Aliphatic Polyesters: Synthesis, Properties and Applications

In Vitro and In Vivo Hydrolytic Degradation Behaviors of a Drug-Delivery System Based on the Blend of PEG and PLA Copolymers

This paper presents the in vitro and in vivo degradation of BEPO, a marketed in situ forming depot technology used for the formulation of long-acting injectables. BEPO is composed of a solution of a blend of poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) triblock and diblock in an organic solvent, where a therapeutic agent may be dissolved or suspended. Upon contact with an aqueous environment, the solvent diffuses and the polymers precipitate, entrapping the drug and forming a reservoir. Two representative BEPO compositions were subjected to a 3-month degradation study in vitro by immersion in phosphate-buffered saline at 37 °C and in vivo after subcutaneous injection in minipig. The material erosion rate, as a surrogate of the bioresorption, determined via the depot weight loss, changed substantially, depending on the composition and content of polymers within the test item. The swelling properties and internal morphology of depots were shown to be highly dependent on the solvent exchange rate during the precipitation step. Thermal analyses displayed an increase of the depot glass transition temperature over the degradation process, with no crystallinity observed at any stage. The chemical composition of degraded depots was determined by 1H NMR and gel permeation chromatography and demonstrated an enrichment in homopolymers, i.e., free PLA and (m)PEG, to the detriment of (m)PEG-PLA copolymers in both formulations. It was observed that the relative ratio of the degradants within the depot is driven by the initial polymer composition. Interestingly, in vitro and in vivo results showed very good qualitative consistency. Taken together, the outcomes from this study demonstrate that the different hydrolytic degradation behaviors of the BEPO compositions can be tuned by adjusting the polymer composition of the formulation.

Optimization of the Poly(glycerol citraconate) Synthesis Using the Box-Behnken Design

This work aimed to obtain poly(glycerol citraconate) (PGCitrn) for biomedical applications, analyze the obtained polyester by spectroscopic methods, and optimize its preparation. Polycondensation reactions of glycerol and citraconic anhydride were carried out. It was provided that the results in the reaction are oligomers of poly(glycerol citraconate). Optimization studies were carried out based on the Box-Behnken design. The input variables in this plan were the ratio of functional groups, temperature, and time and occurrence in coded form: -1, 0, or 1. Three output variables were optimized: the degree of esterification, the percentage of Z-mers, and the degree of carboxyl group conversion; they were determined by titration and spectroscopic methods. The optimization criterion was to maximize the values of output variables. A mathematical model and an equation describing it were determined for each output variable. The models predicted the experimental results well. An experiment was conducted under determined optimal conditions. The experimental results were very close to the calculated values. Poly(glycerol citraconate) oligomers with an esterification degree of 55.2%, a Z-mer content of 79.0%, and a degree of rearrangement of carboxyl groups of 88.6% were obtained. The obtained PGCitrn can serve as a component of an injectable implant. The obtained material can be used to produce nonwoven fabrics (with the addition of PLLA, for example), which can be subjected to a cytotoxicity test which can then serve as a dressing material.

Crystallization and molecular mobility in renewable semicrystalline copolymers based on polycaprolactone and polyisosorbide

A series of novel block copolymers based on two biodegradable polymers, poly(ε-caprolactone), PCL, and poly(isosorbide), PIS, with PIS fractions 5, 10, and 25 wt%, are studied herein. The aim is to assess the effects of the amorphous PIS phase on the properties of the semicrystalline PCL (majority), in addition to the synthesis strategy. The latter involved the polymerization of caprolactone onto initial PIS of low molar mass, resulting, thus, in gradually shorter PCL blocks when the starting amount of PIS is increased. The structure-property relationship investigation, with an emphasis on molecular mobility and crystallization, involves the following sum of complementary techniques: differential scanning calorimetry, dielectric spectroscopy, polarized optical microscopy and X-ray diffraction. The molecular mobility map for these PCL/PIS and initial PIS is drawn here for the first time. Despite the high glass transition temperature of PIS (T_g ∼ 51 °C) compared to that of PCL (-66 °C), the T_g of the copolymers barely changes, as it is mainly ruled by crystallinity. The latter seems to be facilitated in the copolymers, in both the amount and the rate. The local molecular mobility of PCL and PCL/PIS consists of faster γ_PCL relaxation which is unaffected in the copolymers, whereas the slower β_PCL process arising from the backbone ester group rotation exhibits a systematic deceleration in the presence of PIS. A connection between such local motions and the corresponding segmental α relaxation, observed previously in other polyesters, is also found to be true here. Apart from that, the dielectric T_g as well as the cooperativity of the polymer chains drop moderately, which indicates spatial confinement between the PCL crystals, whereas correlations with the looser lamellar chain packing within the spherulites are gained. The relaxations of initial PIS, i.e., γ_PIS, β_PIS and α_PIS, could not be resolved within the copolymers. Along with other properties, such as ionic conductivity, we conclude to the homogeneity of our systems, with sufficient PCL/PIS distribution.

Stereoregulation, molecular weight, and dispersity control of PMMA synthesized via free-radical polymerization supported by the external high electric field

We show the remarkable effect of using static (DC) and alternating (AC) electric fields to control the free-radical polymerization of methyl methacrylate (MMA). The magnitude and/or frequency of the applied electric field (up to 154 kV cm^-1) were found to control the molecular weight, dispersity, and stereochemistry of the produced polymers.

Defining the Macromolecules of Tomorrow through Synergistic Sustainable Polymer Research

Transforming how plastics are made, unmade, and remade through innovative research and diverse partnerships that together foster environmental stewardship is critically important to a sustainable future. Designing, preparing, and implementing polymers derived from renewable resources for a wide range of advanced applications that promote future economic development, energy efficiency, and environmental sustainability are all central to these efforts. In this Chemical Reviews contribution, we take a comprehensive, integrated approach to summarize important and impactful contributions to this broad research arena. The Review highlights signature accomplishments across a broad research portfolio and is organized into four wide-ranging research themes that address the topic in a comprehensive manner: Feedstocks, Polymerization Processes and Techniques, Intended Use, and End of Use. We emphasize those successes that benefitted from collaborative engagements across disciplinary lines.

Preparation of biacidic tin-based ionic liquid catalysts and their application in catalyzing coupling reaction between ethylene carbonate and dimethyl succinate to synthesize poly(ethylene succinate)

A new low-carbon and environmentally friendly process method for the catalytic synthesis of biodegradable polyester by utilizing ionic liquid catalysts.

Enzymatic recycling of polymacrolactones

The use of renewable monomers to make new polyesters which could replace the ones obtained from petrochemical resources employing green processes is a big concern in these days. With this...

Poly(butylene succinate-co-ε-caprolactone) Copolyesters: Enzymatic Synthesis in Bulk and Thermal Properties

This work explores for the first time the enzymatic synthesis of poly(butylene-co-ε-caprolactone) (PBSCL) copolyesters in bulk using commercially available monomers (dimethyl succinate (DMS), 1,4-butanediol (BD), and ε-caprolactone (CL)). A preliminary kinetic study was carried out which demonstrated the higher reactivity of DMS over CL in the condensation/ring opening polymerization reaction, catalyzed by Candida antarctica lipase B. PBSCL copolyesters were obtained with high molecular weights and a random microstructure, as determined by ¹³C NMR. They were thermally stable up to 300 °C, with thermal stability increasing with the content of CL in the copolyester. All of them were semicrystalline, with melting temperatures and enthalpies decreasing up to the eutectic point observed at intermediate compositions, and glass transition temperatures decreasing with the content of CL in the copolyester. The use of CALB provided copolyesters free from toxic metallic catalyst, which is very useful if the polymer is intended to be used for biomedical applications.

Versatility of unsaturated polyesters from electrospun macrolactones: RGD immobilization to increase cell attachment

Poly(globalide) (PGl), an aliphatic polyester derived from unsaturated macrocylic lactone, can be cross-linked during electrospinning and drug-loaded for regenerative medicine applications. However, it lacks intrinsic recognition sites for cell adhesion and proliferation. In order to improve their cell adhesiveness, and therefore their therapeutic potential, we aimed to functionalize electrospun PGl fibers with RGD sequence generating a biomimetic scaffold. First, an amine compound was attached to the surface double bonds of the PGl fibers. Subsequently, the amino groups were coupled with RGD sequences. X-ray photoelectron spectroscopy (XPS) analysis confirmed the functionalization. The obtained fibers were more hydrophilic, as observed by contact angle analysis, and presented smaller Young's modulus, although similar tensile strength compared with non-functionalized cross-linked fibers. In addition, the functionalization process did not significantly alter fibers morphology, as observed by scanning electron microscopy (SEM). Finally, in vitro analysis evidenced the increase in human mesenchymal stromal cells (hMSC) adhesion (9.88 times higher DNA content after 1 day of culture) and proliferation (3.57 times higher DNA content after 8 days of culture) compared with non-functionalized non-cross-linked fibers. This is the first report demonstrating the functionalization of PGl fibers with RGD sequence, improving PGl therapeutic potential and further corroborating the use of this highly versatile material toward regenerative medicine applications.

A Biodegradable Copolyester, Poly(butylene succinate-co-ε-caprolactone), as a High Efficiency Matrix Former for Controlled Release of Drugs

A biodegradable copolyester, poly(butylene succinate-co-ε-caprolactone) (PBS_CL), was used for first time as an excipient for pharmaceutical dosage forms using direct compression and hot processing techniques (ultrasound-assisted compression (USAC) and hot melt extrusion (HME)). Robust binary systems were achieved with hot processing techniques, allowing a controlled release of the drug. With only 12% v/v of PBS_CL, controlled release forms were obtained using USAC whereas in HME over 34% v/v of excipient is necessary. Amounts over 23% v/v allowed a long-extended release for more than 72 h following diffusional kinetic. Thanks to the high melting point of theophylline and the physicochemical properties of PBS_CL selected and synthesized, the structure of the excipient inside the USAC tablets and HME filaments corresponds to a continuum medium. A percolation threshold around 23% v/v was estimated, which agrees with a continuum percolation model. The polymer shows a high excipient efficiency value using HME and USAC. A nanostructured matrix with wall thicknesses lower than 0.1 µm was obtained. This leads to a very effective coating of the drug particles by the excipient, providing a slow and reproducible release. The present study therefore supports the use of PBS_CL, for the preparation of controlled release dosage forms using hot processing techniques.

Effect of Biomedical Materials in the Implementation of a Long and Healthy Life Policy

This paper is divided into seven main parts. Its purpose is to review the literature to demonstrate the importance of developing bioengineering and global production of biomaterials to care for the level of healthcare in the world. First, the general description of health as a universal human value and assumptions of a long and healthy life policy is presented. The ethical aspects of the mission of medical doctors and dentists were emphasized. The coronavirus, COVID-19, pandemic has had a significant impact on health issues, determining the world’s health situation. The scope of the diseases is given, and specific methods of their prevention are discussed. The next part focuses on bioengineering issues, mainly medical engineering and dental engineering, and the need for doctors to use technical solutions supporting medicine and dentistry, taking into account the current stage Industry 4.0 of the industrial revolution. The concept of Dentistry 4.0 was generally presented, and a general Bioengineering 4.0 approach was suggested. The basics of production management and the quality loop of the product life cycle were analyzed. The general classification of medical devices and biomedical materials necessary for their production was presented. The paper contains an analysis of the synthesis and characterization of biomedical materials supporting medicine and dentistry, emphasizing additive manufacturing methods. Numerous examples of clinical applications supported considerations regarding biomedical materials. The economic conditions for implementing various biomedical materials groups were supported by forecasts for developing global markets for biomaterials, regenerative medicine, and tissue engineering. In the seventh part, recapitulation and final remarks against the background of historical retrospection, it was emphasized that the technological processes of production and processing of biomedical materials and the systematic increase in their global production are a determinant of the implementation of a long and healthy policy.

Physical Properties of Electropolished CoCrMo Alloy Coated with Biodegradable Polymeric Coatings Releasing Heparin after Prolonged Exposure to Artificial Urine

In this study, we aimed to determine the effect of long-term exposure to artificial urine on the physical properties of CoCrMo alloy with biodegradable heparin-releasing polymeric coatings. Variants of polymer coatings of poly(L,L-lactide-ɛ-caprolactone) (P(L,L-L/CL)) and poly(D,L-lactide-ɛ-caprolactone) (P(D,L-L/CL)) constituting the base for heparin-releasing (HEP) polyvinyl alcohol (PVA) coatings were analyzed. The coatings were applied by the dip-coating method. Heparin was used to counteract the incrustation process in the artificial urine. The study included tests of wettability, resistance to pitting and crevice corrosion, determination of the mass density of metal ions penetrating into the artificial urine, and the kinetics of heparin release. In addition, microscopic observations of surface roughness and adhesion to the metal substrate were performed. Electrolytically polished CoCrMo samples (as a reference level) and samples with polymer coatings were used for the tests. The tests were conducted on samples in the initial state and after 30, 60, and 90 days of exposure to artificial urine. The analysis of the test results shows that the polymer coatings contribute by improving the resistance of the metal substrate to pitting and crevice corrosion in the initial state and reducing (as compared with the metal substrate) the mass density of metal ion release into the artificial urine. Moreover, the PVA + HEP coating, regardless of the base polymer coatings used, contributes to a reduction in the incrustation process in the first 30 days of exposure to the artificial urine.

Enzymatic Synthesis of Poly(alkylene succinate)s: Influence of Reaction Conditions

Application of lipases (preferentially Candida antarctica Lipase B, CALB) for melt polycondensation of aliphatic polyesters by transesterification of activated dicarboxylic acids with diols allows to displace toxic metal and metal oxide catalysts. Immobilization of the enzyme enhances the activity and the temperature range of use. The possibility to use enzyme-catalyzed polycondensation in melt is studied and compared to results of polycondensations in solution. The experiments show that CALB successfully catalyzes polycondensation of both, divinyladipate and dimethylsuccinate, respectively, with 1,4-butanediol. NMR spectroscopy, relative molar masses obtained by size exclusion chromatography, MALDI-TOF MS and wide-angle X-ray scattering are employed to compare the influence of synthesis conditions for poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS). It is shown that the enzymatic activity of immobilized CALB deviates and influences the molar mass. CALB-catalyzed polycondensation of PBA in solution for 24 h at 70 °C achieves molar masses of up to Mw~60,000 g/mol, higher than reported previously and comparable to conventional PBA, while melt polycondensation resulted in a moderate decrease of molar mass to Mw~31,000. Enzymatically catalyzed melt polycondensation of PBS yields Mw~23,400 g/mol vs. Mw~40,000 g/mol with titanium(IV)n-butoxide. Melt polycondensation with enzyme catalysis allows to reduce the reaction time from days to 3–4 h.

Progress in the Preparation of Functional and (Bio)Degradable Polymers via Living Polymerizations

This review presents the latest developments in (bio)degradable approaches and functional aliphatic polyesters and polycarbonates prepared by typical ring-opening polymerization (ROP) of lactones and trimethylene carbonates. It also considers several recent innovative synthetic methods including radical ring-opening polymerization (RROP), atom transfer radical polyaddition (ATRPA), and simultaneous chain- and step-growth radical polymerization (SCSRP) that produce aliphatic polyesters. With regard to (bio)degradable approaches, we have summarized several representative cleavable linkages that make it possible to obtain cleavable polymers. In the section on functional aliphatic polyesters, we explore the syntheses of specific functional lactones, which can be performed by ring-opening copolymerization of typical lactone/lactide monomers. Last but not the least, in the recent innovative methods section, three interesting synthetic methodologies, RROP, ATRPA, and SCSRP are discussed in detail with regard to their reaction mechanisms and polymer functionalities.

Photocurable Polymeric Blends for Surgical Application

The preparation of photocrosslinkable bioadhesives synthesized from oligomers of lactic acid and polycaprolactone (PCL), both functionalized with 2-isocyanoethyl acrylate (AOI), were studied. The obtained modified macromers of LA-AOI (mLA) and PCL-AOI (mCL) were chemically characterized by ¹H NMR and used to formulate polymeric blends with different mass proportions, 1:1, 1:2 and 2:1, respectively. Subsequently, the produced blends were crosslinked, considering two UV irradiation times: 30 and 120 s. After their production, the thermal and mechanical properties of bioadhesives were assessed, where upon the rheology, gel content, hydrolytic degradation and dynamic contact angles were determined. Furthermore, the cytotoxic profile of bioadhesives was evaluated in contact with human dermal fibroblasts cells, whereas their antibacterial effect was studied monitoring Escherichia coli and S. aureus growth. Overall, flexible and resistant films were obtained, presenting promising features to be used as surgical bioadhesives.

