Comparison of RAFT derived poly(vinylpyrolidone) verses Poly(oligoethyleneglycol methacrylate) for the stabilization of glycosylated gold nanoparticles

Carbohydrates dictate many biological processes including infection by pathogens. Glycosylated polymers and nanomaterials which have increased affinity due to the cluster glycoside effect, are therefore useful tools to probe function, but also as prophylactic therapies or diagnostic tools. Here, the effect of polymer structure on the coating of gold nanoparticles is studied in the context of grafting density, buffer stability and in a lectin binding assay. RAFT polymerization is used to generate poly(oligoethyleneglycol methacrylates) and poly(N-vinyl pyrolidones) with a thiol end-group for subsequent immobilization onto the gold. It is observed that poly(oligoethylene glycol methacrylates), despite being widely used particle coatings, lead to low grafting densities which in turn resulted in lower stability in biological buffers. A depression of the cloud point upon nanoparticle immobilization is also seen, which might compromise performance. In comparison poly(vinyl pyrolidones) resulted in stable particles with higher grafting densities due to the compact size of each monomer unit. The higher grafting density also enabled an increase in the number of carbohydrates which can be installed per nanoparticle at the chain ends, and gave increased binding in a lectin recognition assay. These results will guide the development of new nanoparticle biosensors with enhanced specificity, affinity and stabilit

Unlocking the potential of poly(ortho ester)s : a general catalytic approach to the synthesis of surface erodible materials

Poly(ortho ester)s, POEs, are well established as displaying surface eroding properties and hence present unique opportunities for controlled release and tissue engineering applications. Their development and wide spread investigation has however been severely limited by challenging synthetic requirements via unstable intermediates and is therefore highly irreproducible. Herein, we present the first catalytic method for the synthesis of POEs using air and moisture stable vinyl acetal precursors. The synthesis of a range of POE structures is demonstrated including those that are extremely hard to achieve by other synthetic methodologies. Furthermore, we demonstrate that the application of this chemistry to efficiently install functional groups via ortho ester linkages to an aliphatic polycarbonate

Crystal growth inhibition of tetrahydrofuran hydrate with poly(N-vinyl piperidone) and other poly(N-vinyl lactam) homopolymers

Poly(N-vinyl pyrrolidone) (PVP) containing the 5-ring lactam and poly(N-vinyl caprolactam) (PVCap) containing the 7-ring lactam are well-known kinetic hydrate inhibitors (KHIs). For the first time we have synthesised and studied the performance of poly(N-vinyl piperidone) (PVPip), containing the 6-ring lactam, as a kinetic hydrate inhibitor. In the first part of the study we have investigated the ability of PVPip to inhibit the growth of tetrahydrofuran SII hydrate crystals. The results are compared to those of PVP and PVCap. Various polymer molecular weights have been investigated at varying subcoolings. PVPip shows an intermediate growth inhibition performance compared to PVP and PVCap at similar polymer molecular weights. In addition, the weight percentage concentration of polymer needed to achieve complete THF hydrate crystal growth inhibition increases as the polymer molecular weight decreases

Stereocomplexation in novel degradable amphiphilic block copolymer micelles of poly(ethylene oxide) and poly(benzyl α-malate)

The ring-opening polymerization of 5-(S)-[(benzyloxycarbonyl) methyl]-1,3-dioxolane-2,4-dione (L-malOCA) and 5-(R)-[(benzyloxycarbonyl) methyl]-1,3-dioxolane-2,4-dione (D-malOCA) from poly (ethylene oxide), PEO, macroinitiators using 4-methoxypyridine as the catalyst is reported. The self-assembly of these polymeric amphiphiles was shown to proceed most efficiently by a solvent switch methodology from THF to nanopure H(2)O. Variation of the block lengths revealed that, as expected, larger block copolymers led to increased micelle dimensions as determined by dynamic light scattering (DLS) and transmission electron microscopy (TEM) and longer hydrophobic blocks led to increased micelle stabilities as determined by measurement of the critical micelle concentration (CMC). Furthermore, the self-assembly of equimolar mixtures of PEO-b-P(L-BMA) and PEO-b-P(D-BMA) resulted in micelles of increased sizes by both DLS and TEM analysis. These micelles also have a CMC value of 5.53 x 10(-3) g L(-1) which is markedly lower than micelles formed from either enantiopure block copolymer (CMC values 1.23 x 10(-2) g L(-1) and 9.78 x 10(-3) g L(-1) for micelles formed from PEO-b-P (L-BMA) and PEO-b-P(D-BMA) respectively)

