Modulation of Supramolecular Interactions of Urea-based Supramolecular Polymers via Molecular Structures

Linear bis-urea D230 series and branched tris-urea T403 series of supramolecular monomers were synthesized using low molecular weight polyetheramine D230, T403 and isocyanates with diverse functional groups. Rheological tests reveal that the materials possess special thermal and mechanical properties due to the strong hydrogen bonding interactions between terminal urea groups and the high flexibility of the polyetheramine middle segments. By enhancing the hydrogen bonding interactions through electronic effects of the substituted urea groups, the mechanical properties of the bulk material can be increased. Moreover, the branched T403 series with higher hydrogen bonding density also shows better performance against D230 series with the same substituted urea groups. The presence of π-π stacking between the phenyl groups in samples with phenylurea residues, which complements the hydrogen bonding, was also confirmed by fluorescence spectroscopy, therefore resulting in a stronger supramolecular polymer network.     

Surface amine‐functionalization of UHMWPE fiber by bio‐inspired polydopamine and grafted hexamethylene diamine

Ultrahigh molecular weight polyethylene (UHMWPE) fibers exhibit excellent mechanical property, but their low surface activity limits the application in many fields. In this work, an efficient method was used to improve the surface activity and adhesion property of UHMWPE fibers. The amine functionalized UHMWPE fibers were prepared by the combination of bio‐inspired polydopamine (PDA) and grafted hexamethylene diamine (HMDA). The chemical structure of UHMWPE fibers was characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy. The surface morphologies and mechanical property of the fibers were investigated by scanning electron microscopy and tensile testing respectively. In addition, a single‐fiber pull‐out test was carried out to investigate the adhesion property of the fibers with epoxy resin matrix. The results showed that PDA was coated on the surface of UHMWPE fibers and then HMDA was successfully grafted on the PDA layers. The excellent mechanical property of UHMWPE fibers had no obvious change. Compared with the pristine UHMWPE fibers, the interfacial shear strength of the PDA coated UHMWPE fibers with the epoxy resin matrix improved by 28.3%, while the IFSS of the HMDA grafted UHMWPE fibers had an increase of 82.7%. Copyright © 2017 John Wiley & Sons, Ltd.     

Surface modification of boron nitride by bio‐inspired polydopamine and different chain length polyethylenimine co‐depositing

We established a novel, easy, and versatile method of obtaining diverse and controllable interphases between epoxy resin and fillers. The method involved the co‐deposition of polydopamine (PDA) and polyethyleneimine (PEI) with different molecular lengths on boron nitride (BN) surface. The obtained PDA/PEI‐modified BN composites showed significantly improved mechanical properties, including tensile strength, toughness, and elongation at break. For example, the tensile strength, fracture toughness, and elongation at break of EP composite increased by 51%, 132%, and 170% compared with EP when the PEI molecular weight was 10 000, respectively. These results suggested that the interphases between BN and EP matrix can be adjusted by changing the molecular lengths of grafted modifiers, thereby offering a new method for the reasonable designing and exploitation of the BN‐based composite materials.     

Simultaneous functionalization and reduction of graphene oxide with polyetheramine and its electrically conductive epoxy nanocomposites

Simultaneous functionalization and reduction of graphene oxide(GO) is realized by refluxing of GO suspension with polyetheramine(D2000) followed by thermal treatment at 120 °C. Compared to GO, the D2000-treated GO(GOD2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.     

Validation of experimental results for graphene oxide-epoxy polymer nanocomposite through computational analysis

The change in interfacial interaction behavior of epoxy resin nanocomposites with the incorporation of graphene oxide (GO) was explored experimentally and computationally. GO with different weight (wt) loading was incorporated in epoxy resin by a three-way dispersion method. GO formed mechanical interlocking with epoxy resin, thereby resulting in a remarkable enhancement in mechanical and thermo-mechanical properties of GO-epoxy nanocomposite. In 0.3 wt% GO-epoxy nanocomposites, improvement of 26.7% in flexural strength and 39.2% in flexural modulus was reported. Using dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and differential scanning calorimetry (DSC), glass transition temperature (T_g) of 182.7°C and maximum thermal stability was reported for 0.3% GO-epoxy nanocomposite. The effect of GO on cross-linking in GO-epoxy nanocomposite was analyzed by DSC and Raman spectroscopy. The X-ray photoelectron spectroscopy (XPS) study was utilized to determine the interfacial interaction, and further was verified by density functional theory (DFT). By experimental and computational study, H-bonding was observed to improve interfacial interaction in GO-epoxy nanocomposite.     

