The assembly behavior of diblock copolymers in solution can be modulated by block length, block ratio, solvent properties, and preparation route. Different assembly morphologies such as spherical micelles, cylindrical micelles, vesicles, and large compound vesicles have been obtained for diblock copolymers with shorter solvated block, such as poly(acrylic acid)-b-polystyrene (PAA-b-PSt). In the present work, we reported an easy-going route to prepare PAA-b-PSt assemblies with different morphologies through reversible addition−fragmentation-transfer (RAFT) dispersion polymerization of styrene in methanol with trithiocarbonated PAA as macromolecular chain transfer agent. Because this RAFT dispersion polymerization exhibited controlled features, the consecutive growth of PSt block led to the successive transition of the obtained PAA-b-PSt assemblies from spherical micelles, cylindrical micelles, vesicles, to large compound vesicles, confirmed by the combination of electron microscopy, laser light scattering, and chemical structural analysis. PAA-b-PSt assembly morphologies and their transition have been adjusted by polymerization conversion, St/PAA feed ratio, and methanol amount, which were elucidated in view of thermodynamic consideration. The mechanisms for the formation of vesicle and the reorganization of vesicles were suggested. This polymerization-induced self-assembly and self-organization provides an efficient way to prepare different nano/microsized polymeric structures.

Vesicular nanostructural materials have displayed potential applications in various fields such as in catalysis, biomedical, cosmetic, and food industries. 1 So their preparation attracted much attention in the past decade, and the conventional strategy for preparation of the vesicles is self-assembling of amphiphilic block copolymers in a selective solvent, which is performed by slowly adding a precipitant of hydrophobic chains into a polymer solution for inducing their aggregation. 2 Essentially the variable in this process is the solvent parameter (δ) because the polymers used have fixed molecular weight and fixed chain length ratio of hydrophobic to hydrophilic blocks. But this strategy is difficult to control, is time-consuming, and involves multiple steps. 3 Thus, great efforts have been paid to study the direct chemical preparation of various polymeric nanostructures. One approach is controlled radical polymerization in a selective solvent, which is so-called polymerization-induced self-assembling, but only spherical micelles were always produced. 3-5 So, the question is: could these vesicular morphologies, which are formed by self-assembly of the block copolymers in a selective solvent, be prepared via polymerization? In this Communication, we report a facile and feasible approach to prepare vesicular nanomaterials via controlled radical polymerization.In studying the effect of chain length ratio of polystyrene (PS) to poly(acrylic acid) (PAA) on morphologies including spherical micelles, rodlike micelles, and vesicles formed by self-assembling of PS-b-PAA, the polymers with the lowest chain length ratio of PS to PAA produced spherical micelles. 6 In the polymerizationinduced self-assembling, the hydrophobic chains grow to a critical chain length for phase separation, which always met requirement for formation of spherical micelles. So it is understandable that the controlled radical polymerization in a selective solvent formed always spherical micelles. Thus, a key point for preparation of vesicular morphologies is how to transform the spherical micelles into the desired morphologies.Theoretically, morphology is mainly controlled by a force balance involving stretching of the core chains, surface tension between the core and the outside solvent, and repulsion among the corona polymer chains. 7 So, altering the force balance may induce the morphology transition, which can be achieved by greatly increasing the core chain length or appropriate selection of solvent. Our previous results showed that the propagation rate of core chains in the micelles was very slow, but a fast rate was observed in a comparatively good solvent of the core block. 4 This may be due to high mobility of the core chains, and fast diffusion rate of the monomer from outside into the micelles may be another reason. Thus, we designed a polymerization system where the reversible addition-fragmentation transfer (RAFT) polymerization of styrene (St) was performed in methanol using S-1-dodecyl-S-(R,R 0 -dimethyl-R 00 -acetic acid)trithiocar...

Eleven subjects completed a clinical trial to determine the safety/tolerability of freeze-dried black raspberries (BRB) and to measure, in plasma and urine, specific anthocyanins-cyanidin-3-glucoside, cyanidin-3-sambubioside, cyanidin-3-rutinoside, and cyanidin-3-xylosylrutinoside, as well as ellagic acid. Subjects were fed 45 g of freeze-dried BRB daily for 7 days. Blood samples were collected predose on days 1 and 7 and at 10 time points postdose. Urine was collected for 12 hours predose on days 1 and 7 and at three 4-hour intervals postdose. Maximum concentrations of anthocyanins and ellagic acid in plasma occurred at 1 to 2 hours, and maximum quantities in urine appeared from 0 to 4 hours. Overall, less than 1% of these compounds were absorbed and excreted in urine. None of the pharmacokinetic parameters changed significantly between days 1 and 7. In conclusion, 45 g of freeze-dried BRB daily are well tolerated and result in quantifiable anthocyanins and ellagic acid in plasma and urine.

A facile and feasible strategy for the preparation of vesicular morphologies has been developed using reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymerization of styrene has been performed in a selected solvent, methanol, using S-1-dodecyl-S-(α,α'-dimethyl-α″-acetic acid)trithiocarbonate (TC)-terminated poly(4-vinylpyridine) as chain transfer agent and stabilizer. Various morphologies including spherical vesicles, nanotubes, and compound vesicles with different shapes are obtained by changing the feed ratios and reaction conditions. The final nanostructural materials are formed through formation of the block copolymers, self-assembly, and re-organization of the morphology in a one-pot polymerization. The latter two are induced by the propagation of PS blocks. The preparation of nanostructural materials can be performed at a concentration higher than 0.5 g · mL(-1) , thus this method offers a practical approach to prepare nanostructural materials on a large scale.

No abstract