PLLA Content Research Articles

Green Polymer Electrolytes Prepared by a Cost-Effective Approach.

The preparation of solid polymer electrolytes (SPEs) using poly(ethylene oxide) (PEO) typically involves incorporating fillers or undergoing chemical modifications to reduce crystallinity and enhance conductivity. PEO with a lower molecular weight, known as polyethylene glycol (PEG), exhibits higher conductivity, despite weaker mechanical strength. It is commonly employed as a plasticizer to improve the conductivity of SPEs or to fabricate PEG-based gel polymer electrolytes (GPEs). In this study, we use a straightforward approach to create innovative SPEs by blending liquid polymer electrolytes (LPEs), particularly low-molecular-weight polyethylene glycol (PEG), with a molecular weight of 400 g/mol, and sustainable poly(l-lactide) (PLLA). Solid PEG/PLLA forms are achieved by introducing 30 wt % of PLLA. Subsequently, the addition of lithium salts results in the development of novel PEG/PLLA SPEs. Another focal point of this study involves incorporating 1,3:2,4-dibenzylidene sorbitol (DBS) into these PEG/PLLA systems. DBS, an organic gelator derived from natural sugars, demonstrates self-assembly, leading to the formation of a nanofibrillar network structure. Leveraging DBS's ability to form organogels in liquid organic environments, we facilitate the transformation of low PLLA content LPEs into innovative solvent-free GPEs. Our prepared PEG/PLLA SPEs exhibited a maximum conductivity value of 4.39 × 10-5 S/cm, approximately five times higher than that of neat PEG (10000 g/mol) SPEs. The ionic conductivity exhibited a declining trend as the content of PLLA and DBS increased. However, there was an improvement in electrochemical stability. Furthermore, the incorporation of PLLA and DBS into electrolytes contributed to enhanced mechanical support and stability within the electrolyte layer. This, in turn, mitigated capacity decay and improved the cycling performance of assembled lithium-ion cells.

Topological structure-induced self-assembly of highly asymmetric PLLA-b-QPDMAEMA block copolymers in solution: Linear versus bottlebrush

During self-assembly process of block copolymers in solution, when the volume fraction of solvophobic blocks is too low, usually below 10%, the copolymers generally tend to dissolve, which has caused trouble. Herein, a bottlebrush block copolymer composed of poly(L-lactic acid) (PLLA) and quaternized poly(N,N-dimethylaminoethylmethacrylate) (QPDMAEMA), whose content of solvophobic block PLLA was below 2 wt%, was prepared. Owing to the rigidity derived from the advantages of topological structure of bottlebrush-like molecules, the interfacial curvature between two incompatible microphases is maintained, and this highly asymmetric copolymer unexpectedly spontaneously assembles into uniform spherical micelles with diameters of tens of nanometers. The morphology of aggregates was verified by dynamic light scattering, transmission electron microscopy and atomic force microscope. This study expands the understanding of traditional theory about copolymers self-assembly in solution, which helps to design, prepare, and apply polymer micelles with various structures from a broader perspective.

