Polymerization Of DL-lactide Research Articles

Poly(lactic acid) block improves ambient-temperature ionic conductivity of pentablock copolymer electrolyte

A polystyrene-b-poly(lactic acid)-b-poly(ethylene oxide)-b-poly(lactic acid)-b-polystyrene pentablock copolymer electrolyte (PSLE) is successfully prepared by ring-opening polymerization (ROP) of DL-lactide (DL-LA) with poly(ethylene oxide) (PEO) followed by atom transfer radical polymerization (ATRP) with styrene. Poly(lactic acid) (PLA) block made by the polymerization of DL-LA can not only reduce the crystallinity of PEO, but also balance the coordination properties of Li+, while polystyrene (PS) block acts as a hard block to improve the mechanical properties of PSLE. Here, the obtained PSLE achieves high ionic conductivity (1.3 × 10−4 S cm−1) under ambient temperature and wide electrochemical stable window (4.2 V). In addition, the PSLE shows outstanding stability, allowing the Li/PSLE/Li cell to cycle stably for more than 600 h at 0.1 mA cm−2 without an increase in polarization voltage. And LiFePO4/PSLE/Li cell shows an initial discharge capacity of 159 mA h g−1 and keeps a capacity retention of 94.6 % after 200 cycles at 0.1C under ambient temperature. The LiNi0.6Co0.2Mn0.2O2/PSLE/Li cell also delivers good cycling performance. These results suggest that multiblock copolymer electrolyte is very promising material for the preparation of solid polymer electrolytes (SPEs) suitable for lithium metal batteries.

Polymerization of DL-Lactide induced by Protonated Montmorillonite clay as a solid catalyst: Mechanism study

Maghnite- H+ is Algerian montmorillonite sheet alumino-silicate clay, exchanged with protons (H+). This solid non-toxic catalyst was successfully used as cationic catalyst for the polymerization of D,L-Lactid at 100°C. Interactions between Maghnite-H+ platelets and the monomer (D,L-Lactide) were studied by solid state 1H, 27Al and 29Si NMR spectroscopy. The results show that, the mechanism of the reaction involves both Bronsted and Lewis acid sites on Maghnite surface.

Synthesis of Biodegradable Chitosan-Poly(D,L-Lactide) Hybrid Amphiphiles via Ring Opening Graft Polymerization for Efficient Gene Carrier

Biodegradable chitosan-graft-poly(D,L-lactide) (CHI-PLA) have been prepared by in situ ring-opening polymerization of DL-lactide (LA) grafting from chitosan. The chemical structure and physical properties of these chitosan derivatives were characterized by FTIR, 1H-NMR, TGA and XRD. Formation and characteristics of polymeric micelles based on these chitosan derivatives were studied by fluorescence spectroscopy and dynamic light scattering (DLS). The critical micelle concentration (CMC) in water varied from 0.048 to 0.021 mg/mL as PLA grafting percentage (GP) increased from 92% to 132%. The mean diameters of CHI-PLA micelles have been readily tuned by controlling GP and the pH of micelles solution. The quasi-spherical micelles were observed by transmission electron microscopy (TEM). In particular, complexes formed by CHI-PLA micelles and plasmid DNA were investigated by agarose gel electrophoresis. Compared to chitosan, it could exhibit enhanced transfection efficiency in some cases and lower cell toxicity, as confirmed by in vitro transfection and cytotoxicity assay in L929 cell lines. These results indicated that CHI-PLA may be used as a new nonviral gene delivery vector for future gene therapy applications.

Kinetic and Thermodynamic Evaluation of the Reversible N-Heterocyclic Carbene−Isothiocyanate Coupling Reaction: Applications in Latent Catalysis

Using stopped flow and other spectroscopic techniques, the thermodynamic parameters of the coupling reaction between 1,3-dimesitylimidazolylidene and phenyl isothiocyanate were determined (H(o) = -96.1 kJ mol(-1) and ΔS(o) = -39.6 J mol(-1) K(-1)). On the basis of these data which indicated that the reaction was reversible (K(eq) = 5.94 × 10(14) M(-1) at 25 °C; k(f) = 252 M(-1) s(-1); k(r) = 4.24 × 10(-13) s(-1)), the adduct formed from the two aforementioned coupling partners was used as a latent catalyst to facilitate the [2 + 2 + 2] cyclotrimerization of phenyl isocyanate and the polymerization of DL-lactide.

