Solvothermal synthesis of CdS nanowires templated by polyethylene glycol

CdS nanowires were solvothermally synthesized from Cd(NO₃)₂ and S powder using ethylenediamine as a solvent and polyethylene glycol (PEG) as a template. Hexagonal CdS with P6₃mc space group was detected using XRD and SAED, results which are in good accordance with those obtained by the simulation. SEM, TEM and HRTEM revealed the gradual development of nanowires in the [0 0 1] direction with a number of atoms aligning in a crystal lattice. Raman spectra of different products showed the fundamental and overtone modes at the same wavenumbers of 300 and 601 cm⁻¹, respectively. Their relative intensities at different molecular weight PEG were influenced by the anisotropic geometry of the products. Their photoluminescence peaks were detected at the same wavelengths of 518 nm. A formation mechanism for CdS nanowires was also proposed to relate to the experimental results.     

Single Crystalline Cadmium Sulfide Nanowires with Branched Structure

In this article, we report the synthesis of branched single crystal CdS nanowires. This branched CdS nanostructure is prepared by a simple surfactant-directing method, which is of particular interest as it uses readily available reagents and provides a convenient route to high-yield single crystal nanowires but with branched shape. These branched nanowires have an average diameter of about 40 nm and length up to several micrometers. A possible mechanism has been proposed and the addition of surfactant dodecylthiol into the two mixed-solvents would play an importance effect on the structure of the product. Based on the mechanism, by controlling the synthesis conditions, such as the ratios between the surfactant, inorganic solvent, and organic solvent, other kinds of nanostructures based on CdS nanowires were also prepared. Photoluminescence (PL) measurement reveals that the branched CdS nanowires have a strong emission at about 700 nm which might be due to its special structure.     

Synthesis of syndiotactic polystyrene-graft-poly(ethylene glycol) copolymer by photochemical reaction

Syndiotactic polystyrene-graft-poly(ethylene glycol) (sPS-g-PEG) copolymer was prepared by photochemical attachment of poly(ethylene glycol) chains to the benzoylated syndiotactic polystyrene (BesPS) backbone. BesPS, a functional polymer bearing benzophenone moiety, was prepared in a heterogeneous process through Friedel-Crafts acylation reaction using benzoyl chloride as benzoylating agent. This substrate was then dispersed in o-dichlorobenzene at room temperature and mixed with poly(ethylene glycol) , which was reacted with the benzophenone moieties by illumination with UV light (λ > 340 nm). As a result of the photochemical reaction, the hydrophilic poly(ethylene glycol) was chemically attached to the hydrophobic syndiotactic polystyrene backbone. The resultant copolymer was characterized by FT-IR, NMR, and X-ray photoelectron spectroscopy. In addition, the thermal properties of graft copolymers were also studied by means of DSC.     

Stereocomplexed 8-armed poly(ethylene glycol)–poly(lactide) star block copolymer hydrogels: Gelation mechanism,mechanical properties and degradation behavior

Mixing aqueous poly(ethylene glycol)-poly(d-lactide) and poly(ethylene glycol)-poly(l-lactide) star block copolymer solutions resulted in the formation of stereocomplexed hydrogels within 1 min. A study towards the mechanism of the temperature dependent formation of stereocomplexes in the hydrogels using rheology and nuclear magnetic resonance experiments revealed that the formation of stereocomplexes is facilitated at higher temperatures, due to rearrangement in the micellar aggregates thereby exposing more PLA units available for stereocomplexation. The formed gels became temperature irreversible due to the presence of highly stable semi-crystalline stereocomplexed PLA domains. An enantiomeric mixture of 8-armed star block copolymers linked by an amide group between the poly(ethylene glycol) core and the poly(lactide) arms (PEG–(NHCO)–(PLA)₈) yielded hydrogels with improved mechanical properties and stability at 37 °C in PBS compared to 8-armed star block copolymers linked by an ester group. The possibility to be formed in situ in combination with their robustness make PEG–(NHCO)–(PLA)₈ hydrogels appealing materials for various biomedical applications.     