A novel degradable PCL/PLLA strapping band for internal fixation of fracture

Early fracture fixation is the critical factor in fracture healing. Common internal fracture implants are made of metallic materials, which often affects the imaging quality of CT and MRI. Most patients will choose secondary surgery to remove the internal fixation implants, which causes secondary damage to them. The development of new degradable internal fracture implants has attracted more and more attention from orthopedic surgeons and researchers. Based on these problems, we improved the various properties of medical grade polycaprolactone (PCL) by adding poly(L-lactide) (PLLA). We produced PCL/PLLA strapping bands with different mass ratios by injection molding. We compared the mechanical properties, degradation properties, cell biocompatibility, bone marrow mesenchymal stem cells (BMSCs) adhesion, proliferation, osteogenic differentiation and fracture fixation effect of these strapping bands. The results showed that the tensile strength and yield force of the strapping bands increased with the increase of the content of PLLA. The addition of PLLA could significantly improve the mechanical strength in the early stage and accelerate the degradation rate of the strapping band. PCL/PLLA (80/20) strapping band had no significant cytotoxicity toward rBMSCs and could promote osteogenic differentiation of rBMSCs. The strapping band could ensure femoral fracture healing of beagles in 3 months and didn’t cause damage to the surrounding tissues and main organs. This study will provide some new insights into the biodegradable products of PCL/PLLA blends for internal fixation of fracture.Graphical We produced novel degradable PCL/PLLA strapping bands with different mass ratios by injection molding. We tested the biological safety of the prepared internal fixation strapping bands for fracture, such as cell experiment in vitro and animal experiment, and studied the degradation behavior in vitro. The strapping bands could ensure femoral fracture healing of beagles. This study will provide some new insights into the biodegradable products of PCL/PLLA blends for internal fixation of fracture. A Immunofluorescence staining of rBMSCs (live cells: green; dead cells: red). B Young’s modulus change curve during strapping bands degradation. C The implantation process of strapping bands. D Micro-CT images of the beagle’s fracture recovery after the operation.

Electrospun Poly(L-Lactic Acid)/Gelatin Hybrid Polymer as a Barrier to Periodontal Tissue Regeneration.

Poly(L-lactic acid) (PLLA) and PLLA/gelatin polymers were prepared via electrospinning to evaluate the effect of PLLA and gelatin content on the mechanical properties, water uptake capacity (WUC), water contact angle (WCA), degradation rate, cytotoxicity and cell proliferation of membranes. As the PLLA concentration increased from 1 wt% to 3 wt%, the tensile strength increased from 5.8 MPa to 9.1 MPa but decreased to 7.0 MPa with 4 wt% PLLA doping. The WUC decreased rapidly from 594% to 236% as the PLLA content increased from 1 to 4 wt% due to the increased hydrophobicity of PLLA. As the gelatin content was increased to 3 wt% PLLA, the strength, WUC and WCA of the PLLA/gelatin membrane changed from 9.1 ± 0.9 MPa to 13.3 ± 2.3 MPa, from 329% to 1248% and from 127 ± 1.2° to 0°, respectively, with increasing gelatin content from 0 to 40 wt%. However, the failure strain decreased from 3.0 to 0.5. The biodegradability of the PLLA/gelatin blend increased from 3 to 38% as the gelatin content increased to 40 wt%. The viability of L-929 and MG-63 cells in the PLLA/gelatin blend was over 95%, and the excellent cell proliferation and mechanical properties suggested that the tunable PLLA/gelatin barrier membrane was well suited for absorbable periodontal tissue regeneration.

Facile preparation of highly crystalline poly(L‐lactide) films with inversed wettability and their potential application in oil–water separation

AbstractHighly crystallized poly(L‐lactide) (PLLA) films with enhanced hydrophobicity are easily prepared by casting PLLA solution into a poor solvent like isopropyl alcohol (IPA). The crystallinity of the PLLA film can be controlled by PLLA's concentration, the kind of poor solvent, and the volume ratio of poor solvent dichloromethane (DCM). Results show the addition of poor solvents obviously accelerate the crystallization of PLLA film and enhance the crystallinity up to 48.7%. A lower volume ratio of IPA/DCM at higher PLLA concentration as well as a higher volume ratio of IPA/DCM at lower PLLA concentration is conducive to raising the crystallinity of the PLLA film. In the meanwhile, microscopy observation and wettability tests confirm the PLLA films present multidimensional microstructure including fibrils, lamellas, and flower‐like stacks or spherulite‐like superstructure, and display high porosity as well as enhanced hydrophobicity. Despite the volume ratio of IPA/DCM, the PLLA films prepared at lower concentrations display higher crystallinity, porosity as well as hydrophobicity than those prepared at higher concentrations. The highly crystalline PLLA films with enhanced porosity and hydrophobicity are supposed to be applied in oil–water separation, and so forth.

