Synthesis and catalytic activity of single-site group V alkoxide complexes for the ring-opening polymerization of ε-caprolactone

The synthesis, characterization, and ring-opening polymerization (ROP) activity of a family of niobium and tantalum alkoxide catalysts was studied. The final catalysts are made in a two-step synthesis, first by reacting the desired homoleptic metal ethoxide with a phenolketoimine ligand to form a series of synthetic intermediates, followed by reaction with catechol to produce a catalytic platform with a single ethoxide initiator. By using two separate ligands, the electronic properties of the catalyst can be tuned, and the molecular weight of the polymer can be increased. It was found that synthetic intermediates adopted a mer geometry both in solution and in the solid state. This mer geometry was retained for the final catechol derivatives, however in one case, where catechol was substituted for 3-methoxycatechol, the molecule adopted a highly distorted fac geometry. Catalytic ROP activity of the synthetic intermediates and final catechol derivatives with ε-caprolactone was studied through a kinetic analysis. In all seven cases studied the reactions proceeded through the expected coordination-insertion mechanism, following pseudo first-order kinetics and increasing in Mn linearly vs. conversion. The single-initiator catechol derivatives increased the Mn by three times compared to that of the three-initiator synthetic intermediates with little decrease in the overall reaction rate. Both the nature of the ligand and metal were found to impact the rate of reaction in these systems. By switching from an electron donating ligand to an electron withdrawing ligand, the rate was found to nearly double. Tantalum species were faster than their niobium counterparts by ∼3 times in the synthetic intermediates and ∼1.5 times in the catechol derivatives. This observed periodicity supports recent literature findings in this area.

Using Redox-Switchable Polymerization Catalysis to Synthesize a Chemically Recyclable Thermoplastic Elastomer

In an effort to synthesize chemically recyclable thermoplastic elastomers, a redox-switchable catalytic system was developed to synthesize triblock copolymers containing stiff poly(lactic acid) (PLA) end blocks and a flexible poly(tetrahydrofuran-co-cyclohexene oxide) (poly(THF-co-CHO) copolymer as the mid-block. The orthogonal reactivity induced by changing the oxidation state of the iron-based catalyst enabled the synthesis of the triblock copolymers in a single reaction flask from a mixture of monomers. The triblock copolymers demonstrated improved flexibility compared to poly(l-lactic acid) (PLLA) and thermomechanical properties that resemble thermoplastic elastomers, including a rubbery plateau in the range of -60 to 40 °C. The triblock copolymers containing a higher percentage of THF versus CHO were more flexible, and a blend of triblock copolymers containing PLLA and poly(d-lactic acid) (PDLA) end-blocks resulted in a stereocomplex that further increased polymer flexibility. Besides the low cost of lactide and THF, the sustainability of this new class of triblock copolymers was also supported by their depolymerization, which was achieved by exposing the copolymers sequentially to FeCl3 and ZnCl2 /PEG under reactive distillation conditions.

All-Polyhydroxyalkanoate Triblock Copolymers via a Stereoselective-Chemocatalytic Route

Biodegradable polyhydroxyalkanoate (PHA) homopolymers and statistical copolymers are ubiquitous in microbially produced PHAs, but the step-growth polycondensation mechanism the biosynthesis operates on presents a challenge to access well-defined block copolymers (BCPs), especially higher-order tri-BCP PHAs. Here we report a stereoselective-chemocatalytic route to produce discrete hard-soft-hard ABA all-PHA tri-BCPs based on the living chain-growth ring-opening polymerization of racemic (rac) 8-membered diolides (rac-8DL^R; R denotes the two substituents on the ring). Depending on the composition of the soft B block, originated from rac-8DL^R (R = Et, ⁿBu), and its ratio to the semicrystalline, high-melting hard A block, derived from rac-8DL^Me, the resulting all-PHA tri-BCPs with high molar mass (M_n up to 238 kg mol^-1) and low dispersity (Đ = 1.07) exhibit tunable mechanical properties characteristic of a strong and tough thermoplastic, elastomer, or a semicrystalline thermoplastic elastomer.

