Carbon dioxide is often promoted as a sustainable solvent, as CO 2 is non-flammable, exhibits a relatively low toxicity and is naturally abundant. However, injudicious use of carbon dioxide in a process or product can reduce rather than enhance overall sustainability. This review specifically examines the use of CO 2 to create greener processes and products, with a focus on research and commercialization efforts performed since 1995. The literature reveals that use of CO 2 has permeated almost all facets of the chemical industry and that careful application of CO 2 technology can result in products (and processes) that are cleaner, less expensive and of higher quality.

Supercritical and near-critical CO2 in green chemical synthesis and processing

Development of antifouling reverse osmosis membranes for water treatment: A review.

A recent progress in thin film composite membrane: A review

The replacement of current petroleum-based plastics with sustainable alternatives is a crucial but formidable challenge for the modern society. Catalysis presents an enabling tool to facilitate the development of sustainable polymers. This review provides a system-level analysis of sustainable polymers and outlines key criteria with respect to the feedstocks the polymers are derived from, the manner in which the polymers are generated, and the end-of-use options. Specifically, we define sustainable polymers as a class of materials that are derived from renewable feedstocks and exhibit closed-loop life cycles. Among potential candidates, aliphatic polyesters and polycarbonates are promising materials due to their renewable resources and excellent biodegradability. The development of renewable monomers, the versatile synthetic routes to convert these monomers to polyesters and polycarbonate, and the different end-of-use options for these polymers are critically reviewed, with a focus on recent advances in c...

Catalysis as an Enabling Science for Sustainable Polymers

Increasing the stream of recycled plastic necessitates an approach beyond the traditional recycling via melting and re-extrusion. Various chemical recycling processes have great potential to enhance recycling rates. In this Review, a summary of the various chemical recycling routes and assessment via life-cycle analysis is complemented by an extensive list of processes developed by companies active in chemical recycling. We show that each of the currently available processes is applicable for specific plastic waste streams. Thus, only a combination of different technologies can address the plastic waste problem. Research should focus on more realistic, more contaminated and mixed waste streams, while collection and sorting infrastructure will need to be improved, that is, by stricter regulation. This Review aims to inspire both science and innovation for the production of higher value and quality products from plastic recycling suitable for reuse or valorization to create the necessary economic and environmental push for a circular economy.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.201915651

Beyond Mechanical Recycling: Giving New Life to Plastic Waste

A method has been developed which provides very pure alkyl methacrylate monomers for anionic polymerization. This method takes advantage of the chemistry of trialkylaluminum compounds-their reactivity with alcohols and moisture, and their complex formation with methacrylic esters which facilitates titration of impurities. When coupled with previously known polymerization techniques, this purification methodology allows for both the synthesis of narrow distribution poly(alkyl methacrylates) of controlled and predictable molecular weight and for the utilization of a wide variety of methacrylate monomers. The procedure described herein should be equally applicable to group transfer polymerization.

Preparation of high purity, anionic polymerization grade alkyl methacrylate monomers

To keep pace with the ever-shrinking feature sizes required in the microelectronics industry, suitable developers with high diffusivities, selectivity, and adjustable solvating power are required. ...

Supercritical CO2 Processing for Submicron Imaging of Fluoropolymers

Bifunctional hydrogel coatings for water purification membranes: Improved fouling resistance and antimicrobial activity

The invention relates to a process for generating a negative tone resist image comprising the steps of (1) coating a substrate with a film of a polymeric composition comprising (i) a polymer, (ii) a photosensitive acid generator, and (iii) acid labile groups; (2) imagewise exposing the film to radiation to generate free acid; and (3) developing the image with critical fluid.

Process for generating negative tone resist images utilizing carbon dioxide critical fluid

New polyamide thin film composite membranes were prepared by interfacial polymerization of hexafluoroalcohol (HFA)-containing aromatic diamine and trimesoyl chloride (TMC) on a porous polysulfone support. The surface properties of the resulting membranes were characterized by water contact angle, XPS, and SEM. Additionally, the desalination separation performance was evaluated by the cross-flow filtration of 2000 ppm NaCl solution. Water contact angle and XPS analyses indicated that the HFA-containing polyamide membrane is relatively hydrophobic at neutral conditions but becomes hydrophilic at basic conditions due to ionization of the HFA groups, so we refer to this group as an “ionizable hydrophobe” or “i-phobe”. The membrane showed strongly pH-dependent reverse osmosis behavior with enhanced performance (high water flux and high salt rejection) at high pH (ca. 10). Both the electron withdrawing nature and the steric bulkiness of the HFA functionality are also advantageous in protecting the polyamide membrane from chlorine attack. Based upon NMR studies of model polymers (linear polyamides with and without the HFA functionality) and the membrane performance measured before and after chlorine exposure, the HFA-containing polyamide has improved chlorine stability compared to the reference polyamide made from m-phenylenediamine and TMC.

Robert D. Allen

Papers

Preparation of high purity, anionic polymerization grade alkyl methacrylate monomers

Supercritical CO2 Processing for Submicron Imaging of Fluoropolymers

Bifunctional hydrogel coatings for water purification membranes: Improved fouling resistance and antimicrobial activity

Process for generating negative tone resist images utilizing carbon dioxide critical fluid

Novel thin film composite membrane containing ionizable hydrophobes: pH-dependent reverse osmosis behavior and improved chlorine resistance