Synthesis and reactivity towards DIBAL-H of Cyclo-Siloxanes cyclo-[R2SiOSi(Ot-Bu)2O]2, cyclo-(t-BuO)2Si(OSiR2)2O, and cyclo-R2Si[Osi(Ot-Bu)2]2O (R=Me, Ph)

The six-, eight- and twelve-membered cyclo-siloxanes, cyclo-[R₂SiOSi(Ot-Bu)₂O]₂ (R = Me (1), Ph (2)), cyclo-(t-BuO)₂Si(OSiR₂)₂O (R = Me (3), Ph (4)), cyclo-R₂Si[OSi(Ot-Bu)₂]₂O (R = Me (5), Ph (6)) and cyclo-[(t-BuO)₂Si(OSiMe₂)₂O]₂ (3a) were synthesized in high yields by the reaction of (t-BuO)₂Si(OH)₂ and [(t-BuO)₂SiOH]₂O with R₂SiCl₂ and (R₂SiCl)₂O (R = Me, Ph). Compounds 1 - 6 were characterized by solution and solid-state ²⁹Si NMR spectroscopy, electrospray mass spectrometry and osmometric molecular weight determination. The molecular structure of 4 has been determined by single crystal X-ray diffraction and features a six-membered cyclo-siloxane ring that is essentially planar. The reduction of 1 - 6 with i-Bu₂AlH (DIBAL-H) led to the formation of the metastable aluminosiloxane (t-BuO)₂Si(OAli-Bu₂)₂ (7) along with Me₂SiH₂ and Ph₂SiH₂.

Hydrolysis of (Me3SiCH2)PhSnCl2. Isomerisation of the dimeric tetraorganodistannoxane [(Me3SiCH2)Ph(Cl)SnOSn(Cl)-Ph(CH2SiMe3)]2

The hydrolysis of (Me₃SiCH₂)PhSnCl₂( 1) was studied under two different reaction conditions (i) by using an excess of aqueous NaOH in toluene at reflux temperature and (ii) by using small amounts of NEt₃ and water in CH₂Cl₂ at room temperature. For (i) the products  (Me₃SiCH₂)Ph₂SnOSnPh₂(CH₂SiMe₃)( 2) and [(Me₃SiCH₂Sn)₁₂O₁₄(OH)₆](OH)₂( 3) were isolated indicating that a phenyl group migration took place. For (ii) the dimeric tetraorganodistannoxane [(Me₃SiCH₂)Ph(Cl)SnOSn(Cl)Ph(CH₂SiMe₃)]₂( 4) was obtained. In solution, 4 exists as an equilibrium mixture of all five possible isomers 4a–4e; in the solid state two of these isomers 4d and 4e co-crystallized in the same crystal modification. The observation of interconvertible isomers of 4 was attributed to the kinetic lability of the ladder-like Sn4O2Cl4 structural motif. Compounds 1 and 4 were investigated by X-ray crystallography.

Influence of pH on hygral expansion, relaxation shrinkage and extensibility of wool fabric

The standard tests for relaxation shrinkage and hygral expansion of wool fabric take no account of pH. It is shown in this work that the pH of the solution in which wool fabric is relaxed as part of the procedure for measuring dimensional properties has a significant influence on the results. At around pH 4.8, which is close to the isoelectric point of wool, the hygral expansion reaches its greatest value and drops at both lower and higher pHs. A similar relationship between pH and extensibility of wool fabric was observed. Values of relaxation shrinkage were found to be dependant on pH. The reasons for the pH dependence of dimensional properties are discussed and these include changes in wool fiber swelling, yarn crimp and polymer relaxation phenomena with changes in pH.

Trimethylene-bridged tetraorganodistannoxanes{[Me3SiCH2(RCOO)Sn(CH2)3Sn(OOCR)CH2SiMe3]O}n(R=Ph,2,4-Me2C6H3): control of structure by variation of R*

The synthesis of trimethylene-bridged carboxylate-substituted tetraorganodistannoxanes {[Me_3SiCH_2(RCOO)Sn(CH_2)_3Sn(OOCR)CH_2SiMe_3]O}_n (1, R = Ph; 2, R = 2,4-Me_2C_6H_3) is reported. Depending on the structure of R, in the solid state these compounds are either dimers (1, n = 2, cis-isomer) with a ladder-type structure or tetramers (2, n = 4) with a double ladder-type structure.

