Abstract
In this article we report an easy synthetic route towards hyperbranched polyglycerols (Amm-HBPGs) containing trimethylammonium groups and siloxane or hydroxyl end-groups. Siloxane derivatives of Amm-HBPGs were synthesized in an efficient five-step procedure including an anionic ring opening copolymerization of the phthalimide-epoxy monomer with glycidol, followed by reactions with allyl bromide, hydrosililation with hydrogenheptamethyltrisiloxane, hydrazinolysis of phthalimide groups and quaternization of resulting amine groups with methyl iodide. Hydroxyl derivatives were obtained by quaternization of previously reported aminated HBPG’s with methyl iodide. Polymeric products were characterized using various NMR techniques, FTIR, and elemental analysis. Both Amm-HBPGs were shown to be effective in catalysis of addition of CO2 to oxirane. The hydrophilic catalysts showed higher efficiency but synthesis of ethylene carbonate was accompanied by formation of small amounts of ethylene glycol. The siloxane-containing catalyst was easily separable from reaction mixture showing high potential in the process of converting carbon dioxide into valuable chemical raw materials.
Highlights
The CO2 concentration in the air is at its highest level in the last 650,000 years
FT-IR Spectrometer equipped with iD7 ATR optical base (Thermo Scientific®, Waltham, MA, USA). 1 H, 13 C, COSY and HSQC-DEPT NMR spectra were recorded on a Varian VXR 400 MHz (Palo Alto, Ca, USA) or Bruker AVANCE 500 MHz spectrometers (Bremen, Germany) using tetramethylsilane as an internal standard and deuterated solvents (CDCl3, DMSO-d6 )
The integral of the CH3 group signal coming from the core trimethylolpropane (TMP) molecule was used as a reference
Summary
The CO2 concentration in the air is at its highest level in the last 650,000 years. The values measured at Mauna Loa Observatory, Hawaii, increased in 2020 to the unprecedented level of 415 ppm [1].The unfolding climate catastrophe caused by surplus CO2 in the atmosphere is an immediate threat to our collective security and prosperity [2]. The areas of non-isocyanate and phosgene-free polyurethanes are interesting for polymer chemists [10]. The catalytic chemical fixation of carbon dioxide by cycloaddition to oxiranes represents a versatile green chemistry route to environmentally benign multifunctional cyclic carbonates as intermediates for the formation of non-isocyanate polyurethanes [10,11]. Reaction yields ranged from 70% to 86% and were higher for the higher molar deprotonating agent. Reaction yields ranged from 70% to 86% and were higher for the higher molar mass 2b polymer. In case of 2b the fraction of low molar mass lost during multiple washing procedure mass 2b polymer. In case of 2b the fraction of low molar mass lost during multiple washing procedure was smaller. It was important to have all the hydroxyl groups fully substituted with allyl residues
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