Polyester Backbone Research Articles

Polymerised ionic liquid crystals bearing imidazolium and bipyridinium groups

ABSTRACTNovel kinds of polymerised ionic liquid crystals (PILCs) bearing imidazolium and bipyridinium groups were synthesised and characterised in this work. Some bromo-polyesters were synthesised in an esterification chain reaction using 2,3-dibromosuccinyl dichloride, isophthaloyl chloride and 4,4′-biphenol. The polyester imidazolium bromides (PIBs) and polyester dipyridinium bromides (PDBs) were obtained by a quaternisation reaction between the bromo-polyesters, N-methylimidazole and 4-4′-bipyridine, respectively. The polyester imidazolium tetrafluoroborates (PITs) and polyester dipyridinium tetrafluoroborates (PDTs) were synthesised using the corresponding PIBs and PDBs in an anion-exchange reaction. The chemical structures, liquid crystalline properties and molecular weights of these polymers were characterised by multiple experimental techniques. All the PILCs including PIBs, PDBs, PITs and PDTs display smectic A phase on heating and cooling cycles. The liquid-crystalline properties of bromo-polyesters are influenced by the length of flexible spacer and composition of polyester backbones, while those of PILCs are determined by the ionic groups as additional important influent factors. In comparison with those of the mother bromo-polyesters, the d-spacing of PILCs reduced slightly due to Im+–Br−, Dp+–Br−, Im+–BF4− and Dp+–BF4− ion pairs in the polymer systems. Monocationic imidazolium salts display weaker interionic and intermolecular interaction, higher mobility and lower viscosity than dicationic dipyridinium salts.

Syntheses and thermal properties of polyesters bearing a carbosilane repeating unit

New polyesters bearing a carbosilane repeating unit (–C–Si(CH3)2–C–), 1a and 1b, and reference polyesters with the corresponding carbon-based units 2a and 2b were synthesized and evaluated to study the effect of the carbosilane segment on their thermal properties. DSC analysis revealed that 1a and 1b exhibited glass transition temperatures (Tg) of −72.6 and 11.6 °C, respectively, which were lower than those of 2a and 2b (–53.2 °C for 2a and 63.6 °C for 2b), indicating that the substitution of carbon atoms on polyester backbone with silicone atoms is effective method to change the Tg of polyesters. Furthermore, 1a and 1b showed good thermal stability (Td5 = 304 °C for 1a and 309 °C for 2a). These results indicate that carbosilane segment may be a promising soft segment for developing new polyester-based materials.

Isohexide and Sorbitol-Derived, Enzymatically Synthesized Renewable Polyesters with Enhanced Tg.

Sugar-based polyesters derived from sorbitol and isohexides were obtained via solvent-free enzymatic catalysis. Pendant hydroxyl groups, coming from the sorbitol units, were present along the polyester backbone, whereas the two isohexides, namely, isomannide and isoidide dimethyl ester monomers, were selected to introduce rigidity into the polyester chains. The feasibility of incorporating isomannide as a diol compared to the isoidide dimethyl ester as acyl-donor via lipase-catalyzed polycondensation was investigated. The presence of bicyclic units resulted in enhanced Tg with respect to the parent sorbitol-containing polyester lacking isohexides. The different capability of the two isohexides to boost the thermal properties confirmed the more flexible character provided by the isoidide diester derivative. Solvent-borne coatings were prepared by cross-linking the sugar-based polyester polyols with polyisocyanates. The increased rigidity of the obtained sugar-based polyester polyols led to an enhancement in hardness of the resulting coatings.

Enzyme and pH dual responsive l -amino acid based biodegradable polymer nanocarrier for multidrug delivery to cancer cells

We report a new pH and enzyme dual responsive biodegradable polymer nanocarrier to deliver multiple anticancer drugs at the intracellular compartment in cancer cells. Natural l-aspartic acid was converted into multifunctional monomer and polymerized to yield new classes of biodegradable aliphatic polyester in-build with pH responsiveness. The transformation of side chain BOC urethanes into cationic NH3+ in the acidic endosomal environment disassembled the polymers nanoparticles (pH trigger-1). The biodegradation of aliphatic polyester backbone by esterase enzyme ruptured the nanoassemblies and released the drugs in the cytoplasm (trigger-2). The polymer scaffolds were capable of delivering multiple drugs such as doxorubicin, topotecan, and curcumin (CUR). The cytotoxicity of the nascent and drug-loaded nanoparticles were tested in cervical (HeLa) and breast (MCF-7) cancer cell lines. The nascent polymer nanoscaffolds were found to be nontoxic to cells whereas their drug-loaded nanoparticles exhibited excellent killing. Confocal microscopic images revealed that the drug-loaded polymer nanoparticles were taken up by the cells and the dual degradation process delivered the drugs to nucleus and established the proof-of-concept. The present investigation opens up new platform for l-amino acid based polyester scaffolds, for the first time, in the intracellular drug delivery in cancer treatment. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3279–3293

