Nano-sized metal particles are attracting much interest in industrial and biomedical applications due to the recent progress and development of nanotechnology, and the surface-modifications by appropriate polymers are key techniques to stably express their characteristics. Herein, we applied cyclic poly(ethylene glycol) (c-PEG), having no chemical inhomogeneity, to provide a polymer topology-dependent stabilization for the surface-modification of gold nanoparticles (AuNPs) through physisorption. By simply mixing c-PEG, but not linear counterparts, enables AuNPs to maintain dispersibility through freezing, lyophilization, or heating. Surprisingly, c-PEG endowed AuNPs with even better dispersion stability than thiolated PEG (HS–PEG–OMe). The stronger affinity of c-PEG was confirmed by DLS, ζ-potential, and FT-IR. Furthermore, the c-PEG system exhibited prolonged blood circulation and enhanced tumor accumulation in mice. Our data suggests that c-PEG induces physisorption on AuNPs, supplying sufficient stability toward bio-medical applications, and would be an alternative approach to the gold–sulfur chemisorption.

The AB 2 -and AB 3 -type miktoarm star copolymers consisting of maltoheptaose (MH, as A block) and poly(ε-caprolactone) (PCL, as B block), namely MH-b-(PCL) 2 and MH-b-(PCL) 3 , were synthesized, and their nano-organization was characterized. The syntheses of MHb-(PCL) 2 and MH-b-(PCL) 3 were carried out through two reaction steps: (1) preparation of linear and three-branched PCLs bearing an azido group on the chain center (N 3 -(PCL) 2 and N 3 -(PCL) 3 ) by the diphenyl phosphate-catalyzed ringopening polymerization of ε-caprolactone (ε-CL) using azidofunctionalized di-and triols (N 3 -(OH) 2 and N 3 -(OH) 3 ) as the initiators and (2) the copper-catalyzed azide−alkyne cycloaddition of N 3 -(PCL) 2 and N 3 -(PCL) 3 with the ethynyl-functionalized MH. The miktoarm star copolymers having M n for the PCL block of ca. 5000 (MH-b-(PCL 2.5k ) 2 and MH-b-(PCL 1.7k ) 3 ) and 10 000 (MH-b-(PCL 5k ) 2 and MH-b-(PCL 3.3k) 3 ) were obtained with a very narrow polydispersity index of less than 1.05. Bulk samples of the four types of miktoarm star copolymers exhibited body-centered cubic phases, as determined by small-angle X-ray diffraction experiments. The domain-spacing were determined to be 9.8 nm for MH-b-(PCL 2.5k ) 2 , 8.8 nm for MH-b-(PCL 1.7k ) 3 , 10.5 nm for MH-b-(PCL 5k ) 2 , and 9.8 nm for MH-b-(PCL 3.3k ) 3 , which were smaller than those of the corresponding linear diblock copolymers.

This paper describes the synthesis of systematic sets of figure-eightand tadpole-shaped amphiphilic block copolyethers (BCPs) consisting of poly(decyl glycidyl ether) and poly[2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether], together with the corresponding cyclic counterparts, via combination of the t-Bu-P 4 -catalyzed ring-opening polymerization (ROP) and click cyclization. The clickable linear BCP precursors, with precisely controlled azido and ethynyl group placements as well as a fixed molecular weight and monomer composition (degree of polymerization for each block was adjusted to be around 50), were prepared by the t-Bu-P 4catalyzed ROP with the aid of functional initiators and terminators. The click cyclization of the precursors under highly diluted conditions produced a series of cyclic, figure-eight-, and tadpole-shaped BCPs with narrow molecular weight distributions of less than 1.06. Preliminary studies of the BCPs self-assembly in water revealed the significant variation in their cloud points depending on the BCP architecture, though there were small architectural effects on their critical micelle concentration and morphology of the aggregates.

We report the synthesis, morphology, and properties of poly­(3-hexylthiophene)-block-poly­(butyl acrylate) (P3HT-b-PBA) for stretchable electronics applications, which are consisted of semiconducting P3HT and low glass transistion temperature (T g) PBA blocks. The P3HT-b-PBA thin films self-assembled into fibrillar-like nanostructures and maintained the edge-on oreientation even at a low P3HT composition, based on the results from atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). By varying the P3HT/PBA ratio, the tensile modulus decreased as the block length of PBA increased, from 0.93 GPa for P3HT to 0.19 GPa for P3HT-b-PBA12k. The field effect transistor (FET) using P3HT-b-PBA as the active layer exhibited a high p-type mobility over 10–2 cm2 V–1 s–1, indicating its good charge transporting ability. Furthermore, the P3HT-b-PBA6k based FET under 100% strain had a high mobility of 2.5 × 10–2 cm2 V–1 s–1 with an on/off ratio of 7.2 × 106, and it maintained over 10–2 cm2 V–1 s–1 for 1000 cycles, suggesting the promising stability and reproducbility. The result demonstrated that the newly designed conjugated rod–coil block copolymers could have potential applications in stretchable electronic devices.

To date, the feature size of microphase separation in block copolymers has been downsizing to 10 nm scale. However, morphological control for such a small feature is still a challenging task. The present Letter discusses a phase transition in a natural/synthetic “hybrid” block copolymer system based on an oligosaccharide and poly(ε-caprolactone) via thermal annealing. Time-resolved small-angle X-ray scattering investigation as a function of temperature indicated the phase transition from hexagonally close-packed cylinder to body-centered cubic at 10 nm scale. Atomic force microscope images of the block copolymer thin films annealed at different temperatures clearly confirmed the existence of these morphologies. The driving force of this phase transition (from cylinder to cubic) is the change of volume fraction of the block copolymer due to thermal caramelization.