Enzyme-Catalyzed Ring-Opening Polymerization of ω-Pentadecalactone

Abstract

Lipase-catalyzed ring-opening bulk polymerizations of ω-pentadecalactone (PDL) were investigated. Screening of selected commercial lipases as catalysts for PDL polymerization at 80 °C was carried out. The results of this work showed that polymerizations catalyzed by lipases PS-30, AK, Lipozyme-IM and Novozym-435 gave % PDL conversions ranging from 80 to 100% for 24 h reactions (M n = 15 000−34 400). Lipase PS-30 both physically immobilized onto Celite-521 (I-PS-30) and in the crude powder or nonimmobilized form (NI-PS-30) was selected for further study. Comparison of % conversion vs time for bulk PDL polymerizations at 70 °C catalyzed by NI- and I-PS-30 showed that for short reaction times, the immobilized catalyst gave % conversions that were more than 10 times greater. In fact, the % monomer conversion to poly(PDL) was nearly quantitative (>98%) for 8 h polymerizations catalyzed by I-PS-30. Furthermore, for reactions conducted at 70 °C with careful removal of water, substantially greater poly(PDL) molecular weights resulted by using I-PS-30 instead of NI-PS-30 as the catalyst. Increasing the % conversion above ∼40% for PDL polymerizations at 70 °C resulted in little or no change in PDL M n. This is consistent with chain polymerizations where the rate of propagation is much faster than initiation. The general trends observed by variation of the I-PS-30 catalyzed bulk PDL polymerization temperature were the following: (i) increased % conversion and M n by increasing the reaction temperature from 60 to 70 °C and from 60 to 80 °C, respectively, (ii) similar polymerization rates between 70 and 90 °C, and (iii) a decrease in % monomer conversion and M n as the reaction temperature was increased from 90 to 110 °C. It was found that water was an important factor that controls not only the rate of monomer conversion but also the polymer molecular weight. From an increase in the water content in reactions, enhanced polymerization rates were achieved while the molecular weight of poly(PDL) decreased. At low reaction water levels (0.20% w/w water), the I-PS-30 catalyzed polymerization of PDL at 70 °C gave poly(PDL) with M n and M w/M n of 62 000 and 1.9, respectively. Thus far, this is the highest molecular weight polyester prepared by an enzyme-catalyzed polymerization reaction.

Lipase-catalyzed ring-opening polymerization of 3(S)-isopropylmorpholine-2,5-dione

“…For example, by increasing the water content from 1.1 to 4.4 wt.-%, monomer conversion increases from 11.4 to 50.4% within 48 h. Interestingly, a small increase in water content from 0 to 1.1 wt.-% results in a rather large increase in monomer conversion, i. e., from 2.9 to 23%. These observations are similar to those made for PS-30-catalyzed x-pentadecalactone polymerizations and can be explained in a similar fashion 18) . However, when the water content is increased to 8.4 wt.-%, the conversion is less than that for a water content of 4.4 wt.-% (reaction time 48 and 72 h).…”

Enzymatic Synthesis and Chemical Recycling of Novel Polyester-Type Thermoplastic Elastomers

“…For example, lipases can act as powerful catalysts for polyesterification reactions under mild anhydrous conditions. The syntheses of high molecular weight polyesters by ring-opening polymerization (ROP) of cyclic oligomers have also been reported [6][7][8][9]. In addition, using a lipase as the catalyst in anhydrous dilute solution, polyesters can be easily depolymerized into repolymerizable cyclic oligomers.…”

Synthesis of metal-free poly(1,4-dioxan-2-one) by enzyme-catalyzed ring-opening polymerization

“…This lipase CA is also known as an active catalyst for the ring-opening polymerization of ␤-propiolactone, 21 benzyl ␤-malolactone, 22 trimethylene carbonate (TMC), 18 -caprolactone (-CL), 11-undecanolide, 12-dodecanolide, 23 and -pentadecalactone (PDL). 24 However, it did not catalyze the polymerization of lactide. 25 In addition to the advantage of high polymerization activity, 23,24,26 lipase CA also has the merit of being a metal-free immobilized catalyst.…”

“…24 However, it did not catalyze the polymerization of lactide. 25 In addition to the advantage of high polymerization activity, 23,24,26 lipase CA also has the merit of being a metal-free immobilized catalyst. The catalyst can be easily removed from the product by filtration and does not release any metal elements.…”

“…Bisht et al 24 reported that an increase of the water content in PDL polymerization can enhance the polymerization rate and decrease the molecular weight of PPDL. They proposed a mechanism for TMC polymerization with lipase CA 18 in which water may act as a substrate in the initiation process.…”