Recent Developments in Ring Opening Polymerization of Lactones for Biomedical Applications

Recent advances in the synthesis of aliphatic polyesters by ring-opening polymerization.

Silicone containing copolymers: Synthesis, properties and applications

Recently, poly (є-caprolactone) (PCL) has gained a lot of attention, and shown great potential in biomedical applications. Among synthetic polymers, PCL is one of the easiest to process and manipulate into a large range of shapes and sizes due to its low melting temperature and its superior viscoelastic properties. In this review article the authors focus mainly on the properties of PCL-based biomaterials relevant to drug delivery and tissue engineering applications. The authors provide an insight into the recent developments and challenges of PCL-based biomaterials as a critical component of new therapeutic strategies for many diseases.

Polycaprolactone-based biomaterials for tissue engineering and drug delivery: Current scenario and challenges

http://maldi.ch.pw.edu.pl/pomiary/Artykuly/Characterization%20of%20synthetic%20polymers%20by%20MALDI-MS%20(Prog.%20Polym.%20Sci.%2031(2006)%20277.pdf

Characterization of synthetic polymers by MALDI-MS

2,2-Dibutyl-2-stanna-1,3-dioxepane (DSDOP) was polycondensed at 80 °C in bulk with succinyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, and 1,12-dodecanedioyl chloride. In the case of adipoyl chloride the stoichiometry was varied and the temperature in the case of sebacoyl chloride. With a slight excess of the dicarboxylic acid chlorides, macrocyclic polyesters were obtained as the main reaction products in all cases. Depending on the dicarboxylic acid dichloride the ratio of polycondensation/cyclization steps was of the order of 20/1 to 100/1. The temperature had little influence provided that the reaction mixture remained liquid and homogeneous over the whole course of the polycondensation. Macrocyclic polyesters were also obtained as the main products when the noncyclic 1,3-bis(tributylstannoxy)butane was used as monomer. It is demonstrated that the cyclic oligo- and polyesters are not the result of transesterification and backbiting degradation processes.

Macrocycles. 10. Macrocyclic poly(1,4-butanediol-ester)s by polycondensation of 2-stanna-1,3-dioxepane with dicarboxylic acid chlorides

When commercial oligo- or poly(ethylene glycol)s and dibutyltin dimethoxide were condensed in bulk with elimination of methanol, no linear polycondensates were obtained and tin-containing macrocycles were the only reaction products. In order to improve the hydrolytic stability, stoichiometric amounts of γ-thiobutyrolactone were inserted into the macrocyclic oligoethers, so that the Sn-O bonds were transformed into Sn-S bonds. The formation of monomeric (containing one Bu 2 Sn group) macrocycles was confirmed. The tin-containing macrocyclic polyethers were used as macrocyclic initiators for the ring-expansion polymerization of e-caprolactone. The resulting macrocyclic poly(ether-ester)s were isolated in the form of telechelic A-B-A block copolymers after precipitation into methanol.

Macrocycles, 7. Cyclization of oligo‐ and poly(ethylene glycol)s with dibutyltin dimethoxide – a new approach to (super)macrocycles

It has been demonstrated that the “polycondensation” of poly(tetrahydrofuran)-diols with dibutlytin dimethoxide in bulk yields tin-containing poly(THF) macrocycles and not linear polycondensates. These macrocycles were characterized by 1H and 119Sn NMR spectroscopy, by elemental analyses, viscosity measurements and mass spectroscopy. Furthermore, the stoichiometric insertion of γ-thiobutyrolactones was studied. The tin-containing macrocyclic poly(THF)-2 000 was used as macrocyclic initiator for the polymerization of e-caprolactone. The resulting macrocyclic block copoly(ether-esters) were reacted in situ with terephthaloyl chloride, succinyl chloride, or sebacoyl chloride. High temperatures proved to be advantageous for this polycondensation step. Number-average molecular weights (Mn's) up to 50 000 were obtained with polydispersity indices in the range of 1.6–1.7. The resulting tin-free multiblock copoly(ether-ester)s have the properties of thermoplastic elastomers and show good film-forming properties.

Macrocycles, 8. Multiblock copoly(ether-esters) of poly(THF) andε-caprolactone via macrocyclic polymerization

Summary: Homopolyesters based on cis-1,4-butenediol (cBeD) and aliphatic dicarboxylic acids (ADAs) were prepared by three different methods. First, cBeD was polycondensed with the dimethyl esters of ADAs in bulk. Regardless of the catalyst, only low-molar-mass polyesters were obtained. Second, polycondensations of cBeD with ADA dichlorides catalyzed by pyridine yielded polyesters with in the range of 8 000–13 500 Da. around 20 000 Da were achieved when the ADA dichlorides were polycondensed with DSDEN. These ring-opening polycondensations were optimized by a broad variation of the reaction conditions. Under optimized conditions a high molar fraction of cyclic polyesters was formed. All polyesters proved to be crystalline with melting temperatures (Tm) in the range of 55–120 °C.

Polycondensations of cBeD.

Biodegradable Polyesters Based on cis-1,4-Butenediol

Dibutyltin bisethoxide and bis(2,2,2-trifluoroethoxide), the cyclic alkoxides derived from cis-1,4-butenediol, 1,4-butanediol, 1,8-octanediol and triethylene glycol as well as bis(4-nitrophenoxide), bis(4-meth-oxyphenoxide) and tetrabutylstannoxane bisacetae were used as initiators in the polymerization of e-caprolactone (e-CL) and β-BL). Most polymerizations were conducted at 60°C with 2 M solutions in chlorobenzene, and time-conversion curves were recorded. The less reactive initiators yielded sigmoidal time-conversion curves with autoacceleration during the first stage of polymerization. Dibutyltin bisethoxide and the cyclic 1,8-octane dioxide showed the highest reactivities. The less reactive initiators yielded degrees of polymerization (DPs) exceeding the monomer/initiator (M/I) ratios after short reaction times, but a longer reaction times, an equilibration between unreacted initiator and the poly(e-CL) chain took place. The slower polymerizing β-BL yielded DPs paralleling the M/I ratio even with less reactive initiators. The stannoxane and the dibutyltin bisphenoxides were considerably less reactive than the bisalkoxides were considerably less reactive than the bisalkoxides, and only traces of phenylester endgroups were detectable by 1 H NMR spectroscopy. MALDI-TOF mas spectrometry proved the formation of cyclic oligolactones with masses greather than 600 Da for reaction temperatures ≥60°C.

Polylactones, 50: The reactivity of cyclic and noncyclic dibutyltin bisalkoxides as initiators in the polymerization of lactones

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