Use Of Polyesters Research Articles

Seamless, Self-Transformation of Thermoplastic Polyesters into Vitrimers Through Bond Exchange-Triggered Cross-Linking.

In this study, a seamless, self-transformation system of linear thermoplastic polyesters into the sustainable cross-linked polymers, vitrimers, is demonstrated. The key is the use of polyesters bearing abundant hydroxyl side groups, which are synthesized via the reaction using dithiol molecules bearing ester units and diepoxy molecules. The polymerization reaction progresses efficiently at relatively low temperature due to the click nature of the thiol-epoxy reaction, which provides the hydroxyl side groups along the polyester chain. The tin catalyst (stannous octoate) is added in the initial polymerization, and the catalyst also works to cross-link the polyesters via intermolecular transesterification bond exchange simply by heating at high temperatures. By adjusting the degrees of cross-linking, the mechanical properties as well as the thermal properties are well tuned. The bond exchange can still be activated in the final cross-linked sample; and thus, the material behaves as vitrimers, exhibiting mechanical recyclability. The application of a new type of hot melt adhesive, where the post-coating tuning/enhancement of adhesion strength is realized, is also demonstrated. On the whole, the present system is very simple but proposes a new application window of bond exchange concept into self-transformation polymers.

Low molecular weight poly((D,L)-lactide-co-caprolactone) liquid inks for diluent-free DLP printing of cell culture platforms.

Digital light processing (DLP) printing offers the possibility of fabricating complex objects in a fast and reproducible manner. A main requirement for DLP printing is the use of inks with low viscosities that can flow under the printing platform in a short period of time. Its exploitation in tissue engineering applications has been centered on the use of hydrogel forming materials diluted in aqueous solutions or the use of polyesters in combination with diluents and heating platforms that aid in the reduction of their viscosity. The use of diluents, however, modifies the mechanical properties and reduces the shape fidelity of the printed objects and, the use of heating platforms results in vats with heterogeneous temperatures and ink viscosities. Here, we report on the synthesis of a library of methacrylated low molecular weight (<3000 g mol-1) homopolymers ((P(D,L)LA and PCL) and copolymers (P((D,L)LA-co-CL)) of 2- and 3-arms based on (D,L)-lactide and ε-caprolactone. The resulting inks possessed low viscosity that made them printable in the absence of diluents and heating elements. DLP printing of cubical and cylindrical patterns resulted in objects with a higher shape fidelity than their counterparts fabricated using diluents and with printed features on the order of 300 μm. The printed materials were biocompatible and supported the growth of human mesenchymal stem cells (hMSCs). Moreover, the variations in the composition resulted in polymers that enabled the attachment of hMSCs to different extents, leading to the formation of well-adhered cell monolayers or loosely adhered cell aggregates.

Polyester-Based Coatings for Corrosion Protection.

The article is the first review encompassing the study and the applications of polyester-based coatings for the corrosion protection of steel. The impact of corrosion and the challenges encountered thus far and the solutions encountered in industry are addressed. Then, the use of polyesters as a promising alternative to current methods, such as phosphating, chromating, galvanization, and inhibitors, are highlighted. The classifications of polyesters and the network structure determine the overall applications and performance of the polymer. The review provides new trends in green chemistry and smart and bio-based polyester-based coatings. Finally, the different applications of polyesters are covered; specifically, the use of polyesters in surface coatings and for other industrial uses is discussed.

Use of Polyesters in Fused Deposition Modeling for Biomedical Applications

In recent years, 3D printing techniques experience a growing interest in several sectors, including the biomedical one. Their main advantage resides in the possibility to obtain complex and personalized structures in a cost-effective way impossible to achieve with traditional production methods. This is especially true for fused deposition modeling (FDM), one of the most diffused 3D printing methods. The easy customization of the final products' geometry, composition, and physicochemical properties is particularly interesting for the increasingly personalized approach adopted in modern medicine. Thermoplastic polymers are the preferred choice for FDM applications, and a wide selection of biocompatible and biodegradable materials is available to this aim. Moreover, these polymers can also be easily modified before and after printing to better suit the body environment and the mechanical properties of biological tissues. This review focuses on the use of thermoplastic aliphatic polyesters for FDM applications in the biomedical field. In detail, the use of poly(ε-caprolactone), poly(lactic acid), poly(lactic-co-glycolic acid), poly(hydroxyalkanoate)s, thermoplastic poly(ester urethane)s, and their blends is thoroughly surveyed, with particular attention to their main features, applicability, and workability. The state-of-the-art is presented and current challenges in integrating the additive manufacturing technology in the medical practice are discussed.