The critical importance of size on thermoresponsive nanoparticle transition temperatures : gold and micelle-based polymer nanoparticles

The synthesis and application of thermally-responsive macromolecules and nanoparticles relies on the underpinning control of their transition temperatures. The present study shows that two structurally diverse classes of nanoparticle have very strong diameter-dependent responses to temperature-stimuli, demonstrating that the exact size of the nanostructure can significantly impact its performance

The missing lactam-thermoresponsive and biocompatible poly(N-vinylpiperidone) polymers by xanthate-mediated RAFT polymerization

A new polymer poly(N-vinylpiperidone) (PVPip) (2x, MnNMR 4.5−83 kDa) has been prepared by reversible addition−fragmentation chain-transfer (RAFT) polymerization using a xanthate as a chain-transfer agent. These polymers all exhibited sharp reversible cloud points (in the range 87 and 68 °C) which depended on the molecular weight of the polymer and showed no apparent hysteresis. Furthermore, cytotoxicity studies of the PVPip showed that the polymer is noncytotoxic. Chain extension of PVPip62 with vinyl acetate afforded well-defined amphiphilic diblock copolymers: poly(N-vinylpiperidone)x-block-poly(vinyl acetate)y (PVPipx-b-PVAcy) (for 3, x:y = 62:21; for 4, x:y = 62:32). Both 3 and 4 exhibit phase transitions of 62 and 55 °C, respectively, in water, with the latter showing evidence of a slight hysteresis. Direct dissolution of 3 in nanopure water at 1 mg/mL gave spherical micelles (ca. 24 nm), as confirmed by DLS, TEM, and AFM analysis, which could be reversibly disassembled upon heating above the cloud point of the diblock. The block copolymer 4 was hydrolyzed under basic conditions to give the double hydrophilic biocompatible diblock copolymer poly(N-vinylpiperidone)62-block-poly(vinyl alcohol)32 (5)

Polymers with molecular weight dependent LCSTs are essential for cooperative behaviour

The potential to fine-tune the transition temperatures of polymers displaying lower-critical solution temperatures (LCST) by a simple mixing strategy is investigated. Using a panel of four distinct polymer classes (poly[oligo(ethyleneglycol)methacrylate], poly(N-vinylpiperidone), poly(N-vinylcaprolactam) poly(N-isopropylacrylamide)) it was shown that only those with strong molecular weight dependent LCSTs produced a single, cooperative, transition when blended together. Furthermore, the actual transition temperature was linked to the weight average not the number average molecular weight. The only polymer which did not show strong molecular-weight-LCST correlation was poly(oligo(ethyleneglycol)methacrylate), which showed two independent transitions, one for each polymer

Functional Degradable Polymers by Xanthate-Mediated Polymerization

Herein we report the first example of the controlled synthesis of linear and hyperbranched copolymers of 2-methylene-1,3-dioxepane (MDO) with functional vinyl monomers to deliver a range of functional, degradable polymers by reversible deactivation radical polymerization. The copolymerization was able to be tuned to vary the incorporation of degradable segments to create degradable materials with predictable molar mass, low dispersity values while also featuring side-chain functionality. The formation of nanoparticles by the addition of divinyladipate to form degradable hyperbranched copolymers was proven by DLS and TEM analyses

Functional Degradable Polymers by Xanthate-Mediated Polymerization

Herein we report the first example of the controlled synthesis of linear and hyperbranched copolymers of 2-methylene-1,3-dioxepane (MDO) with functional vinyl monomers to deliver a range of functional, degradable polymers by reversible deactivation radical polymerization. The copolymerization was able to be tuned to vary the incorporation of degradable segments to create degradable materials with predictable molar mass, low dispersity values while also featuring side-chain functionality. The formation of nanoparticles by the addition of divinyladipate to form degradable hyperbranched copolymers was proven by DLS and TEM analyses