Caprolactone, ring-opening polymerization

Figure 1. simplified scheme of the Improved process for caprolactone ring-opening polymerization. 

Converting the "living" prepolymer from oxyl-llthlum to oxy-alumlnum chain end can successfully eliminate the undeslred trans-esterlflcatlon In the e-caprolactone ring-opening polymerization and Its more uniform block polymers with styrene and butadiene were thus prepared. 

D.L., Akkara, J., Swift, G., and Wolk, S. (1995) Enzyme-catalyzed e-caprolactone ring-opening polymerization. Macromolecules, 28 (1), 73-78. 

MNPHP is a well-known irreversible inhibitor of lipases that is highly specific for reaction with active-site serine residues. Thus, MNPHP was selected as the inhibitor to determine, by titration, the fraction of catalytic sites that are accessible and active. Since we are concerned with CALB activity in organic media, inhibition was studied in heptane. LC-MS was used to determine the release of p-nitrophenol (pNP) which corresponds with accessible active sites. To ensure that adsorption of pNP by resins was taken into consideration, pNP concentration was corrected as follows. A fixed quantity of enzyme-free resin was incubated overnight in acetonitrile with different concentrations of j NP. Standard curves of pNP adsorption by each resin as a function of pNP concentration were constructed from LC-MS measurements. MNPHP-inhibited immobilized enzymes were used for e-caprolactone ring-opening polymerizations in toluene (70 C). No conversion of monomer was observed in 30 minutes. Hence, MNPHP titration resulted in complete inhibition of CALB activity. 

Figure 3. Effect of immobilized CALB particle size (given in pm, see legend box in plot) on the time course of e-caprolactone ring-opening polymerizations performed at 70 °C in toluene. (Reproduced from Langmuir 2007, 23, 1381-1387. Copyright 2007 American Chemical Society.)...

Reference 34. MNPHP-inhibited immobilized enzymes were used for e-caprolactone ring-opening polymerizations in toluene (70 °C). No conversion of monomer was observed in 30 minutes. Hence, MNPHP titration resulted in complete inhibition of CALB activity. 

MacDonald, R.T., Pulapura, S.K., Svirkin, Y.Y., Gross, R.A., 1995. Enzyme-catalyzed 6-caprolactone ring-opening polymerization. Macromolecules 28, 73—78. 

The effects of organic solvents on lipase reactivity are complex. Thus, it is difficult to predict the behavior of different lipases in the same solvent system or of different solvents with the same lipase. Previous work in our laboratory studied solvent properties, such as solvent log P (logarithm of partition coefficient), and its correlation to Novozyme-435 activity for E-caprolactone ring-opening polymerizations. Of the solvents studied, those with log P values... 

Poly(f -caprolactone) (PCL), the most representative member of this polyester family, is obtained by the ring-opening polymerization of e-caprolactone. It is a low-7 (60°C), low-Tg (—60°C) semicrystalline polyester that presents mechanical properties resembling those of low-density polyethylene (Table 2.10). 

The preparation of poly( -caprolactone) given below is a bulk ring-opening polymerization of -caprolactone initiated by Ti(OBu)4 in the presence of... 

Preparation and characteristics of ABA type polycaprolactone-b-polydimethyl-siloxane block copolymers have been recently reported 289). In this study, ring-opening polymerization of e-caprolactone was achieved in melt, using a hydroxybutyl terminated PSX as the initiator and a catalytic amount of stannous octoate. Reactions were completed in two steps as shown in Reaction Scheme XIX. 

In recent years homoleptic lanthanide(III) tris(amidinates) and guanidinates have been demonstrated to exhibit extremely high activity for the ring-opening polymerization of polar monomers such as e-caprolactone and trimethylene... 

The poly(glycolide-co-caprolactone) (PGCL) copolymer was mainly synthesized by the ringopening polymerization. A copolymer with 1 1 mole ratio was synthesized by the ring-opening polymerization in the presence of the catalyst Sn(Oct)2 by Lee and coworkers. The polymerization was under vacuum, and heated in an oil bath at 170°C for 20 h. The copolymer was then dried under vacuum at room temperature for 72 h. The schematic reaction equations are shown in Schemes 8.5 and 8.6. 

A star copolymer (SCP) of PCLA was synthesized by Younes and coworkers. This kind of SCP PCLA elastomer was also synthesized in two steps. First, the small molecular SCP was produced by ring-opening polymerization of s-caprolactone (s-CL) with glycerol as initiator and stannous 2-ethyUiexanoate as catalyst. Second, the living SCP was further reacted with different ratios of a cross-linking monomer, such as 2,2-bis(s-CL-4-yl)-propane (BCP) and s-CL. The SCP elastomers had very low glass transition temperature (—32°C). It was reported that the SCPs were soft and weak with physical properties similar to those of natural bioelastomers such as elastin. A logarithmic decrease in each tensile property with time was observed in this SCP PCLA. 

Ring-opening polymerization of 2-methylene-l,3-dioxepane (Fig. 6) represents the single example of a free radical polymerization route to PCL (51). Initiation with AIBN at SO C afforded PCL with a of 42,000 in 59% yield. While this monomer is not commercially available, the advantage of this method is that it may be used to obtain otherwise inaccessible copolymers. As an example, copolymerization with vinyl monomers has afforded copolymers of e-caprolactone with styrene, 4-vinylanisole, methyl methacrylate, and vinyl acetate. 

