Synthesis and Characterization of Biodegradable Homopolymers and Block Copolymers Based on 1,5-Dioxepan-2-one

Abstract

Homopolymers of l,5-dioxepan-2-one (DXO) and block copolymers of DXO and e-caprolactone (e-CL) have been synthesized with aluminum isopropoxide as an initiator in toluene and tetrahydrofuran (THF). The homopolymerization is first order with respect to both monomer and initiator, and the endgroup analysis agrees with a coordination insertion mechanism based on the acyl-oxygen cleavage of the DXO ring. Living poly(e-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) chains are very efficient macroinitiators for the polymerization of DXO and <-CL, respectively, with formation of block copolymers of a narrow molecular weight distribution. Size-exclusion chromatography (SEC) and 13C NMR confirm the blocky structure of the copolymers, in agreement with DSC that shows a melting endotherm for the PCL block and two glass transitions characteristic of the amorphous phases of PDXO and PCL. Because of the crystallinity of the PCL block (Tm = 60 °C) and the low glass transition temperature of the amorphous PDXO block (Tg = -39 °C), poly(e-CL-fe-DXO-6-e-CL) triblocks have the potential of thermoplastic elastomers. Block copolymers of e-CL and DXO are also sensitive to hydrolysis which makes them possible candidates for biomedical applications. Initiation of the DXO polymerization with functional diethylaluminum alkoxides is also discussed.

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

“…Block copolymers have been prepared by sequential addition of the comon-omers as well. So far several combinations have been attempted by copolymerizing successively different lactones or mixtures of them, e.g., (poly(εCL-fr-δVL), poly[εCL-b-(εCL-co-δVL)] [35] and poly(εCL-b-DXO) [26]. In every one of the abovementioned cases, perfectly well-tailored diblock copolyesters are prepared whatever the nature of the comonomer that is polymerized first.…”

“…In fact, po-ly(CL-b-DXOb-CL) symmetrical triblock copolymers with high molecular weights and narrow MWD (PDI=1.20) have been synthesized by sequential co-ordinative ROP of the monomers, i.e., εCL and DXO, as initiated by Al(OfPr) 3 in toluene at RT (Scheme 39) [26,106]. For low PCL contents, the PCL teleblocks form separate semi-crystalline microdomains dispersed in a continuous PDXO rubbery matrix, the glass transition temperature of which is well below RT (T g = -36 0 C, see Table 1).…”

Novel unsaturated ε-caprolactone polymerizable by ringopening and ring-opening metathesis mechanisms

“…However, it is quite a problem to chemically attach active molecules (drug, recognition agent, adhesion promoter, probe) onto these polyesters, which is a limitation for a series of applications. In the recent past, ε-caprolactone has been chemically modified [2][3][4][5][6][7][8], and functionalized aliphatic polyesters have accordingly been made available. Among other achievements, unsaturated ε-caprolactone has been synthesized and polymerized into unsaturated aliphatic polyesters in a controlled manner [6][7][8].…”

“…As an example of combination of ROP and ROMP, some of us have reported that living ROP of ε-caprolactone is an easy way to prepare Mo OC(CF 3 ) 2 norbornene end-capped poly(ε-caprolactone) macromonomers that can be copolymerized by ROMP with norbornene and formation of poly(norbornene)-graft-poly(ε-caprolactone) copolymer [10]. In an alternative strategy, dual monomers can be polymerized by two different mechanisms and lead to polymers with a completely different structure.…”

Desenvolvimento da metodologia de síntese e purificação dos dímeros L-lactídeo e glicolídeo para produção do poli (ácido lático-co-ácido glicólico) para utilização na produção de fontes radioativas

“…No entanto, alcóxidos de estanho (II e IV) e o isopropóxido de alumínio também foram extensivamente estudados e são bastante utilizados [82,[138][139][140][141][142][143][144] 3.2.1.6.1 Polimerização por policondensação A polimerização por policondensação pode ser definida de uma maneira simples como uma condensação sucessiva de grupos funcionais dos materiais iniciais, ocasionando um aumento no tamanho das moléculas, com a formação de subprodutos. Na FIGURA 16 é mostrada a reação de policondensação envolvendo um diácido e um diálcool, gerando um éster como produto e água como subproduto [78,92].…”