Preparation and characterization of smart (solid–gel) shape-stable phase change materials with photoluminescent and thermochromic properties

Journal of Thermal Analysis and Calorimetry - A novel smart solid-gel phase change materials (PCMs) with the photoluminescence and thermochromic properties were designed and fabricated in a simple...     

Synthesis and thermal properties of poly(styrene-co-acrylonitrile)-graft-polyethylene glycol copolymers as novel solid–solid phase change materials for thermal energy storage

A novel poly(styrene-co-acrylonitrile)-graft-polyethylene glycol(SAN-g-PEG) copolymer was synthesized as new solid–solid phase change materials(SSPCMs) by grafting PEG to the main chain of poly(styrene-co-acrylonitrile). The chemical structure of the SAN-g-PEG was confirmed by the Fourier transform infrared(FT-IR) and proton nuclear magnetic resonance(1H NMR) spectroscopy techniques. The thermal energy storage properties and the storage durability of the SAN-g-PEG were investigated by differential scanning calorimetry(DSC). The SAN-g-PEG was endowed with the solid–solid phase transition temperatures within the range of 23–36 8C and the latent heat enthalpy ranged from 66.8 k J/kg to 68.3 k J/kg. Thermal cycling tests revealed that the SAN-g-PEG kept great heat storage durability after 1000 thermal cycles. The thermal stability was evaluated by a thermal gravity analysis(TGA), and the initial decomposition temperature(Td) of SAN-g-PEG is 350 8C, which proves that the SAN-g-PEG possessed good thermal stability.     

Synthesis and thermal energy storage properties of the polyurethane solid–solid phase change materials with a novel tetrahydroxy compound

Based on the phase change theory, a novel tetrahydroxy compound (THCD) was designed and prepared. Depending on the spatial structure of the tetrahydroxy compound, a form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was synthesized via employing PEG as soft segments, while multi-benzene ring structure made by 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound as hard segments. The composition and structure of THCD and TPUPCM, the TPUPCM’s the weight average molecular weight and number average molecular weight, dissolving and melting abilities, phase change behaviors, thermal performances and crystalline morphology were investigated by Fourier transform infrared spectrometer, ¹H nuclear magnetic resonance spectrometer, multiangle laser light scattering apparatus, differential scanning calorimentry, dynamic mechanical thermal analysis, thermogravimetry analysis system, wide-angle X-ray diffraction, polarizing optical microscopy. The results show that the solid–solid phase change material owns excellent phase change properties and a broad processing temperature range. The heating cycle phase change enthalpy is 137.4 J/g, and the cooling cycle phase change enthalpy is 127.6 J/g. The started decomposition temperature and the maximum decomposition temperature are at 323.5 and 396.2 °C, respectively. Furthermore, the solid–solid phase change material is dissolvable, meltable and can be processed directly, and has great potential applications in thermal energy storage.     

Synthesis and characterization of trimethoxysilyl-functionalized poly(phthalazinone ether ketone)

A novel alkoxysilyl-functionalized poly(phthalazinone ether ketone)(PPEK)was prepared for the boundary lubricant application in micro-electro-mechanical system(MEMS).The synthesis of functionalized PPEK was started from the hydro- xylation of PPEK,then following with the corresponding ring-opening reaction of 3-glycidoxypropyltrimethoxysilane(GPTMS). The structures of the functional PPEK were confirmed by FTIR,~1H NMR,~(29)Si NMR,and UV-vis spectrum.     

Low-temperature heat capacities, and thermodynamic properties of solid–solid phase change material bis(1-octylammonium) tetrachlorocuprate

A new crystalline complex (C₈H₁₇NH₃)₂CuCl₄(s) (abbreviated as C₈Cu(s)) was synthesized by liquid phase reaction. Chemical analysis, elemental analysis, and X-ray crystallography were applied to characterize the composition and crystal structure of the complex. Low-temperature heat capacities of the complex were measured by a precision automatic adiabatic calorimeter over the temperatures ranging from 78 to 395 K, and two solid–solid phase changes appeared in the heat capacity curve. The temperatures, molar enthalpies and entropies of the two phase transitions of the complex were determined to be: T _{trs, 1} = 309.4 ± 0.35 K, Δ_trs H _{m, 1} = 16.55 ± 0.41 kJ mol^?1, and Δ_trs S _{m, 1} = 53.49 ± 1.3 J K^?1 mol^?1 for the first peak; T _{trs, 2} = 338.5 ± 0.63 K, Δ_trs H _{m, 2} = 6.500 ± 0.10 kJ mol^?1, and Δ_trs S _{m, 2} = 19.20 ± 0.28 J K^?1 mol^?1 for the second peak. Two polynomial equations of the heat capacities as a function of the temperature were fitted by least-square method. Smoothed heat capacities and thermodynamic functions of the complex relative to the standard reference temperature of 298.15 K were calculated based on the fitted polynomial equations.     