Controlled and effective ring-opening (co)polymerization of rac-lactide, ε-caprolactone and ε-decalactone by β-pyrimidyl enolate aluminum complexes

A series of β-pyrimidyl enolate aluminum complexes (1–6) were found to promote controlled and living ROP of rac-LA, ε-CL, and ε-DL. Six well-defined diblock copolymers and the perfect random copolymer poly(l-LA-r-CL) were successfully synthesized.

Block Poly(carbonate-ester) Ionomers as High-Performance and Recyclable Thermoplastic Elastomers

Thermoplastic elastomers based on polyesters/carbonates have the potential to maximize recyclability, degradability and renewable resource use. However, they often underperform and suffer from the familiar trade-off between strength and extensibility. Herein, we report well-defined reprocessable poly(ester-b-carbonate-b-ester) elastomers with impressive tensile strengths (60 MPa), elasticity (>800 %) and recovery (95 %). Plus, the ester/carbonate linkages are fully degradable and enable chemical recycling. The superior performances are attributed to three features: (1) Highly entangled soft segments; (2) Fully reversible strain-induced crystallization and (3) Precisely placed ZnII -carboxylates dynamically crosslinking the hard domains. The one-pot synthesis couples controlled cyclic monomer ring-opening polymerization and alternating epoxide/anhydride ring-opening copolymerization. Efficient convresion to ionomers is achieved by reacting vinyl-epoxides to install ZnII -carboxylates.

Development of Biodegradable Polyesters: Study of Variations in Their Morphological and Thermal Properties through Changes in Composition of Alkyl-Substituted (ε-DL) and Non-Substituted (ε-CL, EB, L-LA) Monomers

Three series of polyesters based on monomer combinations of ε-caprolactone (ε-CL), ethylene brassylate (EB), and l-Lactide (LLA) with the alkyl substituted lactone ε-decalactone (ε-DL) were synthesized at different molar ratios. Copolymers were obtained via ring opening polymerization (ROP) employing TBD (1,5,7-triazabicyclo-[4.4.0]-dec-5-ene), an organic catalyst which can be handled under normal conditions, avoiding the use of glove box equipment. The molar monomer composition of resulting copolymers differed from theoretical values due to lower ε-DL reactivity; their M_n and M_w values were up to 14 kDa and 22.8 kDa, respectively, and distributions were (Ɖ) ≤ 2.57. The thermal stability of these materials suffered due to variations in their ε-DL molar content. Thermal transitions such as melting (T_m) and crystallization (T_c) showed a decreasing tendency as ε-DL molar content increased, while glass transition (T_g) exhibited minor changes. It is worth mentioning that changes in monomer composition in these polyesters have a strong impact on their thermal performance, as well as in their crystallization degree. Consequently, variations in their chemical structure may have an effect on hydrolyic degradation rates. It should be noted that, in future research, some of these copolymers will be exposed to hydrolytic degradation experiments, including characterizations of their mechanical properties, to determine their adequacy in potential use in the development of soft medical devices.

Switchable Polymerization: A Practicable Strategy to Produce Biodegradable Block Copolymers with Diverse Properties

With the global demand for sustainable development, there has been an increasing interest in using natural biomass as raw resources to produce sustainable polymers as an alternative to petroleum-based polymers. Because monocomponent biodegradable polymers are often insufficient in performance, copolymers with well-engineered block structures are synthesized to reach wide tunability. Switchable polymerization is such a practical strategy to produce biodegradable block copolymers with diverse performance. This review focus on the performance of block copolymers bearing biodegradable polymer segments produced by diverse switchable polymerization. We highlight two main segments that are critical for biodegradable block copolymers, i. e., polyester and polycarbonate, summarize the multiple characters of materials from switchable polymerization such as antibacterial, shape memory, adhesives, etc. The state-of-the-art research on biodegradable block copolymers, as well as an outlook on the preparation and application of novel materials, are presented.

