Copolymerization Of L-lactide Research Articles

Raman evaluation of the crystallinity degree and composition of poly(L-lactide-co-ε-caprolactone)

In this work, we study two series of the copolymers of L-lactide (LLA) and ε-caprolactone (CL) with the CL molar content of 5, 15, and 30 %. The first series was the commercial semicrystalline granules (Corbion, Netherlands), which we analyzed without any additional modification. The second series was amorphous films, prepared from the granules by hot pressing with the subsequent fast quenching in order to avoid the crystallization. We used Raman spectroscopy in conjunction with the quantum chemical modeling to evaluate the structure of the copolymers. As additional methods, we applied X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC). The main result of our study is the elaboration of the Raman methods of quantitative analysis of the relative contents of the comonomers and the crystallinity degree of the poly(L-lactide-co-ε-caprolactone). These methods are based on measurements of the ratios of the peak intensities of the poly(L-lactide) (PLLA) bands at 411 and 874 cm−1, the PLLA band at 2947 cm−1 and the poly(ε-caprolactone) band at 2914 cm−1. Raman study shows that growth of the CL content causes the monotonous decrease in the crystallinity degree of PLLA blocks. Density functional theory analysis of LLA decamer in the conformation of helix 103 allows us to assign the PLLA Raman bands. The Raman data on the composition and crystallinity degree of the copolymers correlate very well with the results of XRD and DSC studies, as well as with the information on the composition of the copolymers provided by manufacturer.

The Influence of Ionizing Radiation on Paclitaxel-Loaded Nanoparticles Based on PLGA

The effect of ionizing radiation (γ-rays and electron beam) on anticancer drug delivery systems (DDSs) properties was evaluated concerning potential sterilization. For this purpose, paclitaxel (PTX)-loaded nanoparticles were obtained using a biodegradable, self-developed copolymer of l-lactide and glycolide (PLGA), synthesized in the presence of bismuth 2-ethylhexanoate catalyst. The nanoparticles were obtained with a high encapsulation efficiency of PTX (EE = 94.2%). The average size of the nanoparticles was 253.5 nm. The influence of irradiation (sterilization dose, 25 kGy) on the microstructure and the physicochemical and thermal properties of the polymer matrix was investigated, as well as the effect of irradiation on the morphology and physicochemical properties of the pharmaceutical formulations of the nanoparticles. Additionally, an in vitro drug release study was conducted regarding any alterations in the kinetic profiles of drug release. It was confirmed that the irradiation with both types of ionizing radiation, i.e., γ-rays and electron-beam (EB), slightly decreased the average molecular weight of the polymer matrix. While only negligible changes in the microstructure and thermal properties of PLGA were observed after irradiation with EB, the average length of lactidyl blocks (lLL) in the copolymer chains irradiated with γ-rays decreased from 4.33 to 3.35. Moreover, the contribution of crystalline phase (Xc) in γ-irradiated samples decreased significantly from 35.1% to 22.7%, suggesting a dominant mechanism of chain scission over cross-linking in PLGA samples irradiated with γ-rays. In vitro drug release results demonstrate a sustained and controlled release of PTX from the nanoparticles based on PLGA. The kinetics of drug release was defined as first order with non-Fickian diffusion. Only negligible differences in the kinetic profiles of PTX release from PLGA drug carriers were observed after irradiation. The overall results suggest good resistance of PLGA nanoparticles to irradiation within the conditions used and the great potential of EB in the sterilization process of the polymeric DDSs.

