Droplet Microfluidic Optimisation Using Micropipette Characterisation of Bio-Instructive Polymeric Surfactants

Droplet microfluidics can produce highly tailored microparticles whilst retaining monodispersity. However, these systems often require lengthy optimisation, commonly based on a trial-and-error approach, particularly when using bio-instructive, polymeric surfactants. Here, micropipette manipulation methods were used to optimise the concentration of bespoke polymeric surfactants to produce biodegradable (poly(d,l-lactic acid) (PDLLA)) microparticles with unique, bio-instructive surface chemistries. The effect of these three-dimensional surfactants on the interfacial tension of the system was analysed. It was determined that to provide adequate stabilisation, a low level (0.1% (w/v)) of poly(vinyl acetate-co-alcohol) (PVA) was required. Optimisation of the PVA concentration was informed by micropipette manipulation. As a result, successful, monodisperse particles were produced that maintained the desired bio-instructive surface chemistry.     

The sulfhydryl groups in 4-amino- and 4-methoxy-thiophenol prefer the plane normal to the molecular frame

In 4-aminothiophenol and 4-methoxythiophenol the conformations of lowest energy are those in which the S—H bond lies in a plane perpendicular to the benzene plane. V₂ is 2.9 ± 0.4 and 1.9 ± 0.4 $\text{kJ}\text{mol}$, respectively. By way of contrast, V₂ in 4-nitrothiophenol is 9.0 ± 0.8 $\text{kJ}\text{mol}$ and the S—H bond prefers the molecular plane.     

A new particle mounting method for surface analysis

The chemical analysis of microparticles is challenging due to the need to mount the particles on a substrate for analysis; double-sided adhesive tape is often used (sometimes conductive), however that is usually coated with poly (dimethyl siloxane) (PDMS) that is often used as a release agent. PDMS is a common surface contamination that can mask surface chemistries and hinder material performance where it is dependent on this contaminated interface. It is known that PDMS contains a very mobile oligomeric fraction that readily diffuses across surfaces resulting in the contamination of mounted particulate samples before and during surface chemistry analysis. This makes it impossible to determine whether the PDMS has arisen from the analysis procedure or from the sample itself. A new sample preparation method is proposed where polymer microparticles are mounted on a poly (hydroxyethyl methacrylate) (pHEMA) polymer solution, which we compare with particles that have been mounted on adhesive discs using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 3D OrbiSIMS analysis. Particles mounted on the pHEMA substrate results in a reduction of PDMS signal by 99.8% compared with microparticles mounted on adhesive discs. This illustrates how a simple, quick and inexpensive polymer solution can be used to adhere particles for analysis by ToF-SIMS, or other surface chemical analysis techniques such as X-ray photoelectron spectroscopy (XPS), without introduction of large amounts of silicone contaminant.     

Synthesis and Structures of Two Functionalized Isobenzofurans: (3aR,7aR,4S,5S)-1,3,3a,4,5,7a-Hexahydro-5-methyl-3-oxoisobenzofuran-4-carboxylic acid and (3aα,4β,7β,7aα)-4-[(Acetyloxy)methyl]-3a,4,7,7a-tetrahydro-7-methyl-1,3-isobenzofurandione

Abstract  

The title compounds, C₁₀H₁₂O₄ and C₁₂H₁₄O₅, were prepared as part of an ongoing study to explore the practical aspects of solventless reaction methods. As confirmed by the crystal structures, treatment of maleic anhydride with (2E,4E)-hexa-2,4-dien-1-ol or its acetate counterpart resulted in cis bicyclo [4.3.0] molecular frameworks. The racemic product derived from the dienol synthon crystallized in chiral space group P2₁2₁2₁ via a pasteurian resolution process with molecules organized by carboxyl⋯carboxyl and C–H⋯O contacts. The acetate derivative crystallizes in space group Cc.     

Temperature dependence of hydrogen tunnelling rate constants

A theoretical model based on tunnelling through a two-dimensional barrier is developed and used to interpret hydrogen transfer rate constants that deviate stronly from the standard Arrhenius equation, such as those of hydrogen abstraction by methyl and phenyl radicals.     

Na 32P-32D line broadening by Ne,Ar, and Xe

The normalized emission intensity in the wings of the optically thin Na 3²P-3²D lines broadened by Ne, Ar, and Xe has been measured in emission from a high-pressure discharge. A blended satellite occurs about 80 cm^-1 into the Na-Xe red wing and a progression of increasing red wing intensity from Ne to Ar to Xe is observed. Xe densities of 2.5 and 9.1 × 10¹⁹ cm^-3 were used, and the pressure dependence of the NaXe line shape indicates that multiple perturber interactions are important in the far wing at the higher noble gas densities.