Nanocomposite phase change materials based on NaCl–CaCl2 and mesoporous silica

The synthesis of phase change materials based on NaCl–CaCl₂ molten salt mixture and mesoporous silica was investigated. The influence of mesoporous silica porosity and salt concentration on the thermal energy storage properties of the resulting materials is discussed. The nanocomposite samples were characterized by X-ray diffraction, differential scanning calorimetry, infrared spectroscopy, thermogravimetry, scanning electron microscopy and X-ray photoelectron spectroscopy. The mesoporous silica was found to act as a reactive matrix for the molten salts. Composite samples with up 95% wt. salt can be obtained and used as shape-stabilized phase change materials. The materials have heat of fusion values of up to 60.8 J g^?1 and specific heat capacity between 1.0 and 1.1 J g^?1 K^?1. The samples exhibit thermal stability up to 700 °C and can be used for high-temperature thermal energy storage through both latent and sensible heat storage mechanisms.

     

Synthesis and characterization of sol–gel-derived molecular imprinted polymeric materials for cholesterol recognition

The sol–gel-derived host matrices are well known for biosensor applications where various types of organic and biological molecules can be immobilized and can act as recognition elements. The molecular imprinting technology is an attractive alternative method where expensive and labile biorecognition elements can be replaced by molecular imprinted polymers (MIPs), which are capable of recognizing a target molecule of an interest. In the present study, hybrid sol–gel MIPs were synthesized in the form of crushed powder (CP) by both non-hydrolytic and hydrolytic method for cholesterol recognition. These MIPs were characterized by scanning electron microscopy (SEM), fourier transform-infrared (FT-IR), liquid chromatography-mass spectrometry (LC–MS) and nitrogen adsorption–desorption isotherm measurements. The template molecule was extracted by means of soxhlet extraction and calcination method. The cholesterol adsorption experiments were performed by using non-imprinted (NI) and extracted crushed powder (ExCP) and the percentage of adsorption was determined by measuring the residual quantity in the analyte solution using Liebermann-Burchard (L-B) reagent. The adsorption studies with non-imprinted crushed powder (NICP) showed interference with L-B reagent as well as non-specific binding between analyte molecules and silica matrix. The percentage of adsorption or rebinding was found to be higher for phenyl triethoxysilane (PhTEOS)-derived ExCP (composition 3) which was synthesized by the aqueous sol–gel processing method at low pH as compared to PhTEOS-derived (composition 1) and 3-aminopropyltriethoxysilane (APTES)-derived ExCP (composition 2) prepared by non-hydrolytic method. The reusability of used ExCP after re-extraction was also investigated. The various factors affecting rebinding of template molecules were discussed along with interference study. The study provided information on molecular imprinting of cholesterol in sol–gel matrix and highlighted the importance of characterization of MIPs before applying it for sensing applications.     

Synthesis and characterization of poly(phthalazinone biphenyl ether sulfone ketone)s from 4,4′-dichlorobenzophenone

A series of poly(aryl ether sulfone ketone)s containing phthalazinone and biphenyl moieties were synthesized by aromatic nucleophilic displacement polycondensation of 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (DHPZ), 4,4′-dichlorobenzophenone (DCB), 4,4′-dichlorodiphenyl sulfone (DCS) and 4,4′-biphenol (BP) in different molar ratios. The obtained copolymers were characterized by different instrumental techniques (FTIR, TGA, DSC, WAXD, etc.). The inherent viscosities of these polymers were in the range of 0.43–0.56 dL g⁻¹. They were amorphous and had good solubility in polar aprotic organic solvents. The copolymers exhibited high glass transition temperatures (T _gs) between 225°C and 256°C and excellent thermal stability up to 517–526°C (thermal decomposition temperatures for 5% weight loss, T _{d, 5%}) in nitrogen. The tensile strength and elongation at break of the polymers ranged from 63 MPa to 71 MPa and from 18% to 21%, respectively. The processability of the material was effectively improved by the introduction of biphenyl group into polymer backbone.     

Synthesis and characterization of a dipeptide–copper(II)– 2-aminomethylbenzimidazole ternary complex

A new ternary complex [Cu(glygly)(AMBZ)(H₂O)]Cl·H₂O (1) (glygly?=?glycylglycine anion, AMBZ?= 2-aminomethylbenzimidazole) has been prepared and characterized by single-crystal X-ray diffractometry and ESR, electronic and IR spectroscopy. The copper(II) ion has a slightly distorted square-pyramidal coordination, being equatorially coordinated by the bidentate 2-aminomethylbenzimidazole and the bidentate glycylglycine anion and axially by a water molecule. The individual complex molecules are hydrogen bonded to their neighbors, forming a polymeric hydrogen-bonded lattice. Spectroscopic data are in accordance with the crystal structure.     