A mechanistic study on homo- and copolymerization of L-Lactide and ε-caprolactone catalyzed by an aluminum complex bearing a Bis(phenoxy)amine ligand: A DFT study

Polymerization of biodegradable lactide and lactone has been the subject of intense research during the past decade. We used density functional theory (DFT) calculations to investigate the initiation and first propagation for ring-opening polymerization (ROP) mechanisms of L-lactide (LA) and ε-caprolactone (CL) on aluminum complexes bearing the bis(phenoxy)-amine ligand with pyridine (Catalyst I) and diethylamine (Catalyst II) sidearm. Here, the ROP mechanisms of LA and CL on both catalysts were classified into 3 parts: (1) LA homopolymerization, (2) CL homopolymerization, and (3) LA and CL copolymerization. For homopolymerization, Catalyst I shows a greater performance than Catalyst II on both LA and CL due to its less bulky sidearm. However, CL homopolymerization on Catalyst I is more favorable than that of LA, which is caused by the stronger CL coordination on the catalyst. For LA and CL copolymerization, the amine sidearm variation and the vdW interactions of monomers on Catalysts I and II provide different copolymer products, the tapered and random copolymers, respectively. These calculated results are in good agreement with our previous experimental reports. The understanding gained in the current study might be helpful in the development of high-performance catalysts for the ROP reaction of biodegradable lactide and lactone.

PLDLA/TPU Matrix Enriched with Cyclosporine A as a Therapeutic Platform for Immune-Mediated Keratitis (IMMK) in Horses.

The purpose of this study was to describe the use of PLDLA/TPU matrix enriched with cyclosporine A (CsA) as a therapeutic platform in horses with immune-mediated keratitis (IMMK) with an in vitro evaluation CsA release and degradation of the blend as well as determination of the safety and efficacy of that platform used in the animal model. The kinetics of the CsA release from matrices constructed of thermoplastic polyurethane (TPU) polymer and a copolymer of L-lactide with DL-lactide (PLDLA) (80:20) in the TPU (10%) and a PLDL (90%) polymer blend were studied. Moreover, we used the STF (Simulated Tear Fluid) at 37 °C as a biological environment to assess the CsA release and its degradation. Additionally, the platform described above was injected subconjunctival in the dorsolateral quadrant of the globe after standing sedation of horses with diagnosed superficial and mid-stromal IMMK. The obtained results indicated that the CsA release rate in the fifth week of the study increased significantly by the value of 0.3% compared to previous weeks. In all of the cases, the TPU/PLA doped with 12 mg of the CsA platform effectively reduced the clinical symptoms of keratitis, leading to the complete remission of the corneal opacity and infiltration four weeks post-injection. The results from this study showed that the PLDLA/TPU matrix enriched with the CsA platform was well tolerated by the equine model and effective in treating superficial and mid-stromal IMMK.

Biodegradable Block Poly(ester amine)s with Pendant Hydroxyl Groups for Biomedical Applications.

The article presents the results of the synthesis and characteristics of the amphiphilic block terpolymers, built of a hydrophilic polyesteramine block, and hydrophobic blocks made of lactidyl and glycolidyl units. These terpolymers were obtained during the copolymerization of L-lactide with glycolide carried out in the presence of previously produced macroinitiators with protected amine and hydroxyl groups. The terpolymers were prepared to produce a biodegradable and biocompatible material containing active hydroxyl and/or amino groups, with strong antibacterial properties and high surface wettability by water. The control of the reaction course, the process of deprotection of functional groups, and the properties of the obtained terpolymers were made based on 1H NMR, FTIR, GPC, and DSC tests. Terpolymers differed in the content of amino and hydroxyl groups. The values of average molecular mass oscillated from about 5000 g/mol to less than 15,000 g/mol. Depending on the length of the hydrophilic block and its composition, the value of the contact angle ranged from 50° to 20°. The terpolymers containing amino groups, capable of forming strong intra- and intermolecular bonds, show a high degree of crystallinity. The endotherm responsible for the melting of L-lactidyl semicrystalline regions appeared in the range from about 90 °C to close to 170 °C, with a heat of fusion from about 15 J/mol to over 60 J/mol.

Biomechanical Behaviors and Degradation Properties of Multilayered Polymer Scaffolds: The Phase Space Method for Bile Duct Design and Bioengineering.

This article reports the electrospinning technique for the manufacturing of multilayered scaffolds for bile duct tissue engineering based on an inner layer of polycaprolactone (PCL) and an outer layer either of a copolymer of D,L-lactide and glycolide (PLGA) or a copolymer of L-lactide and ε-caprolactone (PLCL). A study of the degradation properties of separate polymers showed that flat PCL samples exhibited the highest resistance to hydrolysis in comparison with PLGA and PLCL. Irrespective of the liquid-phase nature, no significant mass loss of PCL samples was found in 140 days of incubation. The PLCL- and PLGA-based flat samples were more prone to hydrolysis within the same period of time, which was confirmed by the increased loss of mass and a significant reduction of weight-average molecular mass. The study of the mechanical properties of developed multi-layered tubular scaffolds revealed that their strength in the longitudinal and transverse directions was comparable with the values measured for a decellularized bile duct. The strength of three-layered scaffolds declined significantly because of the active degradation of the outer layer made of PLGA. The strength of scaffolds with the PLCL outer layer deteriorated much less with time, both in the axial (p-value = 0.0016) and radial (p-value = 0.0022) directions. A novel method for assessment of the physiological relevance of synthetic scaffolds was developed and named the phase space approach for assessment of physiological relevance. Two-dimensional phase space (elongation modulus and tensile strength) was used for the assessment and visualization of the physiological relevance of scaffolds for bile duct bioengineering. In conclusion, the design of scaffolds for the creation of physiologically relevant tissue-engineered bile ducts should be based not only on biodegradation properties but also on the biomechanical time-related behavior of various compositions of polymers and copolymers.

Copolymerization of l-lactide and ε-caprolactone using aluminum aminobisphenolate as an initiator: a quantum chemical study

Copolymerization of l-lactide and ε-caprolactone using aluminum aminobisphenolate as an initiator: a quantum chemical study

Shape memory performances of homogeneous poly(L-lactide-co-ε-caprolactone)/polytrimethylene carbonate-grafted functionalized graphene oxide nanocomposites

Biodegradable shape memory polymers (SMPS) have attracted great interest because of their wide application prospects in biomedical field. In this study, PLCL/FGO-g-PTMC nanocomposites were prepared through the simple solution blending of copolymer of L-lactide (LLA) and ε-caprolactone (ε-CL), (PLCL), with acyl chloride functionalized graphene oxide (FGO) grafted with polytrimethylene carbonate (PTMC), (FGO-g-PTMC). The functionalized modification of FGO increases the interaction between FGO and polymer matrix and improves its dispersion in the matrix. FGO was uniformly dispersed in the polymer matrix to form a homogeneous system. The appearance of FGO did not change the crystalline structure of poly(L-lactide) (PLLA). However, as a nucleating agent, it can greatly improve the crystallization rate and crystallinity of polymers. The dynamic mechanical behaviors of the obtained nanocomposites are related to the physical crosslinking formed by the entanglement of polymer chains on the surface of FGO. The presence of FGO in PLCL/FGO-g-PTMC nanocomposites strengthens the stationary phase within the matrixes, and significantly improves the modulus and shape recovery ratio of the materials. Nanocomposites with high FGO content exhibit high electrical conductivity and fast shape recovery properties. This kind of intelligent polylactide-based nanocomposites with excellent mechanical properties is expected to be used in the fields of intelligent medicine, tissue engineering and flexible electronics.

Toughening Poly(l-lactide) Blends: Effectiveness of Sequence-Controlled Six-Arm Star-Branched Block Copolymers of Poly(l-lactide) and Poly(ε-caprolactone).