The effect of different treatment methods of multiwalled carbon nanotubes on thermal and flexural properties of their epoxy nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were oxidized using four different acid‐treatment methods followed by their functionalization with 3‐aminopropyltriethoxysilane (3‐APTES). Diglycidyl ether of bisphenol A (DGEBA) nanocomposites with unmodified and silanized MWCNTs (0.2 wt %) were prepared by a cast molding method. The effect of functionalization of MWCNTs on thermal, flexural, and morphological properties of the epoxy nanocomposites were studied. The epoxy/MWCNTs nanocomposites were characterized by thermogravimetric analysis, flexural testing, and field emission electron microscopic analysis. The results showed that the silanization of MWCNTs which were oxidized by a two‐step process using nitric acid and hydrochloric acid showed better thermal and flexural properties due to good interfacial adhesion between MWCNTs and the epoxy matrix. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1175–1184, 2010     

Enhancement of tensile,electrical and thermal properties of epoxy nanocomposites through chemical hybridization of polypyrrole and graphene oxide

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid Polypyrrole-Graphene Oxide (PPy-GO) filler, via in-situ chemical polymerization, at various filler loadings (i.e., 0.5–2 w. t %). The microstructures and properties of the PPy-GO hybrids and epoxy nanocomposites were studied via Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), mechanical (Tensile Properties), electrical, Dynamic mechanical thermal analysis (DMTA) and thermogravimetric analyses (TGA). Morphological study demonstrated that varying the nanofiller nature (PPy-GOs, PPy or GO) lead to different states of dispersion. Mechanical, electrical and thermal analysis demonstrated that the hybrid concentration and its architecture (PPy:GO ratio) are interesting factors significantly affected the properties of the epoxy based nanocomposites. On the other hand, the mechanical performance of the cured nanocomposites outperformed the PPy-GO, with enhancements of 78% and 51% of Young's modulus and strength, respectively. Here it has been established that the embedding of PPy-GO hybrids into pristine epoxy endows optimum dispersion of PPy and GO as well as better interfacial adhesion between the fillers and matrix, which results in a significant improvement in load transfer effectiveness. Electrical conductivity measurements showed that conductivity of epoxy filled nanocomposites increased up 10⁻⁴ S/cm for Epoxy/PPy-GO nanocomposites. DMTA test indicated that incorporation of PPy-GO resulted in a significantly increase in Tg of the resultant nanocomposites, which is attributed to the highly exfoliation structure and the stronger interfacial interaction. The PPy-GO particles enhanced electrical, thermal and mechanical properties of nanocomposites, confirming the synergistic effect of PPy-GO as multifunctional filler.     

Synergy effects of multi-walled carbon nanotube and graphene nanoplate filled epoxy adhesive on the shear properties of unidirectional composite bonded joints

In this paper, multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were dispersed into epoxy adhesive by sonication method to investigate their synergy effects on the shear properties of unidirectional composite bonded single lap joints (SLJs). The effect of the viscosity of epoxy resin and hardener on the dispersion process was studied. Testing results showed that the incorporation of MWCNTs and GNPs significantly improved the shear strength and elongation of SLJs at failure. 0.75 wt% MWCNTs/GNPs hybrids reached the highest enhancement of shear strength and elongation by 36.6% and 33.2%, respectively. In addition, the thermal stability of epoxy adhesive was improved by nanofillers in some extent. Finally, the failure mode of SLJs and fracture surfaces of the bonding area as well as the damage mechanism of nanofillers were analyzed.     

聚多巴胺功能化硅胶沉积单分散Pd纳米粒子的简易原位合成及用作醇需氧氧化反应的多相可循环使用的纳米催化剂（英文）

本文报道了一种不使用任何稳定剂或还原剂,原位合成硅胶/聚多巴胺复合物(SiO_2/PDA)负载的Pd纳米颗粒(Pd NPs)的简易方法.该方法先将PDA涂覆的SiO_2颗粒浸在Pd镀液中,然后利用PDA中含N基团的还原能力将Pd物种原位还原为纳米簇合物.并采用高分辨透射电镜、前场扫描电镜、能量散射谱、X射线衍射、X射线光电子能谱、诱导耦合等离子体和红外光谱等手段对所得纳米复合物的结构、形貌和物化性质进行了表征.被PDA基团锚合的Pd NPs具有显著的小颗粒(30–40 nm)特性.作为一个可循环使用的纳米催化剂,SiO_2/PDA/Pd NPs在醇的需氧氧化反应中表现出高活性.另外,催化剂经回收和多次重复使用时未出现明显的失活.     

