Polycaprolactone structure

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... 

Aliphatic polyesters based on monomers other than a-hydroxyalkanoic acids have also been developed and evaluated as drug delivery matrices. These include the polyhydroxybutyrate and polyhydroxy valerate homo- and copolymers developed by Imperial Chemical Industries (ICI) from a fermentation process and the polycaprolactones extensively studied by Pitt and Schindler (14,15). The homopolymers in these series of aliphatic polyesters are hydrophobic and crystalline in structure. Because of these properties, these polyesters normally have long degradation times in vivo of 1-2 years. However, the use of copolymers and in the case of polycaprolactone even polymer blends have led to materials with useful degradation times as a result of changes in the crystallinity and hydrophobicity of these polymers. An even larger family of polymers based upon hydroxyaliphatic acids has recently been prepared by bacteria fermentation processes, and it is anticipated that some of these materials may be evaluated for drug delivery as soon as they become commercially available. 

The morphology of spin-cast film, thickness of 180 nm, from polycaprolactone shows many spherulitic structures with fibrillar nanostructures formed of lamellae lying edge on (about 10 nm thick) and areas with lamellar sheets lying flat on. Different crystalline structures are found when the sample is melted and crystallized as a function of temperature. These two studies reinforce the complex inner relationship between physical treatment and nanostructure. 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aliphatic polyesters with inoiganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibility of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and bio degradability is attempted. Starch and additives have been evaluated in detail from the perspective of structure and compatibility with starch (214). 

Chemically-Controlled Systems. In these systems, the polymer matrix contains chemically-labile bonds. On exposure to water or enzymes the bonds hydrolyze, erode the three dimensional structure of the polymer and release the incorporated reagent into the surrounding medium. Depending on the polymer used, the erosion products may act as interferences, such as by altering the pH of the solution. Examples of these systems are polyglycolic acid (PGA) and a polyglycolic acid - polylactic acid (PGA/PLA) copolymer. PGA hydrolyzes to hydroxyacetic acid, and PGA/PLA hydrolyzes to lactic acid and hydroxyacetic acid. Other chemically-controlled systems are based on polyorthoesters, polycaprolactones, polyaminoacids, and polyanhydrides. 

A wide range of thermoplastic starch compounds have been claimed in recent years. Formulations of thermoplastic starch with linear, biodegradable polyesters, including polycaprolactone and PHBV,174 176 and with polyamides175 have been reported. Laminated structures have been claimed using thermoplastic starch or starch blends as one or more of the layers.175,177,178 The use of polymers latexes as components of thermoplastic starch blends has also been claimed.179 181 Blends with natural polymers are also claimed, including cellulose esters182,183 and pectin.184 A crosslinked thermoplastic material of dialdehyde starch and protein has been reported.185... 

For the LC structure, each elementary sheet results from the superposition of two layers a layer of thickness dA formed by the solvated amorphous block (polystyrene or polybutadiene) and a layer of thickness dB formed by the crystalline and folded chains (polyethylene oxide) or polycaprolactone)265,269,271 ... 

Huang ZM, Zhang YZ (2005) Micro-structures and mechanical performance of co-axial nanofibers with drug and protein cores and polycaprolactone shells. Chem J Chin Univ Chin 26(5) 968-972... 

Solid-state carbon NMR with MAS has been used to study the structure and dynamics of semicrystalline polycaprolactone (PCL) and its inclusion complexes formed with a- and y-cyclodextrins (a- and y-CDs), which are shown to have channel structures occupied by single and two parallel, side-by-side chains, respectively. ... 

Fig. 4 Migration of 6-hydroxyhexanoic acid from different polycaprolactone homopolymers during hydrolysis in phosphate buffer (A) porous structure, ( ) linear disc and (x) network. Reprinted from [73] with permission of Taylor Francis. Taylor Francis (2007)...

The promising results by Huber et al. [37] and Choi and Kwak [38] with a reduction in the migration of highly branched polyesters to hexane and polymer substrates suggested that the introduction of branches in the plasticizer structure could be an effective way to prevent the release of plasticizer also in aqueous environments. Volatihty, extractabihty, and exudation tests for PVC/hyperbranched polycaprolactone showed that there was no plasticizer migration even at very harsh conditions, while 7-78% of additives in PVC/DEHP migrated out of the samples [91]. 

Until recently, the polyol component was restricted to poly(oxytetramethylene)glycol (PTMG), polycaprolactone diol and to adipate ester diols such as poly(ethyleneadipate)diol. The structures of these polyols are shown in Figure 2. 

Rheological studies of PET nanocomposites are not ample, but show very interesting features. In the low frequency range, the nanocomposites display a more elastic behavior than that of PET. It appears that there are some physical network structures formed due to filler interactions, collapsed by shear force, and after all the interactions have collapsed, the melt state becomes isotropic and homogeneous. Linear viscoelastic properties of polycaprolactone and Nylon-6 [51] with MMT display a pseudo-solidlike behavior in the low frequency range of... 

A large number of biodegradable polyesters are based on petroleum resources, obtained chemically from synthetic monomers [Okada, 2002 Albertsson and Varma, 2002 Vert et al., 1995 Sinclair, 1996 Lunt, 1998 Steinbuchel, 2003 Bigg, 1996]. According to the chemical structures, we can distinguish polycaprolactone, aliphatic copolyesters, and aromatic copolyesters. All these polyesters are soft at room temperature [Averous and Pollet, 2012]. 

Feng, L., Zhou, Z., Dufresne, L., Huang, J., Wei, M., An, L.J. Structure and Properties of New Thermoforming Bionanocomposites Based on Chitin Whisker-Graft-Polycaprolactone. 

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