Controlled synthesis of amphiphilic biodegradable polylactide-grafted dextran copolymers (original) (raw)
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Biodegradable nanoparticles made from polylactide-grafted dextran copolymers
Journal of Colloid and Interface Science, 2009
Polysaccharide-covered polyester nanoparticles were prepared using the emulsion/solvent evaporation process. The core of the nanoparticles was made either of PLA or of a blend of polylactide and polylactide-grafted dextran copolymer in various proportions. The surface of the nanoparticles was covered by dextran chains via the use of water-soluble polylactide-grafted dextrans as polymeric stabilizers during the emulsification step. The characteristics of the nanoparticles (size, surface coverage, thickness of superficial layer, colloidal stability) were correlated to the structural parameters (length and number of polylactide grafts) of the copolymers as well as to their surface active properties. The complete biodegradability of the nanoparticles was evaluated by considering the rate of hydrolysis of polylactide grafts in phosphate buffer and the rate of enzymatic degradation of dextran backbone by dextranase.
Polysaccharides Grafted with Polyesters: Novel Amphiphilic Copolymers for Biomedical Applications
Macromolecules, 2002
New amphiphilic polysaccharides with controlled structure were synthesized by coupling between a carboxylic function present on preformed polyester chains and a hydroxyl group naturally present on polysaccharides. First, the synthesis of poly( -caprolactone) monocarboxylic acid (R-PCL-CO 2H) was carried out by ring-opening uncatalyzed polymerization of monomer in the presence of a carboxylic acid (R-CO2H). R-PCL-CO2H was then reacted with carbonyl diimidazole, and the resulting activated intermediate (imidazolide) was further reacted with dextran (Dex) at different molar ratios to obtain amphiphilic copolymers with various hydrophilic-lipophilic balance. The coupling reaction was followed by GPC, indicating a total conversion. The copolymers were further characterized by GPC, 1 H NMR, and FTIR. Nanoparticles of less than 200 nm, with potential interest for controlled release of bioactive compounds, were successfully prepared by using these new materials.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2019
Bio-degradable/bio-compatible poly(lactide-co-glycidyl methacrylate), P(LA-co-GMA), a copolymer has been synthesized. The material contains curable C_C groups, which enable its self-curing and grafting reactions with other vinyl monomers. The copolymer was grafted with a pH-responsive polyacrylamide (PAAm), by UVassisted reactions using acrylamide (AAm) and N,N′-methylene bisacrylamide monomers, and various photoinitiator systems. The original copolymer and its partially-cured counterpart were employed in the grafting reaction. Chemical structures and properties of the resulting materials were characterized. Standard quantitative analysis techniques for measurement of the grafted AAm content and the degree of C_C conversion have been developed by 1 H NMR and FTIR spectroscopy. FTIR offers more advantages, in terms of non-destructive analysis, ease of operation, and lower cost of analysis. The results show that the grafted products from pre-cured P(LA-co-GMA) copolymers contain higher grafted AAm contents than their uncured counterparts. The highest grafted AAm content was obtained by using benzophenone (BP) as an initiator, while camphorquinone (CQ) led to the lowest content. In contrast, the degree of C_C conversion of the copolymer from the two initiator systems shows a reverse trend. These amphiphilic and pH-responsive grafted copolymers with tunable AAm contents have a high potential for use in various applications, especially in biomedical and environmental fields.