Well-defined six-arm star-branched bio-degradable block copolymers of l-lactide and ε-caprolactone were prepared using controlled ring-opening polymerization and a sequential monomer addition method using dipentaerythritol as the initiator core and organocatalysts at low temperatures in solution. Sequence of enchainment was changed by reversing the order of monomer addition giving, either, a crystalline PLA block or an amorphous PCL block as the outer segment. Well-defined six-arm poly(ε-caprolactone-b-l-lactide, 6s-PCL-b-PLA) block copolymers were obtained with a range of segment molecular weights. However, in the case of six-arm poly(l-lactide-b-ε-caprolactone, 6s-PLA-b-PCL), disruption of the block structure was observed on account of competing transesterification reactions accompanying a chain-growth reaction. Such sequence-controlled block copolymers showed interesting phase morphologies, as evidenced by differential scanning calorimetry (DSC) studies. 6s-PCL-b-PLA showed two glass-transition temperatures and two melting temperatures characteristic of the amorphous and crystalline blocks. 6s-PCL-b-PLA and 6s-PLA-b-PCL with different segment chain lengths were solution blended (10 wt %) with a commercially sourced PLA. All the blends were highly transparent. The structure and properties of the blend were examined by DSC, measurement of mechanical properties, and scanning electron microscopy. The results show that a phase-separated 6s-PCL-b-PLA copolymer results in two- to three-fold improvement in tensile toughness without the loss of modulus. A possible hypothesis for the mechanism of tensile toughness in the blend has been proposed.

Synthesis of Polyacids by Copolymerization of l-Lactide with MTC-COOH Using Zn[(acac)(L)H2O] Complex as an Initiator.

This work presents the results of research on the preparation of bioresorbable functional polyestercarbonates containing side carboxyl groups. These copolymers were synthesized in two ways: the classic two-step process involving the copolymerization of L-lactide and a cyclic carbonate containing a blocked side carboxylate group in the form of a benzyl ester (MTC-Bz) and its subsequent deprotection, and a new way involving the one-step copolymerization of L-lactide with this same carbonate, but containing an unprotected carboxyl group (MTC-COOH). Both reactions were carried out under identical conditions in the melt, using a specially selected zinc chelate complex, with Zn [(acac)(L)H2O] (where: L-N-(pyridin-4-ylmethylene) phenylalaninate ligand) as an initiator. The differences in the kinetics of both reactions and their courses were pictured. The reactivity of the MTC-COOH monomer without a blocking group in the studied co-polymerization was much higher, even slightly higher than L-lactide, which allowed the practically complete conversion of the comonomers in a much shorter time. The basic final properties of the obtained copolymers and the microstructures of their chains were determined. The single-step synthesis of biodegradable polyacids was much simpler. Contrary to the conventional method, this made it possible to obtain copolymers containing all carbonate units with carboxyl groups, without even traces of the heavy metals used in the deprotection of the carboxyl groups, the presence of which is known to be very difficult to completely remove from the copolymers obtained in the two-step process.

Additive Manufacturing of α-Amino Acid Based Poly(ester amide)s for Biomedical Applications.

α-Amino acid based polyester amides (PEAs) are promising candidates for additive manufacturing (AM), as they unite the flexibility and degradability of polyesters and good thermomechanical properties of polyamides in one structure. Introducing α-amino acids in the PEA structure brings additional advantages such as (i) good cytocompatibility and biodegradability, (ii) providing strong amide bonds, enhancing the hydrogen-bonding network, (iii) the introduction of pendant reactive functional groups, and (iv) providing good cell–polymer interactions. However, the application of α-amino acid based PEAs for AM via fused deposition modeling (FDM), an important manufacturing technique with unique processing characteristics and requirements, is still lacking. With the aim to exploit the combination of these advantages in the creation, design, and function of additively manufactured scaffolds using FDM, we report the structure–function relationship of a series of α-amino acid based PEAs. The PEAs with three different molecular weights were synthesized via the active solution polycondensation, and their performance for AM applications was studied in comparison with a commercial biomedical grade copolymer of l-lactide and glycolide (PLGA). The PEAs, in addition to good thermal stability, showed semicrystalline behavior with proper mechanical properties, which were different depending on their molecular weight and crystallinity. They showed more ductility due to their lower glass transition temperature (Tg; 18–20 °C) compared with PLGA (57 °C). The rheology studies revealed that the end-capping of PEAs is of high importance for preventing cross-linking and further polymerization during the melt extrusion and for the steadiness and reproducibility of FDM. Furthermore, our data regarding the steady 3D printing performance, good polymer–cell interactions, and low cytotoxicity suggest that α-amino acid based PEAs can be introduced as favorable polymers for future AM applications in tissue engineering. In addition, their ability for formation of bonelike apatite in the simulated body fluid (SBF) indicates their potential for bone tissue engineering applications.

