Preparation of Mg–Al layered double hydroxides intercalated with alkyl sulfates and investigation of their capacity to take up N,N-dimethylaniline from aqueous solutions

This study examined the effect of the interlayer spacing of a Mg–Al layered double hydroxide (Mg–Al LDH) on the ability of the Mg–Al LDH to take up a nonionic organic material. Mg–Al LDHs, intercalated with 1-propanesulfonate (PS^?), 1-hexanesulfonate (HS^?), and 1-dodecanesulfonate (DS^?), were prepared by coprecipitation, yielding PS·Mg–Al LDH, HS·Mg–Al LDH, and DS·Mg–Al LDH, respectively. The increase in the alkyl chain lengths of the Mg–Al LDHs (PS^? < HS^? < DS^?) resulted in the perpendicular orientation of the organic acid anions in the interlayer of Mg–Al LDH, which in turn resulted in more organic acid anions being accommodated in the interlayer space. An organic acid anion with a large molecular length was more easily intercalated in the interlayer of Mg–Al LDH than one with a small molecular length. This was attributed to the hydrophobic interaction between the alkyl chains, affecting the intercalation of the organic acid anions. The uptake of N,N-dimethylaniline (DMA) by Mg–Al LDHs increased in the order PS·Mg–Al LDH < HS·Mg–Al LDH < DS·Mg–Al LDH. The uptake was attributed to the hydrophobic interactions between DMA and the intercalated PS^?, HS^?, and DS^?. Thus, Mg–Al LDH, which has a lot of large interlayer spacings when intercalated with organic acid anions, can take up a large number of DMA molecules from an aqueous solution.     

Thermodynamic equilibrium analyses of the uptake of aromatic compounds from an aqueous solution by magnesium–aluminum (Mg–Al) layered double hydroxide intercalated with 1-naphthol-3,8-disulfonate

Magnesium–aluminum layered double hydroxide (Mg–Al LDH) intercalated with 1-naphthol-3,8-disulfonate (1-N-3,8-DS²⁻) was prepared by coprecipitation. Thermodynamically, the prepared Mg–Al LDH showed greater preferential uptake of 1,3-dinitrobenzene (DNB) than of 1,2-dimethoxybenzene (DMB). This preferential uptake of aromatic compounds, which is adequately expressed by the Dubinin–Radushkevich adsorption isotherm, was attributed to the π–π stacking interactions between the benzene ring of the aromatic compounds and the naphthalene core of 1-N-3,8-DS²⁻ intercalated in the interlayer spaces of Mg–Al LDH. Negative values of ΔG for DNB and DMB indicate that the adsorption process is spontaneous at all temperatures. The value of ΔS for DNB was much lower than that for DMB. This implies that DNB was far more strongly adsorbed to 1-N-3,8-DS²⁻ than was DMB, resulting in a lower degree of freedom for and higher uptake of DNB than those in the case DMB. The absolute values of |ΔH| for DNB and DMB were less than 20 kJ mol⁻¹, indicating that the uptake of DNB or DMB by 1-N-3,8-DS·Mg–Al LDH can be considered a physical adsorption process caused by π–π stacking interactions.     

层状水滑石对吡啶二甲酸异构阴离子的选择性插层行为

本文采用焙烧复原法研究了镁铝水滑石与吡啶二甲酸异构阴离子单体及其混合体的插层反应，实验发现镁铝水滑石对吡啶二甲酸异构阴离子存在着明显的选择性，有机酸异构体优先进入层间的顺序是：2,3-吡啶二甲酸>2,5-吡啶二甲酸>2,4-吡啶二甲酸>3,5-吡啶二甲酸>3,4-吡啶二甲酸>2,6-吡啶二甲酸。利用XRD、IR和TG测试技术对样品进行了表征，同时采用Gaussian-98软件包中ab initio 分子轨道法（HF/6-31G）计算了吡啶二甲酸异构阴离子的分子结构，理论结合实验探讨了阴离子在水滑石层间可能的空间构型，分析了其结构与插层行为的关系。研究表明镁铝水滑石层状材料插层过程中具有分子识别能力，可用于分离有机异构阴离子。     

Preparation of sodium oleate/layered double hydroxide composites with acid-resistant properties

