Multicomponent polymerization of sulfur, chloroform and diamine toward polythiourea

The efficient utilization of elemental sulfur(S8) for developing high value-added chemicals is a global concern considering its abundant sources and yearly accelerating environmental issues. However, it has been a long-standing challenge to directly transform elemental sulfur to sulfur-containing polymer, especially via an environmentally benign manner. Herein, a unique chemo-differentiating multicomponent polymerization(MCP) of elemental sulfur, chloroform, and diamine is reported to construct polythiourea based on amine-involved two sequential reactions including isothiocyanation and nucleophilic addition.This strategy features isocynide-free monomers as starting materials, mild conditions, high molecular weights(up to72,900 g/mol) and desired yields(up to 83%). With the advantages of inactive isocyanation and active nucleophilic addition, the stoichiometric balance of amine and isothiocyanate could be delicately controlled to afford various polythioureas with high molecular weights. The polythioureas have been further utilized in the Cu-based aqueous catalysis and Hg-based ion adsorption.

Diamines,CS2 and Monoisocyanide-participated Polymerizations for Large-scale Synthesis of Polythioureas and Thioformamide

Multicomponent polymerizations(MCPs)are powerful tools to synthesize functional polymers with great structural diversity,low cost and high efficiency,which usually generate single polymer product.Herein,a robust one-pot diamines,CS_(2)and monoisocyanide-participated catalyst-free polymerization was developed at room temperature to produce polythiourea and thioformamide simultaneously in equal equivalent,which was featured with cheap monomers,simple operation and mild condition,affording various polythioureas with high Mws of up to 4.75×10^(4)g/mol in high yields of up to 98%.Polythioureas with varied chain composition and sequence-controlled structure could be synthesized in 62 g-scale from copolymerization or multicomponent tandem polymerization,enabling facile tuning of thermal property,crystallinity,mechanical property,and fluorescence.The abundant irregular hydrogen bonds endowed the polythioureas excellent glassy state self-healing property at room temperature or below 0℃.This polymerization provided an efficient and economic approach to access functional polythioureas.

氢键调控提升聚硫脲介电储能特性

为理解氢键对聚硫脲(polythiourea,PTU)介电储能特性的影响,该文采用实验和分子模拟方法,研究脂环族PTU(AcPTU)和芳香族PTU(ArPTU)中氢键作用模式和强度对介电常数、击穿场强和储能特性的影响。利用红外光谱和核磁共振氢谱表征化学组成和分子构型,利用宽频介电谱、击穿和电滞回线测试获得介电储能特性,基于H-N公式提取偶极极化特征参数,利用热刺激去极化电流法提取了陷阱深度,采用Multiwfn软件识别氢键作用模式和强度。结果显示,氢键作用模式和强度可以通过改变偶极极化和陷阱特性影响介电性能。脂环结构可以增多由反式/反式构型硫脲组装成的双氢键阵列,增强其介电松弛强度,进而提高介电常数;苯环结构可以增强π氢键数目和作用强度,加深由苯环碳原子和硫原子等氢键受体贡献的深陷阱能级,进而提高击穿场强。AcPTU具有高介电常数,归因于脂环结构增强了双氢键阵列的介电松弛强度;ArPTU的击穿场强高达855 MV/m,是因为苯环结构强化了氢键的电荷捕获效应。此外,当电场强度为300 MV/m时,AcPTU的储能密度和效率分别达到2.62 J/cm3和93.31%。该研究为提升本征型聚合物介电储能特性提供了理论依据。

Stable dielectric response of low-loss aromatic polythiourea thin films on Pt/SiO_(2) substrate

We have investigated dielectric properties of aromatic polythiourea(ArPTU,a polar polymer containing high dipolar moments with very low defect levels)thin films that were developed on Pt/SiO_(2) substrate.The detected response is compared to the response of commercially available polymers,such as high density polyethylene(HDPE)and polypropylene(PP),which are at present used in foil capacitors.Stable values of the dielectric constantε'≈5(being twice higher than in HDPE and PP)over broad temperature and frequency ranges and dielectric losses as low as in commercial systems suggest ArPTU as a promising candidate for future use in a variety of applications.

聚硫脲缓释微胶囊的制备及其性能表征

以对苯二甲酰异硫氰酸酯和邻苯二胺为原料通过界面缩聚法合成了聚硫脲缓释微胶囊。用傅里叶变换红外光谱、扫描电子显微镜和热重-差热分析对微胶囊的化学结构、表面形态、粒径及其分布和热稳定性进行了表征。以2,3-二氢-2,2-二甲基-7-苯并呋喃基-N-甲基氨基甲酸酯(克百威)为模型药物,研究了微胶囊的缓释行为。实验结果表明,在对苯二甲酰异硫氰酸酯0.793g、邻苯二胺0.350g、克百威0.300g、搅拌转速500r/min的条件下,合成的微胶囊平均粒径约为3μm,粒径较均一,球形度好,表面光滑。微囊化克百威具有较好的热稳定性,累积释放达到14d以上。

淬火温度对聚硫脲介电储能特性影响的分子动力学模拟

为了提高聚硫脲(polythiourea,PTU)的储能密度,对PTU进行了淬火处理,并采用分子动力学模拟研究了PTU中氢键动力学性质对介电储能特性的影响机理。首先,借助热波动指数(thermalfluctuationindex,TFI)和约化梯度密度(reduction gradient density,RDG)描述了氢键作用模式和强度随淬火温度升高的演变规律。其次,计算了氢键供体分别与受体和氢原子的径向分布函数、自相关函数等,提取了氢键密度和平均寿命。最后,建立了氢键特征参数与介电常数的关联,揭示了淬火提高PTU储能密度的机理。研究发现,淬火温度升高,氢键作用模式发生了由双氢键至单氢键,并最终超过氢键阈值而断裂的演变规律,这造成氢键密度减少,表现为强极性双氢键硫脲阵列数目的减少,导致介电常数减小;同时,氢键强度持续减弱,氢键寿命缩短,动态变化加快,导致硫脲阵列转向势垒降低,这有利于增大介电常数。受氢键作用模式和强度的共同影响,PTU的介电常数随淬火温度升高呈现先增大后减小的变化趋势。当淬火温度为393 K时,PTU的介电常数增大至10,储能密度高达16.3 J/cm~3。

硫脲树脂对水溶液中Cd^(2+)吸附性能的实验研究与理论模拟

以硫脲与甲醛为原料一步合成含硫脲树脂.采用静态吸附的方法吸附溶液中的Cd^(2+),分别考察温度、时间、初始浓度等因素对吸附量的影响,并进行吸附等温模型模拟.在实验基础上,采用B3LYP方法研究硫脲与Cd^(2+)配位作用特征.发现树脂对Cd^(2+)的吸附在2 h达到吸附平衡,初始浓度为1.000 0 mg·mL-1、pH为6.00时吸附效果最佳,吸附量为19.68 mg·g-1.理论计算显示Cd^(2+)离子与硫脲S配位作用的稳定化能为624.3 kJ/mol,显著高于N配位约163.3 kJ/mol,说明硫脲S原子为主要吸附活性位点.

硫脲甲醛树脂吸附银离子的实验研究与理论模拟

以硫脲和甲醛为原料制备硫脲甲醛树脂然后进行红外表征.将制备树脂应用于银离子静态吸附,研究吸附时间、浓度、吸附温度和p H对树脂吸附量的影响,同时进行等温拟合.为进一步研究该吸附特征,在B3LYP水平上对树脂有效官能团与Ag(I)作用特点进行理论分析.