Primitive Extracellular Lipid Components on the Surface of the Charophytic Alga Klebsormidium flaccidum and Their Possible Biosynthetic Pathways as Deduced from the Genome Sequence.

Klebsormidium flaccidum is a charophytic alga living in terrestrial and semiaquatic environments. K. flaccidum grows in various habitats, such as low-temperature areas and under desiccated conditions, because of its ability to tolerate harsh environments. Wax and cuticle polymers that contribute to the cuticle layer of plants are important for the survival of land plants, as they protect against those harsh environmental conditions and were probably critical for the transition from aquatic microorganism to land plants. Bryophytes, non-vascular land plants, have similar, but simpler, extracellular waxes and polyester backbones than those of vascular plants. The presence of waxes in terrestrial algae, especially in charophytes, which are the closest algae to land plants, could provide clues in elucidating the mechanism of land colonization by plants. Here, we compared genes involved in the lipid biosynthetic pathways of Arabidopsis thaliana to the K. flaccidum and the Chlamydomonas reinhardtii genomes, and identified wax-related genes in both algae. A simple and easy extraction method was developed for the recovery of the surface lipids from K. flaccidum and C. reinhardtii. Although these algae have wax components, their surface lipids were largely different from those of land plants. We also investigated aliphatic substances in the cell wall fraction of K. flaccidum and C. reinhardtii. Many of the fatty acids were determined to be lipophilic monomers in K. flaccidum, and a Fourier transform infrared spectroscopic analysis revealed that their possible binding mode was distinct from that of A. thaliana. Thus, we propose that K. flaccidum has a cuticle-like hydrophobic layer composed of lipids and glycoproteins, with a different composition from the cutin polymer typically found in land plant cuticles.

Understanding the Limitations of the Solvent-Free Enzymatic Synthesis of Sorbitol-Containing Polyesters

Enzymatic catalysis is an attractive approach toward the synthesis of sustainable polyesters, which also provides advantages in terms of selectivity compared to conventional methods. Furthermore, the use of immobilized enzymes allows for solvent-free, ecofriendly polycondensation routes, but also leads to some limitations in terms of applicability to certain systems. A systematic study has been performed on the synthesis of close to linear aliphatic polyesters from biobased, commercially available sorbitol, 1,10-decanediol, and dimethyl adipate. Polycondensation reactions were carried out in the melt using SPRIN liposorb CALB (trade name for the immobilized form of Candida antarctica lipase B) as catalyst, targeting a number-average molecular weight between 4 and 6 kg/mol, and an amount of pendant and terminal hydroxyl groups within the range commonly used for coating applications. The efficacy with which the increasing amounts of sorbitol were built into the polyester backbone was studied in detail via 1...

Incorporating Pendent Fullerenes with High Refractive Index Backbones: A Conjunction Effect Method for High Refractive Index Polymers

To achieve high refractive index polymers (HRIPs), we report here the design and synthesis of four fullerene polyesters (P1–P4), based on the conjunction effect from the high refractive index polyester backbones and pendent fullerene side chains. At sodium D line (589 nm), the refractive indices of the fullerene polyesters are all higher than 1.80, the used believed upper limitation of intrinsic organic polymers. To achieve precise pendent fullerene structure, these polyesters were synthesized via condensation polymerization by a fullerene diol with different aromatic diacyl chlorides, where the diacyl chlorides with high molar refraction increment value moiety were selected by molecular tailoring according to Lorentz–Lorenz equation. The fullerene polyesters are characterized by gel permeation chromatography (GPC), ultraviolet–visible (UV–vis) spectroscopy, and the molecular weights are obtained by a quantitative NMR technique with end-group estimation. The formation of fullerene polyesters is also prove...