Functionalized graphene/thermoplastic polyester elastomer nanocomposites by reactive extrusion‐based masterbatch: preparation and properties reinforcement

A reactive extrusion process was developed to fabricate polymer/graphene nanocomposites with good dispersion of graphene sheets in the polymer matrix. The functionalized graphene nanosheet (f‐GNS) activated by diphenylmethane diisocyanate was incorporated in thermoplastic polyester elastomer (TPEE) by reactive extrusion process to produce the TPEE/f‐GNS masterbatch. And then, the TPEE/f‐GNS nanocomposites in different ratios were prepared by masterbatch‐based melt blending. The structure and morphology of functionalized graphene were characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, X‐ray diffraction and transmission electron microscopy (TEM). The incorporation of f‐GNS significantly improved the mechanical, thermal and crystallization properties of TPEE. With the incorporation of only 0.1 wt% f‐GNS, the tensile strength and elongation at break of nanocomposites were increased by 47.6% and 30.8%, respectively, compared with those of pristine TPEE. Moreover, the degradation temperature for 10 wt% mass loss, storage modulus at ?70°C and crystallization peak temperature (T_cp) of TPEE nanocomposites were consistently improved by 17°C, 7.5% and 36°C. The remarkable reinforcements in mechanical and thermal properties were attributed to the homogeneous dispersion and strong interfacial adhesion of f‐GNS in the TPEE matrix. The functionalization of graphene was beneficial to the improvement of mechanical properties because of the relatively well dispersion of graphene sheets in TPEE matrix, as suggested in the TEM images. This simple and effective approach consisting of chemical functionalization of graphene, reactive extrusion and masterbatch‐based melt blending process is believed to offer possibilities for broadening the graphene applications in the field of polymer processing. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of composition and drying method on glass transition temperature,water sorption characteristics and surface morphology of newly designed β-lactoglobulin/retinyl palmitate/disaccharides systems

Epoxy-based nanocomposites containing different concentrations (0–3%) of surface-modified graphene nanosheets (GNS) with 3-aminopropyltriethoxysilane were prepared and their thermal and mechanical properties including dynamic mechanical analysis, tensile strength, hardness, and abrasion tests were evaluated in order to have a database for thermo-mechanical properties of epoxy nanocomposites. The main aim of this study was to understand the optimum percentage of GNS which would perform the best reinforcing influence on mechanical and physical performance of an epoxy nanocomposite. The results explain how applying the analysis of variance (ANOVA) method as a useful tool in optimization of GNS concentration in preparation of high-performance epoxy-based nanocomposites.     

Marrying mussel inspired chemistry with SET‐LRP: A novel strategy for surface functionalization of carbon nanotubes

Surface functionalization of carbon nanotubes (CNTs) with a thermo responsive polymer was achieved via combination of mussel inspired chemistry and surface initiated single electron transfer living radical polymerization (SET‐LRP). In this procedure, CNTs were first coated with polydopamine (PDA) through self polymerization under a rather mild condition. And then PDA functionalized CNTs bearing with amino and hydroxyl groups were further reacted with bromo isobutyryl bromide. Finally, a thermo responsive polymer poly(N‐isopropylacrylamide) (PNIPAM) was introduced on the CNTs via SET‐LRP. The successful surface modification of CNT‐PDA‐PNIPAM was evidenced by a series of characterization techniques. The resulting CNT‐PDA‐PNIPAM showed significant enhancement of dispersibility in both aqueous and organic solvents. More importantly, these CNT‐polymer nanocomposites showed obvious thermo responsive behavior due to the surface coating CNTs with PNIPAM. As compared with previous methods, this method is not required oxidation of CNTs to introduce funcitonal groups for immobilization of the polymerization initiators. More importantly, this method could also be utilized for fabricating many other polymer nanocomposites because of the strong and universal adhesive of PDA to various materials. It is therefore, the novel strategy via marrying mussel inspired chemistry with SET‐LRP should be a simple, general and effective method for surface functionalization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1872–1879     

Synthesis,characterization, and functionalization of zirconium tungstate (ZrW2O8) nano‐rods for advanced polymer nanocomposites

