High Molecular Weight Polyesters Research Articles

Synthesis of long-chain aliphatic poly(β-thioester)s via thiol-Michael polyaddition and their applications in noble metal recovery and information encryption

Long-chain aliphatic polyesters are recognized as the most promising polyethylene mimics in that these materials show comparative physicochemical properties to polyolefins and own the unique merits of degradability and/or recyclability. Nevertheless, the application scenarios of these polymers are rather limited owing to the lack of functional groups. Herein, sulfur atoms are incorporated into the microstructures of long-chain aliphatic polyesters to decipher the variations of physicochemical properties upon replacing specific methylene units by thioether moieties and simultaneously impart polyethylene-like materials with functionalities. First of all, high molecular weight polyesters P1-P4 and poly(β-thioester)s P5-P8 were obtained via condensation polymerization and thiol-Michael polyaddition, respectively. As for phase transition behaviors, poly(β-thioester)s show inferior crystallization/melting temperatures and the corresponding enthalpy changes than their polyester counterparts, and a loosely packed crystalline structure should be responsible for such thermal property degradation. It is reasonable that replacing specific methylene units of long-chain aliphatic polyesters by sulfur atoms, the much bulkier functional entities, will definitely cause great disturbance to the regular arrangement of polymer chains. The rapid hydrolytic degradation of poly(β-thioester)s in acidic and alkaline media can be ascribed to the easy penetration of water molecules into their incompact amorphous/crystalline regions. In the meantime, these poly(β-thioester)s exhibit great prospects in noble metal recovery and information encryption (optical anticounterfeiting). For instance, poly(β-thioester) P5 is an excellent adsorbent to abstract gold ions from water due to its outstanding metal coordination capability. Moreover, poly(β-thioester) P5 emits bright blue photoluminescence in concentrated solution and solid state upon UV irradiation as a result of the clustering-triggered through space electron delocalization and rigidified polymer chain conformation.

Highly active aggregate catalysts for the synthesis of high-molecular-weight polyesters via copolymerization of epoxides and cyclic anhydrides

Aggregate catalysts efficiently produce high molecular weight polyesters and exhibit high activity and low concentration tolerance in the copolymerization of epoxides and cyclic anhydrides.

Synthesis of High Molecular Weight Biobased Aliphatic Polyesters Exhibiting Tensile Properties Beyond Polyethylene.

Synthesis of high molecular weight polyesters prepared by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enoate) with isosorbide (M1), isomannide (M2), and 1,3-propanediol (M3) and the subsequent hydrogenation have been achieved by using a molybdenum-alkylidene catalyst. The resultant polymers (P1) prepared by the ADMET polymerization of M1 (in toluene at 25 °C) possessed high Mn values (Mn = 44400-49400 g/mol), and no significant differences in the Mn values and the PDI (Mw/Mn) values were observed in the samples after the hydrogenation. Both the tensile strength and the elongation at break in the hydrogenated polymers from M1 (HP1) increased upon increasing the molar mass, and the sample with an Mn value of 48200 exhibited better tensile properties (tensile strength of 39.7 MPa, elongation at break of 436%) than conventional polyethylene, polypropylene, as well as polyester containing C18 alkyl chains. The tensile properties were affected by the diol segment employed, whereas HP2 showed a similar property to HP1.

Preparation of high‐performance polyurethane elastomers via direct use of alcoholyzed waste PET by high molecular weight polyester diols

AbstractProducts obtained by alcoholysis of waste PET are promising raw materials for the synthesis of polyurethane elastomers (PUEs). Alcoholysis of PET by low molecular weight diols such as ethylene glycol yields low molecular weight products. The latter need to be polymerized to high molecular weight polyols which are subsequently used as soft segments for the synthesis of PUEs. This work aims to look for suitable high molecular weight diols for the alcoholysis of waste PET to yield high molecular weight products which can be directly used as soft segments for the synthesis of PUEs. This approach allows to save the polymerization step for the formation of high molecular weight polyols. Specifically, polyester diols such as polycaprolactone diol (Mn = 2000) were used for the alcoholysis of waste PET. The resulting PUEs exhibited very good mechanical properties: a tensile strength of up to 40.95 MPa, an elongation at break of up to 1219%, and a toughness of up to 237 MJ·m−3, along with good transparency and thermal stability.