Impact of starch content on protein adsorption characteristics in amphiphilic hybrid graft copolymers

Amphiphilic hybrid graft copolymers were synthesized using a graft-to methodology and their protein adsorption profiles studied. Three different hydrophilic side chains were studied: hydroxypropylated high amylose starch, maltodextrin, and polyethylene glycol (PEG). In the high amylose starch compositions, there was a pronounced decrease in protein adsorption with increasing polysaccharide content. As the starch content in the graft copolymers increased from 10wt% to 53wt%, BSA protein adsorption decreased by 83% whereas fibrinogen adsorption was reduced by 40%. Comparisons between the starch-containing hybrid polymers and their respective hydrophobic urethane-linked polyesters were also made. Hybrid 53, containing 53wt% starch, showed a 85% reduction in BSA adsorption and 51% reduction in fibrinogen relative to their urethane-linked polyester backbone controls. Grafting branched high amylopectin-derived maltodextrin to the synthetic polymer backbones also conferred modest protein resistance to the hydrophobic backbone polymer. Lastly, it was found that a high amylose graft structure provided comparable, if not slightly more effective, protein resistance compared to a similarly constructed PEG-containing amphiphilic copolymer.

Novel Disulfide-Containing Poly(β-amino ester)-Functionalised Magnetic Nanoparticles for Efficient Gene Delivery

Poly(β-amino ester)s (PBAEs) have been proved to effectively transfer DNA to various cell types. However, PBAEs with high molecular weights also show considerable toxicities, partly resulting from inadequate degradation of their polyester backbone. In this study, we created novel poly(β-amino ester)s (SF-1, 2, 3, and 4; notation SFs refers to all the four polymers) which were characterised by the cleavable disulfide bonds. Moreover, a new technique, termed magnetofection that uses magnetic nanoparticles to enhance gene expression, has recently been well developed. The negatively charged magnetic nanoparticles (MNPs) with good biocompatibility in vitro were prepared here to subsequently combine with SFs and DNA via electrostatic interaction, leading to the formation of the magnetic gene complexes MNP/SFs/DNA. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and transfection experiments were performed in A549 cells to investigate all the resulting complexes. Studies indicated that the synthesised PBAEs exhibited good biodegradation and regulated release of DNA as a result of the reductive cleavage of the disulfide bonds, giving higher transfection efficiency along with much lower cytotoxicity compared with commercially available transfection agent polyethylenimine (Mw 25 kDa). Furthermore, when MNP was involved at a MNP/DNA weight ratio of 0.5, the magnetic gene complexes MNP/SFs/DNA showed enhanced levels of gene expression while maintaining low cytotoxicity.

O-Carboxyanhydrides: Useful Tools for the Preparation of Well-Defined Functionalized Polyesters.

Over the last ten years, O-carboxyanhydrides (OCA) have attracted increasing attention as ring-opening polymerization (ROP) monomers. They are readily available from α-hydroxyacids and are significantly more reactive than 1,4-dioxane-2,5-diones. Thus, softer catalysts and milder reaction conditions can be used, allowing for a better control of the polymerization. Most attractive are the functionalized OCA that enable the introduction of functional groups along the polyester backbone and thereby vary and finely tune their physicochemical properties. In this viewpoint, the achievements made over the last years are critically overviewed. Particular attention is paid to the different catalytic approaches that have been reported for the ROP of these heterocycles and to the comparison with lactide ROP. In addition, the most representative examples of functionalized polyesters and polymer conjugates prepared from OCA are discussed.

Surface-Functionalized Biodegradable Nanoparticles Consisting of Amphiphilic Graft Polymers Prepared by Radical Copolymerization of 2-Methylene-1,3-Dioxepane and Macromonomers.

Biodegradable polyester-based nanoparticles were prepared by the precipitation of amphiphilic graft copolymers, which were prepared by the ring-opening radical copolymerization of 2-methylene-1,3-dioxepane (MDO) and amphiphilic macromonomers. The diameter of the nanoparticles was controlled by the degree of grafting and the molecular weight of the grafting oligomer. PMDO-g-poly(ethylene glycol) nanoparticles were degraded by the alkaline hydrolysis of the polyester backbone. Although the colloidal stability of nanoparticles was retained due to the reorientation of the PEG chains during hydrolysis, the size of the nanoparticles decreased with increasing hydrolysis time. We also prepared PMDO-g-poly(N-isopropylacrylamide) nanoparticles, which show aggregation in response to increasing temperature.

