HO-PEG-OH

Seo, Kwang Su, et al. RSC Advances 4.4 (2014): 1683-1688.

This is a report on quantitative vinyl chain-end functionalization of polyethylene glycol (PEG) with reduced environmental impact and renewable catalysis. Divinyl adipate (DVA) was transesterified using Candida antarctica lipase B (CALB) supported on acrylic resin at 50°C, dry nitrogen and solvent-free conditions. After the reaction, CALB was removed by filtration and excess DVA was recovered by hexane extraction and then distilled for reuse. The effects of DVA excess and PEG chain length were investigated. Model experiments with tetraethylene glycol (TEG) resulted in polycondensation. When HO-PEG-OH was reacted with M=1000 g DVA/PEG 20/1 molar ratio, no polycondensation occurred and only 2% of coupling products were found, while HO-PEG-OH with M=2000 g gave pure telechelic vinyl-PEG-vinyl plastics under the same conditions.
Reaction of DVA with OH-PEG-OH. HO-PEG-OH (1.0 g, 1.00 mmol) was reacted with DVA [20.0 eq. (3.96 g, 20.00 mmol, 3.77 mL, 5.31 mol L)] in the presence of CALB (100 mg, 6.0 10 mmol) at 50 °C for 4 h. Samples were taken at 2 h reaction time for MALDIToF analysis. After 4 h, 5 mL of dry THF was added to the mixture and the solid CALB was removed by a syringe equipped with a 0.45 mm PTFE filter. The mixture was cooled to room temperature to obtain a solid polymer with excess liquid DVA. Excess DVA was removed by washing twice with hexane and recovered by distilling off the hexane using a rotary evaporator. The polymer was dried in a vacuum oven at room temperature. The same process was repeated with HO-PEG-OH.