Gaëlle Morandi

Synthesis of cellulose nanocrystals bearing photocleavable grafts by ATRP

Cellulose nanocrystals (CNC) were grafted with photocleavable polymeric chains using Atom Transfer Radical Polymerisation (ATRP). The nanoparticle synthesis relies on two main steps: first the grafting of a photosensitive moiety bearing an ATRP initiating site onto the surface of CNC, followed by surface initiated ATRP from the modified surface outwards. An original UV-sensitive linker bearing one ATRP initiating site and one anchoring hydroxyl functionality, which was grafted to the CNC surface using a diisocyanate linker, was designed to achieve this goal. Polystyrene (PS) was then polymerized from the modified CNC, resulting in CNC-g-photolinker-PS nanoparticles. The possibility to degraft the PS chains using UV-irradiation was further investigated, and PS grafts with a narrow polydispersity index (1.08) and molecular weights close to those of formed homopolymers through sacrificial initiator addition were obtained. This is the first example where it has been proven that good control of SI-ATRP from CNC can be achieved. It also confirms that homopolymers initiated by sacrificial initiator in the polymerization medium can be an indication of the grafted polymer brush length. These materials further offer potential as smart delivery vehicles and smart materials.

Synthesis of lipid-b-poly(2-isopropyl-2-oxazoline) and successive study of pH- and thermo-sensitive mixed micelles by combination with lipid-b-poly(acrylic acid)

This paper reports the synthesis of a thermo-sensitive amphiphilic copolymer from linseed oil and its successive engagement in micelles formation. A CROP lipoinitiator was first synthesized in two steps and engaged in the polymerization of 2-isopropyl-2-oxazoline. The physico-chemical behavior of the final lipid-b-poly(2-isopropyl-2-oxazoline) copolymer was studied. This copolymer presents a cloud point temperature of 32 °C at pH = 4.6 (in the presence of 0.1 mol L−1 NaCl) and self-organizes into well-defined micelles (10 nm) with a critical micellar concentration of 10 mg L−1. The combination of this copolymer with a pH-sensitive lipid-b-poly(acrylic acid) then allowed the preparation of mixed micelles, leading to a system sensitive to both pH and temperature modifications.