F-caprolactone

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). 

Star-shaped polylactones with functional end groups via ring-expansion polymerization of f-caprolactone or y-o,i-butyrolactonc with a spiroinitia-tor was synthesized as shown in Fig. 44 [146]. The spirocyclic polylactones formed were reacted with various carboxylic acid chlorides and yielded fourarmed stars with the elimination of Bu2SnCl2. Star arms with chloroacetate, 4-bromobenzoate, 4-nitrobenzoate, cinnamate, stearate, or methacrylate end groups were obtained by varying the acid chlorides. 

Fig. 21. Top Experimental ( H)- C cross-polarization spectrum of freshly prepared poly-e-caprolactone nanospheres in an aqueous dispersion (wc—100 MHz, full proton decoupling). Five polymer signals ( P ) are detected within the given spectral range, other resonances can be assigned to the surfactant polyvinyl alcohol and small amounts of polyvinyl acetate. Bottom Corresponding ( H)- C cross-polarization spectrum of a solid bulk sample of poly-f-caprolactone under static conditions.

Fig. 23. Experimental ( H)- C cross-polarization spectra of poly-f-caprolactone nanospheres in aqueous dispersion after different freezing histories (wc 100MHz, full proton decoupling) (a) dispersion after 4 weeks storage at room temperature, (b) after freezing for 1 h and thawing, (c) after freezing for 22 h and thawing, (d) after two freezing/thawing cycles. The signals at 23 and 45 ppm correspond to the surfactant polyvinyl alcohol and residual polyvinyl acetate, respectively. ...

PC, modified SEBS and hydroxyethyl acrylate terminated f -caprolactone WHkey, 1994 ... 

Oxepan-2-one 18 (hexano-6-lactone, f caprolactone) is of commercial importance for the production of the polyester poly-s -caprolactone. It is obtained by a Baeyer-Villiger oxidation of cyclohexanone with peroxy acids ... 

Fluorene stirred and refluxed 20 hrs. with 1.1 moles f-caprolactone and 1.3 moles KOH with collection of the resulting water in a trap co-9-fluorenylcaproic acid. Y 96%. F. e. in an autoclave, also with indene, and analogous reaction with hydroxycarboxylic acids, s. H. E. Fritz, D. W. Peck, and K. E. Atkins, J. Org. Chem. 33, 2575 (1968). 

Similarly, the biodegradable polyesters polyglycolic acid and poly(f-caprolactone), also used for implantable devices (degradation even slower than that of PLA), drug delivery, and suture materials, are prepared by CROP using stannous octanoate and other catalysts as cationic initiators [8]. 

Figure 36.9 Inclusion complexes of a-CD with poly(f-caprolactone).

Rg.19 Chemical structures of thermoplastic SMPs. (a) Aliphatic polyetherurethane TFX, which is prepared from methylene bis(p-cyclohexyl isocyanate) (H12 MDI), 1,4-butanediol (BD), and poly(tetramethylene glycol) (PTMG). (b) Multiblock copolymer PDC prepared from PPDO-diol, poly(p-dioxanone-diol) TMDl, 2,2(4),4-trimethylhexanediisocyanate PCL-diol, poly(f-caprolactone-diol). Reprinted by permission from ref. [85]. Copyright 2006, Nationtil Academy of Sciences, U.S.A. 

For the preparation of block copolymers, c-caprolactone is polymerized into a prepolymer and then reacted tvith p-dioxanone monomer. This results in a copol)Tner with a center block of c-caprolactone and one or two end blocks of p-dioxanone. This forms block copol) mers with a diblock (AB) or triblock (ABA) architecture (Fagpre 9). Diblock copolymers can be prepared by first prepolymerizing f-caprolactone with a monofunctional initiator such as 1-dodecanol, followed by polymerization with p-dioxanone monomer. 

Thus, a diblock copolymer is formed by adding to a flame dried, 250 ml round bottom three-neck flask equipped with a flame dried overhead mechanical stirrer, nitrogen inlet and stopper, 10 grams (8.9 wt. percent) of monohydroxy-terminated poly(f-caprolactone) prepolymer with a weight average molecular weight of 10,000 (gel permeation chromatography. Scientific Polymer Products, Inc). The reaction... 

Both poly(f-caprolactone) (PCL) and poly [3,3-bis(chIoromethyi)oxetane] (Penton) are crystalline polymers and the thermal behavior of the blends was investigated as a function of composition by using DSC [69],... 

The first synthesis of f-caprolactone was reported by Carothers(1). He also investigated its polymerization under the influence of heat cmd catalysts. Since then the polymerizations of this as well as that of other lactones were studied by many researchers. Throughout the 1950 s to the 1970 s the polymer formation and its properties were the subject of several investigations in our laboratories(2-5). Union Carbide is presently the commercial producer of the monomer and of a series of polymers which range in molecular weights from 500 to 40,000. The starting f-caprolac-tone is produced by the peracetic acid oxidation of cyclohexanone as shown in Equation (I). 

The overall mechanism of an anionic-coordination catalyzed polymerization of f-caprolactone is dependent upon a number of factors. The most important of these are the type of catalyst and whether a coinitiator is used. A very large number of both have been reported( ). If R M represents the catalyst-initiator, R2OH an active hydrogen containing coinitiator, and CL the f-caprolactone monomer, the following steps have to be considered in order to arrive at a meaningful kinetic expression ... 

Various authors11) have suggested that the polymerization of f-caprolactone proceeds via a "living" mechanism. This should yield polymers with very narrow molecular weight distributions referred to as a "Poisson distribution"(3>12). In this case, the kinetics of the polymerization would be expected to be rather simple emd straight forward. 

If the polymerization of f-caprolactone were to proceed in this manner (Mw/Mn=l) it would be followed by ester Interchange reactions until the establishment of the most probable distribution. This would result in a continuing increase in and hence of the melt viscosity (Figure 3). The polymerization of -cap-rolactone does in fact fulfill the second requirement above. However, fulfillment of conditions one and three are questionable making two alternative polymerization profiles possible. 

Figure 2. Melt viscosity vs. time for the polymerization of f-caprolactone...

I Nanofibers The first example is a study on the organization of lamellae in electrospun fibers of a semicrystalline polymer. Poly(f-caprolactone) has been spun into submicron fibers by electrospinning [30,31]. The fiber morphology can be imaged successfully by intermittent contact mode AFM, as shown in Figure 6.19a, where a rather dense web of electrospun poly( -caprolactone) fibers can... 

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