Novel hyperbranched poly (amine-ester)-poly (lactide-co-glycolide) polymeric micelles as amphotericin B carriers

A series of amphiphilic hyperbranched poly (amine-ester)-poly (lactide-co-glycolide) (HPAE-co-PLGA) copolymers were synthesized by ring-opening polymerization of dl-lactide, glycolide and a fourth generation hyperbranched poly (amine-ester) (HPAE-OHs4) with Sn(Oct)2 as catalyst. The chemical structure of copolymers was characterized by Fourier transform infrared (FT-IR), nuclear magnetic resonance (1H-NMR, 13C-NMR), thermo gravimetric analysis apparatus (TGA), and different scanning calorimetry (DSC). Formation and characteristics of polymeric micelles of the amphiphilic copolymer were studied by environmental scanning electron microscopy (ESEM), fluorescence spectroscopy, and dynamic light scattering (DLS). In order to estimate the feasibility as novel drug carriers, a lipophilic model drug amphotericin B was incorporated into polymeric micelles and the drug release behavior was investigated. The micelle size and drug-loading content were found increased, and the drug-release rate decreased with the increase of molar ratio of dl-lactide/glycolide to HPAE.

PREPARATION AND CELL COMPATIBILITY OF FUNCTIONALIZED BIODEGRADABLE POLY(DL-LACTIDE-co-RS-β-MALIC ACID)

In order to create a functionalized biodegradable polymer for vascular tissue engineering application, poly(DL-lactide-co-RS-β-malic acid) (PDLLMAc) was synthesized. PDLLMAc was obtained after hydrogenolysis of poly(DL-lactide-co-RS-β-benzyl malolactonate) (PDLLMA), which was from the ring-opening polymerization of DL-lactide (DLLA) and RS-β-benzyl malolactonate (MA) using stannous octoate as catalyst. The copolymers were characterized by 1H-NMR, FTIR, GPC and DSC. The tensile strength and water uptake of the copolymers were measured. In copolymerization, the proportion of MA in the derived copolymers was lower than that in the feeding dose, a consequence of its lower reactivity. The molecular weight of the copolymers decreased with increasing MA content. The protective benzyl groups were completely removed in hydrogenolysis. The glass transition temperature (Tg) of the protected copolymers decreased with increasing MA content. The mechanical strength test showed that the tensile strength of PDLLMA decreased while elongation increased with MA content increasing, and the tensile strength increased and elongation decreased with increasing malic acid content in PDLLMAc for the formation of hydrogen bonding. The water uptake showed that more hydrophilic malic acid adsorbed more water in PDLLMAc. In order to test the reactivity of functional pendant groups, bioactive RGD peptide was immobilized on the functionalized polymer film surface and smooth muscle cells (SMCs) were cultured on it. The results showed that the functionalized copolymer was biocompatible and could be potentially applied in vascular tissue engineering.

Stereoselective Controlled Polymerization of dl-Lactide with [Ti(trisphenolate)O-i-Pr]2 Initiators

Stereoselective Controlled Polymerization of <scp>dl</scp>-Lactide with [Ti(trisphenolate)O-<i>i</i>-Pr]₂ Initiators

In Vitro Evaluation of 3T3 and MDBK Cells Attachment and Proliferation on Collagen and Fibronectin Immobilized Nonwoven Polylactide Matrices