Exploiting Sodium Coordination in Alternating Monomer Sequences to Toughen Degradable Block Polyester Thermoplastic Elastomers

Thermoplastic elastomers (TPEs) that are closed-loop recyclable are needed in a circular material economy, but many current materials degrade during recycling, and almost all are pervasive hydrocarbons. Here, well-controlled block polyester TPEs featuring regularly placed sodium/lithium carboxylate side chains are described. They show significantly higher tensile strengths than unfunctionalized analogues, with high elasticity and elastic recovery. The materials are prepared using controlled polymerizations, exploiting a single catalyst that switches between different polymerization cycles. ABA block polyesters of high molar mass (60–100 kg mol^–1; 21 wt % A-block) are constructed using the ring-opening polymerization of ε-decalactone (derived from castor oil; B-block), followed by the alternating ring-opening copolymerization of phthalic anhydride with 4-vinyl-cyclohexene oxide (A-blocks). The polyesters undergo efficient functionalization to install regularly placed carboxylic acids onto the A blocks. Reacting the polymers with sodium or lithium hydroxide controls the extent of ionization (0–100%); ionized polymers show a higher tensile strength (20 MPa), elasticity (>2000%), and elastic recovery (>80%). In one case, sodium functionalization results in 35× higher stress at break than the carboxylic acid polymer; in all cases, changing the quantity of sodium tunes the properties. A leading sample, 2-COONa75 (M_n 100 kg mol^–1, 75% sodium), shows a wide operating temperature range (−52 to 129 °C) and is recycled (×3) by hot-pressing at 200 °C, without the loss of mechanical properties. Both the efficient synthesis of ABA block polymers and precision ionization in perfectly alternating monomer sequences are concepts that can be generalized to many other monomers, functional groups, and metals. These materials are partly bioderived and have degradable ester backbone chemistries, deliver useful properties, and allow for thermal reprocessing; these features are attractive as future sustainable TPEs.

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.

Reducing the crystallinity of PCL chains by copolymerization with substituted δ/ε-lactones and its impact on the phase separation of PCL-based block copolymers

Various substituted δ/ε-lactones have been copolymerized with ε-caprolactone (ε-CL) with the aim to inhibit the crystallization of polycaprolactone (PCL). Among the studied co-monomers, the best results were obtained with the...

Synthesis of copolyesters based on substituted and non-substituted lactones towards the control of their crystallinity and their potential effect on hydrolytic degradation in the design of soft medical devices

ROP synthesis of polyesters at different molar ratios of monomers ε-caprolactone (ε-CL) in combination with alkyl substituted lactones δ-decalactone (δ-DL), ε-decalactone (ε-DL) and δ-dodecalactone (δ-DD), as well copolymers based on ε-DL and δ-DD.

Biodegradable Elastomers Enabling Thermoprocessing Below 100 °C

Biodegradable and biocompatible elastomers are highly desirable for many biomedical applications. Here, we report synthesis and characterization of poly(ε-caprolactone)-co-poly(β-methyl-δ-valerolactone)-co-poly(ε-caprolactone) (PCL-PβMδVL-PCL) elastomers. These materials have strain to failure values greater than 1000%. Tensile set measurements according to an ASTM standard revealed a 98.24% strain recovery 10 min after the force was removed and complete strain recovery 40 min after the force was removed. The PβMδVL midblock is amorphous with a glass-transition temperature of -51 °C, and PCL end blocks are semicrystalline and have a melting temperature in the range of 52-55 °C. Due to their thermoplastic nature and the low melting temperature, these elastomers can be readily processed by printing, extrusion, or hot-pressing at 60 °C. Lysozyme, a model bioactive agent, was incorporated into a PCL-PβMδVL-PCL elastomer through melt blending in an extruder, and the blend was further hot-pressed into films; both processing steps were performed at 60 °C. No loss of lysozyme bioactivity was observed. PCL-PβMδVL-PCL elastomers are as cytocompatible as tissue culture polystyrene in supporting cell viability and cell growth, and they are degradable in aqueous environments through hydrolysis. The degradable, cytocompatible, elastomeric, and thermoplastic properties of PCL-PβMδVL-PCL polymers collectively render them potentially valuable for many applications in the biomedical field, such as medical devices and tissue engineering scaffolds.

