Dispersity effects in polymer self-assemblies: a matter of hierarchical control

Polymersomes: Breaking the Glass Ceiling?

Polymer vesicles, also known as polymersomes, have garnered a lot of interest even before the first report of their fabrication in the mid-1990s. These capsules have found applications in areas such as drug delivery, diagnostics and cellular models, and are made via the self-assembly of amphiphilic block copolymers, predominantly with soft, rubbery hydrophobic segments. Comparatively, and despite their remarkable impermeability, glassy polymersomes (GPs) have been less pervasive due to their rigidity, lack of biodegradability and more restricted fabrication strategies. GPs are now becoming more prominent, thanks to their ability to undergo stable shape-change (e.g., into non-spherical morphologies) as a response to a predetermined trigger (e.g., light, solvent). The basics of block copolymer self-assembly with an emphasis on polymersomes and GPs in particular are reviewed here. The principles and advantages of shape transformation of GPs as well as their general usefulness are also discussed, together with some of the challenges and opportunities currently facing this area.

Up in the air: oxygen tolerance in controlled/living radical polymerisation

The requirement for deoxygenation in controlled/living radical polymerisation (CLRP) places significant limitations on its widespread implementation by necessitating the use of large reaction volumes, sealed reaction vessels as well as requiring access to specialised equipment such as a glove box and/or inert gas source. As a result, in recent years there has been intense interest in developing strategies for overcoming the effects of oxygen inhibition in CLRP and therefore remove the necessity for deoxygenation. In this review, we highlight several strategies for achieving oxygen tolerant CLRP including: "polymerising through" oxygen, enzyme mediated deoxygenation and the continuous regeneration of a redox-active catalyst. In order to provide further clarity to the field, we also establish some basic parameters for evaluating the degree of "oxygen tolerance" that can be achieved using a given oxygen scrubbing strategy. Finally, we propose some applications that could most benefit from the implementation of oxygen tolerant CLRP and provide a perspective on the future direction of this field.

Inline Coupling of Electrokinetic Preconcentration Method to Taylor Dispersion Analysis for Size-Based Characterization of Low-UV-Absorbing Nanoparticles

The inline coupling of the field-amplified sample injection (FASI) to Taylor dispersion analysis (TDA) was used to characterize low-UV absorbing carboxylated silica nanoparticles (cNPs). The hydrodynamic diameters (D_h) were measured by using a commercial capillary electrophoresis instrument. The proposed methodology did not require any complicated instruments or chromophoric dye to increase the detection sensitivity. A practical method based on a half-Gaussian fitting was proposed for the data processing. The results obtained by this method were compared with those derived from dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. From these results, it appeared that the size derived by TDA is in excellent agreement with those measured by DLS and TEM, as demonstrated by stable nanoparticles with narrow size distributions. Intermediate precision relative standard deviations less than 5% were obtained by FASI-TDA. The effect of the FASI-induced cNP peak dispersion on the reliability of the results was discussed in detail.

Palladium-polymer nanoreactors for the aqueous asymmetric synthesis of therapeutic flavonoids

Polymeric core–shell micelles incorporating a chiral palladium pyridinooxazoline catalyst are presented as nanoreactors for the aqueous asymmetric synthesis of flavanones, a class of flavonoids, with therapeutic properties.

The downside of dispersity: why the standard deviation is a better measure of dispersion in precision polymerization

Dispersity gives a deceptively rosy picture of the extent of dispersion in molecular weight distributions. For complex structures or relatively narrow molecular weight distributions, the standard deviation of the number distribution is a better choice.