Synthesis and characterization of soluble intrinsic black polyimide with excellent comprehensive properties

Black polyimides(BPIs)have attracted increasing attention owing to their growing demand in optoelectronics.However,commonly used black polyimides doped with black fillers suffer from poor mechanical and electrical properties.To address these issues,a new diamine(2,5-bis(4′-amino-[1,1′-biphenyl]-4-yl)-3,4-bis(4-fluorophenyl)cyclopenta-2,4-dien-1-one,TPCPFPDA)bearing a tetraphenylcyclopentadienone(TPCP)moiety bonded with benzene and fluorine units was synthesized.The diamine was reacted with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)to yield a soluble intrinsic black polyimide(TPCPFPPI).Bonding fluorine(auxochrome group)and benzene units to TPCP can increase the conjugation ofπ-electrons systems and facilitate the movement of electron throughout the bigπbond,respectively.Owing to the structural features,the synthesized TPCPFPPI exhibited complete visible-light absorption with high blackness and opacity.Its cutoff wavelength(λ_(cut))and CIE(Commission Internationale de I′Eclairage)parameter L^(*)were 684 nm and 1.33,respectively.Moreover,TPCPFPPI displayed exceptional electrical,mechanical,and thermal properties as well as excellent solubility.A detailed theoretical calculation was conducted to gain better insight into the electronic properties of the TPCPFPPI.Results showed that the blackness of TPCPFPPI was chiefly attributed to the electron transition from highest occupied molecular orbital(HOMO)to lowest unoccupied molecular orbital(LUMO)in the diamines,where the charges primarily migrated from the aryl groups in the 2-and 5-positions to the cyclopentadienone center.The as-obtained intrinsic BPI(TPCPFPPI),exhibiting both high solubility and outstanding overall properties,has important applications in photo-electronics.

Synthesis and Properties of High Performance Functional Polyimides Containing Rigid Nonplanar Conjugated Fluorene Moieties

A diamine(WuFDA) containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C―F)was designed and synthesized through three steps of reactions(halogenated reaction, Suzuki coupling reaction, and reduction reaction).Four kinds of high performance functional polyimides(WuFPI-6 F, WuFPI-BP, WuFPI-BT, and WuFPI-PM) were thus prepared by the condensation polymerization of WuFDA with four commercial dianhydride 6 FDA, BPDA, BTDA, and PMDA, respectively. The polyimides exhibited low dielectric constant, excellent thermal stability, outstanding solubility, good film-forming property, and mechanical properties. The dielectric constants of the polyimides were in the range of 2.28-2.88(f = 10~4 Hz). The 5% weight-loss temperatures(Td 5%)in nitrogen were in the range of 555-584 °C, and the glass transition temperatures(T_g) were in the range of 408-448 °C. The weight loss of WuFPI-BP maintaining at 450 and 500 °C for half an hour was only 0.33% and 1.26%, respectively. All the WuFPIs could be dissolved in almost all organic solvents, even chloroform. The tensile strength and tensile modulus of these films were in the ranges of 78.6-85.7 MPa and 3.1-3.2 GPa, respectively. In addition, the polyimides displayed light color with special fluorescent and resistive switching(ON-OFF) characteristics; the maximum fluorescence emission was observed at 422-424 nm in NMP solution and at 470-548 nm in film state. The memory devices with the configuration of indium tin oxide/WuFPIs/aluminum(ITO/WuFPIs/Al) exhibited distinct volatile memory characteristics of static random access memory(SRAM), with an ON/OFF current ratio of 10~5-10~6. These functional polyimides showed attractive potential applications in the field of high performance flexible polymer photoelectronic devices or polymer memory devices.

Multifunctional Polypyrrole-silver Coated Layered Double Hydroxides Embedded into a Biodegradable Polymer Matrix for Enhanced Antibacterial and Gas Barrier Properties

In this study,polypyrrole-silver coated layered double hydroxides(LDHs@PPy-Ag)was prepared by chemical polymerization of pyrrole(Py)with silver ions.Silver nanoparticles(AgNPs)could be uniformly reduced onto PPy coatings in situ by redox reaction during simultaneous polymerization process.And LDHs@PPy-Ag/poly(ε-caprolactone)(PCL)nanocomposites were fabricated by solution casting method.It is revealed that spherical AgNPs are loaded on PPy coatings uniformly.Particularly,compared with pure PCL,LDHs@PPy-Ag/PCL nanocomposites with incorporation of only 1 wt%LDHs@PPy-Ag show a 17%increase in tensile strength(36.5 MPa)and a 29%increase in elongation at break(822%).Upon PPy-Ag coatings onto original LDHs,oxygen relative permeability of LDHs@PPy-Ag/PCL nanocomposites decreases to 52%with the same addition.Meanwhile,due to the double antibacterial activity of PPy and AgNPs,the antibacterial rate of LDHs@PPy-Ag reaches 100%.And the corresponding LDHs@PPy-Ag/PCL nanocomposites also show outstanding antibacterial activity.Considering the superiority of their comprehensive performance,antibacterial LDHs@PPy-Ag/PCL nanocomposites can be used further for the application as biodegradable polymeric active packaging materials.

无模板法合成具有增强催化活性的分级纳米孔结构MIL-101(Cr)

MIL-101(Cr)是最重要的金属有机框架(MOFs)材料之一,稳定的框架结构和超高的比表面积使其在众多科学领域得到了广泛研究和应用.但是MIL-101(Cr)的合成条件比较苛刻,且稳定性较强,因此,有关于其分级结构的研究报道仍比较少.本文提出了一种简单制备分级纳米孔结构MIL-101(Cr)的方法,即以乙酸作为调节剂,采用水热合成的方法,一步得到具有微孔-介孔-大孔分级结构的MIL-101(Cr)材料.实验结果表明,该分级结构的MIL-101(Cr)与无分级结构的MIL-101(Cr)相比,其大分子染料吸附能力和催化能力均有显著提高.而且分级结构MIL-101(Cr)负载了磷钨酸催化剂之后,表现出了与均相催化剂(纯磷钨酸)相当的催化能力.进一步研究发现,使用其他短碳链的一元羧酸作为调节剂,如丙酸、丁酸等,也可获得类似分级纳米结构MIL-101(Cr).

高蒸发速率的耐盐织物基全天候可用光热-电热蒸发器

太阳能驱动水蒸发是利用太阳能进行海水脱盐和清洁水生产的实用方法,具有最低的碳排放.但该方法在弱光照的阴天或夜间蒸发速率较低.本文基于光热和电热加热的耦合效应,提出了一种可以根据光照条件调节表面温度和蒸发速率的织物基全天候可用光热-电热蒸发器(P/ET-SG).由于电热层与光热层均匀的热分布,该P/ET-SG在1 V电压和1个太阳光辐照下其表面温度及蒸发速率可达52℃和2.61 kg m^(-2) h^(-1).P/ET-SG所采用的单向流体结构设计使其在连续24小时的海水脱盐过程中具备极高的耐盐性,且能除去蒸发表面的盐颗粒.此外,在高浓度盐水和污水净化中,P/ET-SG展现了高的蒸发速率(2.58 kg m^(-2) h^(-1))和净化效率(>99.9%).本文为全天候可用的高效太阳能蒸发器的设计提供了新思路,并提供了高浓度盐水和污水高效净化的新策略.