Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm, Sweden.
Langmuir. 2013 Jul 16;29(28):8873-81. doi: 10.1021/la401076m. Epub 2013 Jul 5.
Nonagglomerating polylactide (PLA) particles with various interaction forces were designed by covalent photografting. PLA particles were surface grafted with hydrophilic poly(acrylic acid) (PAA) or poly(acrylamide) (PAAm), and force interactions were determined using colloidal probe atomic force microscopy. Long-range repulsive interactions were detected in the hydrophilic/hydrophilic systems and in the hydrophobic/hydrophilic PLA/PLA-g-PAAm system. In contrast, attractive interactions were observed in the hydrophobic PLA/PLA and in the hydrophobic/hydrophilic PLA/PLA-g-PAA systems. AFM was also used in the tapping mode to determine the surface roughness of both neat and surface-grafted PLA film substrates. The imaging was performed in the dry state as well as in salt solutions of different concentrations. Differences in surface roughness were identified as conformational changes induced by the altered Debye screening length. To understand the origin of the repulsive force, the AFM force profiles were compared to the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory and the Alexander de Gennes (AdG) model. The steric repulsion provided by the different grafted hydrophilic polymers is a useful tool to inhibit agglomeration of polymeric particles. This is a key aspect in many applications of polymer particles, for example in drug delivery.
采用共价光接枝的方法设计了具有各种相互作用力的无团聚聚乳酸（PLA）颗粒。通过胶体探针原子力显微镜（AFM）测定了 PLA 颗粒表面接枝亲水性聚（丙烯酸）（PAA）或聚（丙烯酰胺）（PAAm）后的相互作用力。在亲水/亲水体系和疏水性/亲水性 PLA/PLA-g-PAAm 体系中检测到长程排斥相互作用。相比之下，在疏水性 PLA/PLA 和疏水性/亲水性 PLA/PLA-g-PAA 体系中观察到了吸引力相互作用。AFM 还用于在干态以及不同浓度盐溶液中对纯 PLA 和表面接枝 PLA 薄膜基底的表面粗糙度进行测定。通过改变德拜屏蔽长度引起的构象变化来识别表面粗糙度的差异。为了理解排斥力的起源，将 AFM 力曲线与德贾金、朗道、维尔威和奥弗贝克（DLVO）理论和亚历山大·德热纳（AdG）模型进行了比较。不同接枝亲水性聚合物提供的空间排斥是抑制聚合物颗粒团聚的有效工具。这是聚合物颗粒许多应用的关键方面，例如药物输送。
