Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide

Abstract

Novel biodegradable and biocompatible polyesters have been prepared by random copolymerization of ε-caprolactone (ε-CL) and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO) initiated by Al(OiPr)3. Copolyesters of molecular weight (M̄ n) up to 104 and containing up to 90 mol % TOSUO repeating units have been prepared. The copolymer molecular weight is controlled by the molar ratio of the consumed comonomers and the initiator. The TOSUO constitutive units have been quantitatively deacetalized into ketones, which have also been efficiently reduced into hydroxyl groups without any apparent chain degradation. Therefore, poly(ε-caprolactone) (PCL) with well-defined content of ketone or hydroxyl pendent groups have been made available. The ε-CL and TOSUO comonomer units are randomly distributed within the copolymers, as assessed by the 13C-NMR sequence analysis. Indeed, the reactivity ratios (r C and r T) have been calculated from the average length of the ε-CL sequences (L C) and the TOSUO sequences (L T) and found to be 1.3 (r C) and 1.0 (r T), respectively. There is an interesting parallelism between the crystallinity and the average length of the ε-CL sequences. Copolyesters containing a molar fraction of TOSUO units smaller than 0.15 are semicrystalline, whereas the incorporation of larger amounts of TOSUO units results in amorphous copolyesters. Conversion of the ethylene acetal pendent groups into ketones and ultimately into hydroxyl pendent groups results in increasing glass transition temperature (T g), melting temperature (T m), and melting enthalpy (ΔH m). The thermal stability depends on the copolyester composition, since it decreases as the molar fraction of TOSUO units is increased.

Biodegradable and biocompatible inorganic-organic hybrid materials: 2. Dynamic mechanical properties, structure and morphology

“…biocompatibility, permeability and biodegradability [4][5][6][7] . Depending on the polymerisation mechanism, PCL can be end-capped by hydroxyl or vinyl groups [8][9][10][11] , which are reactive toward alkoxysilane 1,3 , i.e. a reagent commonly used in the sol-gel process.…”

Novel Macromolecular Architectures Based on Aliphatic Polyesters: Relevance of the “Coordination-Insertion” Ring-Opening Polymerization

“…Accordingly, copolymerization of εCL with δVL [35], TOSUO [36], and γBL [37] initiated with Al(OfPr) 3 in toluene at 25 0 C leads to highly statistical copolymers as confirmed by triad analysis by 13 C NMR spectroscopy. At the same time, the control over the molecular parameters and the narrow molecular weight distributions already observed in the respective homopolymerizations are maintained.…”

“…Although important efforts have been devoted to the synthesis of functipnal-ized monomers, which is very often complex and tedious, only one example of controlled/living (co)polymerization has been reported so far. This is the case of the 5-ethylene ketal ε-caprolactone, precisely l,4,8-trioxa(4,6)spiro-9 undecan-one (TOSUO), which is readily synthesized by a one-step oxidation reaction of the commercially available monoethylene ketal of the 1,4-cyclohexanedione [36]. TOSUO has proved to homopolymerize in a "living" way when initiated by Al(OfPr) 3 in toluene at 25 0 C (Scheme 12) [66].…”

“…TOSUO has proved to homopolymerize in a "living" way when initiated by Al(OfPr) 3 in toluene at 25 0 C (Scheme 12) [66]. As a result, well-defined homo PTOSUO, but also random and block copolymers with εCL, were prepared [36,40]. Treatment of the (co)polyester chain with (C 6 Hg) 3 CBF 4 in CH 2 Cl 2 at RT allows for the quantitative deprotection of the pendant ketone functions.…”

Synthesis of new substituted lactones by "click" chemistry

“…2 Nevertheless, the lack of pendant functional groups along the chains is a severe limitation for many applications. In order to tackle this drawback, the usual strategy relies on the ring-opening polymerization of lactones, duly substituted by a functional group 3,4 , e.g., pendant unsaturation, [5][6][7] alkyne, 8 protected carboxylic acid, 9 alcohol, 10,11 diol, 12 protected alcohol, 9,13-15 protected diol, 16 ketal, 17,18 ketone 19 and halogen 20,21 . Nevertheless, the synthesis of a new lactone requires a specific strategy.…”