Polyesters from lactones

The polymer can be spun into an elastic yam of very fine denier. It is also claimed to exhibit good mechanical properties for molding and compares favorably with commercial polyesters and nylons. Also, polycaprolactone was reported to be used in some medical applications in biodegradable surgical sutures and postoperative support pins and splints. Similar uses are also found for two other polyesters, poly (lactic acid) and poly(glycolic acid). The two polymers form from their cyclic dimers by cationic ring-opening polymerizations with the aid of Lewis acids  

7 Step-Growth Polymerization and Step-Growth Polymers 

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Polyesters from Lactones Deriving from 1,3-Propanediol.149... 

The production of polyesters from lactones (cyclic esters) avoids the problems usually encountered in traditional polyester synthesis due to esterification equilibrium and water production. In fact, they yield in a single step, in the presence of ROP catalysts, high molecular weight polymers endowed with optimum mechanical properties. This is particularly true when large lactones are used as starting monomers. On the other hand, one of the main drawbacks connected with their use lies in their high cost. 

Lewis acid-assisted high-speed living anionic polymerization can be applied not only to the accelerated synthesis of naiTOw MWD poly(methacrylic esters) but also to the synthesis of polyethers from epoxides (11) and polyesters from lactones (14 and 15) with aluminum porphyrins as initiators. Furthermore, ring-opening polymerization of episulfides (18) with zinc AT-substituted porphyrins (5) can also be accelerated by Lewis acids. 

By selecting appropriate transfer agents, immortal polymerizations can be applied to controlled synthesis of polyesters from lactones (13-15) and lactide (Ifi)." -" A thiolate complex of zinc IV-substituted poiphyrin (5g) leads to an immortal polymerization of epoxides (11) ... 

S. (2000) Enzymatic synthesis of polyesters from lactones, dicarboxylic add divinyl esters and glycols through combination of ring-opening polymerization and polycondensation. Biomacromolecules, 1,... 

The melt condensation of acid and hydroxyl functional group normally requires exact stoichiometry, elevated temperature, and a long reaction cycle. Such a route would not be possible to utilize to produce block polymers from lactones and other vinyl monomers. However, a rather facile route leading to polyester formation can be realized by the ring-opening polymerization of lactones as seen from the scheme ... 

Enzymatic polymerization and oligomerization can be used to make polyesters, polypeptides, polysaccharides, polymers from phenols, polymers from anilines, and many others. This approach could lead to fewer side reactions, higher regio- and stereoselectivity, under milder conditions. Oligomeric polyesters can be prepared from lactones. Caprolactone can be polymerized in bulk with lipases (9.43) to polymers with molecular weights of 7000.305... 

Baeder, E. and Rohe, L. (1969) inventors (Deutsche Gold- und Silber-Scheideanstalt vorm. Roessler), assignee. Possibly branched polyester-polyols from lactones. DE Patent 1969-1955848 1955848 1971 19691106. 

The second process, ring-opening polymerisation of lactones, lactides and glycolide (Fig. 4.3), is free from these limitations. High molecular weight polyesters can be easily prepared under mild conditions from lactones of different ring size, substituted or not by functional groups (Lou et al, 2003). 

Anionic polymerization has an essential role in the polyester synthesis from lactones because it enables the correct design of the polymer s molecular weight, structure and properties. As has been widely reviewed, the anionic ROP of four-membered lactone monomers takes place by the nucleophilic attack of a negatively charged initiator on the carbonyl carbon, or on the carbon atom adjacent to the endocyclic ether oxygen atom, resulhng in linear polyester (Scheme 9.5). 

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