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首页> 外文期刊>Cogent Chemistry >Investigation on the structure of temperature-responsive N-isopropylacrylamide microgels containing a new hydrophobic crosslinker
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Investigation on the structure of temperature-responsive N-isopropylacrylamide microgels containing a new hydrophobic crosslinker

机译：含新型疏水交联剂的温度响应性N-异丙基丙烯酰胺微凝胶的结构研究

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Temperature-responsive poly(N -isopropylacrylamide) microgels crosslinked with a new hydrophobic chemical crosslinker was prepared by surfactant-mediated precipitation emulsion polymerization. The temperature-responsive property of the microgel and the influence of the crosslinker on the swelling behaviour was studied systematically by light scattering and small-angle X-ray scattering (SAXS). The radius of gyration (R _(g )) and the hydrodynamic radius (R _(h )) of the microgels decreased with increase in temperature due to the volume-phase transition from a swollen to a collapsed state. The ratio of R _(g )/R _(h ) below the transition temperature was lower than that of hard-spheres due to the lower crosslinking density of the microgels. The SAXS data were analysed by a model in which the microgels were modelled as core-shell particles with a graded interface. The model at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low crosslinking density. In the fully swollen state, the microgels were modelled with a single component with a broad graded surface. In the collapsed state, they were modelled as homogeneous and relatively compact particles. The polymer volume fraction inside the microgel was also derived based on the model and was found to increase with increase in the temperature as a result of collapse of the microgel to compact particles. The polymer volume fraction in the core of the microgel in the collapsed state was about 60% which is higher than that of similar microgels crosslinked with hydrophilic and flexible crosslinkers.
机译：通过表面活性剂介导的沉淀乳液聚合反应制备了与新型疏水化学交联剂交联的温度响应型聚（N-异丙基丙烯酰胺）微凝胶。通过光散射和小角度X射线散射（SAXS）系统研究了微凝胶的温度响应特性和交联剂对溶胀行为的影响。微凝胶的回转半径（iR _（ig））和流体力学半径（iR _（h））随温度的升高而降低，这是由于从肿胀到崩溃的状态。低于转变温度的R _（i g）/ R _（h）的比率由于硬凝胶的较低的交联密度而低于硬球的比率。通过模型分析SAXS数据，其中微凝胶被建模为具有渐变界面的核壳颗粒。处于中间温度的模型包括一个中心核和一个扩散程度更高的外层，这些外层描述了具有低交联密度的悬而未决的聚合物链。在完全溶胀的状态下，微凝胶用具有宽梯度表面的单一组分建模。在折叠状态下，将它们建模为均匀且相对紧凑的粒子。微凝胶内部的聚合物体积分数也基于该模型得出，并且由于微凝胶塌缩成致密颗粒而发现随着温度的升高而增加。处于塌缩状态的微凝胶核心中的聚合物体积分数约为60％，高于与亲水性和柔性交联剂交联的类似微凝胶的聚合物体积分数。

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