State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
Langmuir. 2010 Feb 2;26(3):2076-82. doi: 10.1021/la9025766.
There exists a great number of publications concerning the synthesis of core-shell and/or hairy particles by means of controlled/living polymerization. Nevertheless, how to fabricate ultrafine nanosized hairy particles, especially polymeric soft hairy particles, remains a significant challenge. This paper presents a simple self-developed approach consisting of a two-step photoinduced polymerization of cross-linked polyacrylamide (CLPAM) soft hydrogel nanoparticles (5-10 nm in diameter) grafted with poly(N-isopropylacrylamide) (PNIPAm) chains. The architecture of such ultrafine soft water-swollen CLPAM@PNIPAm core/shell nanoparticles (20-35 nm in diameter) demonstrated very specific temperature sensitive behaviors. During heating a fast association process was observed at approximately 33-34 degrees C and the singular hairy particles with 34 nm diameters clustered into aggregates that were approximately 120 nm in diameter. Raising the temperature further, however, led to a decrease in size to about 100 nm at 45 degrees C. This behavior was attributed to the formation of hydrophobic shell layers accompanying the shrinkage of PNIPAm chains with chain polar transformations. With the contraction pressure produced by further shrinkage of the hydrophobic shell layers, the soft fully swollen PAM cores expelled water and diminished in size. During the cooling process, these contracted cores that were trapped in the aggregates gave rise to an early dissociation. The hydrophilic hairy CLPAM@PNIPAm particles are believed to be potentially useful as carriers to specific target regions, e.g., cells for controlled drug delivery and other smart biomaterial applications.
存在大量关于通过受控/活性聚合合成核壳和/或多毛颗粒的出版物。然而，如何制造超细微纳米多毛颗粒，特别是聚合软多毛颗粒，仍然是一个重大挑战。本文提出了一种简单的自开发方法，包括两步光诱导交联聚丙烯酰胺 (CLPAM) 软水凝胶纳米颗粒 (直径 5-10nm) 的接枝聚 (N-异丙基丙烯酰胺) (PNIPAm) 链的聚合。这种超细微软水膨胀 CLPAM@PNIPAm 核/壳纳米颗粒（直径 20-35nm）的结构表现出非常特殊的温度敏感行为。在加热过程中，在大约 33-34°C 时观察到快速缔合过程，具有 34nm 直径的奇异多毛颗粒聚集形成直径约为 120nm 的聚集体。然而，进一步提高温度会导致在 45°C 时尺寸减小到约 100nm。这种行为归因于 PNIPAm 链的收缩伴随链极性转变形成疏水性壳层，同时伴随着疏水性壳层的进一步收缩产生收缩压力，使软的完全溶胀的 PAM 核排斥水并减小尺寸。在冷却过程中，这些被困在聚集体中的收缩核导致早期解离。亲水的 CLPAM@PNIPAm 颗粒有望作为载体用于特定的靶区，例如细胞用于控制药物释放和其他智能生物材料应用。
