Reactive Multifunctional Polymer Films Using Thermally Stimulated Cascade-like Reactions: Potential Strategy Employing Modified <i>ortho</i>-Allylation in Polyimides

Polymeric materials, undergoing thermally stimulated reaction cascades, are promising materials and techniques for future custom tailoring of high-performance materials, such as in coating or film, heat resistance, and energy applications. The high atom economy and stimulation in the solid state of readily processable precursors, which lead to complex and usually difficult-to-process materials, make them highly attractive when it comes to the design of new materials. Polyimides and polybenzoxazoles are both known as thermally resistant high-performance materials. Polyimides have been used for the conversion to polybenzoxazoles (PBO) at high temperatures. In our study, we report a set of allylated ortho-hydroxy polyimides (HPIs) that are capable of undergoing a set of consecutive thermally stimulated reactions in a reaction cascade-like manner. The reactions have been investigated in detail by thermokinetic and spectroscopic experiments, supported by means of quantum chemical and molecular dynamic simulations. A significant change regarding the extent of consecutive Claisen rearrangement reactions was observed, depending on the type of allyl derivative and course of annealing. βM-PI thus showed a very high conversion to benzofuran rings, followed by an HPI-to-PBO rearrangement to full conversion at an annealing procedure using only 350 °C, which is the highest conversion at a sub-400 °C annealing protocol for a fluorinated HPI. This is even surpassed in our study by γE-PI, which shows the lowest ever reported onset temperature for a modified HPI and especially for a hexafluoroisopropylidene group-containing HPI backbone, which has been identified as a promising backbone material for membrane applications. These results point out that applying thermal reaction cascades, using modified allyl groups in polyimides, could be a universal strategy to improve the materials’ performance of polyimides for various applications

Thermally and Chemically Stable Isoporous Block Copolymer Membranes

Ultrafiltration (UF) membranes, particularly membranes fabricated from self-assembled diblock copolymers, hold promise in wastewater treatment, dairy, and food industries. Membrane development goals involve combining a highly porous selective layer with a narrow pore size distribution with a mechanically stable supporting layer to achieve constant flux. To date, isoporous integral asymmetric membranes have been formed either as flat sheets or hollow fibers, and a surface-selective layer determines membrane separation performance. A unique isoporous membrane of the poly(4-vinylbenzocyclobutene)-b-poly(4-vinylpyridine) (PVBCB-b-P4VP) diblock copolymer with a substructure of almost homogeneous porosity throughout the body of the material (three-dimensional porosity) has been developed. Moreover, the matrix of the membrane (PVCB) enables it to undergo cross-linking, allowing the membrane to be thermally sterilized and applied in high-temperature UF applications

Covalent Attachment of Polymersomes to Surfaces

We show that vesicles made of block copolymers with aldehyde end groups can be covalently attached to aminated and non-aminated, untreated glass surfaces. The attached vesicles were sufficiently stable to allow a detailed investigation of vesicle shapes by confocal laser scanning microscopy (CLSM) and AFM in aqueous solutions allowing reconstruction of 3D images of the vesicle structure. Covalently attached PCL−PEO, PLA−PEO, and PI−PEO block copolymer vesicles have different footprint areas and different shapes due to their differences in bilayer stiffness

Data_Sheet_1_A Combined Ultrafiltration/Diafiltration Step Facilitates the Purification of Cyanovirin-N From Transgenic Tobacco Extracts.PDF

The production of biopharmaceutical proteins in plants offers many advantages over traditional expression platforms, including improved safety, greater scalability and lower upstream production costs. However, most products are retained within plant cells or the apoplastic space instead of being secreted into a liquid medium, so downstream processing necessarily involves tissue and cell disruption followed by the removal of abundant particles and host cell proteins (HCPs). We investigated whether ultrafiltration/diafiltration (UF/DF) can simplify the purification of the model recombinant protein cyanovirin-N (CVN), an ~ 11 kDa HIV-neutralizing lectin, from tobacco extracts prior to chromatography. We compared different membrane types and process conditions, and found that at pH 8.0 and 50 mS cm−1 an UF step using a 100 kDa regenerated cellulose membrane removed more than 80% of the ~ 0.75 mg mL−1 total soluble protein present in the clarified plant extract. We recovered ~ 70% of the CVN and the product purity increased ~ 3-fold in the permeate. The underlying effects of tobacco HCP retention during the UF/DF step were investigated by measuring the zeta potential and particle size distribution in the 2–10,000 nm range. Combined with a subsequent 10 kDa DF step, this approach simultaneously reduced the process volume, conditioned the process intermediate, and facilitated early, chromatography-free purification. Due to the generic, size-based nature of the method, it is likely to be compatible with most products smaller than ~50 kDa.</p

Two-Dimensional Nanoporous Cross-linked Polymer Networks as Emerging Candidates for Gas Adsorption

