Influence of microstructural variations on morphology and separation properties of polybutadiene-based polyurethanes

Polybutadiene-based polyurethanes with different cis/trans/1, 2-vinyl microstructure contents are synthesized. The phase morphology and physical properties of the polymers are investigated using spectroscopic analysis (FTIR and Raman), differential scanning calorimetry (DSC), X-ray scattering (WAXD and SAXS) and atomic force microscopy (AFM). In addition, their gas transport properties are determined for different gases at 4 bar and 25 °C. Thermodynamic incompatibility and steric hindrance of pendant groups are the dominant factors affecting the morphology and properties of the PUs. FTIR spectra, DSC, and SAXS analysis reveal a higher extent of phase mixing in high vinyl-content PUs. Moreover, the SAXS analysis and AFM phase images indicate smaller microdomains by increasing the vinyl content. Smaller permeable soft domains as well as the lower phase separation of the PUs with higher vinyl content create more tortuous pathways for gas molecules and deteriorate the gas permeability of the membranes

Graphene oxide-fullerene nanocomposite laminates for efficient hydrogen purification

Graphene oxide (GO) with its unique two-dimensional structure offers an emerging platform for designing advanced gas separation membranes that allow for highly selective transport of hydrogen molecules. Nevertheless, further tuning of the interlayer spacing of GO laminates and its effect on membrane separation efficiency remains to be explored. Here, positively charged fullerene C₆₀ derivatives are electrostatically bonded to the surface of GO sheets in order to manipulate the interlayer spacing between GO nanolaminates. The as-prepared GO-C₆₀ membranes have a high H₂ permeance of 3370 GPU (gas permeance units) and an H₂/CO₂ selectivity of 59. The gas separation selectivity is almost twice that of flat GO membranes because of the role of fullerene

Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes.

排ガスを膜でキャッチ -空気洗浄技術、実用化に期待-. 京都大学プレスリリース. 2014-09-10.Organic open frameworks with well-defined micropore (pore dimensions below 2 nm) structure are attractive next-generation materials for gas sorption, storage, catalysis and molecular level separations. Polymers of intrinsic microporosity (PIMs) represent a paradigm shift in conceptualizing molecular sieves from conventional ordered frameworks to disordered frameworks with heterogeneous distributions of microporosity. PIMs contain interconnected regions of micropores with high gas permeability but with a level of heterogeneity that compromises their molecular selectivity. Here we report controllable thermal oxidative crosslinking of PIMs by heat treatment in the presence of trace amounts of oxygen. The resulting covalently crosslinked networks are thermally and chemically stable, mechanically flexible and have remarkable selectivity at permeability that is three orders of magnitude higher than commercial polymeric membranes. This study demonstrates that controlled thermochemical reactions can delicately tune the topological structure of channels and pores within microporous polymers and their molecular sieving properties

Structural colour enhanced microfluidics

マイクロ流体デバイスの製造に革新をもたらす新手法. 京都大学プレスリリース. 2022-05-19.New process revolutionizes microfluidic fabrication. 京都大学プレスリリース. 2022-05-19.Advances in microfluidic technology towards flexibility, transparency, functionality, wearability, scale reduction or complexity enhancement are currently limited by choices in materials and assembly methods. Organized microfibrillation is a method for optically printing well-defined porosity into thin polymer films with ultrahigh resolution. Here we demonstrate this method to create self-enclosed microfluidic devices with a few simple steps, in a number of flexible and transparent formats. Structural colour, a property of organized microfibrillation, becomes an intrinsic feature of these microfluidic devices, enabling in-situ sensing capability. Since the system fluid dynamics are dependent on the internal pore size, capillary flow is shown to become characterized by structural colour, while independent of channel dimension, irrespective of whether devices are printed at the centimetre or micrometre scale. Moreover, the capability of generating and combining different internal porosities enables the OM microfluidics to be used for pore-size based applications, as demonstrated by separation of biomolecular mixtures