Melt Polycondensation Strategy for Amide-Functionalized l-Aspartic Acid Amphiphilic Polyester Nano-assemblies and Enzyme-Responsive Drug Delivery in Cancer Cells.

Aliphatic polyesters are intrinsically enzymatic-biodegradable, and there is ever-increasing demand for safe and smart next-generation biomaterials including drug delivery nano-vectors in cancer research. Using bioresource-based biodegradable polyesters is one of the elegant strategies to meet this requirement; here, we report an l-amino acid-based amide-functionalized polyester platform and explore their lysosomal enzymatic biodegradation aspects to administrate anticancer drugs in cancer cells. l-Aspartic acid was chosen and different amide-side chain-functionalized di-ester monomers were tailor-made having aromatic, aliphatic, and bio-source pendant units. Under solvent-free melt polycondensation methodology; these monomers underwent polymerization to yield high molecular weight polyesters with tunable thermal properties. PEGylated l-aspartic monomer was designed to make thermo-responsive amphiphilic polyesters. This amphiphilic polyester was self-assembled into a 140 ± 10 nm-sized spherical nanoparticle in aqueous medium, which exhibited lower critical solution temperature at 40-42 °C. The polyester nano-assemblies showed excellent encapsulation capabilities for anticancer drug doxorubicin (DOX), anti-inflammatory drug curcumin, biomarkers such as rose bengal (RB), and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt. The amphiphilic polyester NP was found to be very stable under extracellular conditions and underwent degradation upon exposure to horse liver esterase enzyme in phosphate-buffered saline at 37 °C to release 90% of the loaded cargoes. Cytotoxicity studies in breast cancer MCF 7 and wild-type mouse embryonic fibroblasts cell lines revealed that the amphiphilic polyester was non-toxic to cell lines up to 100 μg/mL, while their drug-loaded polyester nanoparticles were able to inhibit the cancerous cell growth. Temperature-dependent cellular uptake studies further confirmed the energy-dependent endocytosis of polymer NPs across the cellular membranes. Confocal laser scanning microscopy assisted time-dependent cellular uptake analysis directly evident for the endocytosis of DOX loaded polymer NP and their internalization for biodegradation. In a nutshell, the present investigation opens up an avenue for the l-amino acid-based biodegradable polyesters from l-aspartic acids, and the proof of concept is demonstrated for drug delivery in the cancer cell line.

Rare Earth Metal‐Containing Ionic Liquid Catalysts for Synthesis of Epoxide/Cyclic Anhydride Copolymers

AbstractThe perfectly alternating ring‐opening copolymerization of epoxides and cyclic anhydrides has been an emerging route to diverse polyesters. Simple catalysts have been targeted for this polymerization to decrease the cost and air‐sensitivity of the catalysis. This report improves upon the recently reported YCl3 ⋅ 6H2O/[PPN]Cl (bis(triphenylphosphine)iminium chloride) binary catalyst system, which shows fast rates of polymerization but suffers from low molecular weights due to the presence of many water chain transfer agents. In this study, use of a phosphonium chloride ionic liquid as both the cocatalyst and solubilizing agent for the metal salt to form a metal‐containing ionic liquid (MIL) leads to polymerization of high molecular weight polyesters at significantly faster rates than the original system. The identity of the ionic liquid, dryness of MIL, and synthetic prep of the MIL were all found to have a greater impact on the polymerization rate than the metal choice.

Study on Properties and Degradation Behavior of Poly (Adipic Acid/Butylene Terephthalate-Co-Glycolic Acid) Copolyester Synthesized by Quaternary Copolymerization

