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首页> 外文学位 >Heterogeneous polyelectrolyte gel membranes: Effect of morphology on stimulus-responsive permeation control.
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Heterogeneous polyelectrolyte gel membranes: Effect of morphology on stimulus-responsive permeation control.

机译：异质聚电解质凝胶膜：形态对刺激响应渗透控制的影响。

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Poly(methacrylic acid)-poly(dimethyl siloxane) (PMAA-PDMS) composites and interpenetrating polymer networks (IPNs) were prepared in order to examine the effect of a heterogeneous hydrogel-elastomer morphology on the variable transport properties of stimuli-responsive membranes. The composites consisted of PMAA particles (≅40 μm diameter) dispersed within a PDMS network and IPNs were composed of PMAA channels (≅0.1 μm diameter) which spanned the thickness of the PDMS network.; The mechanism of permeation control for the composite was based on the percolation or connectivity of the dispersed PMAA particles. The fast swelling-deswelling rates of the surface-resident PMAA particles resulted in a dynamic permeation response to pH change in the order of minutes and an ON/OFF (pH 7/pH 3) permeability ratio of 160 for vitamin B12. This compared favourably to the ON/OFF permeability ratio of 7 estimated for homogeneous PMAA membranes.; The mechanism of permeation control for IPNs was based on size exclusion of the permeant from the PMAA channel. Although the ON/OFF permeability ratio (1400) improved over both PMAA and composite membranes, the response time for the dynamic 24 h permeation cycle was very slow. The slow swelling kinetics of the membrane-spanning PMAA channel from pH 3 to 7 resulted in a lag time of 15 h before permeation resumed at pH 7. A combination of the composite and IPN morphologies is expected to improve upon the deficiencies of the two membrane types. For example, a hydrogel-PDMS IPN can be prepared where the gel channel in the surface region is stimuli-responsive and that within the bulk remains hydrated and non-responsive.; A novel monomer immersion method was developed to prepare stimuli-responsive, bicontinuous, PMAA PDMS IPN membranes. The method involved immersing the pre-IPN in methacrylic acid (MAA) during IPN formation in order to obtain a uniform MAA concentration profile within the pre-IPN.; A unique approach was used to examine PMAA-PDMS IPN morphology with the laser scanning confocal microscope and fluorescent probes of varying diameters. The results revealed complex, superimposed structures of PMAA domains of varying sizes and spatial distributions. These observations had not been reported previously and present a new understanding of morphology development in IPNs.
机译：制备聚（甲基丙烯酸）-聚（二甲基硅氧烷）（PMAA-PDMS）复合材料和互穿聚合物网络（IPN），以检查非均质水凝胶-弹性体形态对刺激响应膜可变运输特性的影响。复合材料由分散在PDMS网络中的PMAA颗粒（直径约40μm）组成，而IPNs由横跨PDMS网络厚度的PMAA通道（直径约0.1μm）组成。复合材料的渗透控制机理是基于分散的PMAA颗粒的渗透或连通性。表面驻留的PMAA颗粒的快速溶胀-消溶率导致对维生素B12的pH变化的动态渗透响应在几分钟左右，开/关（pH 7 / pH 3）渗透率为160。这与均质PMAA膜估计的7的开/关渗透率相比具有优势。 IPN的渗透控制机制是基于PMAA通道中渗透物的尺寸排阻。尽管在PMAA和复合膜上的开/关渗透率（1400）均得到改善，但动态24 h渗透周期的响应时间却很慢。跨膜PMAA通道从pH 3到7的缓慢溶胀动力学导致滞后时间为15 h，然后在pH 7处恢复渗透。复合材料和IPN形态的组合有望改善两种膜的缺陷类型。例如，可以制备水凝胶-PDMS IPN，其中在表面区域中的凝胶通道是刺激响应性的，而本体中的凝胶通道保持水合和无响应的。开发了一种新型的单体浸没方法来制备刺激响应，双连续，PMAA PDMS IPN膜。该方法包括在IPN形成过程中将前IPN浸入甲基丙烯酸（MAA）中，以便在前IPN内获得均匀的MAA浓度分布。使用独特的方法通过激光扫描共聚焦显微镜和不同直径的荧光探针检查PMAA-PDMS IPN形态。结果显示了大小和空间分布不同的PMAA域的复杂，重叠结构。这些观察以前没有被报道过，它们对IPN的形态发展提出了新的认识。

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