A Mechanistic Study on Homo- and Copolymerization of L-Lactide and Ε-Caprolactone Catalyzed by an Aluminum Complex Bearing a Bis(Phenoxy)Amine Ligand: A Dft Study

A Mechanistic Study on Homo- and Copolymerization of L-Lactide and Ε-Caprolactone Catalyzed by an Aluminum Complex Bearing a Bis(Phenoxy)Amine Ligand: A Dft Study

Effect of stereochemistry on nanoscale assembly of ABA triblock copolymers with crystallizable blocks

We report on the nanoscale assembly of poly(lactic acid)-b-poly(ethylene oxide)-b-poly(lactic acid) (PLA-PEO-PLA) triblock copolymers in water, focusing on the effect of stereochemistry, where the PLA blocks are statistical copolymers of l-lactide and d-lactide with l/d ratios of 100/0, 95/5, 90/10, 85/15, 75/25, and 50/50. Small-angle neutron scattering (SANS) shows a nearly constant d-spacing as concentration varies in triblock systems with l/d ratios of 90/10 and 95/5, which we attribute to inhomogeneity in the structure of these gels, supported by previous USANS and confocal microscopy studies. The SANS data fit well to a core-shell ellipsoid form factor model with a hard-sphere structure factor. Polymeric micelles with l/d ratios from 75/25 to 85/15 displayed very high aggregation numbers, consistent with a strong interaction between PLA chains and the enhanced storage modulus observed in rheological studies of these systems. While the 90/10 and 95/5 samples showed lower aggregation numbers, their SANS profiles shows close spacing between micelles, which may promote a high fraction of intermicellar bridging chains, also consistent with a higher storage modulus. Overall, these results provide insight into the micellar assembly behavior of block copolymers with a crystallizable block, and indicate that tuning stereochemistry of PLA-based block copolymers is an effective means of modifying micellar properties for specific applications.

Concurrent ring-opening and atom transfer radical polymerization for synthesis of block copolymers, and their comprehensive chromatographic characterization

In this study, we report concurrent ring-opening and atom transfer radical polymerization for synthesis of the block copolymers of L-lactide and styrene. Simultaneous polymerization of two different polymerization mechanisms requires careful selection of reaction conditions and reagents for targeted comparable propagation of both types. Several different di-block copolymers are synthesized having different total molar mass, chemical composition, and individual block lengths. Such simultaneous polymerization mechanisms require different reagents, and the regents required for one type of polymerization may hamper the other parallel mechanism. Hence, synthesized block copolymers are analysed comprehensively using different polymer chromatographic techniques and NMR spectroscopy. Total molar mass and chemical composition of BCPs are determined by size exclusion chromatography and NMR, respectively. PLA block length in PS-b-PLA and quantification of PS homopolymers is revealed by liquid chromatography at critical conditions of PS. For determination of PS block length in PS-b-PLA and quantification of PLA homopolymers, a gradient polymer elution chromatography (GPEC) method is applied. The comprehensive analysis of synthesized PS-b-PLA by parallel polymerization mechanisms revealed uninterrupted simultaneous polymerization of both monomers under applied conditions.