MgAlCO3 type layered double hydroxides (LDHs) with Mg/Al ratios ranging from 2 to 5 were synthesized by coprecipitation. Composites with sodium oleate/LDH were prepared by ion exchange and reconstruction of the LDH in sodium oleate solution. The amount of sodium oleate in the composites prepared by this reconstruction method was higher than that in samples prepared by the ion-exchange method. The basal spacings of the LDHs increased to 3.9 and 1.8 nm after synthesis of the composites, these spacings being in good agreement with models based on the assumption that the oleate ions are intercalated as bilayer and/or micelle structures, and as monolayers in the LDH interlayers, respectively. The number of sorbed oleate ions was higher than calculated from the anion-exchange capacities of the LDHs in most of the samples, increasing as the Mg/Al ratios of the LDHs were increased from 2 to 5. These results suggest that the oleate ions are present not only in the interlayers but also on the surfaces of the LDH particles. The acid-resistant properties of the composites were found to be much higher than for the pure LDHs. It is thus confirmed that the surfaces of the LDH particles in the composites are mostly covered with sorbed oleate ions and that the composites are good candidates as drug delivery materials.     

软模板法制备三维花状MgAl-LDH及其吸附性能

采用软模板法,以十二烷基硫酸钠(SDS)为模板剂,经水热合成制得三维花状双金属(Mg Al)氢氧化物(3D-Mg Al LDH)。通过XRD、FT-IR、SEM及TEM等表征手段,研究了原料Mg/Al物质的量之比、SDS浓度及反应时间对产物微观结构和表面形貌的影响规律,并初步探讨了3D-Mg Al LDH的形成机理。结果表明,当n_(Mg)/n_(Al)=2,SDS浓度为0.1 mol·L~(-1),水热反应时间为6 h时,可形成结晶度良好、花球形貌完整,纳米片厚度均一的三维花状LDH。在3D-Mg Al LDH的形成过程中,SDS既以阴离子形态参与LDH形成,又因其类球状胶束特性附着在已形成的LDH表面或边缘诱导LDH纳米片交叉生长形成三维花状。吸附实验表明,3D-Mg Al LDH对非离子型有机污染物具有良好的吸附作用,最大吸附量约为31 mg·g~(-1),去除率达到100%。     

A composite of layered double hydroxides obtained through random costacking of layers from Mg–Al and Co–Al LDHs by delamination–restacking: Thermal decomposition and reconstruction behavior

A composite of dodecylsulfate intercalated Mg–Al and Co–Al LDHs in which the layers of the two LDHs are randomly costacked was prepared starting from the monolayer colloidal dispersions of the individual surfactant intercalated LDHs obtained through delamination in 1-butanol. The surfactant ion of the composite could be exchanged for acetate ions. The thermal decomposition and reconstruction behavior of the acetate-intercalated composite was found to be different from those of an LDH in which each layer contains Mg, Co and Al and a physical mixture of Mg–Al and Co–Al LDHs. While the composite shows partial reconstruction to LDH phase even after heating up to 1000 °C the other samples do not show reconstruction beyond 800 °C.     

12-磷钨酸插层MgAl水滑石的合成、表征及催化酯化原油脱酸性能

采用离子交换法合成了不同Mg/Al物质的量比的12-磷钨酸(H_3PW_(12)O_(40),HPW)插层水滑石(LDHs),采用XRD、FT-IR、Raman、ICP-AES、TG-DSC等分析手段表征其物化性质,Hammett指示剂-正丁胺滴定法测定其酸强度和酸量分布。进一步将其用于原油催化酯化脱酸反应,并与NO_3型LDHs对比,探讨酯化活性与催化剂性质之间的关系。结果表明,催化剂的活性主要受酸性和比表面积的影响。HPW插层LDHs的酯化活性明显优于NO3型LDHs,归因于增强的酸性和增大的比表面积。对于弱酸性的NO_3型LDHs,酯化活性与比表面积呈正向关系,Mg/Al物质的量比为4时,具有最大的比表面积和脱酸活性。而对于较强酸性的HPW插层LDHs,酯化活性主要受到酸量的影响,Mg/Al物质的量比为2的催化剂具有最高的酸量和脱酸活性。     

喜树碱插层的镁铝型层状双金属氢氧化物的合成及表征

采用共沉淀法把抗癌药物喜树碱（Camptothecin, CPT）插入层状双金属氢氧化物(layered double hydroxide, LDH)层间, 合成了CPT-LDH纳米杂化物。结果表明,在CPT-LDH纳米杂化物中,CPT在层间的排布方式有两种,即平行于层板的单层排列和垂直于层板的双层排列;缓释研究表明,CPT-LDH在pH 7.5的磷酸缓冲液中具有明显的缓释效果,其释放速率较相同pH值时CPT和LDH物理混合物的释放速率明显降低;考察了CPT-LDH的药物释放机理,在 pH 7.5的缓冲溶液中,释放过程受粒内扩散过程控制;CPT-LDH纳米杂化物的释放动力学符合准一级动力学过程。     

