Copolymerization Of E-caprolactone Research Articles

Ring-opening copolymerization of ε-caprolactone with 2,2-dimethyltrimethylene carbonate using N-heterocyclic carbene organocatalysts

Random copolymer of e-caprolactone with 2,2-dimethyltrimethylene carbonate has been synthesized by using N-heterocyclic carbene organocatalysts for the first time. A series of N-heterocyclic carbenes namely, imidazol-2-ylidenes substituted at 1,3 position by benzyl, isopropyl, ethyl and methyl were demonstrated to bring about the metal-free ring-opening copolymerization of e-caprolactone and 2,2-dimethyltrimethylene initiated by benzyl alcohol in THF. The influences of reaction conditions, such as monomer, catalyst, and initiator concentration, as well as reaction temperature and time on the copolymerization have been examined in detail. The results show that 1-isopropyl-3-benzyl imidazol-2-ylidene carbene was potent organic catalyst for the ring-opening copolymerization of cyclic esters to generate well-defined linear polyesters of controlled molecular weight and narrow polydispersity. 1H NMR spectral data of copolymer obtained showed that the polymerization mechanism is in agreement with the activated monomer mechanism.

Synthesis and enzymatic degradation of poly(ε-caprolactone-co-ethylene carbonate-co-ethylene oxide) copolymer

Poly(e-caprolactone-co-ethylene carbonate-co-ethylene oxide) (CL-co-EC-co-EO) copolymer was synthesized via ring-opening copolymerization of e-caprolactone (CL) and 1,3-dioxolan-2-one with a metal-free phosphazene catalyst (t-BuP4). The monomer conversion and molecular weight in CL-co-EC-co-EO copolymer were characterized by nuclear magnetic resonance and gel permeation chromatography, respectively. Moreover crystallization behavior of CL-co-EC-co-EO copolymer was investigated by differential scanning calorimeter and wide-angle X-ray diffraction. The enzymatic degradation of the copolymer has been investigated by quartz crystal microbalance with dissipation. Our studies demonstrate that as PCL content in the copolymer decreases, the degree of crystallinity and crystal size decrease, while the enzymatic degradation rate increases. The copolymer exhibits layer-by-layer degradation.

Copolymerization of ε-caprolactone with Epichlorohydrin by a Green Catalyst, Maghnite

Most of the cationic initiators used in the synthesis of copolymers are expensive. They may be poisoned by products of the reaction or impurities present in the monomer feed, and contain heavy metals, such as chromium, mercury, antimony, etc., that presents environmental disposal problems for the user. Maghnite is a montmorillonite sheet silicate clay that is exchanged with protons to produce Maghnite-H+ (Mag-H+). This non-toxic and cheaper cationic catalyst was used for the copolymerization of ε-caprolactone (CL) with epichlorohydrin (ECH). The effects of the amounts of Mag-H+ and the temperature on the synthesis of poly (ε-caprolactone-co-epichlorohydrin) were studied. Increasing Maghnite-H+ proportion and temperature produced the increase in copolymerization yield. The copolymer obtained was characterized by 1H-NMR and IR spectroscopy. © 2012 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Long-Term Results of Cell-Free Biodegradable Scaffolds for In Situ Tissue-Engineering Vasculature: In a Canine Inferior Vena Cava Model

We have developed a new biodegradable scaffold that does not require any cell seeding to create an in-situ tissue-engineering vasculature (iTEV). Animal experiments were conducted to test its characteristics and long-term efficacy. An 8-mm tubular biodegradable scaffold, consisting of polyglycolide knitted fibers and an L-lactide and ε-caprolactone copolymer sponge with outer glycolide and ε-caprolactone copolymer monofilament reinforcement, was implanted into the inferior vena cava (IVC) of 13 canines. All the animals remained alive without any major complications until euthanasia. The utility of the iTEV was evaluated from 1 to 24 months postoperatively. The elastic modulus of the iTEV determined by an intravascular ultrasound imaging system was about 90% of the native IVC after 1 month. Angiography of the iTEV after 2 years showed a well-formed vasculature without marked stenosis or thrombosis with a mean pressure gradient of 0.51±0.19 mmHg. The length of the iTEV at 2 years had increased by 0.48±0.15 cm compared with the length of the original scaffold (2–3 cm). Histological examinations revealed a well-formed vessel-like vasculature without calcification. Biochemical analyses showed no significant differences in the hydroxyproline, elastin, and calcium contents compared with the native IVC. We concluded that the findings shown above provide direct evidence that the new scaffold can be useful for cell-free tissue-engineering of vasculature. The long-term results revealed that the iTEV was of good quality and had adapted its shape to the needs of the living body. Therefore, this scaffold would be applicable for pediatric cardiovascular surgery involving biocompatible materials.

