Temperature-sensitive core-shell microgel particles with dense shell
Temperature-sensitive core-shell microgel particles with dense shell
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DOI：
10.1002/anie.200503888
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Richtering, W
中科院分区：
文献类型：
--
作者：
Berndt, I;Pedersen, JS;Richtering, W
具有核壳形态的高分子纳米颗粒在生物医学和工业领域的应用具有广阔的前景自组装成胶束的嵌段共聚物属于这类粒子。在胶束中，不溶性块形成一个致密的核，核周围是一层可溶块的冕然而，胶束结构缺乏单体的分子间连接，因此可能由于盐浓度、机械力或简单稀释的作用而溶解，这限制了它们作为“智能”材料的应用。然而，通过共价交联核或壳可以合成具有更好的抗稀释稳定性的嵌段共聚物胶束其他方法采用树枝状大分子或超支化聚合物当加入对环境敏感的聚合物时，可以获得具有更复杂性能的颗粒利用这些物质，可以制备出在胶体长度尺度上具有不同灵敏度区域的空间分离纳米颗粒具有核-壳（或核-电晕）形态的体系大多表现出从粒子中心到外围衰减的密度分布。核-壳纳米粒子的壳层比芯层密度更大，这可能为许多应用提供优越的性能，例如在控制释放或传感器中。树状大分子最初被认为具有一个相当开放的内部区域的结构，随着树状大分子的产生，末端基的数量呈指数增长，其周围的壳层密度更大。[6a]然而，只有在非常特殊的条件下才能观察到致密壳的存在，[6b]并且通常树状大分子具有致密的核，其密度分布单调衰减，这一点通过中子散射研究和计算机模拟得到了证明。[6c， d]最近，多响应核-壳微凝胶被引入并通过各种实验技术进行了研究，如荧光光谱、量热法和小角中子散射（SANS）。这些研究揭示了核和壳对温度依赖性膨胀的相互影响。然而，该体系的典型壳密度低于
Polymeric nanoparticles with core–shell morphology offer promising properties for applications in biomedical as well as industrial fields.[1] Block copolymers which self-assemble into micelles belong to this type of particle. In the micelles, the insoluble blocks form a dense core which is surrounded by a corona of the soluble blocks.[2] Micellar structures, however, lack an intermolecular connection of the unimers and thus may dissolve as a function of, for example, salt concentration, mechanical forces, or simple dilution, which limits their application as “smart” materials. However, block-copolymer micelles with improved stability against dilution could be synthesized by covalently cross-linking core or shell.[3] Other approaches employed dendrimers or hyperbranched polymers.[4] Particles with even more sophisticated properties can be obtained when environmentally responsive polymers are incorporated.[1] Using these species, nanoparticles with spatial separation of regions with different sensitivities on colloidal length scales can be prepared.[5] Systems with core–shell (or core–corona) morphology mostly display a density profile that decays from the particle center to its periphery. Core–shell nanoparticles where the shell has a denser structure than the core might provide superior properties useful for many applications, as for example, in controlled release or sensors. Dendrimers were originally assumed to have a structure with a rather open interior region that is surrounded by a denser shell as the number of end groups grows exponentially with the dendrimer generation.[6a] However, the presence of a dense shell could be observed only under very distinct conditions,[6b] and usually dendrimers have a dense core with a monotonically decaying density profile as was demonstrated by means of neutron-scattering investigations and computer simulations.[6c, d]Recently, multiresponsive core–shell microgels have been introduced and investigated by various experimental techniques, such as, fluorescence spectroscopy, calorimetry, and small-angle neutron scattering (SANS). These studies have revealed the mutual influence of core and shell on the temperature-dependent swelling. However, the systems characteristically had a shell density which is lower than that of the