Composition and ionic change capacity variation of surfactant-intercalated MgFe-layered double hydroxides in the one step synthesis

Surfactant-intercalated MgFe-layered double hydroxides (MgFe-LDHs) were successfully synthesized via one-step self-assembly of the surfactants (sodium dodecyl sulfate, 1-hexadecane sulfate, and sodium dodecyl benzene sulfonate) and the LDH precursors without avoiding dissolved CO₃ ^2?. As a control, p-toluene sulfonic acid was used to further study the functions of surfactants. The detailed characterization of the surfactant intercalated MgFe-LDHs and their intermediates confirm that the basal spacing changes of the formed LDHs derive from the release of surfactants out of LDH interlayers or the adsorption of surfactants from the solution in the reaction. Besides, the Mg/Fe ratio of the LDH sheets increases with the reaction and the corresponding ionic exchange capacity (IEC) of the MgFe-LDHs decreases. The final surfactant intercalated MgFe-LDH particles are the mixture of MgFe-LDH sheets with different composition and IEC, which can be the basic principle of LDH preparation for different applications. Also the Mg/Fe ratio of the surfactant intercalated MgFe-LDHs decreases with the increase of molecular length of surfactants used.     

Decarbonation of MgAl-LDHs (layered double hydroxides) using acetate-buffer/NaCl mixed solution

By using acetate-buffer (sodium acetate and acetic acid)/NaCl mixed solutions, the deintercalation of carbonate ions (CO(2-)3) was conducted on MgAl--LDHs at different Mg/Al ratios-LDH2 (LDH with Mg/Al approximately 2) and LDH3 (LDH with Mg/Al approximately 3). When only an acetate-buffer solution was used, decarbonation did not take place even if the buffer solution was made acidic enough to dissolve LDH itself; however, the addition of NaCl to the buffer solution caused deintercalation of the carbonate ions from the MgAl-LDHs and the reaction was conducted without any morphological and weight change at 25 degrees C. Under the optimum conditions, full decarbonation was attained for the two MgAl-LDHs in minutes, and the obtained LDHs contained Cl(-) in the interlayer space without incorporation of any acetate anions due to their extremely low anion selectivity of acetate ion. The allowable range for the concentration of the decarbonation solution is wide, and the change in pH due to the decarbonation reaction is slight because of the buffering effect. The decarbonation was affected by the Mg/Al ratio of the LDH; i.e., the present LDH2 was slightly more difficult to decarbonate than LDH3, probably due to the higher layer-charge density of LDH2.     

Application of simplified version of advanced isoconversional procedure in non-isothermal kinetic study

Thermogravimetric analysis (TG) and powder X-ray diffraction (PXRD) were used to study some selected Mg/Al and Zn/Al layered double hydroxides (LDHs) prepared by co-precipitation. A Mg/Al hydrotalcite was investigated before and after reformation in fluoride and nitrate solutions. Little change in the TG or PXRD patterns was observed. It was proposed that successful intercalation of nitrate anions has occurred. However, the absence of any change in the d ₍₀₀₃₎ interlayer spacing suggests that fluoride anions were not intercalated between the LDH layers. Any fluoride anions that were removed from solution are most likely adsorbed onto the outer surfaces of the hydrotalcite. As fluoride removal was not quantified it is not possible to confirm that this has happened without further experimentation. Carbonate is probably intercalated into the interlayer of these hydrotalcites, as well as fluoride or nitrate. The carbonate most likely originates from either incomplete decarbonation during thermal activation or adsorption from the atmosphere or dissolved in the deionised water. Small and large scale co-precipitation syntheses of a Zn/Al LDH were also investigated to determine if there was any change in the product. While the small scale experiment produced a good quality LDH of reasonable purity; the large scale synthesis resulted in several additional phases. Imprecise measurement and difficulty in handling the large quantities of reagents appeared to be sufficient to alter the reaction conditions causing a mixture of phases to be formed.     

