RESUMO
The density of the side chain introduced to a polymer main chain greatly influences the properties and functions of the polymer. This work first reports on the packing structure and properties at an interface of a poly(substituted methylene) where an azobenzene side chain is introduced at every carbon atom in the main chain (C1PAz). The structure and properties are compared with those of a conventional vinyl polymer [poly(methacrylate)] possessing an identical side-chain structure (C2PAz). The packing structure in the bulk state analyzed by X-ray measurements revealed that C1PAz adopts a highly ordered rectangular unit cell structure, whereas C2PAz shows a less ordered lamellar one. Langmuir film balance experiments indicated that both polymers with the trans-azobenzene give essentially the identical 2D side-chain occupying area on water, which agrees well with the smectic B (hexatic packing) model based on the X-ray data. Upon transfer onto a solid substrate, only C1PAz shows a conformational transformation to a spread bilayer-type layer, most probably due to conformational frustration stemming from the crowding of the side chains. This study proposes new insights into the effects of side-chain density on the self-assembly and photoreaction of azobenzene-containing polymers, which are expected to expand the possibilities of polymer design for various applications.
RESUMO
The original synthetic strategy for a new type of poly(arylene vinylene) (PAV) is presented, where the C=C-bond-forming coupling of bis(alkoxycarbonyldiazomethyl)aromatic compounds is utilized as propagation. The strategy is unique in that the resulting PAVs have an alkoxycarbonyl group as an electron-withdrawing substituent on each vinylene carbon atom in the polymer main chain. Among the transition-metal catalysts examined in this study, RuCl(cod)Cp* (cod = 1,5-cyclooctadiene, Cp* = pentamethylcyclopentadienyl) is the most efficient, affording PAVs from a series of bis(alkoxycarbonyldiazomethyl)aromatic compounds with a high trans-C=C-forming selectivity of up to 90%. A PAV sample with a fluorenylene framework as an arylene moiety prepared by the Ru catalyst exhibited a hole mobility of 4 × 10-6 cm2 V-1 s-1.
RESUMO
The cyclotriphosphazene-substituted diazoacetate homopolymer (polyPNDA') (PNDA' = hexaphenoxy-substituted phosphazene-containing methylene) and a novel poly(substituted methylene) block copolymer, polyPNDA'-block-poly(hexyloxycarbonylmethylene) (polyPNDA'-b-polyHDA'), were synthesized, and the self-assembly behavior of these polymers was studied in detail. A hexagonally packed aggregated structure was observed in the self-assembled structure of polyPNDA', whereas a lamellar structure was observed in the microphase-separated nanoassembly of polyPNDA'-b-polyHDA'. These results indicate that a hierarchical structure composed of highly regular polyPNDA' nanoaggregates and the long-range microphase-separated polyPNDA' and polyHDA' domains had formed.
RESUMO
For development of tumor-specific chemotherapy, we designed liposomes with temperature-triggered drug release and magnetic resonance imaging (MRI) functions. We prepared multi-functional liposomes by incorporating thermosensitive poly(2-ethoxy(ethoxyethyl)vinyl ether) chains with a lower critical solution temperatures around 40 °C and polyamidoamine G3 dendron-based lipids having Gd(3+) chelate residues into pegylated liposomes. These stable doxorubicin (DOX)-loaded liposomes retained DOX in their interior below physiological temperature but released DOX immediately at temperatures greater than 40 °C. They exhibited excellent ability to shorten the longitudinal proton relaxation time. When administered intravenously into colon 26 tumor-bearing mice, accumulated liposomes in tumors increased with time, reaching a constant level 8 h after administration by following T(1)-weighted MRI signal intensity in tumors. Liposome size affected the liposome accumulation efficiency in tumors: liposomes of about 100 nm diameter were accumulated more efficiently than those with about 50 nm diameter. Tumor size also affected accumulation: more efficient accumulation occurred in larger tumors. Tumor growth was strongly suppressed when liposomes loaded with DOX were administered intravenously into tumor-bearing mice and the tumor was heated mildly at 44 °C for 10 min at 8 h after administration. Multi-functional liposomes having temperature-triggered drug release and MRI functions might engender personalized chemotherapy, providing efficient patient-optimized chemotherapy.