Comparative Experimental and Theoretical Study of Mg, Al and Zn Aryloxy Complexes in Copolymerization of Cyclic Esters: The Role of the Metal Coordination in Formation of Random Copolymers.

Homogeneity of copolymers is a general problem of catalytic coordination polymerization. In ring-opening polymerization of cyclic esters, the rational design of the catalyst is generally applied to solve this problem by the equalization of the reactivities of comonomers—however, it often leads to a reduction of catalytic activity. In the present paper, we studied the catalytic behavior of BnOH-activated complexes (BHT)Mg(THF)2nBu (1), (BHT)2AlMe (2) and [(BHT)ZnEt]2 (3), based on 2,6-di-tert-butyl-4-methylphenol (BHT-H) in homo- and copolymerization of L-lactide (lLA) and ε-caprolactone (εCL). Even at 1:5 lLA/εCL ratio Mg complex 1 catalyzed homopolymerization of lLA without involving εCL to the formation of the polymer backbone. On the contrary, Zn complex 3 efficiently catalyzed random lLA/εCL copolymerization; the presence of mono-lactate subunits in the copolymer chain clearly pointed to the transesterification mechanism of copolymer formation. Both epimerization and transesterification side processes were analyzed using the density functional theory (DFT) modeling that confirmed the qualitative difference in catalytic behavior of 1 and 3: Mg and Zn complexes demonstrated different types of preferable coordination on the PLA chain (k2 and k3, respectively) with the result that complex 3 catalyzed controlled εCL ROP/PLA transesterification, providing the formation of lLA/εCL copolymers that contain mono-lactate fragments separated by short oligo(εCL) chains. The best results in the synthesis of random lLA/εCL copolymers were obtained during experiments on transesterification of commercially available PLLA, the applicability of 3/BnOH catalyst in the synthesis of random copolymers of εCL with methyl glycolide, ethyl ethylene phosphonate and ethyl ethylene phosphate was also demonstrated.

Effect of infill on resulting mechanical properties of additive manufactured bioresorbable polymers for medical devices

The crossover between additive manufacturing (AM) and bioresorbable materials play a critical role in development of new bioresorbable medical devices. When combined with the innovation and technological advances of additive manufacturing, the use of bioresorbable polymers could prove tremendous to the development of custom bioresorbable implants. However, a key question for the use of thermoplastic-based resorbable polymers lies in the potential changes in properties experienced during manufacturing, and thus the effect of process parameters on the performance of the final device is of critical importance. Specific resorbable materials are selected for mechanical and resorption rate properties based on bulk measurements. The implanted mechanical properties of a device are significantly affected by processing parameters and are the leading concern of clinicians during development and patient use of a new device. In this work, additive manufacturing of medical grade polymers and copolymers of L-lactide, ε-caprolactone were extruded into filaments of 1.75 mm in diameter and printed at different infill percentages. The molecular, thermal, and mechanical properties of homopolymers of L-lactide and ε-caprolactone, along with a unique copolymer of L-lactide, ε-caprolactone, and trimethylene carbonate, LactoflexⓇ 7415 were evaluated. Through variance of material composition and the infill parameter of AM, an order of magnitude range in tensile strength and modulus properties were observed as feasible and optimizable.

Effect of Infill on Resulting Mechanical Properties of Additive Manufactured Bioresorbable Polymers for Medical Devices

The crossover between additive manufacturing (AM) and bioresorbable materials play a critical role in development of a new bioresorbable medical devices. When combined with the innovation and technological advances of additive manufacturing, the use of bioresorbable polymers could prove tremendous to the development of custom bioresorbable implants. However, a key question for the use of thermoplastic based resorbable polymers lies in the potential changes in properties experienced during manufacturing, and thus the effect of process parameters on the performance of the final device is of critical importance. Specific resorbable materials are selected for mechanical and resorption rate properties based on bulk measurements. The implanted mechanical properties of a device are significantly affected by processing parameters and are the leading concern of clinicians during development and patient use of a new device. In this work, additive manufacturing of medical grade polymers and copolymers of L-lactide, e-caprolactone were extruded into filaments of 1.75 mm in diameter and printed at different infill percentages. The molecular, thermal, and mechanical properties of homopolymers of L-lactide and e-caprolactone, along with a unique copolymer of L-lactide, e-caprolactone, and trimethylene carbonate, Lactoflex® 7415 were evaluated. Through variance of material composition and the infill parameter of AM, an order of magnitude range in tensile strength and modulus properties were observed as feasible and optimizable.

Ring-Opening Polymerization (ROP) of cyclic esters by a versatile aluminum Diphenoxyimine Complex: From polylactide to random copolymers

Aluminum complex [AlMeL2] (1), (L = N-(2,6-diisopropylphenyl)-phenoxyimine), promotes the Ring-Opening Polymerization (ROP) of L- and rac-lactide, and the copolymerization of L-lactide with rac-β-butyrolactone and ε-caprolactone. This complex exhibits good control over the ROP of rac-lactide producing heterorich-PLA (Pr = 0.69) with narrow dispersity (ÐM < 1.10). When the ratio of the co-initiator (BnOH) is increased the polymerization is immortal in nature. Furthermore, a series of copolymers PLLA-co-PHB and PLLA-co-PCL with wide ranging monomer compositions were synthesized and characterized by NMR spectroscopy and differential scanning calorimetry (DSC). The microstructure disclosed by 13C NMR analysis suggested a random distribution of the monomers along the polymer chain for both the PLLA-co-PHB and PLLA-co-PCL copolymers. In all cases, the copolymers displayed a single glass transition temperature with values intermediate between those of the corresponding homopolymers and in perfect agreement with the theoretical values calculated by the Fox equation. These data further support the random structure of the PLLA-co-PHB and PLLA-co-PCL copolymers obtained by 1/BnOH. DFT calculations have been carried out to justify the unusual but similar reactivity observed for LA and BBL with the catalyst.

Synthesis and Properties of Bioresorbable Block Copolymers of l-Lactide, Glycolide, Butyl Succinate and Butyl Citrate.

The paper presents the course of synthesis and properties of a series of block copolymers intended for biomedical applications, mainly as a material for forming scaffolds for tissue engineering. These materials were obtained in the polymerization of l-lactide and copolymerization of l-lactide with glycolide carried out using a number of macroinitiators previously obtained in the reaction of polytransesterification of succinic diester, citric triester and 1,4-butanediol. NMR, FTIR and DSC were used to characterize the materials obtained; wettability and surface free energy were assessed too. Moreover, biological tests, i.e., viability and metabolic activity of MG-63 osteoblast-like cells in contact with synthesized polymers were performed. Properties of obtained block copolymers were controlled by the composition of the polymerization mixture and by the composition of the macroinitiator. The copolymers contained active side hydroxyl groups derived from citrate units present in the polymer chain. During the polymerization of l-lactide in the presence of polyesters with butylene citrate units in the chain, obtained products of the reaction held a fraction of highly branched copolymers with ultrahigh molecular weight. The reason for this observed phenomenon was strong intermolecular transesterification directed to lactidyl side chains, formed as a result of chain growth on hydroxyl groups related to the quaternary carbons of the citrate units. Based on the physicochemical properties and results of biological tests it was found that the most promising materials for scaffolds formation were poly(l-lactide–co–glycolide)–block–poly(butylene succinate–co–butylene citrate)s, especially those copolymers containing more than 60 mol % of lactidyl units.

Benzoic Acid as an Efficient Organocatalyst for the Statistical Ring-Opening Copolymerization of ε-Caprolactone and L-Lactide: A Computational Investigation

Statistical copolymers of l-lactide (L-LA) and e-caprolactone (CL) are of major interest as a result of the desired combination of properties they exhibit for high-added-value applications, includi...