The use of artificial biofilms to strip nutrients from an industrial smelters waste water under conditions of low temperature and high pH

The Victorian Environment Protection Authority (EPA) has identified Alcoa’s Point Henry aluminium smelter as being a major source of recognized pollutant input due to its disposal of effluent into Corio Bay. Historically, the water quality parameters that have most often exceeded Point Henry’s EPA limits have been pH and suspended solids from the smelter’s discharge points. These waste water discharges also experience high nitrogen and phosphorus concentrations which result in algal blooms that occur at the onset of warm weather. The main hypothesis of this study was that “prevention of algal blooming with the onset of warm weather by removal of nutrients during the cooler months, and continued removal thereafter, is better than curing the problems chemically”. Biofilms have been used to remove nutrients from waste waters, but not under the conditions experienced at Point Henry. The aim of this study, therefore, was to determine if significant biofilm growth would be observed on floating structures suspended in the Point Henry waste water stream during the cooler, winter months of the year. Statistically significant biofilm growth occurred on all suspended structures in all discharge ponds during the winter and early spring of 2000. The use of suspended structures, such as AquaMatTM, as an artificial substrate to attract and support periphyton and bacterial communities (biofilms), which are then able to out-compete phytoplankton communities for available nutrients, is therefore a viable option for the Point Henry smelter. However, further research on the competitive performance of biofilms in the Point Henry ponds during the summer months is required before adequate biofilm management strategies can be developed.

Dependence of wool fabric dimensions on temperature and pH

Through a series of experimental analysis of temperature and pH value on the expansion of wool fiber and wool fabrics size change. In the pH2.1 solution, the wool fabric size declines with increasing temperature, changing the magnitude depends on the fabric and fabric shape rate. isoelectric point of pH4.8 in the wool, the fibers expand to reach the minimum, while the size of the fabric, along with the solution acidity increases.

Tensile behaviour of wool fabric as a function of fabric pH

Wool fabric extensibility under a 5 N/cm load was observed to be greatest at the wool isoelectric point of pH 4.8 and lower at both pH 2.1 and pH 7.2. The impact of pH on fabric extensibility is similar to the variation in fabric hygral expansion previously observed. Fabric stress-strain curves at different pHs show that for a given fabric extension level, the work required to stretch a fabric was less at pH 2.1 than at pH 4.8. These results confirm the fact that the strength of wool fabric is at a maximum when the pH of the fibres is close to the isoelectric point.

The effect of pH on wool fiber diameter and fabric dimensions

Wool fabrics are often treated under conditions of varying pH in dyeing and finishing processes. It is known that in air the dimensions of wool fabrics change with the amount of fiber swelling at different regain. In this work, it has been shown that a similar relationship between fiber swelling and fabric dimensions existed in water at different pH values. The diameters of Merino and Corriedale wool fibers in water at different pH values were measured with an OFDA 2000 fiber diameter analyzer, fitted with a specially constructed accessory liquid cell. The results showed that the mean diameters of swollen wool fibers in water varied with pH. Minimum swelling was obtained in the range pH 5-7. It was found that the dimensions of wool fabric in water were dependent on the pH. The changes in fiber diameter in water could be attributed to changes in ionic interactions between charged acid and basic groups in wool protein with variations in pH.

Monolayer behavior of a pyridyl head-group-containing amphiphile and its miscibility with poly(D,L-lactide-co-glycolide) on different pH subphase

In this paper, we investigated the Langmuir film and Langmuir–Blodgett (LB) monolayer film of a nonionic amphiphilic molecule, 4-(6-p-pyridyloxyl)hexyloxyl-4′-dodecyloxylazobenzene (C12AzoC6Py) and its mixture with poly(d,l-lactide-co-glycolide) (PLG) at different subphase pH values (2.0, 2.6, 3.3, 4.4, and 6.5, respectively) by surface pressure–area (π–A) isotherms, in situ interface Brewster angle microscopy (BAM), and ex situ atomic force microscopy (AFM). For pure C12AzoC6Py, its π–A isotherms display a plateau when the subphase pH value is lower than 3.0. The pressure of the plateau increases with the decrease of pH until 2.0. Over the plateau, the π–A isotherms become almost identical to the one under neutral conditions. The appearance of such a plateau can be explained as the coexistence of protonation and unprotonation of pyridyl head groups of the employed amphiphile. In contrast to the homogeneous surface morphology of pure C12AzoC6Py near the plateau by BAM observation, the surface in the case of its mixing with PLG exhibits a dendritic crystalline state under low surface pressure at subphase pH lower than 3.0. The crystalline state becomes soft and gradually melts into homogeneous aggregates with surface pressure increasing to a higher value than that of the plateau. Meanwhile, the hydrolysis of PLG in the mixture system at the interface has been affirmed to be restrained to a very large extent. And the PLG was believed to be compelled to the up layer of the LB film due to the phase separation, which is examined by AFM. Based on the experimental results, the corresponding discussion was also performed.