Synthesis of Functional Polymer Particles from Morita-Baylis-Hillman Polymerization.

Functional synthetic polymers are frequently explored for their use in the biomedical field. To fulfill the stringent demands of biodegradability and compatibility, the materials need to be versatile and tunable. Post-modification is often considered challenging for well-known degradable materials like poly(lactic acid) because of their chemical inertness. In this work a procedure is proposed to produce densely functionalized polymer particles using oligomeric precursors synthesized via the Morita-Baylis-Hillman reaction. This allows for a variety of post-modification reactions to serve bio-conjugation or tuning of the material properties. The particles are subjected to basic media and found to be degradable. Furthermore, cytotoxicity tests confirm good biocompatibility. Finally, as a proof of concept to demonstrate the versatility of the particles, post-modification reactions are carried out through the formation of imines.

Organocatalyzed Photo-Atom Transfer Radical Polymerization of Methacrylic Acid in Continuous Flow and Surface Grafting.

The organocatalyzed photo-atom transfer radical polymerization (photoATRP) using 10-phenylphenothiazine as catalyst is studied toward its use in methacrylic acid (MAA) polymerization and surface grafting. The organocatalyzed photoATRP of methyl methacrylate (MMA) is first optimized for continuous flow synthesis in order to assess the livingness of the polymerization. MMA can be polymerized in batch and in flow; however, conversions are limited by the loss of bromine functionality and hence high conversions have to be traded in with increasing dispersities. Also, MAA is polymerized successfully in continuous flow with similar limitations. Flow conditions are transferred to surface grafting from silanized silicon wafers. The presence of ATRP initiators after silanization is confirmed by secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Dense polymethacrylic acid brush films are successfully produced, which is not directly accessible via classical copper-mediated ATRP techniques.

UV-Induced [2+2] Grafting-To Reactions for Polymer Modification of Cellulose.

Benzaldehyde-functional cellulose paper sheets have been synthesized via tosylation of cellulose (Whatman No 5) followed by addition of p-hydroxy benzaldehyde. Via UV-induced Paterno-Büchi [2+2] cycloaddition reactions, these aldehyde functional surfaces are grafted with triallylcyanurate, trimethylolpropane allyl ether, and vinyl chloroacetate. In the following, allyl-functional polymers (poly(butyl acrylate), pBA, Mn = 6990 g mol(-1) , D = 1.12 and poly(N-isopropyl acrylamide), pNIPAAm, Mn = 9500 g mol(-1) , D = 1.16) synthesized via reversible addition fragmentation chain transfer polymerization are conjugated to the celloluse surface in a UV-induced grafting-to approach. With pBA, hydrophobic cellulose sheets are obtained (water contact angle 116°), while grafting of pNIPAAm allows for generation of "smart" surfaces, which are hydrophilic at room temperature, but that become hydrophobic when heated above the characteristic lower critical solution temperature (93° contact angle). The Paterno-Büchi reaction has been shown to be a versatile synthetic tool that also performs well in grafting-to approaches whereby its overall performance seems to be close to that of radical thiol-ene reactions.