Degradable Elastomers: Is There a Future in Tyre Compound Formulation?

Problems related to non-biodegradable waste coming from vulcanized rubber represent one of the pre-eminent challenges for modern society. End-of-life tyres are an important source of this typology of waste and the increasingly high accumulation in the environment has contributed over the years to enhance land and water pollution. Moreover, the release into the environment of non-degradable micro-plastics and other chemicals as an effect of tyre abrasion is not negligible. Many solutions are currently applied to reuse end-of-life tyres as a raw material resource, such as pyrolysis, thermo-mechanical or chemical de-vulcanisation, and finally crumbing trough different technologies. An interesting approach to reduce the environmental impact of vulcanised rubber wastes is represented by the use of degradable thermoplastic elastomers (TPEs) in tyre compounds. In this thematic review, after a reviewing fossil fuel-based TPEs, an overview of the promising use of degradable TPEs in compound formulation for the tyre industry is presented. Specifically, after describing the properties of degradable elastomers that are favourable for tyres application in comparison to used ones, the real scenario and future perspectives related to the use of degradable polymers for new tyre compounds will be realized.

Sequence Control from Mixtures: Switchable Polymerization Catalysis and Future Materials Applications

There is an ever-increasing demand for higher-performing polymeric materials counterbalanced by the need for sustainability throughout the life cycle. Copolymers comprising ester, carbonate, or ether linkages could fulfill some of this demand as their monomer-polymer chemistry is closer to equilibrium, facilitating (bio)degradation and recycling; many monomers are or could be sourced from renewables or waste. Here, an efficient and broadly applicable route to make such copolymers is discussed, a form of switchable polymerization catalysis which exploits a single catalyst, switched between different catalytic cycles, to prepare block sequence selective copolymers from monomer mixtures. This perspective presents the principles of this catalysis, catalyst design criteria, the selectivity and structural copolymer characterization tools, and the properties of the resulting copolymers. Uses as thermoplastic elastomers, toughened plastics, adhesives, and self-assembled nanostructures, and for programmed degradation, among others, are discussed. The state-of-the-art research into both catalysis and products, as well as future challenges and directions, are presented.

Recent Developments in Lactone Monomers and Polymer Synthesis and Application

Lactones are a group of compounds that have been known for several decades. The commercial importance of lactones results from the possibility of manufacturing of a broad scope of derivatives and polymers with a wide spectrum of applications. In this work the synthesis and characterization of simple lactones are described, which due to the easy methods of the synthesis are of high importance for the industry. The chemical as well as biochemical methods are included with special attention paid to the methods that avoid metal catalysts, initiators or toxic solvents, allowing the use of the final products for the medical applications, e.g., for controlled drug-release systems, resorbable surgical threads, implants, tissue scaffolds or for the production of drugs. Lactone-based derivatives, such as polymers, copolymers, composites or three-dimensional structures are also presented. The work is focused on the methods for the synthesis of lactones and lactones derivates, as well as on the special properties and application of the studied compounds.

Synthesis and characterization of biobased thermoplastic polyester elastomers containing Poly(butylene 2,5-furandicarboxylate)

A series of sustainable and reprocessible thermoplastic polyester elastomers P(BF-PBSS)s were synthesized using dimethyl-2,5-furandicarboxylate, 1,4-butanediol, and synthetic low-molecular-weight biobased polyester (PBSS). The P(BF-PBSS)s contain poly(butylene 2,5-furandicarboxylate) (PBF) as their hard segment and PBSS as their soft segment. The microstructures of the P(BF-PBSS)s were confirmed by nuclear magnetic resonance, demonstrating that a higher content of the soft segment was incorporated into P(BF-PBSS)s with higher PBSS content. Interestingly, dynamic mechanical analysis indicated that P(BF-PBSS)s comprised two domains: crystalline PBF and a mixture of amorphous PBF and PBSS. Consequently, the microphase separations of P(BF-PBSS)s were mainly induced by the crystallization of their PBF segments. More importantly, the thermal, crystallization, and mechanical properties could be tailored by tuning the PBSS content. Our results indicate that the as-prepared P(BF-PBSS)s are renewable, thermally stable, and nontoxic, and have good tensile properties, indicating that they could be potentially applied in biomedical materials.