Processing Polymer Blends of Mater-Bi® and Poly-L-(Lactic Acid) for Blown Film Application with Enhanced Mechanical Strength.

Mater-Bi® is one of the most commercialized starch-based blends used in biodegradable flexible packaging. However, the high ductility and low stiffness of Mater-Bi® might limit its application and developing a solution to tailor the stiffness and mechanical strength is highly desirable. In the present work, blends based on Mater-Bi® and poly-L-(lactic acid) (PLLA) at a different ratio from 70/30 to 50/50 wt% were prepared via melt-extrusion and the effect of the PLLA content and Joncryl ADR® as a reactive compatibilizing agent, on the mechanical properties, melts rheology, morphology and disintegration aptitude were investigated. The inclusion of PLLA in Mater-Bi® has a marked beneficial effect on the tensile strength and stiffness of the blend while maintaining acceptable ductility. The addition of the reactive compatibilizing agent contributed to improving the strength and elongation at the break of the blend. The melt rheology of the blend was also affected by the ratio of the two components, mostly when the Joncryl ADR® was present. The disintegration by biodegradation of the blend was preserved in the presence of PLLA, and it takes less than 30 days for the films to completely decompose and disintegrate under controlled composting conditions. Interestingly, a thin film from Mater-Bi®/PLLA 60/40 was successfully prepared by blown film extrusion, demonstrating a good balance between stretchability (elongation at break exceeding 100%) and stiffness (1.8 GPa). This work opened to broadening the use of starch-based biodegradable plastic toward more demanding applications such as mulching films.

Morphology and mechanical property of quenched poly(L-lactide)/N,N-dimethylacetamide gels

Mechanically tough poly(L-lactide) (PLLA)/N,N-dimethylacetamide (DMAc) gels by rapid quenching using liquid nitrogen (LN) were synthesized. PLLA/DMAc solution at 110 °C was cooled at room temperature (PLLA-RT), or quenched by LN before keeping at RT (PLLA-LN). PLLA-RT with the PLLA concentrations of 5, 8, and 11 wt% did not form gel, while PLLA-RT with 14 and 17 wt% could form brittle gel exhibiting coarse structures. In contrast, PLLA-LN could form stable gel regardless of the PLLA concentration. The storage modulus of the gel with the PLLA concentration of 17 wt% increased from 78.7 kPa (PLLA-RT) to 563.7 kPa (PLLA-LN) at the strain of 0.1%. From the structural analysis, PLLA-RT formed spherulites (100–200 μm in diameter), whereas PLLA-LN formed relatively uniform network structures with continuous microporous skeletons without spherulites. The structural changes significantly contributed to the formation of stable, re-moldable, biodegradable, and biocompatible physical gels with ecofriendly and enhanced mechanical properties.

Flow-induced crystallization of polylactides

In this work, the flow-induced crystallization of two polylactides (PLAs) with different microstructures (different l-lactic acid contents) is studied using simple shear, uniaxial extension and capillary flow experiments. In a simple shear and capillary flow, an increase in shear rate and a decrease in temperature were found to enhance the crystallization kinetics particularly for Weissenberg numbers (based on the reptation relaxation time, Wi) greater than 1 (strong flow causing chain stretching). On the other hand, in a uniaxial extensional flow, once a critical Hencky strain is achieved, crystallization starts independently of strain rate and temperature. The amount of mechanical work per unit volume imposed/dissipated onto the polymers during flow to initialize crystallization was also calculated in the simple shear, capillary, and extensional flow. The critical mechanical work for the onset of flow-induced crystallization was found to be independent of temperature and degree of molecular chain stretch (Wi) as Wi becomes greater than 1. The critical mechanical work for the onset of flow-induced crystallization in an extensional flow was found to be much smaller than that in a shear flow. The PLA sample with higher content of PLLA showed slightly higher zero-shear viscosity and a smaller thermodynamic barrier for the onset of crystallization. Finally, the degree of crystallinity increases linearly from 0% at the start of the flow-induced crystallization region and reaches a plateau at Wi equals to around 1.

