Search results for "Lactide"
showing 10 items of 47 documents
Organobase-Catalyzed Synthesis of Multiarm Star Polylactide With Hyperbranched Poly(ethylene glycol) as the Core
2011
Multiarm star copolymers consisting of the polyether-polyol hyperbranched poly(ethylene glycol) (hbPEG) as core and poly(L-lactide) (PLLA) arms are synthesized via the organobase- catalyzed ring-opening polymerization of lactide using hbPEG as a multifunctional macroinitiator. Star copolymers with high molecular weights up to 792 000 g mol−1 are prepared. Detailed 2D NMR analysis provides evidence for the attachment of the PLLA arms to the core and reveals that the adjustment of the monomer/initiator ratio enables control of the arm length. Size exclusion chromatography measurements show narrow molecular weight distributions. Thermal analysis reveals a lower glass transition temperature, me…
Miscibility and properties of linear poly(l-lactide)/branched poly(l-lactide) copolyester blends
2006
Abstract Polymer blends consisting of linear poly( l -lactide) (PLLA) and different proportions of dendritic PLLA-based copolyesters ( hb -PLLA) characterized by different degrees of branching (DB) were obtained in melt. The solid-state properties of poly( l -lactide)s and their blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and stress–strain measurements. DSC and DMA methods proved miscibility of PLLA/ hb -PLLA blends for the studied composition range. AFM indicated that no phase separation occurs in PLLA/ hb -PLLA blends and that PLLA and hb -PLLA cocrystallize in one single lamellae type. The mechanica…
Poly(isoglycerol methacrylate)-b-poly(d or l-lactide) Copolymers: A Novel Hydrophilic Methacrylate as Building Block for Supramolecular Aggregates
2010
On the basis of a new acetal-protected glycerol monomethacrylate monomer (cis-1,3-benzylidene glycerol methacrylate/BGMA) a series of potentially biocompatible and partially biodegradable homo- and block copolymers were synthesized. ATRP polymerization of BGMA yielded well-defined polyacrylates with pendant benzylidene acetal groups and high glass transition temperatures (115−130 °C). This hydrophobic poly(cis-1,3-benzylidene glycerol methacrylate) could be readily transformed into the hydrophilic and water-soluble poly(1,3-dihydroxypropyl methacrylate), referred to as poly(isoglycerol methacrylate) (PIGMA). It exclusively contains primary hydroxyl groups and therefore differs significantly…
Multi-Arm Star Poly(L-lactide) with Hyperbranched Polyglycerol Core
2007
Biocompatible multi-arm star block copolymers based on poly(L-lactide) (PLLA) have been prepared by a core-first approach, using hyperbranched polyglycerol (PG), a polyether polyol, as a polyfunctional initiator. The molecular weight of the hyperbranched initiator-core was varied from 2 200 to 5 200 g mol -1 , molecular weights of the resulting multi-arm stars were in the range of 6 700-107 000 g mol -1 (NMR), depending on the amount of dilactide (LA) added. Various monomer/initiator ratios have been employed in the Sn-catalyzed LA polymerization in order to vary the length of the lactide arms from DP n (arm) = 2 to 20 units. Detailed NMR analysis using conventional and 2D-NMR techniques (e…
A cell-free approach with a supporting biomaterial in the form of dispersed microspheres induces hyaline cartilage formation in a rabbit knee model
2020
The objective of this study was to test a regenerative medicine strategy for the regeneration of articular cartilage. This approach combines microfracture of the subchondral bone with the implant at the site of the cartilage defect of a supporting biomaterial in the form of microspheres aimed at creating an adequate biomechanical environment for the differentiation of the mesenchymal stem cells that migrate from the bone marrow. The possible inflammatory response to these biomaterials was previously studied by means of the culture of RAW264.7 macrophages. The microspheres were implanted in a 3 mm-diameter defect in the trochlea of the femoral condyle of New Zealand rabbits, covering them wi…
Thermal kinetics for the energy valorisation of polylactide/sisal biocomposites
2018
[EN] The thermal stability and decomposition kinetics of PLA/sisal biocomposites was discussed to evaluate the suitability of their use in energy recovery processes such as pyrolysis and combustion. The influence of the addition of sisal up to 30%wt, the presence of coupling agent, and the atmosphere of operation, i.e. inert or oxidative was discussed by means of multi-rate linear non-isothermal thermogravimetric experiments. All biocomposites showed a mean high heating value of 15 MJ/kg indicating their suitability for energy recovery processes. The thermal requirements of PLA/sisal decomposition were assessed in terms of onset decomposition temperature and apparent activation energy. A mi…
Hydrothermal ageing of polylactide/sisal biocomposites. Studies of water absorption behaviour and Physico-Chemical performance
2014
An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a fast…
Toward potent antibiofilm degradable medical devices: A generic method for the antibacterial surface modification of polylactide
2013
International audience; The effects of biomaterials on their environment must be carefully modulated in most biomedical applications. Among other approaches, this modulation can be obtained through the modification of the biomaterial surface. This paper proposes a simple and versatile strategy to produce non-leaching antibacterial polylactide (PLA) surfaces without any degradation of the polyester chains. The method is based on a one-pot procedure that provides a "clickable" PLA surface via anionic activation which is then functionalized with an antibacterial quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPDMAEMA) by covalent immobilization on the surface. The anti-adherence and an…
Hygrothermal ageing of reprocessed polylactide
2012
[EN] The influence of an accelerated hygrothermal ageing simulation test on a commercial PLA and its three subsequent mechanically-reprocessed materials was studied. The analysis was focused on the water diffusion kinetics and the physico-chemical changes induced by the hygrothermal degradation. Water diffusion proceeded faster than chain relaxation processes, as defined by a Case II absorption model. It was proved that the water diffusion rate decreased with subsequent reprocessing cycles and increased with higher hygrothermal ageing temperatures. Hydrolytic chain scission provoked significant molar mass decays and consequent general losses of thermal and mechanical performance. The rearra…
Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechani…
2012
[EN] This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PLA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PLA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystalli…