Kohori F, Sakai K, Aoyagi T, Yokoyama M, Sakurai Y, Okano T
Department of Applied Chemistry, Waseda University, 3-4-1, Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan.
J Control Release. 1998 Oct 30;55(1):87-98. doi: 10.1016/s0168-3659(98)00023-6.
The thermally sensitive block copolymer, poly(N-isopropylacrylamide-b-dl-lactide) (PIPAAm-PLA), was synthesized by ring-opening polymerization of dl-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm). A PIPAAm bearing a single terminal hydroxyl group was prepared by telomerization using 2-hydroxyethanethiol as a chain-transfer agent. Successful preparation of PIPAAm and the PIPAAm-PLA block copolymer was verified by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. Polymeric micelles were prepared from block copolymers using a dialysis method. Their solutions showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. Dynamic light scattering measurements were used to observe the formation of micellar structures approximately 40 nm in diameter, which do not change between 20 degreesC and 30 degreesC. Above the LCST, polymer micelles aggregated, a phenomenon found to be reversible since the aggregates dissociated again by cooling below the LCST. Further observations using atomic force microscopy (AFM) confirmed this behaviour. The properties of this block copolymer system are interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers.
通过以羟基封端的聚（N-异丙基丙烯酰胺）（PIPAAm）引发的丙交酯开环聚合反应，合成了热敏性嵌段共聚物聚（N-异丙基丙烯酰胺-b-dl-丙交酯）（PIPAAm-PLA）。使用2-羟基乙硫醇作为链转移剂，通过端粒化制备了带有单个末端羟基的PIPAAm。通过凝胶渗透色谱法（GPC）和1H-NMR光谱法验证了PIPAAm和PIPAAm-PLA嵌段共聚物的成功制备。使用透析法由嵌段共聚物制备聚合物胶束。它们的溶液在光学性质上表现出可逆变化：在较低临界溶液温度（LCST）以下是透明的，在LCST以上是不透明的。动态光散射测量用于观察直径约40nm的胶束结构的形成，其在20℃至30℃之间不会改变。在LCST以上，聚合物胶束聚集，发现这种现象是可逆的，因为通过冷却至LCST以下，聚集体再次解离。使用原子力显微镜（AFM）的进一步观察证实了这种行为。从应用和基础的角度来看，这种嵌段共聚物体系的性质都很有趣，特别是作为药物载体进行主动靶向时。