Synthesis, characterization, and micellization of PCL‐g‐PEG copolymers by combination of ROP and “Click” chemistry via “Graft onto” method

AbstractBiodegradable and biocompatible PCL‐g‐PEG amphiphilic graft copolymers were prepared by combination of ROP and “click” chemistry via “graft onto” method under mild conditions. First, chloro‐functionalized poly(ε‐caprolactone) (PCL‐Cl) was synthesized by the ring‐opening copolymerization of ε‐caprolactone (CL) and α‐chloro‐ε‐caprolactone (CCL) employing scandium triflate as high‐efficient catalyst with near 100% monomer conversion. Second, the chloro groups of PCL‐Cl were quantitatively converted into azide form by NaN3. Finally, copper(I)‐catalyzed cycloaddition reaction was carried out between azide‐functionalized PCL (PCL‐N3) and alkyne‐terminated poly(ethylene glycol) (A‐PEG) to give PCL‐g‐PEG amphiphilic graft copolymers. The composition and the graft architecture of the copolymers were characterized by 1H NMR, FTIR, and GPC analyses. These amphiphilic graft copolymers could self‐assemble into sphere‐like aggregates in aqueous solution with diverse diameters, which decreased with the increasing of grafting density. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Poly(ε-Caprolactone)-b-Hyperbranched Polyglycidol for Targeted Drug Delivery

A bolock copolymer of poly(ε-caprolactone) and hyperbranched polyglycidol (PCL-b-HPG) was synthezed by “living” copolymerization of ε-caprolactone (CL) and glycidol. The chemical structure was confirmed by 1H NMR, IR and GPC spectrum. Nanoparticles (NPs) of 50–100 nm were formulated from the PCL-b-HPG copolymer with no evidence of particles aggregation as determined by TEM. RGD peptide was covalently coupled on the end hydroxyl groups that could enable recepter–mediated recongnation onto targeted tissues. In conclusion, a hyperbranched copolymer PCL-b-HPG was synthezed by a novel and simple approach. The numerous functional end-groups could facilitate the attachment of biomolecules for further investigation as targeted drug delivery.

Maghnite, a Green Catalyst for Synthesis ofPoly(ε-caprolactone-co-tetrahydrofuran)

In the present work, the copolymerization of e-caprolactone with tetrahydrofyran using a proton exchanged Montmorillonite clay as initiator is reported. The effects of the amounts of Mag-H and the temperature on the synthesis of poly(e-caprolactone-co-tetrahydrofuran) were studied. The copolymer obtained was characterized by 1H-NMR spectroscopy.

In situ monitoring of enzyme-catalyzed (co)polymerizations by Raman spectroscopy

In situ, fiber optic-based Raman spectroscopy provided real time monitoring of enzyme-catalyzed ring-opening homo- and copolymerizations of e-caprolactone (e-CL) and δ-valerolactone (δ-VL). A custom designed reactor equipped with in situ fiber optic probe was used to measure monomer conversion as a function of time. The results from the in situ technique were in good agreement with those determined by offline 1H NMR analysis. Monomer reactivity ratios for the lipase-catalyzed copolymerization of e-CL and δ-VL were estimated using the Kelen-Tudos method as re-CL = 0.38 and rδ-VL = 0.29.

Ring-opening polymerization of cyclic esters in the presence of choline/SnOct2 catalytic system

Low-molecular weight poly(ε-caprolactone), polylactides, and copolymers of ε-caprolactone and lactide were synthesized by ring-opening polymerization of cyclic monomers with choline (CHOL) as a initiator and SnOct2 as a catalyst. Polymerization was conducted in bulk (120–160 °C) with high yield. Effects of temperature, reaction time, and CHOL dosage on the polymerization process were examined. Structure of products was characterized by means of MALDI-TOF, IR, and NMR.

Development of a Novel, Nearly Insoluble Antiadhesive Membrane

Background: Sodium hyaluronate/carboxymethylcellulose (HA/CMC) is difficult to use in a moist environment because of its susceptibility to moisture. Methods: We developed the three-layered nDM-14R membrane. The surface layers are composed of 1-lactide, glycolide and e-caprolactone copolymers. HA/CMC and nDM-14R were used in all these studies. (1) The central region of 1 × 10 cm specimens (n = 5) was moistened for 0, 5, 10, 20, 30 or 60 s, after which the tensile strength was determined; (2) one side of specimens of 1 × 10 cm (n = 5) was moistened with agar gel for 5, 10, 15 or 30 s, after which the adhesion strength was determined, and (3) Rat cecum (n = 10) was scratched, 3 × 3 cm specimens were placed on the scratched area, and adhesions were evaluated on postoperative day 14. Results and Conclusion: (1) The tensile strength of nDM-14R after contact for 10–30 s was greater than that of HA/CMC. (2) The adhesive strength of HA/CMC after contact for 5–10 s was greater than that of nDM-14R. (3) Adhesion scores in treatment groups were significantly lower than in the control group. The results suggest that nDM-14R has the same antiadhesive effect and allows easier placement under moist conditions than HA/CMC.