Carbohydrate Polymers, 2006
Graft copolymerization of L-lactide (LLA) onto chitosan (CS) was carried out by ring opening polymerisation using Ti(OBu) 4 as catalyst in DMSO at 90 8C in nitrogen atmosphere to obtain chitosan/oligo L-lactide graft copolymers (CL). The ring opening polymerisation of L-lactide using a covalent initiator would significantly reduce the risk of racemization even at high temperatures in comparison to other polymerization methods. It is also expected to provide copolymers having better physico-chemical properties and biodegradability than the homopolymers for applications in biomedical and pharmaceutical fields. Grafting studies indicated that the lactide content in the feed molar ratio influenced the grafting percentage and the amount of lactide in the graft copolymer. The graft copolymers were characterized by FTIR, 1 H NMR, WAXD and thermal methods. Unlike chitosan, all CL graft copolymers were converted to hydrogels in aqueous environment. As expected, the swelling ratio was found to be decreasing on increasing the amount of hydrophobic side chains in the graft copolymers. Similarly, the LLA content of the graft copolymers was found to influence their biodegradation carried out in vitro by hydrolytic and enzymatic means. DSC analysis and SEM micrographs of the hydrolytically degraded samples showed variations in degradation depending on the amount of LLA content. Enzymatic degradation was studied by exposing the samples to two types of enzymes such as papain from Carica Papaya and lipase from Candida Cylindracea. Examinations by SEM, weight loss studies, FTIR and DSC analysis showed that the biodegradation of the graft copolymers could be controlled by the LLA content. In conclusion, the grafting of LLA onto CS results in CL graft copolymers having increased hydrophilicity and controlled degradation rate that may have wide applications in wound dressing and in controlled drug delivery systems. q
Aliphatic polyester-based biodegradable materials: new amphiphilic graft copolymers
Polymer Degradation and Stability, 2001
Biodegradable brush-like amphiphilic graft copolymers were synthesized by covalently grafting poly(e-caprolactone) PCL sequences onto a natural and mainly linear a(1-6) exopolysaccharide backbone, i.e. dextran. A three-step procedure is proposed to control the synthesis which consists in the reversible protection of the hydroxyl groups of the polysaccharide backbone by silylation, followed by the ring-opening polymerization of e-caprolactone initiated by the remaining free hydroxyl groups of the partially silylated dextran after adequate activation into Al alkoxide active species. The third and final step involves the deprotection of the polysaccharide hydroxyl groups under very mild conditions. The high efficiency of grafting and the control over the graft molecular weight and molecular weight distribution rely upon the well-known ''living'' character of the coordination-insertion mechanism of the ring-opening polymerization that is initiated by aluminum alkoxides. Poly(e-caprolactone)-grafted dextran copolymers with precise composition and well controlled number and length of PCL grafts were incorporated into PCL/granular corn starch composites by melt kneading at 130 C. When located at the filler/matrix interface, the copolymers proved to be very efficient compatibilizers, enhancing the interfacial adhesion, and accordingly the mechanical properties of the composite materials as evidenced by tensile testing. To ensure the migration of the amphiphilic graft copolymer at the starch/PCL interface, it is better to first precipitate it onto the filler surface or to blend it with the starch granules before melt blending with the polyester matrix.
Grafting of Oligosaccharides onto Synthetic Polymer Colloids
Biomacromolecules, 2007
A new method to form colloidally stable oligosaccharide-grafted synthetic polymer particles has been developed. The oligosaccharides, of weight-average degree of polymerization ∼38, were obtained by enzymatic debranching of amylopectin. Through the use of a cerium(IV)-based redox initiation process, oligosaccharide chains are grafted onto a synthetic polymer colloid comprising electrostatically stabilized poly(methyl methacrylate) or polystyrene latex particles swollen with methyl methacrylate monomer. Ce(IV) creates a radical species on these oligosaccharides, which then propagates, initially with aqueous-phase monomer, then with the methyl methacrylate monomer inside the particles. Ultracentrifugation, NMR, and total starch analyses together prove that the grafting process has occurred, with at least 7.7 wt % starch grafted and a grafting efficiency of 33%. The surfactant used in latex preparation was removed by dialysis, resulting in particles colloidally stabilized with only linear starch as a steric stabilizer. The debranched starch that comprises these oligosaccharides is found to be a remarkably effective colloidal stabilizer, albeit at low electrolyte concentration, stabilizing particles with very sparse surface coverage.