Synthesis, crystallization, and molecular mobility in poly(ε-caprolactone) copolyesters of different architectures for biomedical applications studied by calorimetry and dielectric spectroscopy

In this work, we synthesized poly(ε-caprolactone) (PCL) and three copolyesters of different architectures based on three different alcohols, namely a three arm-copolymer based on 1% glycerol (PCL_Gly), a four arm-copolymer based on 1% pentaerythrytol (PCL_PE), and a linear block copolymer based on ∼50% methoxy-poly(ethylene glycol) (PCL_mPEG), all simultaneously with the ring opening polymerization (ROP) of PCL. Due to their biocompatibility and low toxicity, these systems are envisaged for use in drug delivery and tissue engineering applications. Due to the in situ ROP during the copolyesters synthesis, the molecular weight of PCL, Wm initially ∼62 kg mol-1, drops in the copolymers from ∼60k down to ∼5k. For the structure-properties investigation we employed differential scanning calorimetry (DSC and TMDSC), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Fourier transform infra red (FTIR) spectroscopy, polarized optical microscopy (POM), broadband dielectric spectroscopy (BDS) and isothermal water sorption. DSC revealed that the crystalline fraction of PCL increases whereas the crystallization rate drops in the copolymers in the order PCL ∼ PCL_Gly > PCL_PE ≫ PCL_mPEG, which coincides with that of decreasing Wm. In PCL_mPEG the major amount of PCL (87%) was found to crystallize while the majority of mPEG (92%) was found amorphous exhibiting constrained amorphous mobility and severely slower/weaker crystallization as compared to neat mPEG. Segmental dynamics in BDS, in agreement with DSC, is similar and in general slow for the samples of star-like structure for Wm ≥ 30k arising from PCL, whereas it is severely faster and enhanced in strength for the linear PCL_mPEG (lower Wm) copolymer arising from mPEG. For the latter system, the data provide indications for the formation of complex structures consisting of many small PCL crystallites surrounded by amorphous mPEG segments with constrained dynamics and severely suppressed hydrophilicity. These effects cannot be easily assessed by conventional XRD and POM, confirming the power of the dielectric technique. The overall recordings indicated that the different polymer architecture results in severe changes in the semicrystalline morphology, which demonstrates the potential for tuning the final product performance (permeability, mechanical).

Development and Characterization of Polyester and Acrylate-Based Composites with Hydroxyapatite and Halloysite Nanotubes for Medical Applications

We aimed to study the distribution of hydroxyapatite (HA) and halloysite nanotubes (HNTs) as fillers and their influence on the hydrophobic character of conventional polymers used in the biomedical field. The hydrophobic polyester poly (ε-caprolactone) (PCL) was blended with its more hydrophilic counterpart poly (lactic acid) (PLA) and the hydrophilic acrylate poly (2-hydroxyethyl methacrylate) (PHEMA) was analogously compared to poly (ethyl methacrylate) (PEMA) and its copolymer. The addition of HA and HNTs clearly improve surface wettability in neat samples (PCL and PHEMA), but not that of the corresponding binary blends. Energy-dispersive X-ray spectroscopy mapping analyses show a homogenous distribution of HA with appropriate Ca/P ratios between 1.3 and 2, even on samples that were incubated for seven days in simulated body fluid, with the exception of PHEMA, which is excessively hydrophilic to promote the deposition of salts on its surface. HNTs promote large aggregates on more hydrophilic polymers. The degradation process of the biodegradable polyester PCL blended with PLA, and the addition of HA and HNTs, provide hydrophilic units and decrease the overall crystallinity of PCL. Consequently, after 12 weeks of incubation in phosphate buffered saline the mass loss increases up to 48% and mechanical properties decrease above 60% compared with the PCL/PLA blend.

Immobilization of FGF on Poly(xylitol dodecanedioic Acid) Polymer for Tissue Regeneration

Fibroblast growth factor (FGF) plays a vital role in the repair and regeneration of most tissues. However, its low stability, short half-life, and rapid inactivation by enzymes in physiological conditions affect their clinical applications. Therefore, to increase the effectiveness of growth factors and to improve tissue regeneration, we developed an elastic polymeric material poly(xylitol dodecanedioic acid) (PXDDA) and loaded FGF on the PXDDA for sustained drug delivery. In this study, we used a simple dopamine coating method to load FGF on the surface of PXDDA polymeric films. The polydopamine-coated FGF-loaded PXDDA samples were then characterized using FTIR and XRD. The in vitro drug release profile of FGF from PXDDA film and cell growth behavior were measured. Results showed that the polydopamine layer coated on the surface of the PXDDA film enhanced the immobilization of FGF and controlled its sustained release. Human fibroblast cells attachment and proliferation on FGF-immobilized PXDDA films were much higher than the other groups without coatings or FGF loading. Based on our results, the surface modification procedure with immobilizing growth factors shows excellent application potential in tissue regeneration.

Lipase-catalyzed synthesis and post-polymerization modification of new fully bio-based poly(hexamethylene γ-ketopimelate) and poly(hexamethylene γ-ketopimelate-co-hexamethylene adipate) copolyesters

A novel full bio-based ketone-containing aliphatic polyester was prepared by enzyme-catalyzed polycondensation of diethyl γ-ketopimelate (DEK) with 1,6-hexanediol (HDO) using immobilized lipase B from Candida antarctica (CALB). The influences of polymerization conditions such as temperature, time, enzyme amount, and solvent amount on the molecular weight of poly(hexamethylene γ-ketopimelate) (PHK) were investigated. New fully bio-based poly(hexamethylene γ-ketopimelate-co-hexamethylene adipate) (poly(HK-co-HA)) copolymers with narrow polydispersity and well-defined composition were synthesized by copolymerization of DEK, HDO, and diethyl adipate. The structures of PHK and poly(HK-co-HA) copolymers were characterized by nuclear magnetic resonance, and their thermal characterization was examined by thermogravimetric analysis and differential scanning calorimetry. The degradation of PHK and poly(HK-co-HA) copolymers was studied. The post-polymerization modification of these polyketoesters via oxime click chemistry was further demonstrated.

A Review on Barrier Properties of Poly(Lactic Acid)/Clay Nanocomposites

Poly(lactic acid) (PLA) is considered to be among the best biopolymer substitutes for the existing petroleum-based polymers in the field of food packaging owing to its renewability, biodegradability, non-toxicity and mechanical properties. However, PLA displays only moderate barrier properties to gases, vapors and organic compounds, which can limit its application as a packaging material. Hence, it becomes essential to understand the mass transport properties of PLA and address the transport challenges. Significant improvements in the barrier properties can be achieved by incorporating two-dimensional clay nanofillers, the planes of which create tortuosity to the diffusing molecules, thereby increasing the effective length of the diffusion path. This article reviews the literature on barrier properties of PLA/clay nanocomposites. The important PLA/clay nanocomposite preparation techniques, such as solution intercalation, melt processing and in situ polymerization, are outlined followed by an extensive account of barrier performance of nanocomposites drawn from the literature. Fundamentals of mass transport phenomena and the factors affecting mass transport are also presented. Furthermore, mathematical models that have been proposed/used to predict the permeability in polymer/clay nanocomposites are reviewed and the extent to which the models are validated in PLA/clay composites is discussed.

Development of antibacterial, ciprofloxacin-eluting biodegradable coatings on Ti6Al7Nb implants to prevent peri-implant infections

Various types of biodegradable polymers containing lactide, glycolide, caprolactone, and trimethylene carbonate units have been used to obtain ciprofloxacin (CFX)-enriched coatings developed on the Ti6Al7Nb alloy, intended for short-term therapy. In the first step, the surface of the Ti6Al7Nb alloy was modified, mostly according to sandblasting and anodic oxidation to obtain the TiO₂ layer. Anodizing can be an effective method for preparing TiO₂ coatings with osteoconductive properties. The polymer containing CFX molecules was deposited on the modified alloy, and Polymer + CFX/TiO ₂ /Ti6Al7Nb systems were developed. CFX-enriched coatings adhered well to the surface of the previously modified alloy. Polymer layers maintain the topography of the alloy due to the development of the surface during the sandblasting method. As polymers intended for the study possess degradation ability, they are capable of releasing the incorporated drug. Antibacterial activity of CFX-enriched coatings was examined to verify the functionality of designed Polymer + CFX/TiO ₂ /Ti6Al7Nb systems, and the bactericidal effect was confirmed for all cases. The presented study is an extension of previous, initial research and creates an overview of polyester or polyestercarbonate CFX-eluting coatings.

Additive-Free Baeyer–Villiger Oxidation of Cyclic Ketone Catalyzed by Carboxylic-Functionalized Poly(Ionic Liquids) and Polyoxometalate Ionic Self-Assemblies

Two carboxylic functionalized poly(ionic liquids) and polyoxometalate ionic self-assemblies with tunable amphiphilic and oxidative activity and porous structure were designed and synthesized. They were used as efficient heterogeneous catalysts exhibiting excellent catalytic activity and quite stable reusability in additive–free Baeyer-Villiger oxidation of cyclic ketones, directly using 30% H2O2 solution in liquids–phase. Under optimum conditions, the corresponding lactones were obtained with yields ranging from 59.6 to 90.5%. The unique combination of carboxylic group with polyoxometalate anion, amphiphilic property, and porous structure is revealed to be responsible for their excellent catalytic performances in oxidation.

Ring opening polymerization of macrocyclic oligoesters derived from renewable sources

A review about the synthesis of renewable alkylene furanoate and dicarboxylate MCOs, their ROP to polyesters and their recycling by cyclodepolymerization.

Syntheses, structures and catalytic activity of tetranuclear Mg complexes in the ROP of cyclic esters under industrially relevant conditions

Tetranuclear magnesium imino(phenolate) complexes Mg₄(L^1–4)₄ are excellent catalysts for the ROP of bulk rac-lactide and ε-caprolactone under industrially relevant conditions.

Nomenclature and terminology for linear lactic acid-based polymers (IUPAC Recommendations 2019)

Lactic acid enantiomers and cyclic lactic acid dimers, the latter referred to as lactides, are sources of degradable aliphatic polymers that are composed of chiral constitutional repeating units. The different synthesis routes and the various combinations of chiral units result in a multitude of chiral structures and of corresponding properties. Distinctive structural identification is often crucial, especially for applications as degradable polymers. This document provides recommendations for the nomenclature, abbreviations, and terminology related to lactic acid-based polymers in order to allow consistent comparison between polymers of different origins and between data collected within different disciplines.

Ionic Organocatalyst with a Urea Anion and Tetra-n-butyl Ammonium Cation for Rapid, Selective, and Versatile Ring-Opening Polymerization of Lactide

A highly active and chemoselective ionic organocatalyst is developed for room-temperature living/controlled ring-opening polymerization of lactide. The catalysts are prepared by a simple dehydration reaction between tetra-n-butyl ammonium hydroxide and an N,N'-diarylurea and used in cooperation with hydroxy initiators. Typically, poly(l-lactide) with near perfect isotacticity and widely tunable molar mass (4-130 kg mol^-1) can be produced in <2 min (turnover frequency up to 120 000 h^-1). Low molar mass distribution is observed in both short and substantially extended reaction times, clearly demonstrating the selectivity of catalyst for monomer enchainment over macromolecular transesterification. Versatile design and construction of diverse polylactide-based macromolecular structures are allowed thanks to the livingness of the polymerization and independence of initiator and catalyst. In addition to the hydrogen bond donor-acceptor type bifunctional activation mechanism, direct nucleophilic attack of the urea anion on the monomer and polymer is also shown which can be suppressed by the added hydroxy initiator.

Synthesis of Poly(N-vinylpyrrolidone)-Based Polymer Bottlebrushes by ATRPA and RAFT Polymerization: Toward Drug Delivery Application

Atom transfer radical polyaddition (ATRPA) was utilized herein to synthesize a specific functional polyester. We conducted ATRPA of 4-vinylbenzyl 2-bromo-2-phenylacetate (VBBPA) inimer and successfully obtained a linear type poly(VBBPA) (PVBBPA) polyester with benzylic bromides along the backbone. To obtain a novel amphiphilic polymer bottlebrush, however, the lateral ATRP chain extension of PVBBPA with N-vinyl pyrrolidone (NVP) met the problem of quantitative dimerization. By replacing the bromides to xanthate moieties efficiently, we thus observed a pseudo linear first order reversible addition-fragmentation chain transfer (RAFT) polymerization to obtain novel poly(4-vinylbenzyl-2-phenylacetate)-g-poly(NVP) (PVBPA-g-PNVP) amphiphilic polymer bottlebrushes. The critical micelle concentration (CMC) and particle size of the amphiphilic polymer bottlebrushes were characterized by fluorescence spectroscopy, dynamic light scattering (DLS), and scanning electron microscopy (SEM) (CMCs < 0.5 mg/mL; particle sizes = ca. 100 nm). Toward drug delivery application, we examined release profiles using a model drug of Nile red at different pH environments (3, 5, and 7). Eventually, low cytotoxicity and well cell uptake of the Madin-Darby Canine Kidney Epithelial (MDCK) for the polymer bottlebrush micelles were demonstrated.