Unimolecular reverse micelles

Meier MAR, Gohy J-F, Fustin C-A, Schubert US (2004) Combinatorial synthesis of starshaped block copolymers host-guest chemistry of unimolecular reversed micelles. J Am Chem Soc 126 11517-11521... 

Figure 2, General methodfor the synthesis of unimolecular reverse micelles from linear polymer precursors.

Unimolecular Reversed Micelle Based on Hyperbranched Glyco-Conjugated Polymer Core... 

Figure 7.17 Synthesis of unimolecular reversed micelle (23a-f) consisting of a hydrophilic hyperbranched polythreitol core and a hydrophobic trityl shell.

Figure 7.20 shows the plot of the absorbance at the /Imax (562 nm) of RB versus the polymer concentration in chloroform. In general, the encapsulation capacities of the unimolecular micelles are invariable at any polymer concentration. Thus, if these polymers act as unimolecular reversed micelles, the absorbance values are expected to proportionally increase with the polymer concentration. RB/23d with a DS of 23.2% shows a proportional and linear relation between the absorbance value and polymer concentration even at extremely low concentrations, indicating that 23d existed as a unimolecular reversed micelle in chloroform. However, a nonlinear relationship with a deflection point at about 1.2 x 10 molL is obtained for RB/23a with the DS of 15.7%. This result suggested that the RB-encapsulation state of 23a was quite different from that of the unimolecular reversed micelle. 

Figure 7.23 Synthesis of unimolecular reversed micelle (24) consisting of poly L-lactide shell and hyperbranched D-mannan core.

Figure 7.28 Synthesis of unimolecular reversed micelle (25) consisting of hydrophilic hyperbranched D-glucan core and hydrophobic L-leucine ethyl ester shell.

Congo red (CR), are discussed from the viewpoint of the unimolecular reversed micelle property of 25. 

The RB-release property for the RB/25a-c systems in water was examined using UV-Vis spectroscopy. Figure 7.34 shows the RB-release results. In order to clarify the effect of the unimolecular reversed micelle on the RB-release, the permeation of RB (free RB) through a cellulose membrane was carried out in the absence of 25 as the control. In contrast to the fast permeation of the free RB through the cellulose membrane, the release of RB/25 was very slow and no initial release burst was observed. The release rate decreased with the increasing DS value, suggesting that the hydrophobic shells in 25 prevented the diffusion of RB from the hydrophilic core in 25. 

The encapsulation ability of 25 toward water-soluble dyes indicated that 25 was a unimolecular reversed micelle with an encapsulation abihty toward hydrophilic dye molecules. In addition, 25 showed a molecular size-selective encapsulation ability and a pH-sensitive controlled-release property. Hence, 25 was a good candidate for mixture-separation systems and pH-sensitive controlled-release systems. 

Kitajyo, Y, Imai, T., Sakai, Y. et al. (2007b) Encapsulation-release property of amphiphiUc hyperlaanchedD-glucan as a unimolecular reverse micelle. Polymer, 48,1237—1244. 

Sat(, T., Tamald, M., Kitajyo, Y. et al. (2006) Synthesis of unimolecular reversed micelle consisting of a poly(L-lactide) ell and hyperbranched D-mannan core. Journal of Polymer Science, Part A Polymer Chemistry, 44,406-413. 

Sat(, T., Kitajyo, Y., Sakai, R. et al. (2009) Size-selective encapsulation property of unimolecular reverse micelle consisting of hyperbranched D-glucan core andL-leucine ethyl ether shelL Macromolecular Symposia, 279,145—150. 

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