Synthesis of Dendrigraft Poly(ϵ‐Caprolactone)s Using Side Hydroxyl Groups for the Grafting of Branch Chains

Dendrigraft poly(ϵ-caprolactone)s with high molecular weight and narrow polydispersity are synthesized via a convenient generation-growth approach. Copolymerization of ϵ-caprolactone (CL) and 4-(2-benzoxyethoxy)-ϵ-caprolactone (BECL) with stannous octanoate as a catalyst affords a functionalized poly(ϵ-caprolactone) (PCL) with benzyl-protected hydroxyl side groups. After removal of benzyl groups by palladium-catalyzed hydrogenolysis, the graft copolymerization of CL and BECL onto the hydroxyl-bearing linear polyester (zero-generation) affords the first-generation graft polyester. Further deprotection and graft polymerization cycles led to dendrigraft polyesters. Molecular weights are multiplied in each graft copolymerization. The second-generation dendrigraft poly(ϵ-caprolactone) has an M(w) of 236 000 g·mol(-1) and M(w) /M(n) of 1.53.

Triblock copolymers of ε-caprolactone, L-lactide, and trimethylene carbonate: Biodegradability and elastomeric behavior

For the triblock copolymer of ε-caprolactone, trimethylene carbonate, and L-lactide, where L-lactide blocks form the two ends, there is a range of compositions over which elastomeric behavior is obtained. Within this composition range, these polymers show good creep and recovery at ambient temperature, and exhibit high elongations to break. Additionally, we demonstrate that the recovery is independent of stress and strain for the elastomer compositions. The range of compositions that yield elastomeric character is rationalized based on the structure; specifically, there must be a minimum crystallinity of the end blocks and no crystallinity in the midblock, in addition to molar mass requirements. These polymers degrade by simple hydrolysis, and the rate of degradation is potentially programmable by manipulation of the molar ratio of hard segment to soft segment. Compared to biodegradable polyurethane, these polymers are expected to yield less harmful degradation products, and offer more variables for manipulation of properties. These polymers are also processable from the melt at temperatures exceeding about 130 °C. We expect to use these polymers in a variety of applications, including stent coatings, fully-degradable stents, and atrial septal defect occluders.

Maghnite, a green catalyst for synthesis of poly(ε-caprolactone-co-tetrahydrofuran)

In the present work the copolymerization of ε-caprolactone with tetrahydrofuran using a proton exchanged Montmorillonite clay as initiator is reported. The effects of the amounts of Maghnite-H+ (Mag-H) and the temperature on the synthesis of poly (ε-caprolactone-cotetrahydrofuran) were studied. The copolymer obtained was characterized by 1 H-NMR and IR spectroscopy.

Amphiphilic Block Co-polyesters Bearing Pendant Cyclic Ketal Groups as Nanocarriers for Controlled Release of Camptothecin

Amphiphilic block co-polymers consisting of hydrophilic poly(ethylene glycol) and hydrophobic polyester bearing pendent cyclic ketals were synthesized by ring-opening co-polymerization of ε-caprolactone (CL) and 1,4,8-trioxaspiro-[4,6]-9-undecanone (TSU) using α-hydroxyl, ω-methoxy, poly(ethylene glycol) as the initiator and stannous octoate as the catalyst. Compositional analyses indicate that TSU was randomly distributed in the hydrophobic blocks. When the TSU content in the co-polymers increased, the polymer crystallinity decreased progressively and the glass transition temperature increased accordingly. The hydrophobic, anticancer drug, camptothecin (CPT), was successfully encapsulated in the block copolymer nanoparticles. The CPT encapsulation efficiency and release kinetics were strongly dependent on the co-polymer composition and crystallinity. CPT release from nanoparticles constructed from co-polymers containing 0, 39 and 100 mol% TSU in the hydrophobic block followed the same trend, with an initial burst of approx. 40% within one day followed by a moderate and slow release lasting up to 7 days. At a TSU content of 14 mol%, CPT was released in a continuous and controlled fashion with a reduced initial burst and a 73% cumulative release by day 7. The in vitro cytoxicity assay showed that the blank nanoparticles were not toxic to the cultured bone metastatic prostate cancer cells (C4-2B). Compared to the free drug, the encapsulated CPT was more effective in inducing apoptotic responses in C4-2B cells. Modulating the physical characteristics of the amphiphilic co-polymers via co-polymerization offers a facile method for controlling the bioavailability of anticancer drugs, ultimately increasing effectiveness and minimizing toxicity.

