Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy.
Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy.
复制标题
通过原子力显微镜探索较低临界溶液温度下单一聚（N-异丙基丙烯酰胺）微凝胶的形态和纳米级力学。
作者：
O. Tagit;N. Tomczak;G. Vancso
采用表面活性剂自由基聚合法合成了亚微米级聚N-异丙基丙烯酰胺（PNIPAM）。个别的形态和纳米力学性能，隔离PNIPAM微凝胶颗粒在硅/空气和硅/水界面，低于和高于PNIPAM体积相变温度（VPTT），探测原子力显微镜。在空气中，以及在低于VPTT的水中，PNIPAM球体被压平并采用煎饼状形状。有趣的是，在VPTT以上，微凝胶采用具有增加的高度和减小的宽度的更球形的形式，这归因于颗粒与基底的相互作用减少。从单个微凝胶球获得的力-压痕曲线计算的弹性模量表明，在水中溶胀后，颗粒表面的刚度降低了两个数量级。此外，当穿过VPTT从膨胀状态到塌陷状态时，PNIPAM球体在水中的模量增加了一个数量级，这表明颗粒表面的链堆积更加紧密。
Submicrometer-sized particles of poly(N-isopropylacrylamide) (PNIPAM) are synthesized by surfactant-free radical polymerization. The morphology and nanomechanical properties of individual, isolated PNIPAM microgel particles at the silicon/air and silicon/water interfaces, below and above the PNIPAM volume-phase-transition temperature (VPTT), are probed by atomic force microscopy. In air, and in water below the VPTT, the PNIPAM spheres are flattened and adopt a pancakelike shape. Interestingly, above the VPTT the microgels adopt a more spherical form with increased height and decreased width, which is attributed to reduced interactions of the particles with the substrate. The elastic modulus calculated from force-indentation curves obtained for individual microgel spheres reveals that the stiffness of the particle's surface decreases by two orders of magnitude upon swelling in water. Additionally, the modulus of the PNIPAM spheres in water increases by one order of magnitude when crossing the VPTT from the swollen to the collapsed states, indicating a more compact chain packing at the particle surface.
影响因子：
3.4
作者：
Dimitriadis, EK;Horkay, F;Chadwick, RS
通讯作者：
Chadwick, RS