Peculiarities in Atom Transfer Radical Copolymerization

In recent literature it is quite common to treat living radical copolymn. completely analogous to its free radical counterpart. When doing so it is often obsd. that small deviations in the copolymn. behavior occur. In this work the obsd. deviations can be interpreted on the basis of reactions specific for living radical polymn., such as the activation - deactivation equil. in atom transfer radical polymn. Reactivity ratios obtained from atom transfer radical copolymn. data, interpreted according to the conventional terminal model deviate from the true reactivity ratios of the propagating radicals. Furthermore, the copolymn. of monomers that strongly deviate in equil. const. between active and dormant species may exhibit for low molar mass copolymers a significant correlation between molar mass distribution and chem. compn. distribution. The rationale behind this correlation is that the chains that happen to add a relatively large fraction of the more dormant monomer lag behind in their growth. The more dormant monomer refers to the monomer creating a chain end with the lower equil. const. in the activation - deactivation process. This monomer will be preferentially present in the low molar mass fraction of the distribution, whereas the other monomer will be present to a larger extent in the high molar mass fraction

Polymer grafting from CdS quantum dots via AGET ATRP in miniemulsion

We report the synthesis of CdS quantum dot (QD)–poly(acrylate) nanocomposites using a recently developed catalytic system where activators are generated by electron transfer for atom-transfer radical polymerization (ATRP) in a miniemulsion. The QD surface was functionalized with a tris(alkyl)phosphine, previously modified with an ATRP chlorine initiator, and subsequent controlled polymerization was carried out from the functionalized surface of nanoparticles. The final material showed a high homogeneity and the QDs were evenly dispersed. The optical-absorption edge in the visible spectra of the nanocomposites attests the presence of the CdS QDs. Quantum confinement effects were assigned, though a blue shift in relation to the optical spectrum of the initial QDs has been observed