Thermal stability and degradation of biological terpolyesters over a broad temperature range

ABSTRACTBecause of high susceptibility to thermal degradation during conventional melt processing of poly(3‐hydroxybutyrate) (P3HB) homopolymer, incorporation of a second or third monomer unit in the polyester backbones is expected to reduce the melting temperature and crystallinity, resulting in a controlled thermal degradation with improved stability. In this work, random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxyvalerate) (P3HB3HV4HV) terpolyesters biologically synthesized by Cupriavidus necator were investigated for the thermal stability and degradation over a broad temperature range (100–300°C) in comparison with P3HB homopolyester. The work revealed that below the complete melting point (around 150°C), the terpolyester exhibited a high thermal stability and became an amorphous semisolid suitable for conventional thermal processing. Size exclusion chromatography plus nuclear magnetic resonance analysis was used to examine the thermal degradation products and the vulnerability of different monomer units at high temperatures (240–290°C). We found that 3HV unit in P3HB3HV4HV copolymers was more vulnerable to thermal degradation than 3HB unit under air. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41715.

Optimization of enzymatic ring-opening copolymerizations involving δ-gluconolactone as monomer by experimental design

Abstract Enzymatic incorporation of carbohydrate-derived monomer units into hydrophobic polyester backbones represents a promising alternative to obtain new biodegradable oligomers and polymers. Immobilized lipases are efficient biocatalysts for copolymerization of β-butyrolactone and δ-gluconolactone, but only a systematic optimization study was able to highlight the influence of the main reaction parameters on the polymerization degree and on the relative copolymer content of the product. Therefore, experimental design was employed for determination of the optimal ring-opening copolymerization conditions in solventless reaction systems, at temperatures up to 80 °C. The obtained products, cyclic and linear polyesters, have been characterized by FT-IR, MALDI-TOF MS, NMR, and TG analysis, demonstrating the incorporation of gluconolactone unit(s) into the hydrophobic backbone of the polyester and the formation of new bio-based products.

Thermoresponsive poly(ϵ-caprolactone)-graft-poly(N-isopropylacrylamide) graft copolymers prepared by a combination of ring-opening polymerization and sequential azide-alkyne click chemistry

A straightforward strategy is described to synthesize poly(ϵ-caprolactone)-graft-poly(N-isopropylacrylamide) (PCL-g-PNIPAAm) amphiphilic graft copolymers consisting of potentially biodegradable polyester backbones and thermoresponsive grafting chains. PCL with pendent chlorides was prepared by ring-opening polymerization, followed by conversion of the pendent chlorides to azides. Alkyne-terminated PNIPAAm was synthesized by atom transfer radial polymerization. Then, the alkyne end-functionalized PNIPAAm was grafted onto the PCL backbone by a copper-catalyzed azide–alkyne cycloaddition. PCL-g-PNIPAAm graft copolymers self-assembled into spherical micelles comprised of PCL cores and PNIPAAm coronas. The critical micelle concentrations of the graft copolymers were in the range 7.8–18.2 mg L−1, depending on copolymer composition. Mean hydrodynamic diameters of micelles were in the range 65–135 nm, which increased as the length of grafting chains grew. PCL-g-PNIPAAm micelles were thermosensitive and aggregated upon heating. © 2014 Society of Chemical Industry

Preparation of Polyesteramides in a Reactive Extrusion Process

The synthesis of poly(ϵ‐caprolactone‐co‐ϵ‐caprolactam) copolymers using reactive extrusion is reported. The copolymers are prepared by anionic ring‐opening polymerization of ϵ‐caprolactam in polycaprolactone melt in a twin‐screw microcompounder using masterbatches of sodium caprolactamate and hexamethylene‐1,6‐dicarbamoylcaprolactam in ϵ‐caprolactam as initiator and activator, respectively. The monomer conversion is found to be almost quantitative. The extrudates possess polyester backbones with integrated short polyamide fragments, forming co‐existing polyamide and polyester crystals. The polyester crystallinity index is quite low and rather constant, whereas the content of the polyamide α‐ and γ‐phases varies with the copolymer composition and initiator/activator concentration.

Organocatalytic ring-opening polymerization of morpholinones: new strategies to functionalized polyesters.

The oxidative lactonization of N-substituted diethanolamines with the Pd catalyst [LPd(OAc)]2(2+)[OTf(-)]2 generates N-substituted morpholin-2-ones. The organocatalytic ring-opening polymerization of N-acyl morpholin-2-ones occurs readily to generate functionalized poly(aminoesters) with N-acylated amines in the polyester backbone. The thermodynamics of the ring-opening polymerization depends sensitively on the hybridization of the nitrogen of the heterocyclic lactone. N-Acyl morpholin-2-ones polymerize readily to generate polymorpholinones, but the N-aryl or N-alkyl substituted morpholin-2-ones do not polymerize. Experimental and theoretical studies reveal that the thermodynamics of ring opening correlates to the degree of pyramidalization of the endocyclic N-atom. Deprotection of the poly(N-Boc-morpholin-2-one) yields a water-soluble, cationic polymorpholinone.