Synthesis, Optical Properties, and Photocatalytic Activity of One-Dimensional CdS@ZnS Core-Shell Nanocomposites

One-dimensional (1D) CdS@ZnS core-shell nanocomposites were successfully synthesized via a two-step solvothermal method. Preformed CdS nanowires with a diameter of ca. 45 nm and a length up to several tens of micrometers were coated with a layer of ZnS shell by the reaction of zinc acetate and thiourea at 180 °C for 10 h. It was found that uniform ZnS shell was composed of ZnS nanoparticles with a diameter of ca. 4 nm, which anchored on the nanowires without any surface pretreatment. The 1D CdS@ZnS core-shell nanocomposites were confirmed by XRD, SEM, TEM, HR-TEM, ED, and EDS techniques. The optical properties and photocatalytic activities of the 1D CdS@ZnS core-shell nanocomposites towards methylene blue (MB) and 4-chlorophenol (4CP) under visible light (λ > 420 nm) were separately investigated. The results show that the ZnS shell can effectively passivate the surface electronic states of the CdS cores, which accounts for the enhanced photocatalytic activities of the 1D CdS@ZnS core-shell nanocomposites compared to that of the uncoated CdS nanowires.     

Preparation of a novel polymer monolith with high loading capacity by grafting block poly(PEGA–mPEGA) for high-efficiency solid phase synthesis

The polymer monolith for solid-phase synthesis with high efficiency was prepared through in situ copolymerization of chloromethylstyrene and ethylene glycol dimethacrylate (PCMS–EDMA). The obtained monolith was grafted by two kinds of poly(ethylene glycol) acrylate oligomer, poly(ethylene glycol) acrylate (PEGA) and poly(ethylene glycol) methyl ether acrylate (mPEGA). The monolith was grafted via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) with the increased number of functional groups (–OH). About 0.61–0.81 mmol/g hydroxyl group resulted from side groups in each grafting polymer chain. PmPEGA in the grafting block copolymer chains can increase the distance between the adjacent reactive sites of PEGA (–OH) in each polymer chain. Therefore, the grafted monoliths with the block copolymer of PEGA-co-mPEGA can give high yield (85%) and purity (93%) of the crude peptide (a difficult sequence-acyl carrier protein fragment 65–74) under the condition of high loading capacity (0.76 mmol/g). These results were higher than those by the grafted monolith with only polymer of PEGA (72% and 81%, respectively) and commercial Wang resin (43% and 39%, respectively). The synthetic efficiency on the grafted monolith with block copolymer in the continuous flow technique was 5–6 folds higher than Wang resins in the manual operation conditions.     

The effects of poly(ethylene glycol) on the low-temperature oxidation reaction of coal as monitored using in situ series diffuse reflectance FTIR

In situ series diffuse reflectance FTIR was used to study the effects of poly(ethylene glycol) as a potential chemical additive inhibiting coal oxidation process at low temperatures. Two coals with different volatile content and, different ash percentages were examined following treatment with 5 wt% poly(ethylene glycol) 200. The surfaces of samples both with and without the additive were analyzed at temperature up to 200 °C in air using in situ diffuse reflectance FTIR. The results showed that poly(ethylene glycol) 200 is capable of inhibiting the oxidation of aliphatic moieties such as methyl and methylene groups, and also reducing the quantity of surface hydroxyl groups through reactions that form more stable ether linkages, thus improving the thermal stability of the coal. A mechanism by which the additive interacts with the coal surfaces is proposed.     

Preparation of waterborne polyurethanes using an amphiphilic diol for breathable waterproof textile coatings

The application of polyurethanes (PUs) on breathable waterproof fabric coatings requires a balance of water vapor permeability (WVP) and water resistance which can be achieved by tailoring hydrophilic and hydrophobic segments. PU prepolymers were prepared from isophorone diisocyanate, dimethylol butanoic acid, and a mixture of various ratios of amphiphilic PPG2050 (copolymer of ethylene oxide and propylene oxide with –OH end groups) and hydrophobic poly(tetramethylene ether glycol) (PTMEG). After neutralization with triethylamine, the prepolymers were chain-extended with ethylene diamine/1,4-butanediol (1:1 by molar). The WVP values of the fabric coatings prepared using various waterborne PUs were very similar (910–990 g/m² × 24 h). When waterborne PUs prepared using a mixture of PPG2050 and PTMEG were employed for the textile coatings, the resulting PU-coated textiles exhibited excellent waterproof properties (>10,000 mm H₂O). The textile coatings prepared from PPG2050/PTMEG-based waterborne PUs were significantly more waterproof than those prepared from poly(ethylene glycol) (PEG)/poly(propylene glycol) (PPG)/PTMEG-based waterborne PU. This is probably due to a more even distribution of hydrophobic segments in the PUs, even though the WVP values of the PEG/PPG/PTMEG-based PU coatings were considerably smaller than those of the PPG2050/PTMEG-based PU coatings.     