ARTICLE Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes

Organic open frameworks with well-defined micropore (pore dimensions below 2 nm) structure are attractive next-generation materials for gas sorption, storage, catalysis and molecular level separations. Polymers of intrinsic microporosity (PIMs) represent a paradigm shift in conceptualizing molecular sieves from conventional ordered frameworks to disordered frameworks with heterogeneous distributions of microporosity. PIMs contain interconnected regions of micropores with high gas permeability but with a level of heterogeneity that compromises their molecular selectivity. Here we report controllable thermal oxidative crosslinking of PIMs by heat treatment in the presence of trace amounts of oxygen. The resulting covalently crosslinked networks are thermally and chemically stable, mechanically flexible and have remarkable selectivity at permeability that is three orders of magnitude higher than commercial polymeric membranes. This study demonstrates that controlled thermochemical reactions can delicately tune the topological structure of channels and pores within microporous polymers and their molecular sieving properties

Nanodiamond mediated interfacial polymerization for high performance nanofiltration membrane

Introducing nanomaterial in interfacial polymerization (IP) system for nanofiltration (NF) membrane synthesis has witnessed a remarkable performance enhancement thus drawing intensive attention. However, the underlying mechanism for nanomaterial induced performance enhancement is still unclear due to the lack of study on nanoparticle dispersity and architecture at polymerization interface. Using nanodiamond (ND) as the example, this study demonstrates nanoparticle undergoes aggregation preferably at the reaction interface and the architecture of ND particles has a direct impact on membrane structure and performance. Through proactively controlling the aggregation extent while employing these ND clusters as the nano-template, the feature morphology of NF membrane is transformed from nodules to ridges at the nanoscale. Such transformation generates a significant augmentation of effective membrane area, leading to the increase of water permeance by 70%. With a low amount of nanodiamond addition (<0.1 wt%), the NF membrane can achieve a high water permeance of 150 L m−2 h−1 MPa−1 with ~98% rejection of Na2SO4. Moreover, the introduction of nanodiamond makes the nanofiltration membrane more hydrophilic, with water contact angle decreased from 50° to 35°. The comparison with contemporary nanofiller studies indicates our nanodiamond strategy yields some of the best performance enhancement

Pore-networked membrane for trace-level molecular separations in environmental water

The wide presence of pharmaceuticals and personal care products (PPCPs) in water is a major concern regarding current emerging pollution and urges their selective monitoring to establish water quality management. Microporous materials have been developed to extract organic contaminants and further embedded as fillers into polymeric composites like matrix-mixed membranes (MMMs) for practical use. Considering the relatively large molecular size of PPCPs and their slow diffusion in the membrane, the MMM configuration is, however, inadequate for liquid-phase separations. Here we report pore-networked membranes (PNMs) based on the concept of interconnecting the microporous fillers within the polymer matrix to form a continuous porous phase. Linked metal-organic polyhedra (MOP) network is designed for the continuous porous phase with tunable micro/mesopores, which are accessible for big PPCP molecules to facilitate their diffusion and adsorption. By contrast to MMMs, PNMs show enhanced stability, capacity and extraction selectivity towards specific pharmaceutical drugs amongst 13 PPCPs in environmental water matrices at trace-level concentrations

Overcoming humidity-induced swelling of graphene oxide-based hydrogen membranes using charge-compensating nanodiamonds

Graphene oxide (GO) can form ultrapermeable and ultraselective membranes that are promising for various gas separation applications, including hydrogen purification. However, GO films lose their attractive separation properties in humid conditions. Here we show that incorporating positively charged nanodiamonds (ND+s) into GO nanolaminates leads to humidity-resistant, yet high-performing, membranes. While native GO membranes fail at a single run, the GO/ND+ composite retains up to ~90% of GO’s H2 selectivity against CO2 after several cycles under an aggressive humidity test. The addition of negatively charged ND to GO brought no such stabilization, suggesting that charge compensation acts as the main mechanism conferring humidity resistance, where ND+s neutralize the negative charge GO sheets. We observed a similar but inferior stabilization effect when positively charged polyhedral oligomeric silsesquioxane replaces ND+. The demonstrated material platform offers a solution for separating H2 gas from its usually humid mixtures generated from fossil fuel sources or water splitting