Thermoresponsive polymer coated gold nanoparticles: from MADIX/RAFT copolymerization of N-vinylpyrrolidone and N-vinylcaprolactam to salt and temperature induced nanoparticle aggregation

Abstract

In the present contribution, we report the MADIX/RAFT polymerization for the synthesis of thermoresponsive homo and statistical copolymers of N-vinylcaprolactam (NVCL) and N-vinylpyrrolidone (NVP). The conditions for the polymerization of NVP were optimized using an automated parallel synthesizer and these optimal conditions were applied for preparing copolymers with systematical variation in composition. The cloud point temperatures (T-CP's) of aqueous solutions of PNVCL and P(NVCL-stat-NVP)'s (CP1-CP5) were found to be tuneable between 40 degrees C and >95 degrees C at 5 mg mL(-1). Next, stable colloidal solutions of AuNPs coated with PNVCL and CP1-CP5 were obtained via an exchange reaction of pre-synthesized citrate stabilized AuNPs with PNVCL and CP1-CP5 by a direct 'grafting to' approach. The maximum absorbance wavelength (lambda(max)) of the surface plasmon resonance (SPR) band and size of all the thermoresponsive polymer coated AuNPs were found to be almost unchanged up to 65 degrees C (above the T-CP of PNVCL and CP5) in MilliQ water which is presumably due to electrostatic stabilization of the AuNPs by residual citrate groups on the surface. However, in 0.1 M NaCl aqueous solution the lambda(max) of the thermoresponsive AuNPs were red shifted when heated up to 65 degrees C which is attributed to the screening of the citrate negative charges on the surface of AuNPs that suppress electrostatic stabilization enabling T-induced aggregation leading to a shift in the SPR band. These thermoresponsive AuNPs may find applications as colorimetric temperature and/or salt sensors

Cellular Uptake of Gold Nanoparticles and Their Movement in 3D Multicellular Tumor Spheroids: Effect of Molecular Weight and Grafting Density of Poly(2‐hydroxyl ethyl acrylate)

“…These polymers can be conveniently sourced using RAFT polymerization after removal of the endgroup 26d,27. Alternatively, polymers obtained by RAFT polymerization can be directly used to coat GNPs as the thiocarbonylthio functionality can bind strongly to the gold surface . Inspired by the simplicity of the latter method, pHEA was incubated under stirring with the prepared gold nanoparticles at room temperature overnight.…”

RAFT Copolymerization of Vinyl Acetate and N-Vinylcaprolactam: Kinetics, Control, Copolymer Composition, and Thermoresponsive Self-Assembly

“…5,14 In the recent years, improvements in RAFT/MADIX polymerization, 9,[28][29][30][31][32][33][34] OMRP, 13,[35][36][37] RITP 38 and ATRP, 39,40 offered opportunities to control the polymerization of the so-called less activated monomers (LAM) such as vinyl acetate, Nvinylcaprolactam (VCL) or N-vinylpyrrolidone (VP). RAFT/MADIX polymerization afforded the possibility to synthesize various LAM-based copolymers such as block copolymers (PVAcb-PVCL, 30 , PVCL-b-PVP 41 ) or statistical copolymers (P(VP-stat-VCL) 12,42 ). Among controlling the molar mass and dispersity via RDRP, copolymerization kinetics and associated effect on copolymer composition assist in the design of statistical copolymers with suitable performances.…”

A star-shaped amphiphilic block copolymer with dual responses: synthesis, crystallization, self-assembly, redox and LCST–UCST thermoresponsive transition

“…37 Chen and Li et al prepared covalent dynamic poly(triazole) gels containing both acylhydrazone and disufide bonds by crosslinking of benzohydrazide-containing poly(triazole) with disulfide-containing dialdehyde in DMF at ambient temperature. [40][41][42][43][44][45][46][47][48][49][50] The majority of these smart materials are based on the lower critical solution temperature (LCST) of the polymer, i.e. 39 Moreover, temperature-responsive amphiphilic polymers have been one of the greatest research focuses in recent years as temperature signal can be operated easily in vivo and a large amount of promising biomaterials can be used for hyperthermia-induced drug delivery, smart bioactive surface, protein chromatography and tissue engineering.…”