Cascade Synthesis of Chiral Block Copolymers Combining Lipase Catalyzed Ring Opening Polymerization and Atom Transfer Radical Polymerization

Abstract

The enantioselective polymerization of methyl-substituted epsilon-caprolactones using Novozym 435 as the catalyst was investigated. All substituted monomers could be polymerized except 6-methyl-epsilon-caprolactone (6-MeCL), which failed to propagate after ring opening. Interestingly, an odd-even effect in the enantiopreference of differently substituted monomers was observed. The combination of 4-methyl-epsilon-caprolactone with Novozym 435 showed good enantioselectivity also in bulk polymerization and resulted in enantiomerically enriched P((S)-4-MeCL) (eep up to 0.88). Subsequently, a novel initiator combining a primary alcohol to initiate the ring opening polymerization and a tertiary bromide to initiate atom transfer controlled radical polymerization (ATRP) was synthesized, and showed high initiator efficiencies (> 90%) in the ring opening polymerization of 4-methyl-epsilon-caprolactone in bulk. In addition, the enantioselectivity was retained (E = 11). By using Ni(PPh3)2Br2 as the ATRP catalyst, Novozym 435 could be effectively inhibited at the desired conversion of 4-methyl-epsilon-caprolactone, thus ensuring a high enantiomeric excess in the polymer backbone. At the same time, Ni(PPh3)2Br2 catalyzed the ATRP of methyl methacrylate resulting in the formation of P((S)-4-MeCL-b-MMA) block copolymers. By this combination of two inherently different polymerization reactions, chiral P((S)-4-MeCL-b-MMA) block copolymers can be conveniently obtained in one pot without intermediate workup.

Unidirectional Dimerization and Stacking of Ureidopyrimidinone End Groups in Polycaprolactone Supramolecular Polymers

“…4-Methyl-caprolactone was obtained by a Baeyer-Villiger oxidation as described in the literature. 50 Hydroxytelechelic poly(methyl-caprolactone) was prepared by ring opening polymerization of 4-methyl-caprolactone using hexane diol (Acros) as initiator and fumaric acid (Acros) as catalyst (see the Supporting Information 19 F chemical shifts are reported in ppm relative to C 6 F 6 but were actually measured relative to R,R,Rtrifluorotoluene (TFT), δ ) -64.00 ppm, as internal standard. Infrared (IR) spectra were recorded on a Perkin-Elmer Spectrum One FT-IR spectrometer with a Universal ATR Sampling Accessory for solids.…”

Recent Developments in Lipase‐Catalyzed Synthesis of Polyesters

“…The enantiomeric excess (ee) value in the polymer of 4-MeCL was 88% ( Figure 5). [91] Lipase CA-catalyzed enantioselective ROP of fluorinated lactones in the ring size from 10 to 14 was reported. Interestingly, the corresponding oxyacid gave an optically inactive polyester.…”

“…[94] A selectivity switch was also observed in the copolymerization from (S)-selectivity for 3-MePL (4-membered) to (R)-selectivity for 5-MeVL (6-membered) (Scheme 12), [85a] 4-alkyl-substituted e-CL (Scheme 13) [86] , and methyl-substituted e-CL ( Figure 5). [91] Optically-active oligoesters were produced by a new method of ROP of 6-methyl-e-CL (6-MeCL) with iterative tandem catalysis (ITC). [95] ITC means a polymerization in which the chain growth is effectuated by a combination of two different catalytic processes that are both compatible and complementary.…”

“…[100] The combination of two different, consecutively-proceeding polymerization reactions is referred to as cascade polymerization. [91] The method allows a versatile synthesis of block copolymers consisting of a polyester chain and a vinyl polymer chain by using a designed bifunctional initiator, the reaction routes of which are shown generally in Figure 8. [91,99,101,102] For example, an initiator having both a hydroxy group for eROP and bromine atom for ATRP is to be used.…”

Immobilization of Candida antarctica lipase B on Polystyrene Nanoparticles

“…[4][5][6][7][8] Many literature reports describe the high utility of immobilized Cal-B for chemical transformations of low molar mass compounds, [9,10] and polymerization reactions. [11,12,13] Adsorption of an enzyme onto a surface can induce conformational changes which affect the rate and specificity of the catalyst. [14] Therefore, immobilization research has largely focused on matrix selection and on optimizing immobilization conditions.…”