ABSTRACT:Hyperbranched polythreitol (1) with different molecular weights (M w,SLS ; 1.18 x 10 4 and 4.79 x 10 4 ) was reacted with trityl chloride in DMF to afford a novel amphiphilic polymer (2) consisting of 1 as the hydrophilic core and the trityl groups as the hydrophobic shell. 2 was tested for its ability to act as a unimolecular nanocapsule toward the water-soluble dye, rose bengal (RB). Their encapsulation and 1 release properties were also evaluated by comparison with the degree of substitution (DS) of the trityl groups, i.e., the hydrophobic shell-density. The polymers were found to have very good unimolecular nanocapsule characteristics even at extremely low concentrations. The average number of RBs per polymer molecule depended on the hydrophilic core size and the hydrophobic shell-density. The increasing DS value led to a decrease in the encapsulated amount due to the decrease in the hydrophilic core space, while the low DS value (< ca. 20 mol-%) led to a destabilization as a unimolecular nanocapsule and a lower encapsulation ability. In particular, 2 with an ca. 23% DS value showed an efficient encapsulation. Based on a release test of the RB-loaded unimolecular nanocapsules, the polymers showed a high RB-holding ability in water.

A novel biodegradable unimolecular reversed micelle consisting of a poly(L‐lactide) (PLA) shell and a hyperbranched D‐mannan (HBM) core, that is, a chestnut‐shaped polymer (PLA–HBM), was synthesized by the polymerization of L‐lactide on HBM with 4‐(dimethylamino)pyridine (DMAP) as the catalyst. The obtained polymers were soluble in dimethyl sulfoxide, tetrahydrofuran, and chloroform but insoluble in H2O. The molecular weights of the PLA chain on PLA–HBM tended to increase with increasing polymerization time. The number of PLA chains on PLA–HBM could be controlled by the ratio of DMAP to the sugar unit in HBM. The obtained copolymer, PLA–HBM, acted as a unimolecular reversed micelle with an encapsulation ability toward the hydrophilic molecule. In addition, the entrapped hydrophilic molecules were slowly released from the core of PLA–HBM, and the release rate was accelerated by the breaking of the PLA chains of the shell when proteinase K as a hydrolase of PLA was used. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 406–413, 2006

ABSTRACT:The synthesis of a novel unimolecular reverse micelle, the hyperbranched D-glucan carbamate (3), was accomplished through the carbamation reaction of the hyperbranched D-glucan (1) with the Ncarbonyl L-leucine ethyl ester (2) in pyridine at 100 ºC. Polymer 3 was soluble in a large variety of organic solvents, such as methanol, acetone, chloroform, and ethyl acetate, and insoluble in water, which remarkably differed from the solubility of 1. The degree of carbamate substitution (DS) for 3 was controlled by the feed rate of 2, and the DS values were in the range of 46.0 to 93.7 %. 3 possessed the encapsulation ability for water-soluble molecules, such as rose bengal, thymol blue, and alizarin yellow in chloroform, and the encapsulation ability depended on the hydrophilicity of 3 and the molecular size of the dye. The rose bengal (RB) encapsulated polymer (RB/3) showed a slow release from the RB/3 system 1 into water at neutral pH, while the release rate was significantly accelerated by the hydrolysis of the hydrophobic polymer shell under basic conditions.

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A hyperbranched polyglycerol bearing imidazolium tosylate units (ITHB) was synthesized through the imidazolium salt-modification of hyperbranched polyglycerol (HB). ITHB was found to possess novel reversible lower critical solution temperature (LCST)-type liquid-liquid and liquid-solid phase transition behaviors in a methanol/chloroform mixed solution. The phase transition temperatures of the liquid-liquid phase transition (PTT 1to2 ) and liquid-solid phase transition (PTT 2toSus ) increased with increasing the ratio of methanol in the mixed solution and decreasing the concentration of ITHB. Additionally, increasing the molecular weight of ITHB decreased the PTT values. The liquid-liquid phase transition was caused by the aggregation of ITHB, which was proved by dynamic light scattering measurement. In contrast, the liquid-solid phase transition was caused by the solvation cleavage between the imidazolium rings and solvents, which was proved by 1 H NMR measurement. V V C 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: [7032][7033][7034][7035][7036][7037][7038][7039][7040][7041][7042] 2009