Cross-linked degradable poly(β-thioester) networks via amine-catalyzed thiol-ene click polymerization

A set of binary and ternary biodegradable cross-linked poly(β-thioester) networks have been synthesized via thiol-ene Michael additions, by reacting combinations of dithiols, diacrylates and multifunctional cross-linkers. Insoluble binary thermoset networks and soluble ternary branched polymers with broad molar mass distributions are obtained in a facile manner after polymerization at room temperature for only few minutes. The networks display excellent thermal stability up to 250 °C and exhibit low glass transition temperatures. The soluble branched polymers show degradation of the polyester backbone upon chemical degradation by acidic and basic solutions. Finally, the (bio)degradability of ternary PBT polymer films is examined via quartz crystal microbalance measurements. Weight loss is measured as a function of time upon exposure to phosphate buffers at different pH. PBTs carrying apolar chain segments display surface degradation, while PBTs with more polar ethylene glycol segments allow for swelling in aqueous solution, which is reflected in concomitant surface and bulk degradation of the materials. Because of their biodegradability, these easy to synthesize poly(β-thioesters) networks are considered to be suitable candidates to use in future biomedical or ecological applications.

Trigger-responsive, fast-degradable poly(β-amino ester)s for enhanced DNA unpackaging and reduced toxicity

Poly(β-amino ester)s (PBAEs) represent an important class of cationic gene delivery materials which, however, suffer from uncontrolled DNA release due in part to the slow degradation of their polyester backbone. Additionally, PBAEs with high molecular weight (MW) also show considerable toxicities. In this study, we designed and developed PBAEs with trigger-responsive domains built-in polymer backbones that can be rapidly cleaved upon external UV light triggering to promote intracellular DNA release as well as reduce material toxicity. Photo-responsive PBAEs were prepared via polyaddition of (2-nitro-1,3-phenylene)bis(methylene) diacrylate and a bifunctional amine. The nitrobenzene moiety was placed in each repeating unit of the PBAE to allow fast response to external UV irradiation, and thus the ester linkers were cleaved and the polymers were degraded within several minutes upon UV irradiation. Cationic PBAEs with high MWs were able to mediate effective intracellular gene delivery, while upon UV irradiation post-transfection, enhanced DNA unpackaging and reduced material toxicity were observed, which collectively contributed to greatly improved transfection efficiencies in various mammalian cell types tested. This strategy allows precise manipulation of material toxicity and gene release profiles of PBAEs, and thus provides an effective design approach to address critical issues in non-viral gene delivery.

Renewable polyesters derived from 10-undecenoic acid and vanillic acid with versatile properties

A series of renewable polyesters were synthesized derived from 10-undecenoic acid and vanillic acid. An outstanding feature is that the incorporation of vanillic acid segments into the polyester backbone results in improved mechanical properties.

Lipase-catalyzed synthesis of azido-functionalized aliphatic polyesters towards acid-degradable amphiphilic graft copolymers

A series of novel aliphatic polyesters with azido functional groups were synthesized via the direct lipase-catalyzed polycondensation of dialkyl diester, diol and 2-azido-1,3-propanediol (azido glycerol) using immobilized lipase B from Candida antarctica (CALB). The effects of polymerization conditions including reaction time, temperature, enzyme amount, substrates and monomer feed ratio on the molecular weights of the products were studied. The polyesters with pendant azido groups were characterized by (1)H NMR, (13)C NMR, 2D NMR, FTIR, GPC and DSC. Alkyne end-functionalized poly(ethylene glycol) containing a cleavable acetal group was then grafted onto the polyester backbone by copper-catalyzed azide-alkyne cycloaddition (CuAAC, click chemistry). Using fluorescence spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM), these amphiphilic graft copolymers were found to readily self-assemble into nanosized micelles in aqueous solution with critical micelle concentrations between 0.70 and 1.97 mg L(-1), and micelle sizes from 20-70 nm. The degradation of these polymers under acidic conditions was investigated by GPC and (1)H NMR spectroscopy. Cell cytotoxicity tests indicated that the micelles had no apparent cytotoxicity to Bel-7402 cells, suggesting their potential as carriers for controlled drug delivery.