Crystallization-Induced Polymer Scaffold Formation in the Polymer/Drug Delivery System Poly(l-lactic acid)/Ethyl Butylacetylaminopropionate (PLLA/IR3535)

Polymer/mosquito-repellent scaffolds exhibit increasing importance in long-lasting human skin protection to be used as wearable devices and allowing for controlled release of repellents. In this study, ethyl butylacetylaminopropionate (IR3535) was used as a human and environmental friendly active mosquito-repellent serving as a solvent to form functional poly(l-lactic acid) (PLLA) scaffolds by crystallization-based solid-liquid thermally induced phase separation. Crystallization of PLLA in the presence of IR3535 is faster than melt-crystallization of neat PLLA, and in the investigated concentration range from 5 to 50 mass % PLLA, its maximum crystallization rate increases with the PLLA content, by both, increases of the maximum crystal growth rate and of the nuclei density. By adjusting the polymer concentration and the crystallization temperature, microporous scaffolds of different fine structures are obtained, hosting the mosquito-repellent in intra- and interspherulitic pores for its intended later evaporation.

One-Pot Synthesis of Supertough, Sustainable Polyester Thermoplastic Elastomers Using Block-Like, Gradient Copolymer as Soft Midblock

It remains challenging to synthesize supertough thermoplastic elastomers (TPEs) since the stretchability and tensile strength are mutually exclusive. Here, we report a one-pot strategy for the prep...

Superhydrophobic Poly(l-lactic acid) Membranes with Fish-Scale Hierarchical Microstructures and Their Potential Application in Oil–Water Separation

In this work, superhydrophobic poly(l-lactic acid) (PLLA) hierarchical membranes exhibiting excellent oil-removal performance, which is of great importance in curbing the oil-pollution environment, were fabricated by a simple solvent-evaporation-induced precipitation method. PLLA membranes with hierarchical micro/nanostructures (fish scales, fibrous sheets, and petal-like morphology) can be conveniently prepared by adjusting the preparation parameters including PLLA concentration, precipitation temperature, type of solvent and nonsolvent, and the addition of nano-SiO2. The results show that the water contact angle of the fish-scale-structured PLLA membrane was 138.6°, revealing that water repellency was significantly improved compared to that of the solvent-casting PLLA membrane (∼72.8°). Moreover, the PLLA/SiO2 nanocomposite membrane with a dense hierarchical micro/nanostructure had a water contact angle greater than 167.1°, which has great potential in oil-water separation.

Controllable surficial and internal hierarchical structures of porous poly (L-lactic acid) membranes for hydrophobicity and potential application in oil-water separation

Focused on the design and construction of controllable surface microtopographyand interconnected pore morphologyof porous poly (L-lactic acid) membrane. Asimple solvent evaporation-induced precipitation methodis proposed to regulate microstructures by one-step method without any additive. Controllable microstructures (fibrous networks, interconnected pores, and crystallized PLLA protrusions) and interconnected pore morphology were facilely achieved by adjusting the PLLA concentration and/or precipitation temperature. In view of the shortcomings of previous foam preparation, the contact area between solvent and non-solvent was broadenedto realize the improvement of porosity and the construction of surface micro-nano structure. The results show that the crystallinity of prepared PLLA membranes is kept in a high range between 61.8% and 75.8% and the maximum watercontact angle (WCA) is largely increased to 142.3°. Surprisingly, surface wettability of PLLA membranes possess the wonderful mechanical damage resistance, and the porosity and oil-absorption capacity are increased to 90.8% and 24.1 g/grespectively. Predictably, the porous PLLA membrane has great application potential as a biodegradable oil-water separation material.

Mechanical and cellular characterization of electrospun poly(l-lactic acid)/gelatin yarns with potential as angiogenesis scaffolds

Electrospun PLLA/gelatin yarns with different compositions were fabricated as tissue engineering scaffolds. The yarns were characterized by scanning electron microscopy (SEM) and tensile mechanical testing. Cell interaction with yarns was investigated by measurements of cell viability, proliferation, morphology, phenotype, and angiogenic activity (measurement of nitric oxide) using human umbilical vein endothelial cells (HUVECs). The SEM images of yarns showed a uniform structure with axial alignment of the fibers in the yarn surface. The mechanical properties of the yarns changed with the amount of PLLA, indicating the yarn of 40% PLLA and 60% gelatin had the highest stress-at-break (2.47 MPa). Also, there was an increase in the toughness with increasing in the amount of PLLA content in the PLLA/gelatin composition. After 7 days, HUVECs exhibited the best viability and proliferation responses on a yarn of 70% PLLA and 30% gelatin, having 223.56% increase in viability and 306.17% increase in proliferation compared with those of HUVECs alone without any yarns (the control group). Measurement of nitric oxide after 5 days suggested potential applications of yarns in angiogenesis, such as cardiovascular disease and wound healing, with a yarn of 70% PLLA and 30% gelatin having the highest ratio of released nitric oxide (156.20% of the control group). Having a uniaxial structure, the PLLA/gelatin yarns introduced in this study can provide more effective implantation in tissue engineering applications facing geometric and accessibility constraints, such as fibrous tissue regeneration.

Confined crystallization of Poly(ethylene glycol) in spherulites of Poly(L-lactic acid) in a PLLA/PEG blend

The intriguing crystallization behavior of poly(ethylene glycol) (PEG) in a blend specimen of PEG with poly(L-lactic acid) (PLLA) was studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The PLLA/PEG (50/50) blend specimen was heated up to 180.0 °C and kept at this temperature for 5 min to obtain a complete melt without liquid-liquid phase separation. Then, a two-step temperature-jump was conducted as 180.0 °C→ 127.0 °C→ 45.0 °C. For this particular condition, it was found that PEG can crystallize only in the preformed spherulites of PLLA, as no crystallization of PEG was found in the matrix of the mixed PLLA/PEG amorphous phase. This is because of the depression of the freezing temperature (Tf) of PEG in the complete mixture of the PLLA/PEG (50/50) blend specimen by noting that Tf for the neat PEG specimen is 52.0 °C. Upon the PLLA crystallization at 127.0 °C, the PEG content in the amorphous region inside the PLLA spherulite was increased because of the formation of the pure solid phase of PLLA (crystalline phase). Namely, the PLLA content was decreased in the amorphous phase of the PLLA/PEG mixture. Then, Tf of PEG increased so that PEG could crystallize but this crystallization was only allowed inside the PLLA spherulite. Thus, the confined crystallization of PEG can be accounted for. It was further found that the ultimate degree of crystallinity (ϕ∞) of PEG was increased and the induction period of the confined crystallization of PEG was decreased with an increase in the PLLA crystallization time at 127.0 °C. This is simply because the PEG content in the amorphous phase was increased due to the increase in the PLLA amount crystallized, which was more clearly recognized as a function of the size of the preformed PLLA spherulite. The direct evidence of the PEG crystallization was obtained by the wide-angle X-ray scattering. The kinetics was also studied for the confined crystallization of PEG. Based on the results of the kinetic study, the effect of the space confinement will be discussed.

PLLA Honeycomb-Like Pattern on Fluorinated Ethylene Propylene as a Substrate for Fibroblast Growth.

