Synthesis and properties of a new class of sugar-carrying amphiphilic block copolymers

本研究采用活性阳离子聚合法合成了一类新型的两亲性含糖嵌段共聚物[CH_2CH（OCH_2CH_2OR）] _m- [CH_2CH（OiBu）] _n-，其中R为D-葡萄糖或D-氨基葡萄糖。为了得到它们，使用HI/Znl_2或TFA/EtAlCl_2引发体系进行异丁基乙烯基醚和带有羟基和/或氨基被保护的单糖的乙烯基醚的顺序活性嵌段共聚。所得嵌段共聚物具有窄的分子量分布（Mw/Mn-1.1）和可控的组成。成功地实现了所得前体聚合物的定量脱保护，以提供目标两亲物。两亲性嵌段共聚物在不同溶剂中的溶解度强烈依赖于嵌段组成（m/n）。在透射电子显微镜下观察到载葡萄糖嵌段共聚物的溶剂浇铸薄膜表现出不同的微相分离表面形貌，如球形、圆柱形和层状，这取决于组成。接触角的测定表明，嵌段共聚物膜的表面性质随环境条件的变化而变化，在水溶液中浸泡可使其表面的疏水性异丁基链段被亲水性链段取代。为了更精确地控制其精细结构，我们将LB技术应用于该嵌段共聚物。发现该嵌段共聚物从氯仿和甲醇的混合溶液铺展到水表面上形成稳定的单分子层，通过LB技术将其成功地转移到基底上。LB膜的层状结构被证明是由共混的均聚物控制。

In this research project, we have succeeded in synthesizing a new class of sugar-carrying amphiphilic block copolymers- [CH_2CH (OCH_2CH_2OR)] _m- [CH_2CH (OiBu)] _n-by living cationic polymerization, where R is a D-glucose or D-glucosamine residue. To obtain them, sequential living block copolymerization of isobutyl vinyl ether and the vinyl ether carrying a monosaccharide whose hydroxyl and/or amino groups are protected was conducted using a HI/Znl_2 or TFA/EtAlCl_2 initiating system. The obtained block copolymers had a narrow molecular weight distribution (M_w/M_n-1.1) and a controlled composition. Quantitative deprotection of the resulting precursor polymers was successfully achieved to afford the target amphiphiles. The solubility of the amphiphilic block copolymers in various solvents depended strongly on the block composition (m/n).The solvent-cast thin films of the glucose-carrying block copolymer were observed, under a transmission electron microscope, to exhibit various microphase-separated surface morphologies such as spheres, cylinders, and lamellae, depending on composition. The contact angle measurement revealed that the block copolymer film changes its surface properties depending on the environmental condition, the hydrophobic isobutyl segment on the surface can be replaced with hydrophilic segment by soaking it in water. To more precisely control its fine structure, we applied the Langmuir-Blodgett (LB) technique to this block copolymer. The block copolymer, spread from a mixture solution of chloroform and methanol onto the water surface, was found to form a stable monolayr, which is successfully transferred onto a substrate by the LB technique. The layred structure of the LB film was demonstrated to be controlled by blending the homopolymer.