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首页> 外文期刊>RSC Advances >Effect of a direct sulfonation reaction on the functional properties of thermally-crosslinked electrospun polybenzoxazine (PBz) nanofibers
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Effect of a direct sulfonation reaction on the functional properties of thermally-crosslinked electrospun polybenzoxazine (PBz) nanofibers

机译：直接磺化反应对热交联电纺 - 聚苯异种嗪（PBZ）纳米纤维功能性能的影响

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Electrospun nanofibers of polybenzoxazines (PBzs) were fabricated using an electrospinning process and crosslinked by a sequential thermal treatment. Functionalization by the direct sulfonation process followed after the post-electrospinning modification treatment. The first stage of experiment determined the effects of varying the concentration of sulfuric acid as the sulfonating agent in the sulfonation reaction under ordinary conditions. The second stage examined the mechanism and kinetics of the sulfonation reaction using only concentrated H _(2) SO _(4) at different reaction time periods of 3 h, 6 h, and 24 h. The mechanism of the sulfonation reaction with PBz nanofibers was proposed with only one sulfonic acid (–SO _(3) H) group attached to each of the repeating units since only first type substitution in the aromatic structure occurs under this condition. The kinetics of the reaction exhibited a logarithmic correlation where the rate of change in the ion exchange capacity (IEC) with the reaction time increased rapidly and then reached a plateau at the reaction time between 18 h and 24 h. Effective sulfonation was confirmed by electron spectroscopy with a characteristic peak associated with the C–S bond owing to the sulfonate group introduced onto the surface of the nanofibers. ATR-FTIR spectroscopy also confirmed these results for varying reaction times. The SEM images showed that sulfonation has no drastic effects on the morphology and microstructure of the nanofibers but a rougher surface was evident due to the wetted fibers with sulfonate groups attached to the surface. EDX spectra exhibited sulfur peaks where the concentration of sulfonate groups present in the nanofibers is directly proportional to the reaction time. From surface wettability studies, it was found that the nanofibers retained the hydrophobicity after sulfonation but the inherent surface property of PBz nanofibers was observed by changing the pH level of water to basic, which switches its surface properties to hydrophilic. The thermal stability of the sulfonated nanofibers showed almost the same behavior compared to non-sulfonated nanofibers except for the 24 h sulfonation case, which has slightly lower onset temperature of degradation.
机译：使用静电纺丝工艺制造静电梭纳米纤维（PBZ），并通过连续热处理交联。通过直接磺化过程的官能化，然后进行后静电纺丝修饰处理。实验的第一阶段确定了在常规条件下在磺化反应中改变硫酸浓度作为磺化反应的效果。第二阶段检查磺化反应的机制和动力学仅使用浓H _（2）所以_（4）在不同的反应时间为3小时，6小时和24小时。用连接到每个重复单元的磺酸（-SO _（3）H）基团提出磺化与PBZ纳米纤维的机制，因为在该条件下仅发生芳族结构中的首批取代。该反应的动力学表现出对数相关的，其中离子交换能力（IEC）的变化率快速增加，然后在18小时至24小时之间达到高原。通过电子光谱法确认有效的磺化，并且由于引入纳米纤维表面上的磺酸盐基团而与C-S键相关的特征峰。 ATR-FTIR光谱也证实了这些结果，可以改变反应时间。 SEM图像表明，磺化对纳米纤维的形态和微观结构没有剧烈影响，但由于湿纤维与附着在表面上的磺酸盐基团的染色纤维，显而易见的表面。 EDX光谱表现出硫峰，其中存在于纳米纤维中存在的磺酸盐基团的浓度与反应时间成正比。从表面润湿性研究中发现，纳面纤维在磺化后保留了疏水性，但通过将水的pH水平改变为碱来观察PBZ纳米纤维的固有表面性能，从而将其表面性能切换为亲水。除了24h磺化壳体外，磺化纳米纤维的热稳定性与非磺化纳米纤维相比，几乎与非磺化纳米纤维相比的特性几乎相同，其发病率略低降低。

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