Electrospun poly(lactic acid) nanofibers loaded with silver sulfadiazine/[Mg–Al]‐layered double hydroxide as an antimicrobial wound dressing

Poly(lactic acid) (PLA) is a versatile, bioabsorbable, and biodegradable polymer with excellent biocompatibility and ability to incorporate a great variety of active agents. Silver sulfadiazine (SDZ) is an antibiotic used to control bacterial infection in external wounds. Aiming to combine the properties of PLA and SDZ, hydrotalcite ([Mg–Al]‐LDH) was used as a host matrix to obtain an antimicrobial system efficient in delivering SDZ from electrospun PLA scaffolds intended for wound skin healing. The structural reconstruction method was successfully applied to intercalate silver sulfadiazine in the [Mg–Al]‐LDH, as evidenced by X‐ray diffraction and thermogravimetric analyses. Observations by scanning electron microscopy revealed a good distribution of SDZ‐[Mg–Al]‐LDH within the PLA scaffold. Kinetics studies revealed a slow release of SDZ from the PLA scaffold due to the intercalation in the [Mg–Al]‐LDH. In vitro antimicrobial tests indicated a significant inhibitory effect of SDZ‐[Mg–Al]‐LDH against Escherichia coli and Staphylococcus aureus. This antibacterial activity was sustained in the 2.5‐wt% SDZ‐[Mg–Al]‐LDH–loaded PLA nanofibers, which also displayed excellent biocompatibility towards human cells. The multifunctionality of the PLA/SDZ‐[Mg–Al]‐LDH scaffold reported here is of great significance for various transdermal applications.     

Benzocarbazole anions intercalated layered double hydroxide and its tunable fluorescence

Luminescent benzocarbazole anions (BCZC) intercalated into the interlayer region of Mg-Al-layered double hydroxides (BCZC/LDH) with different layered charge densities (LCD) were prepared. The structure and chemical composition of the composites were characterized by X-ray diffraction, elemental analysis, thermogravimetry and differential thermal analysis (TG-DTA), infrared spectra (FT-IR), UV-vis absorption and fluorescence spectroscopy. The photoemission behavior of BCZC in the LDH matrix with high (Mg/Al ratio = 1.801) and low (Mg/Al ratio = 3.132) LCD is similar to that of BCZC solid and aqueous solution states respectively, indicating that the luminescence performances of the intercalated dye anions can be tuned by adjusting the LCD of the LDH layer. Moreover, the thermal stability and stacking order of BCZC are largely improved upon intercalation, and the BCZC/LDH thin film exhibits well polarized luminescence with the luminescent anisotropy of 0.15-0.20. In addition, molecular dynamics (MD) simulation was employed to calculate the basal spacing and molecular arrangement of the intercalated BCZC within the LDH matrix. The simulation results show that the distribution of BCZC anions is much broader in the gallery of Mg-Al-LDH with high LCD, while BCZC anions exhibit a more ordered arrangement in LDH with low LCD. Furthermore, the radial distribution functions of interlayer water molecules were also studied. Based on the combination of experiment and theoretical simulation, this work provides a detailed understanding of the tunable photoluminescence, orientation and diffusion behavior of the luminescent molecules confined within the gallery of a 2D inorganic matrix.     

Preparation and Characterization of Cu(II) Phthalocyanine Tetrasulfonate Intercalated and Supported on Layered Double Hydroxides

The aim of the present work was to synthesize and characterize layered doublehydroxides (LDHs), in the magnesium/aluminum form, intercalated with copper(II)phthalocyanine tetrasulfonate (CuPcTs). The metal complex was immobilized intothe LDH gallery region through the reconstitution method and this material wascharacterized by X-ray diffraction (XRD), surface area and porosity measurements,elementary analysis, thermogravimetry (TGA), vibrational (IR) and electronic(UV-visible) spectroscopies, and electronic paramagnetic resonance (EPR). Thecatalytic performance of CuPcTs intercalated and supported on the LDH wasevaluated by carrying out the hydrogen peroxide dismutation. The CuPcTs wassuccessfully intercalated into the LDH layers according to XRD data (the basalspacing of the carbonate precursors increases by approximately 15Å inthe intercalated samples). The surface area and porosity analysis suggested thatthe CuPcTs intercalated materials are not microporous solids. Samples containingthe metal complex confined between the LDH layers have an appreciable thermalstability: decomposition is not observed at least up to 400 °C. TGA experiments also show that the weight-loss curves of the CuPcTs supported samples superimpose those recorded for the CuPcTs complex and the LDH-carbonate while the curves for theintercalated materials are unique. CuPcTs intercalated or supported on LDHs is notactive in the hydrogen peroxide dismutation although the free form shows activity at pH above 8.     