Various cyclic esters have been subjected to hpase-catalyzed ring-opening polymerization. Lipase catalyzed the ring-opening polymerization of 4- to 17-membered non-substituted lactones.In 1993, it was first demonstrated that medium-size lactones, 8-valerolactone (8-VL, six-membered) and e-caprolactone (e-CL, seven-membered), were polymerized by lipases derived from Candida cylindracea, Burkholderia cepacia (lipase BC), Pseudomonas fluorescens (lipase PF), and porcine pancreas (PPL). °... 

Optically active polyesters were synthesized by lipase CA-catalyzed ring-opening polymerization of racemic 4-methyl or ethyl-e-caprolactone. The (5 )-isomer was enantioselectively polymerized to produce the polyester with >95% ee. Quantitative reactivity of 4-substituted e-caprolactone using lipase CA as catalyst was analyzed. The polymerization rate decreased by a factor of 2 upon the introduction of a methyl substitutent at the 4-position. Furthermore, 4-ethyl-8-caprolactone polymerized five times slower than the 4-methyl-8-caprolactone. This reactivity difference is strongly related to the enantioselectivity. Interestingly, lipase CA displayed 5 -selectivity for 4-methyl or ethyl-8-caprolactone, and the enantioselectivity was changed to the (f )-enantiomer in the case of 4-propyl-8-caprolactone. 

Lipase catalyzed the ring-opening polymerization of medium-size lactones, d-valerolactone (<5-VL, six-membered) and -caprolactone (c-CL, seven-mem-bered). Lipases CC, PF and PPL showed high catalytic activity for the polymerization of <5-VL [74,75]. The molecular weight of the polymer obtained in bulk at 60 °C was relatively low (less than 2000). 

Ring-opening polymerization of a-methyl-substituted medium-size lactones, a-methyl-y-valerolactone and a-methyl-c-caprolactone, proceeded by using lipase CA catalyst in bulk [82]. As to (R)- and (S)-3-methyl-4-oxa-6-hexa-nolides (MOHELs), lipase PC induced the polymerization of both isomers. The apparent initial rate of the S-isomer was seven times larger than that of the R-isomer, indicating that the enantioselective polymerization of MOHEL took place through lipase catalysis [83]. 

The cationic ring opening polymerization of e-caprolactone, CL, and 8-valerolactone, VL, was investigated using n-Bu0H/HCl-Et20 as the initiation system [56]. It was observed that narrow molecular weight distribution samples were obtained. These results were combined with those previously... 

Table 2 Ring-opening polymerization of lactones initiated by lanthanide complexes (CL = e-caprolactone LA = lactide TMC = trimethylene carbonate). 

Five-coordinate aluminum alkyls are useful as oxirane-polymerization catalysts. Controlled polymerization of lactones102 and lactides103 has been achieved with Schiff base aluminum alkyl complexes. Ketiminate-based five-coordinate aluminum alkyl (OCMeCHCMeNAr)AlEt2 were found to be active catalyst for the ring-opening polymerization of -caprolactone.88 Salen aluminum alkyls have also been found to be active catalysts for the preparation of ethylene carbonate from sc C02 and ethylene oxide.1 4 Their catalytic activity is markedly enhanced in the presence of a Lewis base or a quaternary salt. 

Over the years we have developed methods for the direct synthesis of hydrolytically and/or enzymatically degradable microspheres by ring-opening polymerization of e-caprolactone and lactides [6-12]. The diameters of these microspheres are usually less than 3 xm. In this chapter we discuss... 

Surface-initiated ring-opening polymerization of e-caprolactone on pCP SAM initiators equipped with an oligo-ethylenoxide function is reported by Hawker et al. [346]. Choi and hanger used a similar SAM initiator system to polymerize L-lactide [347]. 

Materials. PCL and polypropiolactone (PPL) were prepared by ring opening polymerization of e -caprolactone ( ) and S -propiolactone respectively in benzene in a nitrogen atmosphere at 60 C with a di-... 

The first example of a catalytic reaction at the core of dendrimers was provided by Frechet (79) using dendritic alcoholates such as 86 as macro-initiators for anionic ring-opening polymerization of a-caprolactone. Usually the alkali... 

Bailey WJ, Ni Z, Wu S-R (1982) Synthesis of poly-e-caprolactone via a free radical mechanism. Free radical ring opening polymerization of 2-methylene-l,3-dioxepane. J Polym Sci A Polym Chem 20 3021-3030... 

McLain SJ, Drysdale NE (1992) Living ring-opening polymerization of e-caprolactone by yttrium and lanthanide alkoxides. Polymer Preprints, American Chemical Society 33(1) 174-175... 

Martin E, Dubois P, Jerome R (2000) Controlled ring-opening polymerization of e-caprolactone promoted by in situ formed yttrium alkoxides. Macromolecules 33 1530-1535... 

Oshimura M, Takasu A (2010) Controlled ring-opening polymerization of E-caprolactone catalyzed by rare-earth perfluoroalkanesulfonates and perfluoroalkanesulfonimides. Macromolecules 43 2283-2290... 

Stassin F, Halleux O, Jerome R (2001) Ring-opening polymerization of E-caprolactone in supercritical carbon dioxide. Macromolecules 34 775-781... 

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