At present, the development and usage of degradable plastics instead of traditional plastics is an effective way to solve the pollution of marine microplastics. Poly (butylene adipate-co-terephthalate) (PBAT) is known as one of the most promising biodegradable materials. Nevertheless, the degradation rate of PBAT in water environment is slow. In this work, we successfully prepared four kinds of high molecular weight polyester copolyesters (PBATGA) via quaternary copolymerization. The results showed that the intrinsic viscosity of PBATGA copolymers ranged from 0.74 to 1.01 dL/g with a glycolic acid content of 0-40%. PBATGA copolymers had excellent flexibility and thermal stability. The tensile strength was 5~40 MPa, the elongation at break was greater than 460%, especially the elongation at break of PBATGA10 at 1235%, and the thermal decomposition temperature of PBATGA copolyesters was higher than 375 °C. It was found that PBATGA copolyester had a faster hydrolysis rate than PBAT, and the weight loss of PBATGA copolymers showed a tendency of pH = 12 > Lipase ≈ pH = 7 > pH = 2. The quaternary polymerization of PBAT will have the advantage of achieving industrialization, unlike the previous polymerization process. In addition, the polymerization of PBATGA copolyesters not only utilizes the by-products of the coal chemical industry, but also it can be promising in the production of biodegradable packaging to reduce marine plastic pollution.

Overcoming the low reactivity of biobased, secondary diols in polyester synthesis

Shifting away from fossil- to biobased feedstocks is an important step towards a more sustainable materials sector. Isosorbide is a rigid, glucose-derived secondary diol, which has been shown to impart favourable material properties, but its low reactivity has hampered its use in polyester synthesis. Here we report a simple, yet innovative, synthesis strategy to overcome the inherently low reactivity of secondary diols in polyester synthesis. It enables the synthesis of fully biobased polyesters from secondary diols, such as poly(isosorbide succinate), with very high molecular weights (Mn up to 42.8 kg/mol). The addition of an aryl alcohol to diol and diacid monomers was found to lead to the in-situ formation of reactive aryl esters during esterification, which facilitated chain growth during polycondensation to obtain high molecular weight polyesters. This synthesis method is broadly applicable for aliphatic polyesters based on isosorbide and isomannide and could be an important step towards the more general commercial adaption of fully biobased, rigid polyesters.

Ring-Opening Polymerization of a Bicyclic Lactone: Polyesters Derived from Norcamphor with Complete Chemical Recyclability.

Chemical recycling of polymers is an elegant approach to achieve a circular economy and address the sustainability and end-of-life issues of plastics. Herein, we report the ring-opening polymerization of a bicyclic lactone that is easily accessible from norcamphor. High molecular weight polyesters (Mn up to 164 kg mol-1) are obtained using ZnEt2 as catalyst, while the polymerizability of the monomer is good even at high temperatures. More importantly, the polymers can be completely depolymerized under thermolysis conditions to selectively recover the pristine monomer. Thus, the monomer design strategy of using ring-fused/hybridized lactones enables an innovative monomer-polymer system that shows both high polymerizability and high depolymerizability.

Comparison of accelerated and enzyme-associated real-time degradation of HMW PLLA and HMW P3HB films

Designing laboratory-scale degradation experiments for polymer-based biomaterials is crucial for the development of safe and functional implants, in particular regarding high molecular weight polyesters. Within this work, we compared accelerated degradation of solvent cast HMW-PLLA and HMW-P3HB films at 55 °C (16 weeks) with enzyme-associated (proteinase K and lipases) real-time degradation at 37 °C (108 weeks). During real-time degradation, PLLA showed mass loss up to 83%, in contrast to accelerated conditions, where no changes occurred. Moreover, we observed wave-shape development of crystallinity for PLLA and PHB for both degradation conditions applied, whereby PLLA χ value nearly doubled to up to 75%. These results were used to develop a correlation model based on molecular weight decrease and were furthermore discussed in light of a detailed literature review. In summary, real-time in vitro studies could be adapted to accelerated protocols providing the same limiting conditions such as molecular weight and initial crystallinity are given.

Simple yttrium salts as highly active and controlled catalysts for the atom-efficient synthesis of high molecular weight polyesters.

The ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides is a promising route to sustainable aliphatic polyesters with diverse mechanical and thermal properties. Here, simple yttrium chloride salts (YCl3THF3.5 and YCl3·6H2O), in combination with a bis(triphenylphosphoranylidene)ammonium chloride [PPN]Cl cocatalyst, are used as efficient and controlled catalysts for ten epoxide and anhydride combinations. In comparison to past literature, this simple salt system exhibits competitive turn-over frequencies (TOFs) for most monomer pairs. Despite no supporting ligand framework, these salts provide excellent control of dispersity, with suppression of side reactions. Using these catalysts, the highest molecular weight reported to date (302.2 kDa) has been obtained with a monosubstituted epoxide and tricyclic anhydride. These data indicate that excellent molecular weight control and suppression of side reactions for ROCOP of epoxides and cyclic anhydrides can coincide with high activity using a simple catalytic system, warranting further research in working towards industrial viability.

Green enzymatic synthesis and processing of poly (cis-9,10-epoxy-18-hydroxyoctadecanoic acid) in supercritical carbon dioxide (scCO2)

• Use of a green and sustainable synthetic strategy to CHA-based polyesters. • Low temperature (35–55 °C) polycondensation in scCO 2 achieved. • The valuable epoxy groups of the monomers were preserved. • Our process led to reasonably high molecular weight polyesters. There is significant potential for industrial use of renewables for a wide range of materials demanded by society. Plants, trees and algae are increasingly attracting attention as sustainable sources for functionalised and polymerizable building blocks. In particular, the outer bark of the birch tree ( Betula pendula ) is a side stream of the forestry industry with so far very little utilisation besides energy recovery. It is composed of a macromolecular network, suberin, that could provide a renewable, low cost and competitive resource. Within raw suberin is the potentially very useful multifunctional extract cis -9,10-epoxy-18-hydroxyoctadecanoic acid (CHA). Our drive has been to develop a green and sustainable synthetic strategy to CHA-based polyesters, by exploiting supercritical carbon dioxide (scCO 2 ) as a reaction medium and leveraging the regio- and chemo-selective properties of the biocatalyst Novozym 435 (Lipase B). Low temperature (35–55 °C) polycondensation in scCO 2 shows significant advantages compared to traditional polymerisation methods leading to reasonably high molecular weight polyesters. The mild synthetic conditions also preserve the valuable epoxy groups of the CHA which we show can be exploited by post-polymerisation functionalisation to create sustainable resins for bio-renewable coatings.

Polymer Chemistry Applications of Cyrene and its Derivative Cygnet 0.0 as Safer Replacements for Polar Aprotic Solvents.

This study explores a binary solvent system composed of biobased Cyrene and its derivative Cygnet 0.0 for application in membrane technology and in biocatalytic synthesis of polyesters. Cygnet‐Cyrene blends could represent viable replacements for toxic polar aprotic solvents. The use of a 50 wt % Cygnet‐Cyrene mixture makes a practical difference in the production of flat sheet membranes by nonsolvent‐induced phase separation. New polymeric membranes from cellulose acetate, polysulfone, and polyimide are manufactured by using Cyrene, Cygnet 0.0, and their blend. The resultant membranes have different morphology when the solvent/mixture and temperature of the casting solution change. Moreover, Cyrene, Cygnet 0.0, and Cygnet‐Cyrene are also explored for substituting diphenyl ether for the biocatalytic synthesis of polyesters. The results indicate that Cygnet 0.0 is a very promising candidate for the enzymatic synthesis of high molecular weight polyesters.

Synthesis and characterization of biphenyl polyesters derived from divanillic acid and cyclic diols

This work synthesized a series of symmetrical methylated dialkoxydivanillic acid monomers (Me-RDVAs) with different side-chain lengths (meaning the number of carbons, n, in alkoxy groups, where n = 1, 2, 3 or 4) and methyl (Me), ethyl, propyl or butyl R groups. Homopolyesters were obtained from Me-RDVAs and 1,4-benzenedimethanol, 1,4-cyclohexanedimethanol and 4,4ʹ-biphenyldimethanol, with the aim of producing improved thermal properties. Copolyesters composed of Me-MeDVA together with aliphatic linear diols and cyclic diols were also synthesized. The weight average molecular weights of the resulting polyesters ranged from 1.5 to 11.0 × 104 g/mol and all were thermally stable. Glass transition temperatures varied from 58 to 134 °C. A semi-crystalline polyester with a high melting point of 220 °C was obtained from Me-MeDVA and trans-1,4-cyclohexanedimethanol, and was assessed using polarized optical microscopy and one-dimensional wide-angle X-ray diffraction. Self-standing films of several high molecular weight polyesters were prepared and their mechanical properties assessed.