This paper illustrates the gas adsorption properties of newly synthesized nanoporous cross-linked polymer networks (CPNs). All synthesized CPNs possess N-rich functional groups and are used for the utilization of carbon dioxide and methane. Good gas adsorption and selectivities are obtained for all of the samples. Among the materials, HEREON2 outperforms better selectivity for methane separation from nitrogen rather than zeolites, activated carbons, molecular sieves, covalent organic frameworks, and metal–organic frameworks (MOFs). The accessibility of the N-rich functionalities makes these materials potential candidates for the separation of hydrocarbons via increased polarizabilities. High-pressure adsorption experiments showed that the synthesized two-dimensional nanoporous materials also have a high affinity toward carbon dioxide. HEREON2 powders showed an increased experimental CO2/N2 selectivity of ∼25,000 at 50 bar due to the presence of nitrogen groups in the structure. Fourier-transform infrared spectroscopy (FTIR), solid-state NMR, X-ray diffraction, thermogravimetric analysis, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were applied for the characterization of the synthesized nanoporous CPNs. The results show a potential new pathway for future CPN membrane development

Postfunctionalization of Nanoporous Block Copolymer Membranes via Click Reaction on Polydopamine for Liquid Phase Separation

In this work, an azido-modified dopamine derivative was synthesized and subsequently used to postfunctionalize the surface of nanoporous poly­(styrene)-<i>block</i>-poly­(4-vinylpyridine) diblock copolymer membranes. On the basis of this layer a continuative modification was realized by performing a “Click” reaction, namely, the Cu­(I)-catalyzed 1,3-dipolar cycloaddition, with different alkynes. While the Click reaction was monitored by X-ray photoelectron spectroscopy, the morphology of the membranes in the different states of modification was examined with scanning electron microscopy and atomic force microscopy. The membrane properties were characterized by measurements of contact angle and clean water permeance, retention tests, and protein adsorption. Independent from the alkyne applied during the Click reaction, the clean water permeance is approximately 1200 L m^–2 bar^–1 h^–1 and therefore slightly below the permeance of the pristine membrane. While the sharp molecular weight cutoff of the pristine membrane and all modified membranes is similar, antifouling properties as studied on the interaction of two model proteins (bovine serum albumin, hemoglobin) with the membranes turned out to be best for the membranes modified with 1-nonyne

Continuous Equilibrated Growth of Ordered Block Copolymer Thin Films by Electrospray Deposition

Deposition of block copolymer thin films is most often accomplished in a serial process where material is spin coated onto a substrate and subsequently annealed, either thermally or by solvent vapor, to produce a well-ordered morphology. Here we show that under appropriate conditions, well-ordered block copolymer films may be continuously grown under substrate equilibrated conditions by slow deposition of discrete subattoliter quantities of material using electrospray. We conduct time-resolved observations and investigate the effects of process parameters that underpin film morphology including solvent selectivity, substrate temperature, block-substrate selectivity, and flow rate of the feed solution. For a PEO cylinder-forming poly(styrene-b-ethylene oxide) block copolymer, we uncover a wide temperature window from 90 to 150 °C and an ideal flow rate of 2 μL/min for ordered film deposition from dilute acetone solutions. PEO cylinders aligned with their long axes perpendicular to the film–air interface at optimal spray conditions. Using poly(styrene-b-methyl methacrylate) deposited onto neutrally selective surfaces, we show that the substrate-equilibrated process results in vertically oriented microdomains throughout the film, indicating a preservation of the initial substrate-dictated morphology during the film deposition. Electrospray offers a new and potentially exciting route for controlled, continuous growth of block copolymer thin films and manipulation of their microstructure

Additional file 1: of Covalently Modified Graphene Oxide and Polymer of Intrinsic Microporosity (PIM-1) in Mixed Matrix Thin-Film Composite Membranes

Supporting information (DOCX 9050 kb

Design of Modified Polymer Membranes Using Machine Learning

Surface modification is an attractive strategy to adjust the properties of polymer membranes. Unfortunately, predictive structure–processing–property relationships between the modification strategies and membrane performance are often unknown. One possibility to tackle this challenge is the application of data-driven methods such as machine learning. In this study, we applied machine learning methods to data sets containing the performance parameters of modified membranes. The resulting machine learning models were used to predict performance parameters, such as the pure water permeability and the zeta potential of membranes modified with new substances. The predictions had low prediction errors, which allowed us to generalize them to similar membrane modifications and processing conditions. Additionally, machine learning methods were able to identify the impact of substance properties and process parameters on the resulting membrane properties. Our results demonstrate that small data sets, as they are common in materials science, can be used as training data for predictive machine learning models. Therefore, machine learning shows great potential as a tool to expedite the development of high-performance membranes while reducing the time and costs associated with the development process at the same time