Stereocomplexes formation from enantiomeric star-shaped block copolymers of ε-caprolactone and lactide

AbstractEnantiomeric star-shape block copolymers of ε-caprolactone and lactide with different molar masses and compositions were synthesized using pentaerythritol/tin(II) 2-ethylhexanoate as initiating system. Stereocomplex formation between pair of enantiomeric blocks of star arms was investigated. Thermal properties of both copolymers and obtained stereocomplexes were examined. A rise of above 50 °C of melting temperature of polylactide phase was observed as a consequence of stereocomplex creation.

Enhanced Mechanical Relaxation below the Glass Transition Temperature in Partially Supramolecular Networks

Cross-linked polymers in which part of the covalent cross-links have been replaced by reversible cross-links have potential application in coatings with improved stress relaxation. Here we present a detailed study of materials based on copolymers of ε-caprolactone and l-lactic acid, containing different ratios of covalent and ureidopyrimidinone (UPy) dimer cross-links. Their thermal and mechanical properties were tested by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric relaxation spectroscopy (DRS). By extrapolation of the α* relaxation process in DMA (arising from dynamics of the reversible UPy cross-links) to temperatures below the glass transition temperature (Tg), it was shown that the reversible cross-links contribute significantly to the relaxation of stress below Tg that was observed in creep measurements.

Random Copolymerization of ε-Caprolactone with Lactide Using a Homosalen−Al Complex

The bulky substituents of homosalen complexes decelerate the ring-opening polymerization of racemic lactide (LA). The substituent effects provide the first catalysis for the random copolymerization of epsilon-caprolactone (CL) with LA (CL/LA = 1:1). The copolymerization of CL with LA (CL/LA = 1:1) by the iPr(3)Si-substituted homosalen-Al complex 2 affords the practically random copolymer in a controlled manner. The reactivity ratios, average sequence lengths of CL and LA during the copolymerization, abundance ratios of the triad caproyl sequences, and T(g) value of the obtained copolymer indicate that the copolymer was random with a somewhat alternative tendency (r(CL)r(LA) = 0.80).

Living Ring-Opening Homo- and Copolymerization of ε-Caprolactone and l- and d,l-Lactides by Dimethyl(salicylaldiminato)aluminum Compounds

The dimethylaluminum compounds {3-tBu-2-(O)C6H3CH═N−R}AlMe2 [R = C6H5 (1); 2,6-iPr2C6H3 (2); C6F5 (3)] were used as initiators in the ring-opening polymerization (ROP) of ε-caprolactone, l-lactide, and d,l-lactide. Compound 3, in combination with 1 equiv of methanol, exhibited a living behavior in the ROP of the cyclic esters. Such a feature allowed the preparation of poly(d,l-lactide-block-ε-caprolactone) and poly(l-lactide-block-ε-caprolactone) copolymers. Random copolymers of ε-caprolactone and l-lactide and of ε-caprolactone and d,l-lactide were also synthesized by compound 3. NMR and DSC characterization confirmed a highly random structure of these copolymers, even in the absence of transesterification reactions. All the materials, characterized by GPC, showed high molecular weight and narrow molecular weight distributions.

Electrospinning of synthesized triblock copolymers of ε-caprolactone and L-lactide for the application of vascular tissue engineering

Biodegradable triblock copolymers of ε-caprolactone and L-lactide with varying compositions and molecular weights have been synthesized. They were then used to fabricate compliant small-diameter tissue engineered vascular scaffolds by using an electrospinning technique. The in vitro and in vivo degradation of the ultrafine fabrics was monitored to be faster than their counterpart cast films. A favorable interaction between the scaffolds and the mouse fibroblast L929 cells was demonstrated via MTT assay. A confluent, adherent monolayer of canine mesenchymal stem cells was observed in the tubular scaffold lumen after culture in a bioreactor for 3 days. The scaffold mechanical strength was strong enough to be transplanted into the canine carotid artery.

2D- and 3D-microstructured biodegradable polyester resins

Biodegradable polyester resins were prepared via photo crosslinking of functional polyesters obtained by copolymerization of ε-caprolactone and the functional cyclic esters γ-acryloyloxy-ε-caprolactone (ACL) and γ-methacryloyloxy-ε-caprolactone (MCL). The cyclic esters were prepared via Baeyer-Villiger oxidation of the corresponding 4-acyloyloxy-cyclohexanone derivatives. Copolymers with different content of either acryloyloxy or methacryloyloxy functional groups were prepared via catalyzed ring-opening polymerization (ROP) of γ-acyloyloxy-ε-caprolactones and ε-caprolactone using Al(OiPr)3 as catalyst and initiator. 2D- and 3D-micropatterning of the copolymers was performed via UV-crosslinking of polymer films on a suitable substrate and by UV replica molding on both rigid and elastic masters, showing the processability of these novel functional polyesters and their potential as substrates for biomedical devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6789–6800, 2008