Mieke Lammens

Polymeric ligands as homogeneous, reusable catalyst systems for copper assisted click chemistry

Tris-(benzyltriazolylmethyl)amine (TBTA) has been immobilized onto a styrenic monomer and subsequently copolymerized with styrene to afford catalytically active and reusable copolymers for the CuAAC reaction.

Design and Use of Organic Nanoparticles Prepared from Star-Shaped Polymers with Reactive End Groups

Star-shaped poly(isobornyl acrylate) (PiBA) was prepared by atom transfer radical polymerization (ATRP) using multifunctional initiators. The optimal ATRP conditions were determined to minimize star-star coupling and to preserve high end group functionality (>90%). Star-shaped PiBA with a narrow polydispersity index was synthesized with 4, 6, and 12 arms and of varying molecular weight (10,000 to 100,000 g x mol(-1)) using 4 equiv of a Cu(I)Br/PMDETA catalyst system in acetone. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis, NMR spectroscopy, and size exclusion chromatography (SEC) confirmed their controlled synthesis. The bromine end group of each arm was then transformed to a reactive end group by a nucleophilic substitution with methacrylic acid or cinnamic acid (conversion >90%). These reactive star polymers were used to prepare PiBA nanoparticles by intramolecular polymerization of the end groups. The successful preparation of this new type of organic nanoparticles on a multigram scale was proven by NMR spectroscopy and SEC. Subsequently, they have been used as additives for linear, rubbery poly(n-butyl acrylate). Rheology measurements indicated that the viscoelastic properties of the resulting materials can be fine-tuned by changing the amount of incorporated nanoparticles (1-20 wt %), as a result of the entanglements between the nanoparticles and the linear polymers.

Star-shaped polyacrylates: Highly functionalized architectures via CuAAC click conjugation

Well-defined functional star-shaped polymer structures with up to 29 arms have been successfully synthesized by the combination of atom transfer radical polymerization (ATRP) and click chemistry. First, azide end-functionalized poly(isobornyl acrylate) (PiBA) star-shaped polymers were prepared by successive ATRP and bromine substitution. Subsequently, alkyne end-functionalized molecules and polymers were introduced onto the star-shaped PiBA bearing pendant azide moieties by copper-catalyzed azide-alkyne cycloaddition (CuAAC). The possibilities and limits for the CuAAC on such highly branched polyacrylates are described.

From Novel Block-Like Copolymers to Reactive Nanoparticles: ATRP and “Click” Chemistry as Synthetic Tools

In this chapter, we report on the synthesis and characterization of well-defined amphiphilic block copolymers, ‘block-like’ copolymers and star copolymers composed of poly(isobornyl acrylate) (PiBA) and poly(acrylic acid) (PAA) by ATRP. As PiBA polymers exhibit interesting physical characteristics, we report first a detailed study of the homopolymerization of iBA. The precursor monomers 1-ethoxyethyl acrylate as well as tert-butyl acrylate have been used to synthesize the precursor polymers for the PiBA-co-PAA block copolymers. Furthermore, a combination of ATRP and ‘click’ chemistry was used to prepare block and graft copolymers using a modular approach. The PiBA-PAA block and ‘block-like’ copolymers were investigated as pigment stabilizers for aqueous pigment dispersions. In the second part of the research, well-defined PiBA star copolymers were prepared, and reactive nanoparticles were obtained by end group modification of the PiBA star polymers with reactive moieties. Finally, the control of the visco-elastic properties by the incorporation of these nanoparticles in an acrylate polymer matrix was investigated.