Thermoresponsive Amphiphilic Diblock Copolymers Synthesized by MADIX/RAFT: Properties in Aqueous Solutions and Use for the Preparation and Stabilization of Gold Nanoparticles

Abstract

Well-defined diblock copolymers comprising thermosensitive poly(N-isopropyl acrylamide) (PNIPAM) and poly(n-butylacrylate) (PBA) blocks were synthesized by macromolecular design by interchange of xanthates (MADIX)/reversible addition-fragmentation chain transfer polymerization (RAFT) using a xanthate-type mediating agent. Their behavior in aqueous solution as a function of temperature was studied by scattering and microscopy techniques. The cloud point temperature values were strongly correlated to the hydrophobic content of the copolymers. Moreover, above the cloud point, the block copolymer structure led to the formation of large reversible aggregates with well-defined sizes. Those polymers were then used to study the synthesis and stability of gold nanoparticles (AuNPs) dispersions either by coating preformed AuNPs or by in situ preparation. In this latter case, we showed that the appropriate choice of polymer concentration allows one to control the size of the AuNPs. Furthermore, the AuNPs were embedded within globules of diblock copolymers, this type of architecture providing long-term stability as well as a thermosensitivity to the AuNPs.

Temperature induced phase separation of luminescent silica nanoparticles in Triton X-100 solutions

“…The obtained results contribute to rapidly developing sphere of colloid chemistry, dealing with stimuli responsive aggregation and phase behavior of nanoparticles [23,24,[45][46][47][48][49][50][51][52]. The modification of nanoparticles by the background-supporting colloid fluids provides a simple new concept of a stimuli responsive separation, recovery and redistribution of nanoparticles.…”

“…The covalent modification of mesoporous silica nanoparticles [21] and quantum dots [22] by poly(N-isopropylacrylamide) results in temperature responsive surface properties of these polymer-coated core-shell nanoparticles. The non-covalent modification of gold nanoparticles by thermoresponsive polymers results in reversibly thermosensitive swelling/ shrinking [23] or phase separation [24] behavior. Thus the present work is inspired by the idea to develop stimuli responsive luminescent colloidal systems, exhibiting reversible phase separation and aggregation as an answer on a temperature rise.…”

Living Radical Polymerization by the RAFT Process – A Third Update

“…A* [103,493] (St) [510,511] (BA) [112] (BA) [511] (MA) [511] NIPAm [112] VAc [512] VPv [513] NVC [514] NVP [103,493,515] NVP [513] NVPip [516] NVC [514,515] VAc/VPv [513] (BA-b-St) [511] (MA-b-St) [511] BA-b-NIPAm [112] NVC-b-Ac [514] NVP-b-NVC [515] NVPip-b-VAc [516] NVC-b-NVP [515] NVC-b-VAc [514] (NIPAm/NVPI) [517] (Continued ) [512] (VAc) [512] (230) [512] (230-b-VAc) [512] 231…”

“…Diblock copolymer poly(BA)-b-poly(NIPAm) with xanthate ends and a derived thiol were used to form colloidally stable gold nanoparticles. [112] Thiol terminated methacrylamide polymers were prepared by post RAFT polymerization modification of poly (PFPMA). [226] These were used to form a library of gold nanoparticles.…”

The effect of polymer branching and average molar mass on the formation, stabilization and thermoresponsive properties of gold nanohybrids stabilized by poly(N-isopropylacrylamides)

“…However, even with this approach, for wide distributions, the difference of sensitivity of light scattering between high and low molecular masses leads to an underestimated polydispersity index. 7 Furthermore, these polymers (as well as PAMAM dendrimers) have been observed to trap solvent molecules even after prolonged drying. Thus, the measured molecular weights should be considered only as indicative values.…”