A series of sustainable and reprocessible thermoplastic polyester elastomers P(BF-PBSS)s were synthesized using dimethyl-2,5-furandicarboxylate, 1,4-butanediol, and synthetic low-molecular-weight biobased polyester (PBSS).

β-Methyl-δ-valerolactone-containing Thermoplastic Poly(ester-amide)s: Synthesis, Mechanical Properties, and Degradation Behavior

Poly(ester-amide)s (PEAs) have been prepared from (glucose-derived) β-methyl-δ-valerolactone (MVL) by reaction of MVL-derived diamidodiols with diacid chlorides in solution to form poly(ester-amide)s having alternating diester-diamide subunits. The PEAs formed by this method exhibit plastic properties and are of sufficiently high molecular weight to be tough, ductile materials (stress at break: 41-53 MPa, strain at break: 530-640%). The length of the methylene linker unit (n = 1,2,3) between amide groups of the diamidodiols affects the Young's modulus; longer linkers reduce the stiffness of the materials. This allows tuning of the properties by judicious choice of precursors. MVL was also converted to a diacid chloride that was then used to prepare a PEA that is 76 wt% MVL-derived. The degradation rates of suspensions of these new PEAs in basic aqueous media were benchmarked and their instability in aqueous acid was also observed. NMR studies were used to detect the hydrolytic degradation products of both these PEAs as well as a structurally simpler analog.

Ortho-vanillin derived Al(iii) and Co(iii) catalyst systems for switchable catalysis using ε-decalactone, phthalic anhydride and cyclohexene oxide

Switchable catalysis is a useful one-pot method to prepare block polyesters utilising a single catalyst exposed to a mixture of monomers.

A study on sisal-based polyurethane foam with multi-shape memory properties

SMPU-PSF exhibited a high compression rate, high controllability, and good shape recovery rate.

Triblock polyester thermoplastic elastomers with semi-aromatic polymer end blocks by ring-opening copolymerization

Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-alt-phthalate)-b-poly(ε-decalactone)-b-poly(cyclohexene-alt-phthalate) {PE-PDL-PE}. The synthesis is accomplished using a zinc(ii)/magnesium(ii) catalyst, in a one-pot procedure where ε-decalactone ring-opening polymerization yielding dihydroxyl telechelic poly(ε-decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85-98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (f hard = 0.4) and variable molar masses 40-100 kg mol-1; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol-1) and variable hard-block volume fractions (0.12 < f hard < 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼-51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (f hard < 0.4 and N > 1300) with linear stress-strain relationships, high ultimate tensile strengths (σ b = 1-5 MPa), very high elongations at break (ε b = 1000-1900%) and excellent elastic recoveries (98%). There is a wide operating temperature range (-51 to +138 °C), an operable processing temperature range (+100 to +200 °C) and excellent thermal stability (T d,5% ∼ 300 °C). The polymers are stable in aqueous environments, at room temperature, but are hydrolyzed upon gentle heating (60 °C) and treatment with an organic acid (para-toluene sulfonic acid) or a common lipase (Novozyme® 51032). The new block polyesters show significant potential as sustainable thermoplastic elastomers with better properties than well-known styrenic block copolymers or polylactide-derived elastomers. The straightforward synthesis allows for other commercially available and/or bio-derived lactones, epoxides and anhydrides to be developed in the future.

Turning natural δ-lactones to thermodynamically stable polymers with triggered recyclability

Extending the use of natural δ-lactones in circular materials via a synthetic strategy yielding thermodynamically stable polyesters with triggered recyclability.