Synthesis and characterization of Na2O–CaO–SiO2 glass–ceramic

The Na₂O–CaO–SiO₂ ternary glass–ceramic with the composition of 49 mass% Na₂O, 20 mass% CaO, and 31 mass% SiO₂ was prepared by the conventional method. The ternary glass–ceramic was characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The Na₂CaSiO₄ phase, having the cubic crystal system, with the crystallite size of 25.14 nm and lattice parameter of 0.7506 nm was determined from the XRD pattern. The activation energy of the glass–ceramic calculated from the DTA curves was found to be 162.02 kJ mol^?1. The Avrami exponent was found to be ~2 indicating a one-dimensional growth process. The mass loss percent from ambient temperature to 1,173 K is less than 1 %. The density was calculated to be 2,723 kg m^?3. The fine-grained microstructure with the particle sizes less than 1 μm was confirmed by the scanning electron microscope micrograph.     

Biodegradable and biocompatible inorganic–organic hybrid materials. I. Synthesis and characterization

The hydroxyl or vinyl end-groups of linear or three-arm star-shaped poly(ε-caprolactone) (PCL) chains have been derivatized into triethoxysilane groups reactive in the sol-gel process. New transparent hybrid materials that combine tetraethylorthosilicate (TEOS) and PCL known for biodegradability and biocompatibility have accordingly been prepared. The sol-gel process is, however, limited by the early vitrification of the reactive system. However, thermal posttreatment can overcome these diffusional and/or kinetic limitations as assessed by a set of analytical methods. The thermal stability of PCL is improved by incorporation into the silica network. Conversely, the thermal stability of the ceramer depends on the effective PCL content. The extent of PCL incorporation into the silica network depends on PCL molecular weight, number, and reactivity of the PCL functional groups. IR spectroscopy has shown that hydrogen bonding occurs between the ester groups of PCL and residual OH groups of the silicate component. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2295–2309, 1997     

Enantiospecific Synthesis of (–)-Cuspareine and (–)-Galipinine

An enantiospecific route to the synthesis of tetrahydroquinoline alkaloids (–)-cuspareine and (–)-galipinine is reported. Coupling of an iodide derivative of D-serine with aromatic dithianes and Pd-catalyzed intramolecular C–N coupling are the key steps in the synthesis.     

Synthesis and characterization of cobalt acrylate–melamine co-crystals

A new co-crystal of tetraaqua acrylato cobalt (II) complex and melamine, [Co(acr)₂(H₂O)₄]·4MA·2DMF (acr = acrylate, MA = melamine, DMF = dimethylformamide), has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis, and single-crystal X-ray diffraction. The complex contains discrete unities of [Co(acr)₂(H₂O)₄], melamine, and DMF linked by hydrogen bonds. Investigations evidenced that Co(II) has an octahedral stereochemistry and both acrylate ions present unidentate coordination mode. Thermal decomposition occurs in four steps and denotes that melamine is lost at high temperatures, and this indicates a greater stability that may be associated with the presence of hydrogen bonds network.

     

Synthesis and characterization of sol–gel alumina nanofibers

Abstract Alumina nanofibers of high aspect ratio with surface area of >300 m² g⁻¹ has been prepared successfully in bulk quantities by the sol–gel method. The synthesis parameters including the binary water–alcohol solvent system to aluminium isopropoxide ratio, pH, type of solvent and aging temperature affect the uniformity and formation of nanofibers. It is proposed that alumina nanofibers were formed by the curling of the nanosheets upon condensation after the hydrolysis. The phase evolution of alumina nanofibers from pseudoboehmite to α phase has been shown by XRD and FTIR. ²⁷Al NMR investigations show that the Al atoms are six and four coordinated. The morphology of the alumina nanofibers does not change much as the calcination temperature was increased. In addition, the average pore size increases and the BET surface area decreases as a function of calcination temperature. The thermal behavior of alumina nanofibers was investigated by TGA. Graphical Abstract      

Synthesis of novel polyaryl(ether–ketones) with tert-butyl pendent groups

Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether–ketones). The current polyaryl(ether–ketones) showed glass transition temperatures in the range 170–240°C and decomposition temperatures, as measured by TGA, of about 500°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1251–1256, 1998     

Synthesis of polyfluoroalkylated glycerol and crown ether

Perfluoroalkylated glycerol (5, 9) and crown ethers (22, 23, 24) were synthesized starting from glycerol. 5 was synthesized by allylation of glycerol 1,2-acetonide followed by perflu-oroalkylation initiated with sodium dithionite, reduction of iodide and hydrolysis in good overall yield and was shown to poccess good surface activities. Glycerol bis-ether (9) was synthesized in a similar way. Allyloxymethyl crown ethers (15, 16, 18) were prepared as key intermediates through multi-step reactions, which were then perfluoroalkylated to give the title crown ethers 22, 23 ,24.