Synthesis of medical grade PLLA, PDLLA, and PLGA by a reactive extrusion polymerization

Due to their biodegradability and biocompatibility, aliphatic polyesters received a considerable attention for a wide range of applications, in particular in medical and pharmaceutical fields. Aliphatic polyesters are usually synthesized by ring opening polymerization in a batch mode. In this work, a reactive extrusion polymerization was optimized to synthesise in a continuous way poly-l-lactide, poly-d,l-lactide, and poly-d,l-lactide-co-glycolide 50:50. A lab scale co-rotating twin screw extruder adapted for pharmaceutical products and medical devices was used after optimizing the geometry of screws and barrel. Polymerization was conducted in the presence of tin(II) 2-ethylhexanoate as catalyst and a monohydroxylated polyethylene glycol as initiator. The optimized procedure allowed producing high molecular weight polyesters (Mn in the range [15−100 kDa]) in a controlled way on a time scale of some minutes, with a capacity of at least 100 g/h and with monomer residues lower than 5%. Comparison of macromolecular features and thermal properties of the resulting polyesters of different Mn with those prepared in a batch process allowed concluding to the similarity of these materials. Reactive extrusion polymerization represents therefore a very attractive methodology to produce in a continuous, rapid and robust way aliphatic polyesters suitable for a wide range of pharmaceutical, medical or nowadays applications.

Physical and mechanical properties of polymer nanocomposites of penton - carbon nanotubes system

The work is dedicated to the solution of an important task - the creation and study of new polymer compositions, which, unlike traditional polymeric materials, are characterized by polyfunctionality and high performance characteristics.Over the past few decades, among nanofillers, considerable attention has been paid to carbon nanotubes (CNTs) due to their special mechanical and thermal properties, geometric parameters, low mass density and their inherent electrical properties. As a polymer matrix for studying systems with an active interaction of components, it is proposed to use polymers that are capable of crystallization and include polar groups. A typical representative of such polymers is the high molecular weight polyester - penton. Such composite systems are favorably distinguished by the presence of two phase instabilities in the temperature range under study, namely, the melting of the crystalline phase and the glass transition of the amorphous component of the polymer matrix, which will provide more complete and deeper information about the mutual influence of the components of such systems. The ultrasonic method has been used for experimental study of the acoustic properties and structure of polymer nanocomposites of the penton - carbon nanotubes system. An analysis of the studied concentration dependences of the characteristics at frequencies of 5, 7.5, and 10 MHz indicates a strong character of the interaction between the penton - CNT system components. The research results indicate that the ultrasound velocity in filled systems in the entire studied concentration region is significantly higher than for an unfilled penton, and for thecarbon nanotubesfilled penton, a significant increase in the elasticity of the composite compared with an unfilled polymer matrix takes place. Obviously, this can occur due to a significant change in the structure of the polymer component of the system and the formation of an interfacial layer around the CNT with a more ordered structure respectively to pure penton. Additional information is provided by the dependences of the “jump” of the absorption coefficient on the frequency and the dependences of the tangent of the angle of mechanical losses (tgδ), which indicate that the size of carbon nanotube aggregates in the penton matrix as an obstacle to a mechanical wave is much smaller than the size of the penton particles, and the constancy of all studied characteristics when the concentration of CNTs φ ≈ 0.3 vol. % indicates the transition of the penton at this concentration to the state of the wall layer.

High Molecular Weight Polyester Obtained by Polymerization of Dimethylketene Using Metallocene Initiators: A Step toward Ziegler-Natta Supporting Application in Non-Olefin Systems.

In this report, highly active metallocene initiators are used for the polymerization of a ketene monomer, dimethylketene, which typically contains two adjacent double bonds (R2 CCO). By using the methylzirconocene methyltriarylborate complex (Cp2 ZrMe+ MeB(C6 F5 )3 - ) as the activation system, associated with the possible cleavage of CC and CO bonds in ketene monomers, a structure-specific and high-molecular-weight polyester ( > 300 000 g mol-1 ) can be afforded. The resulting polyester structure, comprehensively characterized by NMR, indicates a significant reactive selectivity of the "bent-sandwich" cationic site Cp2 ZrMe+ . It reveals that the positively charged zirconium (Zr+ ) prefers to coordinate with a negatively charged oxygen (O- ) when it is already bonded to the carbon, while a negatively charged carbon (C- ) will be assigned in priority if the oxygen-zirconium bond exists. This report allows for broadening the application field of metallocene initiators in non-olefin reactions and deepening our insight into the mechanism of the living insertion/Ziegler-Natta polymerization.