Bioresorbable and Mechanically Optimized Nerve Guidance Conduit Based on a Naturally Derived Medium Chain Length Polyhydroxyalkanoate and Poly(ε-Caprolactone) Blend.

Severe peripheral nerve injuries represent a large clinical problem with relevant challenges such as the development of successful synthetic scaffolds as substitutes to autologous nerve grafting. Numerous studies have reported the use of polyesters and type I collagen-based nerve guidance conduits (NGCs) to promote nerve regeneration through critical nerve defects while providing protection from external factors. However, none of the commercially available hollow bioresorbable NGCs have demonstrated superior clinical outcomes to an autologous nerve graft. Hence, new materials and NGC geometries have been explored in the literature to mimic the native nerve properties and architecture. Here, we report a novel blend of a natural medium chain length polyhydroxyalkanoate (MCL-PHA) with a synthetic aliphatic polyester, poly(ε-caprolactone) (PCL), suitable for extrusion-based high-throughput manufacturing. The blend was designed to combine the excellent ability of PHAs to support the growth and proliferation of mammalian cells with the good processability of PCL. The material exhibited excellent neuroregenerative properties and a good bioresorption rate, while the extruded porous tubes exhibited similar mechanical properties to the rat sciatic nerve. The NGCs were implanted to treat a 10 mm long sciatic nerve defect in rats, where significant differences were found between thin and thick wall thickness implants, and both electrophysiological and histological data, as well as the number of recovered animals, provided superior outcomes than the well-referenced synthetic Neurolac NGC.

Recent advances in aliphatic polyesters for drug delivery applications.

The use of aliphatic polyesters in drug delivery applications has been a field of significant interest spanning decades. Drug delivery strategies have made abundant use of polyesters in their structures owing to their biocompatibility and biodegradability. The properties afforded from these materials provide many avenues for the tunability of drug delivery systems to suit individual needs of diverse applications. Polyesters can be formed in several different ways, but the most prevalent is the ring-opening polymerization of cyclic esters. When used to form amphiphilic block copolymers, these materials can be utilized to form various drug carriers such as nanoparticles, micelles, and polymersomes. These drug delivery systems can be tailored through the addition of targeting moieties and the addition of stimuli-responsive groups into the polymer chains. There are also different types of polyesters that can be used to modify the degradation rates or mechanical properties. Here, we discuss the reasons that polyesters have become so popular, the current research focuses, and what the future holds for these materials in drug delivery applications. WIREs Nanomed Nanobiotechnol 2017, 9:e1446. doi: 10.1002/wnan.1446 For further resources related to this article, please visit the WIREs website.

Evaluating the effects of crystallinity in new biocompatible polyester nanocarriers on drug release behavior

Four new polyesters based on 1,3-propanediol and different aliphatic dicarboxylic acids were used to prepare ropinirole HCl-loaded nanoparticles. The novelty of this study lies in the use of polyesters with similar melting points but different degrees of crystallinity, varying from 29.8% to 67.5%, as drug nanocarriers. Based on their toxicity to human umbilical vein endothelial cells, these aliphatic polyesters were found to have cytotoxicity similar to that of polylactic acid and so may be considered as prominent drug nanocarriers. Drug encapsulation in polyesters was performed via an emulsification/solvent evaporation method. The mean particle size of drug-loaded nanoparticles was 164–228 nm, and the drug loading content was 16%–23%. Wide angle X-ray diffraction patterns showed that ropinirole HCl existed in an amorphous state within the nanoparticle polymer matrices. Drug release diagrams revealed a burst effect for ropinirole HCl in the first 6 hours, probably due to release of drug located on the nanoparticle surface, followed by slower release. The degree of crystallinity of the host polymer matrix seemed to be an important parameter, because higher drug release rates were observed in polyesters with a low degree of crystallinity.

Thermoplastic polyester resins for containers

AbstractAn overview of the use of polyesters for containers is presented. The market for polyethylene terephthalate container resin should reach 760 million pounds by 1989. Diethylene glycol, a polymerization by‐product, and other comonomers reduce the polymer melting point and crystallization tendency, yielding wider container processing latitude. The effect of these modifications on creep and tensile strength is discussed. Improved gaseous barrier approaches and hot‐fillable container opportunities are presented, Newer applications for thermoplastic polyester containers are summarized.