Academic literature on the topic 'Polydimethylsiloxane. Monodisperses System. Permeation'

Purpose – The purpose of this paper is to produce an electroactive monomer containing ketonic resins and then to investigate redox reaction between Fe+3 and bounded thiophene in comonomers. First, thiophene functionalised ketonic resins (Th-CFPDMSR) were synthesised by esterification reaction of thiophene-2-carbonyl chloride (ThCCl) and hydroxyl groups of cyclohexanone formaldehyde resin (CFR). Th-CFPDMSR was then polymerised by ferric salt. Thiophene modified ketonic resins (Th-CFPDMSR) as comonomers were characterised by common techniques such as gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimeter and scanning electron microscope. Design/methodology/approach – Th-CFPDMSR comonomers were synthesised by esterification reaction of ThCCl and hydroxyl groups of ketonic resins. Then, the in-situ chemical oxidation (ISCO) of ThC-CFR in the presence of iron (III) chloride salt (FeCl3) was accomplished in chloroform/acetonitrile mixture solutions at room temperature. Findings – Important structural factor determined quantitatively for Th-CFPDMSR is the CFPDMS/TCCl ratio after reaction. The mole ratio effect of TCCl and ketonic resin on the solubility, molecular weight, melting temperature (Tm) and glass transition temperature (Tg) values of the comonomers (TCCl-CFPDMSR) was investigated. Research limitations/implications – The ferric ion (Fe+3) has a standard oxidation potential. Furthermore, FeCl3 can react with thiophene to produce a cation radical. FeCl3 cannot react with hydroxyl groups of ketonic resins. When ferric is used for ISCO application at relatively low temperatures (e.g. < 20°C), the oxidation reactions are usually less aggressive. Practical implications – This work provides technical information for the synthesis of conducting block copolymer and for the synthesis of chain-extended resins. The modified resins contain thiophene. The chemical oxidation system has been used to polymerise these thiophene groups, and resins with much higher molecular weight might be produced. The resins may also promote the adhesive strength of a coating and corrosion inhibition to metal surfaces of a coating. Originality/value – Novel Th-CFPDMSR comonomers were synthesised. These comonomers have higher Tg and Tm values than CF-PDMSR alone. The chemical oxidation system has been used to polymerise these thiophene functionalised ketonic resins.

The novel copolymerization polyimide (PI) hollow fibers (HFs) of 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) containing –CF3 groups were prepared and investigated through both simulation and experiment. To demonstrate the alteration attributable to the introduction of fluoromonomers, the condensed states of pyromellitic dianhydride (PMDA)/4,4′-oxybisbenzenamine (ODA), PMDA/6FDA/ODA, and 6FDA/ODA PI were constructed by Material Studio, and we simulated the mobility of molecular chain, free volume fraction, and O2/N2 dissolution–diffusion process. The molecular dynamics simulation results demonstrated that the properties of the copolymerized PI system with 6FDA were significantly improved, while the selectivity remained almost unchanged. Then, the films of copolymerized PI and HFs were prepared by the two-step method, and O2/N2 permeability of the PI copolymer films was characterized, indicating that although the gas permeation performance was greatly improved, the selectivity was not so satisfactory. However, the selection factor increased heavily after polydimethylsiloxane coating.

Microfluidic devices with the gas permeability through polymer membranes were developed for further high-efficiency of gas-liquid chemical reactions and high-accuracy of environmental diagnosis. The devices were composed of a cover glass and a polydimethylsiloxane (PDMS) chip which has the ability to permeate various gases, because PDMS is made of the elastomeric material. In the chip, microchannels with a width ranging from a few micrometers to a few hundred micrometers were manufactured by using the cryogenic micro machining. The gas permeation phenomena in microchannels are dominated by several factors, such as the gas and liquid flow rates, the membrane thickness between gas and liquid flow, and the surface area of membranes. The advantage of the present work is to realize the simple control of the gas permeability by changing the surface roughness of PDMS, because the cryogenic micro machining enables to control the surface roughness of microchannels and the increase in its roughness yields that in the surface area of membranes. For the evaluation of the gas permeability, the velocity and dissolved gas concentration distribution in the liquid flow field were measured by utilizing micron-resolution particle image velocimetry combined with laser induced fluorescence, and the measurement system was based on the confocal microscope to improve the depth resolution drastically. The experiments were performed under the several conditions with a change in the gas flow rate, the PDMS membrane thickness and the surface roughness, which affect the gas permeation phenomena. The results indicate that the velocity-vector distributions in the liquid flow have a similar pattern and the magnitudes of the velocity are approximately the same values under all conditions, while the dissolved gas concentration distributions have different patterns. It was quantitatively clear that the gas permeability through PDMS membranes was increased with an increase in the surface roughness and has the linearity to the surface area of membranes. The important conclusion is that the proposed device achieves to control the gas permeability by using the elastomeric material and changing the surface roughness.