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen‐containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s‐b‐polyacrylonitrile, poly(ethylene glycol)s‐b‐poly(acrylonitrile‐co‐vinyl acetate), poly(ethylene glycol)s‐b‐polyacrylamide, poly(ethylene glycol)s‐b‐poly(acrylamide‐co‐vinyl acetate), poly(1‐chloromethyl ethylene glycol)‐bpoly(acrylonitrile‐co‐vinyl acetate), and bis[poly(ethylene glycol terephthalate)]‐b‐poly(acrylonitrile‐co‐vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999     

PET synthesis in the presence of new aluminum catalysts

A new polycondensation catalyst (ethylene glycol aluminum) was synthesized and applied in PET synthesis. It has been characterized by spectral studies (IR, NMR). The catalytic activity of organic aluminum compound was discussed in this paper. In this investigation, the synthesis of poly(ethylene terephthalate) (PET) is presented using ethylene glycol (EG) and terephthalic acid (TPA). The result proved that ethylene glycol aluminum was the real catalytic material. And it was proved to be the most efficient catalyst for the polycondesation reaction among the organic aluminum compounds. Similar catalytic activity has been observed for ethylene glycol aluminum compared to ethylene glycol antimony. The esterification reaction was monitored by measuring the distilled water as a function of time and the modeling of this process was carried out from these data. The received PET samples were characterized by viscometry, carboxyl end-group content and diethylene glycol (DEG) content. A mechanism of aluminum catalysis has been proposed to explain these observations.     

Synthesis and evaluation of biodegradable segmented multiblock poly(ether ester) copolymers for biomaterial applications

Based on 1,4‐succinic acid, 1,4‐butanediol, poly(ethylene glycol)s and dimethyl terephthalate, biodegradable segmented multiblock copolymers of poly[(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol)] (PTSG) were synthesized with different poly(butylene succinate) (PBS) molar fractions and varying the poly(ethylene glycol) (PEG) segment length, and were evaluated as biomedical materials. The copolymer extracts showed no in vitro cytotoxicity. However, sterilization of the copolymers by gamma irradiation had some limited effect on the cytotoxicity and mechanical properties. A copolymer consisting of PEG‐1000 and 20 mol% PBS, assigned as 1000PBS20 after SO₂ gas plasma treatment, sustained the adhesion and growth of dog vascular smooth muscle cells. The in vivo biocompatibility of this sample was also measured subcutaneously in rats for 4 weeks. The assessments indicated that these poly(ether ester) copolymers are good candidates for anti‐adhesion barrier and drug controlled‐release applications. Copyright © 2004 Society of Chemical Industry     

Lipase Catalyzed Synthesis and Thermal Properties of Poly(dimethylsiloxane)–Poly(ethylene glycol) Amphiphilic Block Copolymers

Resin immobilized lipase B from Candida antarctica (CALB) was used to catalyze the condensation polymerization of two difuctional siloxane and poly(ethylene glycol) systems. In the first system, 1,3-bis(3-carboxypropyl)tetramethyldisiloxane was reacted with poly(ethylene glycol) (PEG having a number-average molecular weight, M_n = 400, 1000 and 3400 g mol⁻¹, respectively). In the second system, α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (HAT-PDMS, M_n = 2500 g mol⁻¹) was reacted with α,ω-(diacid) terminated poly(ethylene glycol) (PEG, M_n = 600 g mol⁻¹). All the reactions were carried out in the bulk (without use of solvent) at 80 °C and under reduced pressure (500 mmHg vacuum gauge). The progress of the polyesterification reactions was monitored by analyzing the samples collected at various time intervals using FTIR and GPC. The thermal properties of the copolymers were characterized by DSC and TGA. In particular, the effect of the chain length of the PEG block on the molar mass build up and on the thermal stability of the copolymers was also studied. The thermal stability of the enzymatically synthesized copolymers was found to increase with increased dimethylsiloxane content in the copolymers.     