Fibroblast-like, 3T3 (Mouse Swiss Albino) and epithelial-like MDBK (Madine Darby Bovine Kidney) cells were selected as model cell lines and the adhesion of these cells on nonwoven poly DL-lactide (PDLLA) matrices were investigated. PDLLA was synthesized by ring-opening polymerization of DL-lactide. Nonwoven PDLLA matrices were prepared by an extrusion/winding process. Surface modification of these matrices was achieved by glow-discharge treatment, which was followed by glutaraldehyde incorporation. Biologically modification was performed by immobilization of collagen and/or fibronectin for cell attachment and proliferation. Adhesion values of fibroblast-like and epithelial-like cells after incubation for 2 h was 90 and 85% of initial cells, respectively. The 3T3 cells grown on PDLLA, after 11 days of incubation, was 9 105 cells while the control group was 1.2 106 cells. MDBK cells grown on the same polymeric matrices were determined to be 1.5 106 cells and 1.8 106cells for the control group. These results indicate that biodegradable nonwoven PDLLA matrices can be used for adhesion and proliferation of primary cell cultures and that implants of polymer-cells composites can be used in wound healing. An important advantage of these matrices is that a second surgical operation is not necessary to remove the implant due to the biodegradation of polymer in tissue.

Synthesis and characterization of poly(DL-lactide)-grafted gelatins as bioabsorbable amphiphilic polymers

A series of poly(DL-lactide) grafted gelatins, as new bioabsorbable amphiphilic polymers useful in parenteral drug delivery systems and in tissue engineering, were synthesized by the ring opening polymerization of DL-lactide onto a fractionated gelatin with the molecular weight of 1.02 × 105. Using tin(II) bis(2-ethylhexanoate) as catalyst, the bulk copolymerization at 140°C and solution copolymerization in dimethylsulfoxide (DMSO) at 80°C were firstly performed in the presence of gelatin. The results showed that the solution copolymerization in DMSO could afford the expected copolymers but the bulk copolymerization would result in an insoluble crosslinked product. The number of grafting sites on gelatin chain could be adjusted by the partial trimethylsilylation of side hydroxy, amino and carboxylic groups in gelatin. The solution copolymerization of DLlactide on the partially protected gelatin in DMSO was also successful in providing copolymers with different molecular weights. The synthesized copolymers were characterized on the basis of elemental analysis, IR, 1H-NMR and thermal analysis. The IR and 1H-NMR data of these produced copolymers suggested that polylactide branches could be grafted onto gelatin via the side groups such as hydroxyl and amino groups in the solution copolymerization as well as carboxylic groups in bulk copolymerization. The molecular weights of the copolymers could be calculated from the difference of nitrogen contents between a copolymer and free gelatin. The results indicated that molecular weight of the copolymers and those of polylactide branches were increased with the feeding ratio of DL-lactide to gelatin in the copolymerization. However, because of the steric hindrance of some grafting sites on gelatin and the transesterifications of the propagating polylactide branches on gelatin with possibly formed homo-polymeric polylactide chains, the finally formed polylactide branches on gelatin were not very large and the highest average molecular weight of a polylactide branch was not over 4500 in any solution copolymerizations. The results from the thermal analysis of some copolymers, including thermogravimetry and differential scanning calorimetry, showed that the absorbed water in the samples could be lost at a temperature range below 150°C and melting point decreased with increase of polylactide branches in the poly(DL-lactide)-grafted gelatins.

Polymerization of lactides and lactones. III. Ring-opening polymerization ofDL-lactide by the (?3-C3H5)2Sm(?2-Cl)2(?3-Cl)2Mg(tmed)(?2-Cl)Mg(tmed) complex

Ring-opening polymerization of DL-lactide (LA) has been initiated with the (η 3 -C 3 H 5 ) 2 Sm(μ 2 -Cl) 2 (μ 3 -Cl) 2 Mg(tmed)(η 2 -Cl)Mg(tmed) complex both in bulk and solution. The effects of reaction conditions, such as reaction time, reaction temperature, and monomer/initiator molar ratio on the polymerization has been discussed. The results showed that (η 3 -C 3 H 5 ) 2 Sm(μ 2 -Cl) 2 (μ 3 -Cl) 2 Mg(tmed)(μ 2 -Cl)Mg(tmed) was more effective for the polymerization of LA, and high molecular weight of polylactide was obtained by this initiator. The solvent affected the polymerization significantly. The polymerization mechanism was in agreement with the coordination mechanism. The polymer was characterized by FTIR, 1 H-NMR, and DSC.