In this study, we present the surface patterning of a biopolymer poly(l-lactide) (PLLA) for fibroblast growth enhancement. The patterning is based on a self-organized pore arrangement directly fabricated from a ternary system of a solvent-nonsolvent biopolymer. We successfully created a porous honeycomb-like pattern (HCP) on a thermally resistant polymer—fluorinated ethylene propylene (FEP). An important preparation step for HCP is activation of the substrate in Ar plasma discharge. The polymer activation leads to changes in the surface chemistry, which corresponds to an increase in the substrate surface wettability. The aim of this study was to evaluate the influence of the PLLA concentration in solution on the surface morphology, roughness, wettability, and chemistry, and subsequently, also on fibroblast proliferation. We confirmed that the amount of PLLA in solution significantly affects the material surface properties. The pore size of the prepared layers, the surface wettability, and the surface oxygen content increased with an increasing amount of biopolymer in the coating solution. The optimal amount was 1 g of PLLA, which resulted in the highest number of cells after 6 days from seeding; however, all three biopolymer concentrations exhibited significantly better results compared to pristine FEP. The cytocompatibility tests showed that the HCP promoted the attachment of cell filopodia to the underlying substrate and, thus, significantly improved the cell–material interactions. We prepared a honeycomb biodegradable support for enhanced cell growth, so the surface properties of perfluoroethylenepropylene were significantly enhanced.

Influence of process parameters on the characteristics of oxygen‐releasing poly (lactic acid) microparticles: A multioptimization strategy

Oxygen‐generating biomaterials have led to promising results in biomedical applications. Yet, the characteristics of these biomaterials need to meet the requirements of a specific application in order to be successful. In this study, hydrogen peroxide (H2O2) was used as the oxygen‐generating substance, and poly (l‐lactic acid) (PLLA) microparticles loaded with polyvinylpyrrolidone/hydrogen peroxide (PVP/H2O2) mixture were prepared using water‐in‐oil‐in‐water double emulsion technique. The experiments were carried out based on full factorial design where the impacts of PLLA concentration, H2O2:PVP molar ratio, and H2O2:organic phase volume ratio on microparticles' properties, including size, encapsulation efficiency, loading content, and percentage of initial burst release were assessed. Individual and multioptimization of responses were performed on the experimental data gained in the current study to investigate the effect of process parameters on the responses and fit the suitable model corresponding to the main and interactive effects. Recording both the H2O2 and O2 release of microparticles revealed that these profiles are also influenced by process variables, PLLA concentration in particular. These results enable accurate selection of optimal process variables for the fabrication of oxygen‐releasing PLLA microparticles with desirable characteristics for a wide variety of applications.

Formation of oriented fishbone-like pores in biodegradable polymer scaffolds using directional phase-separation processing

The scaffold is a dreamed biomaterial of tissue engineers which can culture cells three-dimensionally outgrowing the two-dimensional cell culture in a petri dish to repair or regenerate tissues and organs. To maximize the performance of this dreamed material, complex three-dimensional (3D) structures should be generated with a simple technique and nontoxic ingredients. Many tissues have tubular or fibrous bundle architectures such as nerve, muscle, tendon, ligament, blood vessel, bone and teeth. The concept of mimicking the extracellualr matrix in real tissue has recently been applied to scaffold development. In this study, a novel method for preparing the poly(l-lactic acid) (PLLA) scaffold with a tubular architecture is presented. Solid–liquid phase-separation was applied to form tubular pores in the scaffold using the directional freezing apparatus. Pores formed in this manner exhibited a fishbone like morphology due to the two crystalline phases of 1,4-dioxane. A tubular diameter of ca. 60–250 μm was achieved by regulating the PLLA concentration and the cooling rate. The compressive modulus of the fishbone-like porous scaffold showed higher values than that of non-directional porous scaffold.

Determining the optimal molecular architecture for reactive splicing compatibilization: Toward a better understanding of reactive polymer processing