溶剂热法合成硫化镉材料实验研究

以硫脲、九水硝酸镉为原料,乙二醇为溶剂,聚乙烯吡咯烷酮（PVP）为分散剂,聚丙烯酰胺（PAM）或N,N-二甲基甲酰胺（DMF）为生长调节剂,采用溶剂热法成功制备了硫化镉纳米材料。探究了分散剂与生长调节剂对溶剂热法合成硫化镉纳米材料的影响。研究表明,仅以PVP为分散剂制得的硫化镉颗粒呈现规则的球形且粒度均匀,小球粒径约为500 nm;以PVP为分散剂,DMF为生长调节剂,两者协同作用抑制了硫化镉的生长,得到的硫化镉颗粒粒度均匀,小球粒径约为250 nm;以PVP为分散剂,PAM为生长调节剂,两者协同作用得到的硫化镉颗粒呈现规则的球形且粒度均匀,小球粒径约为125 nm。X射线衍射（XRD）表征结果表明,合成的硫化镉是纯相硫化镉,生长调节剂具有粒径“倍增效应”。     

Blending Modification of PHBV/PBS/PEG and its Biodegradation

This study used poly(butylene succinate) and poly(ethylene glycol) to modify poly(3-hydroxybutyrate-co-3-hydroxyvalerate). The results showed that the incorporation of poly(butylene succinate) and poly(ethylene glycol) improved the mechanical properties of blends. The results showed that crystallinity of the poly(ethylene glycol)-containing blends decreased, so do the crystallization temperature and melting temperature of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) component of blends. Poly(butylene succinate)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(ethylene glycol) ratio of 50:20:30 was chosen owing to its good properties. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) component of blends can be degraded completely by Pseudomonas mendocina DS04-T, whereas this strain cannot degrade poly(butylene succinate) and poly(ethylene glycol). Apart from poly(butylene succinate), Fusarium sp. FS1301 can also biodegrade poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(ethylene glycol).     

Dye Sorption and Water Uptake Properties of Crosslinked Acrylamide/Sodium Methacrylate Copolymers and Semi-Interpenetrating Polymer Networks Composed of PEG

A series of novel semi-interpenetrating polymer networks hydrogels composed of poly(ethylene glycol) and random copolymer of acrylamide/sodium methacrylate were prepared by polymerization of aqueous solution of acrylamide, sodium methacrylate using ammonium persulphate/N,N,N′,N′-tetramethylethylenediamine as a redox-initiating pair in the presence of poly(ethylene glycol) and poly(ethylene glycol)diacrylate as crosslinker. Fourier Transform Infrared spectroscopy was used to identify the presence of different repeating units in the semi IPNs. Water uptake and dye-sorption properties of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs were investigated as a function of chemical composition of the hydrogels. Cationic dye, Janus Green B have been used in sorption studies as a model molecule. This study has given the quantitative information on the swelling and sorption characteristic of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs in many potential applications.     

NMR study of the early stages of gel formation in the PEG/poly(AMPS‐co‐NIPA) semi‐interpenetrating network system

The rate of conversion of the monomers and crosslinker in the formation of a novel semi‐interpenetrating poly(ethylene glycol)/ poly(2‐acrylamido‐2‐methylpropane sulfonic acid‐co‐N‐isopropylacrylamide) copolymer hydrogel was determined by using ¹H‐NMR spectrometry. It was established that poly(ethylene glycol) does not participate in the polymerization reactions and that crosslinking by methylenebisacrylamide occurs predominantly in the early stages of copolymer chain growth. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3635–3641, 2004     

Preparation of waterborne polyurethanes using an amphiphilic diol for breathable waterproof textile coatings