A new functional dilactone, 3-(2-propynyl)-1,4-dioxane-2,5-dione (4), was synthesized from ethyl glyoxalate and propargyl bromide via a 4-step reaction sequence. Ring-opening (co)polymerisation of the alkyne-functionalised monomer 4 with L-lactide was carried out in dichloromethane at 30 C using N,N-dimethylaminopyridine as a catalyst and benzyl alcohol as an initiator. The resulting alkyne-functionalised copolyesters were characterized by 1 H NMR, size exclusion chromatography (SEC) and MALDI-TOF spectroscopy. Azide end-functionalised PEG was then grafted onto the polyester backbone with multiple pendant alkyne moieties using copper-catalysed azide–alkyne cycloaddition (click chemistry). The graft copolymers were characterized by 1 H NMR, SEC and DOSY NMR. The aggregation behavior of the copolymers in water was investigated by fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). The critical aggregation concentration was in the range of 10–50 mg L À1. The nano-sized objects were rod-like in shape with a diameter of 100 nm and a length of around 400 nm.
Polymers
In this work, a novel poly (methylenelactide-g-L-lactide), P(MLA-g-LLA) graft copolymer was synthesized from poly(methylenelactide) (PMLA) and L-lactide (LLA) using 0.03 mol% liquid tin(II) n-butoxide (Sn(OnBu)2) as an initiator by a combination of vinyl addition and ring-opening polymerization (ROP) at 120 °C for 72 h. Proton and carbon-13 nuclear magnetic resonance spectroscopy (1H- and 13C-NMR) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the grafted structure of P(MLA-g-LLA). The P(MLA-g-LLA) melting temperatures (Tm) range of 144–164 °C, which was lower than that of PLA (170–180 °C), while the thermal decomposition temperature (Td) of around 314–335 °C was higher than that of PLA (approx. 300 °C). These results indicated that the grafting reaction could widen the melt processing range of PLA and in doing so increase PLA’s thermal stability during melt processing. The graft copolymers were obtained with weight-average molecular weights (M¯w) = 4200–11,000 g mol−...
2014
Ce travail avait pour but de synthétiser et caractériser des copolymères amphiphiles à base de poly(éthylène glycol) (PEG) et de poly(acide lactique) (PLA) pour la confection de systèmes de délivrance de principes actifs (PA). Les polymères ont été choisis pour leur biocompatibilité et de leur biorésorbabilité. Plusieurs architectures de copolymères amphiphiles ont été créées et leur comportement auto-associatif en milieu aqueux ainsi que leur capacité à encapsuler des principes actifs ont été étudiés. Tout d'abord, un copolymère greffé a été synthétisé par copolymérisation d'un monomère fonctionnel, le glycolide monopropargylé, avec du L-lactide pour obtenir un squelette polyester fonctionnel sur lequel des branches hydrophiles de PEG ont été greffés avec plusieurs degrés de substitution. Ensuite, un copolymère peigne tribloc a été synthétisé à partir d'un bloc central PLA dont les extrémités de chaînes ont été modifiées pour permettre l'amorçage de la polymérisatio...
Journal of Polymer Science Part A: Polymer Chemistry, 2010
Amphiphilic A 3 B mikto-arm copolymers have been synthesized using a t-butyl-diphenyl silyl-based methylglucoside derivative. The latter has been first used as initiator for the polymerization of e-caprolactone leading to three-arm starshaped structures followed by several postpolymerization steps to obtain star-shaped poly(e-caprolactone) macroinitiator. Atom transfer radical polymerization (ATRP) of diisopropylidene galactose methacrylate in THF at 60 C using CuBr ligated with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalytic complex allowed the formation of A 3 B mikto-arm copolymers with different compositions and molecular weights. Selective deprotection of sugar protecting groups finally generated amphiphilic mikto-arm copolymers. The molecular characterization of those copolymers was performed by 1 H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self-assembly of the copolymers into micellar aggregates and the related critical micellization concentration (CMC) in aqueous media were determined by dynamic light scattering (DLS) and UV-visible spectroscopy, respectively. V