Caprolactone polyester,

Some heterocycles have both nucleophilic and electrophilic atoms in their molecule. Thus they can be opened and polymerized by the anionic, cationic or coordination mechanisms. Examples are lactams, lactones, and cyclic siloxanes. Investigations of the mechanism of lactam propagation are complicated by the occurence of side reactions. In principle, the mechanism described in Chap. 3 by the schemes (55)—(57) and (71) is accepted. Anionic polymerization of cyclic esters consists, in most cases (see Chap. 4, Sect. 2.2) of repeated reversible attacks on the carbonyl carbon by the anion 0]-. From e-caprolactone, polyester chains grow according to [315]... 

Bacteria, mildew, fungi and algae are commonly encountered by plastics products during service. Fortunately, few synthetic polymers are attacked by them. The cellulosics, the polyester urethanes, the, caprolactone polyesters and the polysulfides are susceptible, and the ester group in polyesters may be cleaved. 

Caprolactone polyester Another type of polyester which is of interest in the field of solid polyurethanes is that obtained by the addition polymerization of -caprolactone in the presence of an initiator ... 

In addition, polyester polyols are made by the reaction of caprolactone with diols. Poly(caprolactone diols) are used in the manufacture of thermoplastic polyurethane elastomers with improved hydrolytic stabiHty (22). The hydrolytic stabiHty of the poly(caprolactone diol)-derived TPUs is comparable to TPUs based on the more expensive long-chain diol adipates (23). Polyether/polyester polyol hybrids are synthesized from low molecular weight polyester diols, which are extended with propylene oxide. 

Polyester and polyether diols are used with MDI in the manufacture of thermoplastic polyurethane elastomers (TPU). The polyester diols are obtained from adipic acid and diols, such as ethylene glycol, 1,4-butanediol, or 1,6-hexanediol. The preferred molecular weights are 1,000 to 2,000, and low acid numbers are essential to ensure optimal hydrolytic stabihty. Also, caprolactone-derived diols and polycarbonate diols are used. Polyether diols are... 

One variation in polyester intermediates that has roused some interest are those prepared by a ring-opening polymerisation of e-caprolactone and methyl-e-caprolactones with titanium catalysts and diol and triol initiators Figure 27.6). 

Crystalline polyesters are highly important as adhesive raw materials. They are normally crystalline waxes and are highly symmetrical in nature, which can aid the crystallization process [26]. Poly(hexamethylene adipate) and poly(caprolactone), shown in Table 2, are only two of the many crystallizable backbones. Poly(ethylene adipate) and poly(letramethylene adipate) are also commonly used in urethane adhesives. The crystalline polyesters are used in curing hot melts, waterborne polyurethanes, thermoplastic polyurethanes, and solvent-borne urethane adhesives. The adipates are available mostly as diols. The poly(caprolactones) are available as diols and triols. 

The activation energy of thermolysis of the azo group was measured by DSC [14]. Type II MAIs, which are composed of various prepolymers such as aliphatic polyester, poly(caprolactone), and aliphatic poly (carbonate), showed almost the same activation energy irrespective of difference in prepolymer structure, suggesting that the neighboring group only affects the active site. 

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). 

Another important type of condensation polymer are the linear polyesters, such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). Copolymers of polyesters and PA have been studied in detail, and it has been shown that random copolyesteramides have a low structural order and a low melting temperature. This is even the case for structurally similar systems such as when the group between the ester unit is the same as that between the amide unit, as in caprolactam-caprolactone copolymers (Fig. 3.10).22 Esters and amide units have different cell structures and the structures are not therefore isomorphous. If block copolymers are formed of ester and amide segments, then two melting temperatures are present. 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

The anionic method of polymerization is most useful for the synthesis of low molecular weight hydroxy-terminated oligomers and polymers that are to be further processed. For example, the treatment of hydroxy-terminated oligomers with isocyanates has been used to obtain polyester-urethanes (9,20), while triblock copolymers (PCL-PEG-PCL) are prepared by initiating the polymerization of e-caprolactone with the disodium alcoholate from polyethylene glycol (26). 

