Molecular origins of wettability of hydrophobic poly(vinylidene fluoride) microporous membranes on poly(vinyl alcohol) adsorption: Surface and interface analysis by XPS
Molecular origins of wettability of hydrophobic poly(vinylidene fluoride) microporous membranes on poly(vinyl alcohol) adsorption: Surface and interface analysis by XPS
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DOI：
10.1021/jp050806r
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发表时间：
2005-07-28
影响因子：
3.3
通讯作者：
Gopinath, CS
中科院分区：
文献类型：
--
作者：
Gholap, SG;Badiger, MV;Gopinath, CS
研究了聚乙烯醇（PVA）在疏水多孔聚偏氟乙烯（PVDF）膜上的不可逆吸附行为。PVDF微孔膜经PVA吸附后，可观察到水的渗透，且经4%PVA溶液处理后，渗透率达到最大。水渗透率随着PVA浓度的增加而线性增加，直到4%，然后随着PVA浓度的进一步增加发生边际下降。PVA吸附PVDF膜进行了激烈的物理化学分析，特别是与XPS。XPS结果表明，PVA和PVDF之间存在界面，并且对于用4%PVA处理的PVDF膜，界面的结合能（BE）较低。来自CF 2-基团和F 1 s核心水平的碳在PVA吸附后在表面上的含量明显降低，并且在4%PVA时显示出最小的氟含量。F是BE位移0.5 eV的PVA吸附后，是独立的PVA浓度。EDAX分析表明，本体氧含量保持在4.5 +/-0.6%以内，并且与PVA浓度无关。然而，从01 s核水平的大量表面原子百分比的氧（20 +/-4%）显示PVDF表面上PVA含量的增加，并且其主要限于表面。4%PVA处理的PVDF膜清楚地显示出O 1 s核心水平的加宽以降低BE，并表明PVDF和PVA之间的相互作用与任何其他组合物相比显著不同。PVA吸附后，在低BE下出现了一个新的价带特征，这是PVDF上不存在的。这表明最高占据分子轨道（HOMO）的性质主要来自氧的偏移;同时，PVDF衍生带的抑制表明PVA吸附表面的性质从疏水性变为亲水性。上述观察结果还表明PVA和PVDF之间可能通过电荷转移存在不可逆的电子相互作用。
irreversible adsorption of poly(vinyl alcohol) (PVA) on hydrophobic, porous poly(vinylidene fluoride) (PVDF) membranes was carried out using aqueous PVA solution. Water permeation was observed in PVDF microporous membranes after PVA adsorption, and maximum permeability was obtained after treatment with 4% PVA solution. Water permeability increased linearly with increasing PVA concentration up to 4%, and then a marginal decrease with a further increase in PVA concentration occurred. PVA adsorbed PVDF membranes were subjected to intense physicochemical analysis, especially with XPS. XPS results display the presence of an interface between PVA and PVDF, and the binding energy (BE) of the interface is low for the PVDF membranes treated with 4% PVA. Carbon from CF2-groups and F 1s core level clearly showed a decrease in its content on the surface after PVA adsorption and showed a minimum fluorine content at 4% PVA. F Is BE shifts by 0.5 eV upon PVA adsorption and is independent of PVA concentration. EDAX analysis indicates that the bulk oxygen content remains within 4.5 +/- 0.6% and is independent of the PVA concentration. Nonetheless, a large amount of surface atom percentage of oxygen (20 +/- 4%) from 0 Is core level shows an increase in PVA content on the surface of PVDF, and it is restricted mostly to the surface. The 4% PVA treated PVDF membrane clearly shows a broadening of O 1s core level to lower BE and indicates the interaction between PVDF and PVA which is significantly different compared to any other compositions. A new valence band feature at low BE, which is nonexistent on PVDF, develops after PVA adsorption. This indicates that the shift in the nature of the highest occupied molecular orbital (HOMO) derived mostly from oxygen; simultaneously, a suppression in the PVDF derived band indicates the change in nature of the PVA adsorbed surfaces from hydrophobic to hydrophilic. The above observations also suggest an irreversible electronic interaction between PVA and PVDF, possibly through charge transfer.