Removal of Naphthol Green B from Aqueous Solution by Calcined Layered Double Hydroxides:Adsorption Property and Mechanism Studies

The adsorption of naphthol green B (NGB) by Mg/Al‐LDO (layered double oxides) with a Mg/Al molar ratio of 3:1 was investigated in a batch mode. Our study indicates that the maximum capacity of NGB adsorption at equilibrium is 193.4 mg and the percentage of absorption is 96.7%, with an adsorbent dose of 1.0 g/L under the following condition: 200 mg/L NGB concentration, temperature 298 K, pH 10.0 and an equilibrium time of 80 min. Langmuir and Freundlich adsorption models were used for fitting the isotherms, and the thermodynamic parameters have been calculated, which showed that the adsorption process was spontaneous and exothermic in nature. In the light of so called "memory effect", the Mg/Al‐LDO was found to recover their original layered structure after adsorption, and part of NGB ions intercalated into the interlayer of LDH (layered double hydroxides), which has been supported by XRD and FTIR. In addition, the competitive anions for adsorption and the regeneration of Mg/Al‐LDO have also been investigated.     

Intercalation of Sulfanilic Acid‐Phenol‐Formaldehyde Polycondensate into Hydrocalumite Type Layered Double ­Hydroxide

Polycondensates containing sulfonate groups, referred to as concrete superplasticizers, are widely used in the construction industry. A sulfanilic acid–phenol–formaldehyde polycondensate (SPF) with M_w ≈ 100.000 g · mol^–1 was synthesized from sulfanilic acid, phenol and formaldehyde by polycondensation reaction, and its intercalation into hydrocalumite type Layered Double Hydroxide (LDH) was investigated. Preparation was done by rehydration of tricalcium aluminate, a cement constituent, in the presence of the polymer. According to the XRD pattern, SPF was successfully intercalated. A d value of approx. 2.6 nm was found. Elemental composition of the new organo‐mineral phase reveals charge balancing of the cationic LDH main layers by the polycondensate. Thermogravimetry indicates that thermal degradation of intercalated SPF occurs at higher temperature, compared to non‐intercalated SPF. According to SEM imaging, the novel Ca‐Al‐LDH phase exhibits the morphology of intergrown platelets. Ultra‐thin nanosheets (foils) with approx. 50 nm thickness were obtained. The layered structure and d value obtained from diffraction analysis were confirmed by TEM imaging. The new hydride can be used as cement and concrete additive.     

Thermal analysis of W-free Co–(Ni)–Al–Mo–Nb superalloys

CuAl layered double hydroxide (CuAl-LDH) was synthesized by co-precipitation. Sodium phenyl phosphate (SPP) and sodium dodecyl sulfate (SDS) are used to modify CuAl-LDH for preparing CuAl-(SPP)LDH and CuAl-(SDS)LDH, which were incorporated into epoxy resin (EP) to obtain EP/CuAl-(SPP)LDH and EP/CuAl-(SPP)LDH nanocomposites. The results indicate that SPP and SDS are intercalated into the interlayers of CuAl-LDH, and CuAl-(SPP)LDH has larger layer spacing than CuAl-(SDS)LDH. The thermal stability and flame-retardant performances of EP/CuAl-(SPP)LDH nanocomposites were better than those of EP/CuAl-(SDS)LDH composites. Compared with those of EP/4CuAl-(SDS)LDH nanocomposites, the peak heat release rate (PHRR) of EP/4CuAl-(SPP)LDH nanocomposites is reduced 25.8% and 55.6%, and peak smoke production rate (PSPR) value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, value of EP/4CuAl-(SPP)LDH nanocomposites is reduced 27.6% and 46.2%, respectively. The improved flame retardancy and smoke suppression performances of EP/CuAl-(SPP)LDH nanocomposites were attributed to the combination of copper compounds and SPP, promoting the formation of swollen, continuous and compact char layers on the surface of EP nanocomposites during combustion, eventually restraining the decomposition of EP nanocomposites.