Initiation of stannous octoate-catalyzed copolymerization of e-caprolactone with glycerol was used to prepare a series of trifunctional hydroxy-end blocked oligomers, which were then treated with hexane-1,6-diisocyanate to form elastomeric polyesterurethanes with different crosslink densities (49). Initiation of e-caprolactone polymerization with a hydroxypropyl-terminated polydimethylsiloxane in the presence of dibutyl tin dilaurate has been used to prepare a polyester-siloxane block copolymer (Fig. 4) (50). 

II. B polyethylene glycol, ethylene oxide, polystyrene, diisocyanates (urethanes), polyvinylchloride, chloroprene, THF, diglycolide, dilac-tide, <5-valerolactone, substituted e-caprolactones, 4-vinyl anisole, styrene, methyl methacrylate, and vinyl acetate. In addition to these species, many copolymers have been prepared from oligomers of PCL. In particular, a variety of polyester-urethanes have been synthesized from hydroxy-terminated PCL, some of which have achieved commercial status (9). Graft copolymers with acrylic acid, acrylonitrile, and styrene have been prepared using PCL as the backbone polymer (60). 

More definitive evidence of enzymatic attack was obtained with 1 1 copolymers of e-caprolactone and 6-valerolactone crosslinked with varying amounts of a dilactone (98,99). The use of a 1 1 mixture of comonomers suppressed crystallization and, together with the crosslinks, resulted in a low-modulus elastomer. Under in vitro conditions, random hydrolytic chain cleavage, measured by the change in tensile properties, occurred throughout the bulk of the samples at a rate comparable to that experienced by the other polyesters no weight loss was observed. However, when these elastomers were implanted in rabbits, the bulk hydrolytic process was accompanied by very rapid surface erosion. Weight loss was continuous, confined to the... 

The effects of a series of added tertiary amines on the rate of chedn scission of other polyesters, including poly( e-caprolactone-co-lactic acid), has been studied and found to be equally great (65). The mechanism with tertiary amines can only be general base catalysis for the effectiveness of the amines was not related to their pK values or lipophilicities. The acceleration of the hydrolysis of the polyesters was used as a strategy for controlling the drug release rate. 

Schindler, A., Hibionada, Y. M., and Pitt, C. G., Aliphatic polyesters III. Molecular weight and molecular weight distribution in alcohol-initiated polymerization of e-caprolactone, J. Polym. Sci., Part A Polym. Chem., 20. 319-326, 1982. 

Thermodynamics of fusion of poly-p-propiolactone and poly-e-caprolactone. Comparative analysis of the melting of aliphatic polylactone and polyester chains, Eur. Polym. J.. 8, 449-463, 1972. 

Pitt, C. G., Gratzl, M. M., Jeffcoat, A. R., Zweidinger, R., and Schindler, A., Sustained drug delivery systems. II. Factors affecting release rates from poly( e-caprolactone) and related biodegradable polyesters, J. Pharm. Sci.. 68, 1534-1538, 1979. 

The enantioselectivity was greatly improved by the copolymerization with 7- or 13-membered non-substituted lactone using lipase CA catalyst (Scheme 8) the ee value reached ca. 70% in the copolymerization of (3-BL with DDL. ft is to be noted that in the case of lipase CA catalyst, the (5 )-isomer was preferentially reacted to give the (5 )-enriched optically active copolymer. The lipase CA-catalyzed copolymerization of 8-caprolactone (6-membered) with DDL enan-tioselectively proceeded, yielding the (/ )-enriched optically active polyester with ee of 76%. 

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. 

Poly(caprolactone) [poly(6-hydroxyhexanoate) (PCL)] is a synthetic unbranched polyester and has been used by man for a several decades. The biodegradability of PCL is well-known, and many PCL-degrading microorganisms have been described [26,38,112-115]. 

So far, many studies have focused on the development and application of aliphatic polyesters such as PLA [1-3], PGA [41,42], and PCL [43,44], Figure 2 shows the structures of their monomers lactides (LAs), glycolide (GA), e-caprolactone (CL), and some typical comonomers. 

---