The application of polyurethanes (PUs) on breathable waterproof fabric coatings requires a balance of water vapor permeability (WVP) and water resistance which can be achieved by tailoring hydrophilic and hydrophobic segments. PU prepolymers were prepared from isophorone diisocyanate, dimethylol butanoic acid, and a mixture of various ratios of amphiphilic PPG2050 (copolymer of ethylene oxide and propylene oxide with –OH end groups) and hydrophobic poly(tetramethylene ether glycol) (PTMEG). After neutralization with triethylamine, the prepolymers were chain-extended with ethylene diamine/1,4-butanediol (1:1 by molar). The WVP values of the fabric coatings prepared using various waterborne PUs were very similar (910–990 g/m² × 24 h). When waterborne PUs prepared using a mixture of PPG2050 and PTMEG were employed for the textile coatings, the resulting PU-coated textiles exhibited excellent waterproof properties (>10,000 mm H₂O). The textile coatings prepared from PPG2050/PTMEG-based waterborne PUs were significantly more waterproof than those prepared from poly(ethylene glycol) (PEG)/poly(propylene glycol) (PPG)/PTMEG-based waterborne PU. This is probably due to a more even distribution of hydrophobic segments in the PUs, even though the WVP values of the PEG/PPG/PTMEG-based PU coatings were considerably smaller than those of the PPG2050/PTMEG-based PU coatings.     

Synthesis and characterization of ABA triblock and novel multiblock copolymers from ethylene glycol,L‐lactide,and ϵ‐caprolactone

Three types of copolymers were synthesized and characterized. First, triblock ABA copolymers [where A is a homopolymer of ?‐caprolactone and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with ?‐caprolactone in the presence of stannous octoate (Sn(Oct)₂). The spectral, thermal, and mechanical properties of one sample of these copolymers were studied, and it was discovered that these types of copolymers were more hydrophilic, possessed lower melting points, and had superior mechanical properties (greater toughness) than poly(?‐caprolactone). Second, triblock ABA copolymers [where A is a homopolymer of L ‐lactide and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with L ‐lactide in the presence of Sn(Oct)₂. The mechanical properties of these copolymers were studied, and it was found that they were tougher and softer than poly(L ‐lactide). Third, novel ABA triblock copolymers [where A is a copolymer of ?‐caprolactone and L ‐lactide and B is poly(ethylene glycol)] were prepared, and ¹H‐NMR and ¹³C‐NMR spectra of these copolymers indicated a microblock structure for the two end blocks. The stress–strain behavior revealed low yields and high toughness for these copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2072–2081, 2002     

Structural features of poly(alkylene ether carbonate) diol oligomers by capillary gas chromatography

A series of poly(ethylene ether carbonate) diol oligomers were synthesized from ethylene carbonate (EC) using various catalysts and low EC:initiator molar ratios. The structures of these oligomers have been studied by alkaline degradation to the poly(ethylene glycol)s, which make up their backbone, followed by capillary gas chromatographic (CGC) analysis. Comparisons of CGC traces before and after hydrolysis indicate which volatile components contain carbonate moieties. Some poly(ethylene glycol)s were not chemically bound into the polymer backbone and were analyzed directly by CGC. Based on the combination of analytical techniques developed in this study, it is possible for the first time to establish the approximate composition of a given poly(ethylene ether carbonate) diol. A typical composition made using a sodium stannate trihydrate catalyst consists of (1) an oligomeric portion which is a copolymer of carbon dioxide and poly(ethylene glycol)s and (2) a monomeric portion which consists mostly of diethylene glycol with lesser quantities of monoethylene glycol, triethylene glycol, 1,4-dioxane and unreacted ethylene carbonate.     

Awl-like HfC nanowires grown on carbon cloth via Fe-catalyzed in a polymer pyrolysis route

Awl-like hafnium carbide (HfC) nanowires were successfully synthesized on carbon cloth in a polymer pyrolysis route via Fe-catalyzed for the first time. A detailed study of the HfC nanowire morphology was performed. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to investigate the morphology and microstructure of the obtained awl-like HfC nanowires and the growth mechanism was also discussed in detail. Results show that HfC nanowires wrapped by amorphous HfO₂ layer with ~10 nm in thickness display awl-like structure and the nanowire's surface exhibit prismatic geometry. The diameter of the nanowire decreases from the bottom (~500 nm) to the top (~100 nm). The growth mechanism of the awl-like HfC nanowires was mainly affected by the combination of bottom-type vapor-liquid-solid (VLS) and solid-liquid-solid.