     

Dodecyl sulfate-hydrotalcite nanocomposites for trapping chlorinated organic pollutants in water

A series of hybrid organic-inorganic nanocomposite materials was synthesized by three different procedures using sodium dodecyl sulfate (DDS) and magnesium-aluminum layered double hydroxide (Mg/Al LDH with a Mg/Al molar ratio of 2 to 5). Both the pH of the exchange medium (6.5 to 10) and the Mg/Al molar ratio of the LDH affected the basal spacing, the content of DDS retained and the orientation of the DDS chains within the interlamellar space. For LDH with higher charge density (Mg/Al=2 and 3), DDS molecules likely formed a perpendicular monolayer within the LDH interlayer and the solution pH had little effect on the basal spacing, with a mean and standard deviation of 25.5+/-0.4 A. However, for LDH with lower charge density (Mg/Al=4 and 5), DDS molecules more likely formed an interpenetrating bilayer, and the basal spacing significantly increased with increasing pH, with a mean and standard deviation of 32.7+/-5.2 A. Sorption of trichloroethylene and tetrachloroethylene by DDS-LDH varied with synthesis conditions, LDH type and DDS configuration in the interlayer. DDS-Mg(3)Al-LDH had the highest affinity for both trichloroethylene and tetrachloroethylene in water, either comparable to or as much as four times higher than other clay-derived sorbents, followed by DDS-Mg(4)Al-LDH and DDS-Mg(5)Al-LDH. DDS-Mg(2)Al-LDH had the lowest sorption affinity although the highest amount of DDS. The pH of the exchange solution also affected the amount of DDS retained by the LDH as well as the sorption efficiency. Mg(3)Al-LDH has a charge equivalent area of 32.2 A(2)/charge, which allows the formation of optimal DDS configuration within its interlayer, thus resulting in the highest affinity for the chlorinated compounds. The DDS-Mg/Al-LDHs can be easily synthesized either ex situ or in situ at low temperature, indicating the feasibility of practical applications. The results obtained by controlling the synthesis procedure suggest that different arrangements of DDS molecules in the LDH interlayers can be obtained and optimized for the sorption of specific sorbates.     

Layered Double Hydroxides Intercalated by Polyoxometalate Anions with Keggin (alpha-H(2)W(12)O(40)(6)(-)), Dawson (alpha-P(2)W(18)O(62)(6)(-)), and Finke (Co(4)(H(2)O)(2)(PW(9)O(34))(2)(10)(-)) Structures

The pillaring of Mg(3)Al layered double hydroxides (LDHs) by the title polyoxometalates (POMs) was accomplished by ion exchange reaction of the LDH-hydroxide and -adipate precursors with the POM anion at ambient or refluxing temperatures. The structural, thermal and textural properties of the LDH-POM intercalates were elucidated based on XRD, FTIR, TEM, EDS, and N(2) adsorption-desorption studies. A gallery height of approximately 10 ? was observed for the LDH intercalated by the symmetrical Keggin POM, whereas two different gallery heights were found for the cylindrical Dawson (14.5 and 12.8 ?) and Finke (13.3 and 12.6 ?) anions, depending on the preparation temperature. The differences in POM orientations were rationalized in terms of different electrostatic and hydrogen-bonding interactions between the POM pillars and the LDH layers. Upon thermal treatment at >/=100 degrees C, the intercalated Dawson and Finke POM ions exhibited only one gallery orientation, regardless of synthesis conditions. The crystalline microporous structures were retained upon heating each LDH-POM intercalate in N(2) to 200 degrees C. Pillaring in all cases was accompanied by the formation of a poorly ordered Mg(2+)/Al(3+) salt impurity that formed on the external surfaces of the LDH crystals.     

Preparation of an anionic azo pigment-pillared layered double hydroxide and the thermo- and photostability of the resulting intercalated material

A large anionic pigment has been intercalated into a layered double hydroxide (LDH) host by ion-exchange of an Mg/Al LDH-nitrate precursor with a solution of C.I. Pigment Red 48:2 (the calcium salt of 4-((5-chloro-4-methyl-2-sulfophenyl)azo)-3-hydroxy-2-naphthalene-carboxylic acid), in ethane-1,2-diol. After intercalation of the pigment, the interlayer distance in the LDH increases from 0.86 to 1.72 nm. Infrared spectra and TG-DTA curves reveal the presence of a complex system of supramolecular host-guest interactions. The UV-visible diffuse reflectance spectra of C.I. Pigment Red 48:2 show marked changes after heating at 200 °C and above, whereas there are no significant changes in the spectra of the intercalated pigment after heating at temperatures up to 300 °C, showing that the thermostability is markedly enhanced by intercalation in the LDH host. The pigment-intercalated LDHs exhibits much higher photostability to UV light than the pristine pigment, in the case of both the pure solids and their composites with polypropylene, as shown by measurement of CIE 1976 L^*a^*b^* color difference (ΔE) values.