Nanomaterials based on zirconium tungstate (ZrW₂O₈) exhibit numerous outstanding properties that make them ideal candidates for the development of high‐performance composites. Low coefficient of thermal expansion for advanced materials is a promising direction in the field of insulating nanocomposites. However, the agglomeration of zirconium tungstate (ZrW₂O₈)‐based nanomaterials in the polymer matrix is a limiting factor in their successful applications, and studies on surface functionalization ZrW₂O₈ for advanced nanocomposites are very limited. In this work, ZrW₂O₈ nano‐rods were synthesized using a hydrothermal method and subsequently functionalized in a solvent‐free aqueous medium using dopamine. Both pristine and functionalized nano‐rods were thoroughly characterized using Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, X‐ray diffraction, Scanning Electron Microscopy (SEM), and transmission electron microscopy techniques, which confirmed the successful functionalization of the nanomaterials. Polymer nanocomposites were also prepared using epoxy resin as a model matrix. Polymer nanocomposites with functionalized ZrW₂O₈ nano‐rods exhibited low coefficient of thermal expansion and enhanced tensile properties. The improved properties of the nanocomposites render them suitable for electronic applications. Copyright © 2017 John Wiley & Sons, Ltd.     

SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF ORGANOCLAY-MODIFIED POLYSULFONE/EPOXY INTERPENETRATING POLYMER NETWORK NANOCOMPOSITES

Organoclay-modified hydroxylterminated polysulfone (PSF)/epoxy interpenetrating network nanocomposites (oM-PSF/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polysulfone and epoxy resin (PSF/EP) using diaminodiphenylmethane (DDM) as curing agent.The mechanical properties like tensile strength,tensile modulus,flexural strength,flexural modulus and impact properties of the nanocomposites were studied as per ASTM standards.Differ...     

Flexible Conductive Decellularized Fish Skin Matrix as a Functional Scaffold for Myocardial Infarction Repair

Engineering cardiac patches are proven to be effective in myocardial infarction (MI) repair, but it is still a tricky problem in tissue engineering to construct a scaffold with good biocompatibility, suitable mechanical properties, and solid structure. Herein, decellularized fish skin matrix is utilized with good biocompatibility to prepare a flexible conductive cardiac patch through polymerization of polydopamine (PDA) and polypyrrole (PPy). Compared with single modification, the double modification strategy facilitated the efficiency of pyrrole polymerization, so that the patch conductivity is improved. According to the results of experiments in vivo and in vitro, the scaffold can promote the maturation and functionalization of cardiomyocytes (CMs). It can also reduce the inflammatory response, increase local microcirculation, and reconstruct the conductive microenvironment in infarcted myocardia, thus improving the cardiac function of MI rats. In addition, the excellent flexibility of the scaffold, which enables it to be implanted in vivo through “folding-delivering-re-stretehing” pathway, provides the possibility of microoperation under endoscope, which avoids the secondary damage to myocardium by traditional thoracotomy for implantation surgery.     

Enhancement of Nanoclay Dispersion and Exfoliation in Epoxy Using Aminic Hardener Treated Clay

Exfoliation and dispersion of nanoclays in epoxy matrices plays an important role in achieving better physical and mechanical properties of resultant nanocomposites. In this article, modification of clay with an aminic hardener for the increment of dispersion and exfoliation into the epoxy matrix has been investigated. In the solvent media, a slurry of hydrophilic Na-Montmorrilonite was mixed and treated with isophoronediamine (IPDA). The nanocomposites containing epoxy and IPDA-modified clay were produced through a recently developed “slurry compounding” method. Dispersion and exfoliation of the modified clay and the microstructure of the resultant nanocomposite were studied by optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. The samples were then compared with the high shear mixed and sonicated nanocomposites containing commonly used quaternary ammonium modified clays. The comparison showed that dispersion and exfoliation of hardener-modified organoclays in epoxy have been improved due to the treatment of clay and the compounding method.     

Study on structure and performance of surface‐metallized carbon fibers reinforced rigid polyurethane composites

The simultaneous promotion in mechanical and electrical properties of rigid polyurethane (RPU) is an important task for expanding potential application. In this work, carbon fibers (CFs) reinforced RPU composites were prepared with the goal of improving mechanical and electrical properties. Metallized CFs meet our performance requirements and can be easily achieved via electrodeposition. However, the weak bonding strength in fiber‐metal‐RPU interface restricts their application. Inspired by the reducibility and wonderful adhesion of dopamine (DA), we proposed a new and efficient electrochemical method to fabricate metallized CFs, where DA polymerization was simultaneously integrated coupled with the reduction of metal ions (Ni²⁺). The characterization results helped us to gain insight about the reaction mechanism, which was never reported as far as we know. Compared with pure RPU, the tensile, interlaminar shear and impact strength of polydopamine (PDA)‐nickel (Ni) modified CFs/RPU composites were improved by 11.2%, 21.0%, and 78.0%, respectively, which attributed to the strong interfacial adhesion, including mechanical interlocking and chemical crosslinking between treated CFs and RPU. In addition, the PDA‐Ni surface treatment method also affected the dispersion of short CFs in the RPU, which increased the possibility of conductor contact and reduced insulator between fibers networks, resulting in higher electrical conductivity.     

