitation of polymers attached to the dendrimers prevent further polymerization.
Descriptors : *CONTROL, *STABILITY, *POLYMERIZATION, *STYRENES, *CHEMICAL RADICALS, THERMAL PROPERTIES, PROPAGATION, REPRINTS, SIZES(DIMENSIONS), MODELS, METHYL RADICALS, POLYMERS, ATOMS, HYDROGEN, PRECIPITATION, CHAINS, SELF OPERATION, METHACRYLATES, BUTYL RADICALS, MACROMOLECULES, MONOMERS, ACRYLATES, DECOMPOSITION, ACETATES, CLEAVAGE, HOMOGENEITY, VINYL PLASTICS, PEROXIDES, PIPERIDINES.
Subject Categories : Polymer Chemistry
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE