Silicone containing copolymers: Synthesis, properties and applications

This critical review presents an introduction to biocatalysis for synthetic chemists. Advances in biocatalysis of the past 5 years illustrate the breadth of applications for these powerful and selective catalysts in conducting key reaction steps. Asymmetric synthesis of value-added targets and other reaction types are covered, with an emphasis on pharmaceutical intermediates and bulk chemicals. Resources of interest for the non-initiated are provided, including specialized websites and service providers to facilitate identification of suitable biocatalysts, as well as references to recent volumes and reviews for more detailed biocatalytic procedures. Challenges related to the application of biocatalysts are discussed, including how ‘green’ a biocatalytic reaction may be, and trends in biocatalyst improvement through enzyme engineering are presented (152 references).

Expanding the organic toolbox: a guide to integrating biocatalysis in synthesis.

Enzyme-catalysis breathes new life into polyester condensation polymerizations

Nowadays, “green” is a hot topic almost everywhere, from retailers to universities to industries; and achieving a green status has become a universal aim. However, polymers are commonly considered not to be “green”, being associated with massive energy consumption and severe pollution problems (for example, the “Plastic Soup”) as a public stereotype. To achieve green polymers, three elements should be entailed: (1) green raw materials, catalysts and solvents; (2) eco-friendly synthesis processes; and (3) sustainable polymers with a low carbon footprint, for example, (bio)degradable polymers or polymers which can be recycled or disposed with a gentle environmental impact. By utilizing biobased monomers in enzymatic polymerizations, many advantageous green aspects can be fulfilled. For example, biobased monomers and enzyme catalysts are renewable materials that are derived from biomass feedstocks; enzymatic polymerizations are clean and energy saving processes; and no toxic residuals contaminate the final products. Therefore, synthesis of renewable polymers via enzymatic polymerizations of biobased monomers provides an opportunity for achieving green polymers and a future sustainable polymer industry, which will eventually play an essential role for realizing and maintaining a biobased and sustainable society.

Enzymatic Synthesis of Biobased Polyesters and Polyamides

Polymer synthesis by enzymatic catalysis.

Lipase B from Candida antarctica (CALB) has been exploited by many researchers for synthesis of a variety of organic compounds through esterification or transesterification reactions. Among the various immobilization media reported in the literature, the porous acrylic resin utilized in Novozym-435 has been widely studied. However, the thermal stability of free CALB and immobilized CALB (Novozym-435) in organic media at elevated temperatures for prolonged periods of time is largely unexplored. Here, we present the thermal stability and swelling of the Novozyme-435 in organic solvents (toluene and diphenyl ether) where the enzyme activity was quantified using an octyl laurate assay.

Thermal stability of Candida antarctica lipase B immobilized on macroporous acrylic resin particles in organic media

Candida antarctica lipase B (CALB) immobilized on a macroporous acrylic resin (Novozym 435) was used to enzymatically synthesize silicone aromatic polyesters (SAPEs) and silicone aromatic polyamides (SAPAs) in toluene under mild reaction conditions. The SAPEs were synthesized using α,ω-(dihydroxyalkyl)-terminated poly(dimethylsiloxane) (HAT-PDMS, molar mass Mn = 2500 g mol−1), and the SAPAs were synthesized using α,ω-(diaminopropyl)-terminated poly(dimethylsiloxane) (APT-PDMS, having two different molar masses, Mn, 1000 and 4700 g mol−1, respectively). Each of the polymers was made by a transesterification reaction with dimethyl terephthalate (DMT) in toluene (1:2 w/v ratio of monomers to solvent) at a temperature in the range of 80−90 °C under vacuum. Toluene was employed as the solvent in order to solubilize the DMT in the reaction mixture. The methanol byproduct was recovered from the reaction mixture along with the toluene by applying vacuum, and thus the transesterification reaction was driven forwar...

Lipase-Catalyzed Synthesis and Properties of Silicone Aromatic Polyesters and Silicone Aromatic Polyamides

Synthesis of organosiloxane copolymers using enzymatic polyesterification

Lipase catalyzed synthesis of silicone polyesters.

In this work we have compared and contrasted the pervaporation behaviour (separation factor and flux) of fluorosilicone dense membranes based on poly(trifluoropropylmethylsiloxane) (PTFPMS) with poly(dimethylsiloxane) (PDMS) dense membranes. In particular, pervaporation experiments were carried out at 298 K using lab-made PTFPMS, lab-made PDMS and commercial PDMS membranes in order to remove three different organic liquids pyridine (PY), isopropanol (IPA) and methylethylketone (MEK) from dilute (<10 wt.%) binary aqueous mixtures. All of the silicone membranes studied were found to be successful for the desired separations. The permeation flux of pyridine–water liquid mixtures for the PTFPMS membranes was found to increase with the pyridine concentration in the feed mixtures. The separation factor for PDMS membranes for the removal of pyridine, IPA and MEK from aqueous binary mixtures (1 wt.%) was found to be higher than that of PTFPMS membranes while the normalized flux was higher for PTFPMS membranes under identical test conditions. The effect of crosslink density of the PTFPMS membranes on the separation of pyridine–water mixtures was also studied. For a 1 wt.% feed solution the total flux increased with the molar mass between crosslinks, whereas the separation factor for pyridine–water was highest for a molar mass between crosslinks of 15,320 g mol−1.

Yadagiri Poojari

Papers

Thermal stability of Candida antarctica lipase B immobilized on macroporous acrylic resin particles in organic media

Lipase-Catalyzed Synthesis and Properties of Silicone Aromatic Polyesters and Silicone Aromatic Polyamides

Synthesis of organosiloxane copolymers using enzymatic polyesterification

Lipase catalyzed synthesis of silicone polyesters.

Pervaporation of Organic Liquids from Binary Aqueous Mixtures using Poly(trifluoropropylmethylsiloxane) and Poly(dimethylsiloxane) Dense Membranes