大孔-介孔Ag/PDA/MMS复合材料的制备及其催化性能

用双模板法制备了介孔纳米薄膜构筑的毫米级尺寸的大孔-介孔SiO₂(MMS)，通过多巴胺(DA)在其孔道表面氧化自聚合成聚多巴胺(PDA)，得到 PDA 修饰的 MMS(PDA/MMS)，再经 PDA 原位还原 Ag⁺制得大孔-介孔 Ag/PDA/MMS 复合材料。应用扫描电镜、透射电镜、N₂吸附-脱附、X射线光电子能谱、X射线衍射、UV-Vis、FT-IR和热重技术对所制得的材料进行表征。结果表明，MMS兼具纳米介孔材料和宏观尺寸大孔材料的优点。Ag/PDA/MMS在催化还原对硝基苯酚(4-NP)反应中展现出高催化活性，转化频率(TOF)达2.97 min^-1。这归因于其独特的结构：相互连通的大孔孔道大大降低了传质阻力，短孔道的介孔显著增加了活性位点的可达性，大的比表面积为反应物提供了大量的活性位点。而且，毫米级尺寸的Ag/PDA/MMS可以很容易从反应体系中分离出来，在5次循环后仍能将4-NP完全转化为对氨基苯酚(4-AP)。另外，Ag/PDA/MMS对亚甲基蓝(MB)的还原也有良好的催化效果。     

Evaluating the antimicrobial activity and cytotoxicity of polydopamine capped silver and silver/polydopamine core-shell nanocomposites

Fabrication of bioactive nanomaterials with improved stability and low toxicity towards healthy mammalian cells have recently been a topic of interest. Bioactive metal nanomaterials such as silver nanoparticles (AgNPs) tend to lose their stability with time and become toxic to some extent, limiting their biological applications. AgNPs were separately encapsulated and loaded on the surface of a biocompatible polydopamine (PDA) to produce Ag-PDA and Ag@PDA nanocomposites to unravel the issue of agglomeration. PDA was coated through the self-polymerization of dopamine on the surface of AgNPs to produce Ag-PDA core-shells nanocomposites. For Ag@PDA, PDA spheres were first designed through self-polymerization of dopamine followed by in situ reduction of silver nitrate (AgNO3) without any reductant. AgNPs sizes were controlled by varying the concentration of AgNO₃. The TEM micrograms showed monodispersed PDA spheres with an average diameter of 238 nm for Ag-PDA and Ag@PDA nanocomposites. Compared to Ag@PDA, Ag-PDA nanocomposites have shown insignificant toxicity towards human embryonic kidney (HEK-293T) and human dermal fibroblasts (HDF) cells with cell viability of over 95% at concentration of 250 µg/mL. A excellent antimicrobial activity of the nanocomposites was observed; with Ag@PDA possessing bactericidal effect at concentration as low as 12.5 µg/mL. Ag-PDA on the other hand were only found to be bacteriostatic against gram-positive and gram-negative bacteria was also observed.     

Mussel-Inspired Adhesive,Antibacterial, and Stretchable Composite Hydrogel for Wound Dressing

Hydrogels have attracted extensive attention in the field of biomedicine because of their similar structure to extracellular matrix (ECM) and good biocompatibility. However, the adhesiveness, mechanical properties, and antibacterial properties of conventional hydrogels are not satisfactory. In this study, multifunctional chitosan/polydopamine/polyacrylamide (CS/PDA/PAM) hydrogels are prepared through a nature-inspired strategy. The catechol group of polydopamine (PDA) component endows CS/PDA/PAM hydrogels with tissue adhesion and self-healing properties. The introduction of chitosan (CS) not only greatly improves antibacterial ability, but also enhances the mechanical properties of CS/PDA/PAM hydrogels. Skin wound healing experiments show that CS/PDA/PAM hydrogels could accelerate skin tissue regeneration and promote wound healing. Therefore, CS/PDA/PAM hydrogels have great potential in the application of new wound dressings.