More insight into tandem ROMP and ADMET polymerization for yielding reactive long-chain highly branched polymers and their transformation to functional polymer nanoparticles

Abstract

Tandem chain transfer ring-opening metathesis polymerization (ROMP-CT) and acyclic diene metathesis (ADMET) polymerization were carried out in a controlled one-pot procedure, and behaved noticeable differences in polymerization of monomers by different ruthenium catalysts, whereas there indeed had been two distinctly polymerization stages. In the first one, ROMP-CT of functional monomers was conducted in the presence of a symmetrical multi-olefin as chain transfer agent within various reaction time scales, yielding linear telechelic polymers. Next, ADMET polymerization of telechelic polymers was performed and generated a series of reactive long-chain highly branched polymers (LCHBPs) with acrylate and/or azobenzene groups having molecular weights of 8.5–47.9 kDa under varied conditions. LCHBPs were fully characterized by several techniques, and interestingly, UV–vis analysis displayed the specific peak at 278 nm, which offered a new evidence for the existence of internal acrylate structure on the LCHBP backbone, and supported the highly branched architecture of polymers. LCHBP containing a number of pendent acrylate groups was readily converted, by thiol-Michael addition click reaction, to novel thiol-functionalized intra-molecular crosslinked unimolecular polymer nanoparticles with diameter of 40–60 nm, which provided a facile method for post-functionalization of branched polymers.