Metal-free Lewis pair catalyst synergy for fully alternating copolymerization of norbornene anhydride and epoxides: Biocompatible tests for derived polymers

Synthesis of high molecular weight alternating copolymers from epoxides and norbornene anhydride via metal-free catalyst remains a challenge in aliphatic biodegradable polyester synthesis. Metal-free Lewis pair catalyst system, consisting of Lewis acid B(C2H5)3 (triethylborane) and a Lewis base DMAP (4-dimethylaminopyridine); TBD (1, 5, 7-triazabicyclo[4.4.0]dec-5-ene) and DBU (1,8 diazabicyclo[5.4.0]undec-7-ene) as a cooperative catalyst system for fully alternating polyesters synthesis is described here. By using these simple systems we have obtained, high molecular weight (Mn = 2–31.5 kDa) polyesters with narrow molecular weight distributions (MWD’s = 1.948–1.069) via ring-opening alternating copolymerisation (ROAC) of various epoxides (e.g. CHO, cyclohexene oxide; PO, propylene oxide; tBGE, tert-butyl glycidyl ether and PGE, phenyl glycidyl ether) with cis-5 norbornene-endo 2, 3 dicarboxylic anhydride (NB). Furthermore, we demonstrated that these polyesters are biocompatible in nature when tested on human embryonic kidney cells (HEK-293) showing more than 80% cell viability in 72 h and can be used for different biological applications such as drug delivery, tissue engineering or anti-microbial polymeric coatings on biomedical devices. The use of these green functional polyesters for biological studies was realized for the first time by a metal-free Lewis pair approach.

Novel controllable degradation behavior and biocompatibility of segmented poly–ε–caprolactone in rats

Bioresorbable polymers have multiple clinical applications; however, the reaction methods required for their synthesis generally require harsh reaction conditions and long reaction times. This study uses a new conceptual molecular control method that links poly–ε–caprolactone (PCL) diols of differing molar mass with an aliphatic diisocyanate as a coupling agent for polymerization to develop a new type of segmented polycaprolactone (SM-PCL) material. Relative to the polymerization of typical high molecular weight polyester materials, this polymerization process only requires ordinary pressure and low temperature to yield product with sufficiently high molecular weight. The results of in vitro cytotoxicity and in vivo implantation assays show that the newly synthesized SM-PCL exhibits excellent biocompatibility. In addition, in vivo degradation analyses demonstrate that the porous SM-A material was nearly completely degraded at 6 months after implantation in rat tissue (P < 0.01), whereas porous PCL homopolymer was only degraded to 53.25% of the initial molecular weight even after 12 months. The study indicated that the degradation rates of porous and solid thin film SM-PCL were higher than those of PCL homopolymer and that its degradation behavior could be controlled. Moreover, the material did not result in significant adverse pathological reactions and has good tissue compatibility. For clinical application, this material may therefore be suitable as a carrier for controlled drug release or as an artificial material for soft tissue repair.

1,3-Propanediol and its Application in Bio-Based Polyesters for Resin Applications

Polyester resins are important raw materials for a myriad of applications especially in the field of coatings and radical curing polymers, such as wood and powder coatings, molding compounds, and UV-curing applications. In addition, polyols derived from polyester resins are precursors for the synthesis of polyurethanes and polycarbonates. Besides dicarboxylic acid, diols are used as monomers in these polyesters. To date most of the diols utilized are derived from petrochemical feedstock. To increase the bio-based content of polyester resins, novel diols derived from renewable resources are of special interest. In this respect, 1,3-propanediol has drawn considerable attention over the last years. It is accessible via microbial fermentation of glucose from starch at a competitive price in sufficient amounts. Therefore, 1,3-propanediol could be a valuable alternative to petrochemical diols, such as 1,6-hexanediol and neopentylglycol, which are currently used as diols in most resin applications. This article gives a brief overview over the utilization of 1,3-propanediol in high molecular weight polyesters for plastic application followed by a more detailed discussion of the most relevant work in the field of polyester resins derived from 1,3-propanediol.