Various poly(2-hydroxyethyl methacrylate-b-benzyl methacrylate) (PHEMA n –PBzMA m ) and poly(2-hydroxypropyl methacrylate-b-benzyl methacrylate) (PHPMA n –PBzMA m ) nano-objects have been prepared via reversible addition–fragmentation chain transfer (RAFT) alcoholic dispersion polymerization. Using either a PHPMA or PHEMA macro-CTA as a steric stabilizer, chain extension with BzMA was conducted in methanol, ethanol, or isopropanol. In each case, in situ self-assembly is driven by the growing PBzMA chains, which become insoluble in lower alcohols above a certain critical chain length. Empirically, PHPMA macro-CTA proved to be much more effective than PHEMA macro-CTA in such syntheses, since the former conferred higher colloidal stability in alcohol. By constructing two detailed phase diagrams, the final nanoparticle morphology is shown to be sensitive to the DP of the core-forming block (PBzMA), the total solids content, and also the mean DP of the stabilizer block (PHPMA). The latter effect is readily demonstrated for PHPMA macro-CTAs possessing mean DPs of 48 and 63. Using PHPMA48 as a steric stabilizer, a range of nano-objects (spheres, worms or vesicles) can be accessed simply by tuning the DP of the core-forming PBzMA block. In contrast, using the PHPMA63 stabilizer only produces spherical morphologies. Presumably this is because the latter confers more effective steric stabilization, which prevents the efficient fusion of spheres to form worms. Nevertheless the PHPMA63–PBzMA n formulation may still be useful, since it allows access to spherical nanoparticles with tunable mean diameters of 29–100 nm. Such phase diagrams are essential for the reproducible targeting of copolymer morphologies, since they enable mixed phase regions to be avoided and allow the predictable synthesis of pure spheres, worms, or vesicles at a given concentration. Finally, a block copolymer “jellyfish” was observed during these PISA syntheses, which suggests that such intermediates are most likely a generic feature of the in situ conversion of worms into vesicles.

The absorption characteristics of a large set of thiocarbonyl based chain transfer agents (CTAs) were studied by UV-vis spectroscopy in order to identify appropriate conditions for exploiting their absorbance bands in end-group analysis of polymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerisation. Substitution pattern and solvent polarity were found to affect notably the wavelengths and intensities of the Pi-Pi*- and n-Pi*-transition of the thiocarbonyl bond of dithioester and trithiocarbonate RAFT agents. Therefore, it is advisable to refer in end group analysis to the spectral parameters of low molar mass analogues of the active polymer chain ends, rather than to rely on the specific RAFT agent engaged in the polymerisation. When using appropriate conditions, the quantification of the thiocarbonyl end-groups via the Pi-Pi* band of the thiocarbonyl moiety around 300-310 nm allows a facile, sensitive and surprisingly precise estimation of the number average molar mass of the polymers produced, without the need of particular end group labels. Moreover, when additional methods for absolute molar mass determination can be applied, the quantification of the thiocarbonyl end-groups by UV-spectroscopy provides a good estimate of the degree of active end group for a given polymer sample

A series of zwitterionic model polymers with defined molar masses up to 150,000 Da and defined end groups are prepared from sulfobetaine monomer N,N-dimethyl-N-(3-(methacrylamido)propyl)ammoniopropanesulfonate (SPP). Polymers are synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) using a functional chain transfer agent labeled with a fluorescent probe. Their upper critical solution temperature-type coil-to-globule phase transition in water, deuterated water, and various salt solutions is studied by turbidimetry. Cloud points increase with polyzwitterion concentration and molar mass, being considerably higher in D2O than in H2O. Moreover, cloud points are strongly affected by the amount and nature of added salts. Typically, they increase with increasing salt concentration up to a maximum value, whereas further addition of salt lowers the cloud points again, mostly down to below freezing point. The different salting-in and salting-out effects of the studied anions can be correlated with the Hofmeister series. In physiological sodium chloride solution and in phosphate buffered saline (PBS), the cloud point is suppressed even for high molar mass samples. Accordingly, SPP-polymers behave strongly hydrophilic under most conditions encountered in biomedical applications. However, the direct transfer of results from model studies in D2O, using, e.g. (1)H NMR or neutron scattering techniques, to 'normal' systems in H2O is not obvious.

Singlet oxygen fuels anthracenes and forces an axial rotation of aryl substituents during the oxidation. The molecular switch can be synthesized in only one step from commercially available starting materials. Thermal cleavage of the resulting endoperoxides proceeds quantitatively and affords a simple 180° switch with oxygen as the only waste product. The initial trans state is attained by heating, and repetitive cycles are possible.

Amphiphilic dual brush diblock as well as symmetrical triblock polymers were synthesized by the overlay of the reversible addition-fragmentation chain transfer (RAFT) and the nitroxide mediated polymerization (NMP) techniques. While poly(ethylene glycol) brushes served as hydrophilic block, the hydrophobic block was made of polystyrene brushes. The resulting "giant surfactants" correspond structurally to the established amphiphilic diblock and triblock copolymer known as macrosurfactants. The aggregation behavior of the novel "giant surfactants" in aqueous solution was studied by dynamic light scattering, small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) over a large range in reciprocal space. Further, the self-assembled aggregates were investigated by scanning force microscopy (SFM) after deposition on differently functionalized ultraflat solid substrates. Despite the high fraction of hydrophobic segments, the polymers form stable mesoscopic, spherical aggregates with hydrodynamic diameters in the range of 150-350 nm. Though prepared from well-defined individual polymers, the aggregates show several similarities to hard core latexes. They are stable enough to be deposited without much changes onto surfaces, where they cluster and show spontaneous sorting according to their size within the clusters, with the larger aggregates being in the center.