Reactive polymer processing is an effective and environmentally-friendly means of preparing new materials based on combining components with various properties. Numerous investigations have been carried out to explore the reaction processes that occur during the melt blending of polymers. However, reactive processing is far from fully understood because it involves a complicated combination of shear and extensional flows as well as high temperatures and pressures. In this work, a two-step compatibilizing strategy (called reactive splicing compatibilization) has been used to compatibilize immiscible Poly(lactic acid) (PLLA)/Poly(butylene adipate-co-terephthalate) (PBAT) blends with two different PBAT molecular weights (termed H-PBAT and L-PBAT, respectively), using styrene-co-glycidyl methacrylate (SG) as the grafting counterpart. Reactive compatibilizers with various architectures were prepared by pre-grafting either PLLA or PBAT (or both) onto the SG main chains. The remaining unreacted epoxide groups of the pregrafted SG underwent in situ reactions to form double grafted copolymers as compatibilizers for the final blends. The reactivity of SG with these polymers was found to decrease in the order of L-PBAT > PLLA > H-PBAT. Reactive compatibilizers having various architectures were applied to PLLA/PBAT blends with compositions ranging from 90/10 to 10/90 (w/w). The most efficient pre-grafted reactive compatibilizer was determined for the blends with certain composition. A higher proportion of H-PBAT had to be pre-grafted onto the SG to achieve the best compatibilization efficiency when increasing the PLLA content in PLLA/H-PBAT blends. In the case of PLLA/L-PBAT blends, PLLA chains had to be pre-grafted onto the SG for the best compatibilization when L-PBAT was the primary component of the blend. These results provide a better understanding of the reactive processing mechanism. Evidently, the dynamic shear applied during melt processing continuously renews the interface between the different phases to provide sites for reactions between the blend components. These reactions are affected by both the reactivity of the components and the contact time, which in turn is determined by the blend composition. The compatibilizers located at the blend interface were found to have very similar symmetrical binary grafted structures for blends with different compositions.

Structure-properties relationships of novel cyclic olefinic copolymer/poly(L-lactic acid) polymer blends

The structure-properties relationships of novel cyclic olefinic copolymer (COC)/poly(L-lactic acid) (PLLA) polymer blends are investigated by varying the PLLA content from 5–20 wt % in COC matrix, forming an immiscible blends at all concentrations. Despite immiscibility, COC favors the formation of α- crystal form of PLLA in the blends, contrary to the α’- crystal form in neat PLLA due to non-covalent interactions of the chain moieties as evident from x-ray diffraction, Fourier transform infrared spectrometer and differential scanning calorimetry. The COC/PLLA blends revealed tunable superior mechanical and barrier properties as compared to the neat counterparts. The tensile modulus, strength and toughness of COC/PLLA blends at 15 wt% are significantly enhanced ∼ 89 %, 103 % and one order of magnitude, respectively. Such reinforcement and super toughening mechanisms are pertaining to the effective dissipation of loads across the interfaces, enabling them to delay the crack growth by avoiding stress concentration sites. Likewise, the water vapor permeation (WVP) of the blends is reduced ∼ 4 times than neat COC.

Biodegradable Chitosan-graft-Poly(l-lactide) Copolymers For Bone Tissue Engineering.

The design and synthesis of new biomaterials with adjustable physicochemical and biological properties for tissue engineering applications have attracted great interest. In this work, chitosan-graft-poly(l-lactide) (CS-g-PLLA) copolymers were prepared by chemically binding poly(l-lactide) (PLLA) chains along chitosan (CS) via the “grafting to” approach to obtain hybrid biomaterials that present enhanced mechanical stability, due to the presence of PLLA, and high bioactivity, conferred by CS. Two graft copolymers were prepared, CS-g-PLLA(80/20) and CS-g-PLLA(50/50), containing 82 wt % and 55 wt % CS, respectively. Degradation studies of compressed discs of the copolymers showed that the degradation rate increased with the CS content of the copolymer. Nanomechanical studies in the dry state indicated that the copolymer with the higher CS content had larger Young modulus, reduced modulus and hardness values, whereas the moduli and hardness decreased rapidly following immersion of the copolymer discs in alpha-MEM cell culture medium for 24 h. Finally, the bioactivity of the hybrid copolymers was evaluated in the adhesion and growth of MC3T3-E1 pre-osteoblastic cells. In vitro studies showed that MC3T3-E1 cells exhibited strong adhesion on both CS-g-PLLA graft copolymer films from the first day in cell culture, whereas the copolymer with the higher PLLA content, CS-g-PLLA(50/50), supported higher cell growth.