Tailor-made block copolymers of l-, d- and rac-lactides and ε-caprolactone via one-pot sequential ring opening polymerization by pyridylamidozinc(ii) catalysts

Three-coordinated Zn(ii) complexes bearing sterically encumbered bidentate monoanionic [N,N -] pyridylamido ligands efficiently catalyze the ring opening polymerization of lactide (LA) and ε-caprolactone (CL). Owing to the polymerization controlled nature and high rate, precise stereodiblock poly(LLA-b-DLA) with different block lengths can be easily produced by one-pot sequential monomer addition at room temperature in short reaction times. NMR, SEC and DSC analyses confirm the production of highly isotactic diblock copolymers which crystallize in the high melting stereocomplex phase. Stereo-triblock and tetrablock copolymers of l-LA, d-LA and rac-LA have been synthesized similarly. Finally, a diblock poly(CL-b-LA) has been easily obtained by sequential addition of ε-caprolactone and lactide under mild conditions.

Stereoselective Ring-Opening (Co)polymerization of β-Butyrolactone and ε-Decalactone Using an Yttrium Bis(phenolate) Catalytic System

An effective route for ring-opening copolymerization of β-butyrolactone (BBL) with ε-decalactone (ε-DL) is reported. Microstructures of the block copolymers characterized by 13C NMR spectroscopy revealed syndiotactic-enriched poly(3-hydroxybutyrate) (PHB) blocks. Several di- and triblock copolymers (PDL-b-PHB and PDL-b-PHB-b-PDL, respectively) were successfully synthesized by sequential addition of the monomers using (salan)Y(III) complexes as catalysts. The results from MALDI-ToF mass spectrometry confirmed the presence of the copolymers. Moreover, thermal properties of the block copolymers were also investigated and showed that the microphase separation of PDL-b-PHB copolymers into PHB- and PDL-rich domains has an impact on the glass transition temperatures of both blocks.

Poly(glycerol sebacate)-Based Polyester-Polyether Copolymers and Their Semi-Interpenetrated Networks with Thermoplastic Poly(ester-ether) Elastomers: Preparation and Properties

Poly(glycerol sebacate) (PGS), produced from renewable monomers such as sebacic acid and glycerol, has been explored extensively for various biomedical applications. However, relatively less attention has been paid to explore PGS as sustainable materials in applications such as elastomers and rigid plastics, primarily because of serious deficiencies in physical properties of PGS. Here, we present two new approaches for enhancing the properties of PGS; (i) synthesizing block copolymers of PGS with poly(tetramethylene oxide)glycol (PTMO) and (ii) preparing a blend of PGS-b-PTMO with a poly(ester-ether) thermoplastic elastomer. The consequence of molar ratio (hard and soft segments) and M n of soft segment on tensile properties of the material was investigated. The PGS-b-PTMO with 25:75 mole ratios of hard and soft segments and having a medium M n soft segment (5350 g mol-1) exhibits an appreciable increase in percentage of elongation that is from 32% for PGS to 737%. Blends of PGS-b-PTMO and a thermoplastic polyester elastomer, Hytrel 3078, form a semi-interpenetrated polymer network, which exhibits increased tensile strength to 2.11 MPa and percentage of elongation to 2574. An elongation of such magnitude is unprecedented in the literature for predominantly aliphatic polyesters and demonstrates that the simple polyester can be tailored for superior performance.

Printable, Degradable, and Biocompatible Ion Gels from a Renewable ABA Triblock Polyester and a Low Toxicity Ionic Liquid

We have designed printable, biocompatible, and degradable ion gels by combining a novel ABA triblock aliphatic polyester, poly(ε-decalactone)-b-poly(dl-lactide)-b-poly(ε-decalactone), and a low toxicity ionic liquid, 1-butyl-1-methylpyrrolidinium bistrifluoromethanesulfonylimide ([P₁₄][TFSI]). Due to the favorable compatibility between amorphous poly(dl-lactide) and [P₁₄][TFSI] and the insolubility of the poly(ε-decalactone), the triblock polymer forms self-assembled micellar cross-links similar to thermoplastic elastomers, which ensures similar processing conditions and mechanical robustness during the fabrication of printed electrolyte-gated organic transistor devices. Additionally, the ester backbone in the polymer structure enables efficient hydrolytic degradation of these ion gels compared to those made previously using carbon-backbone polymers.

Strong, Resilient, and Sustainable Aliphatic Polyester Thermoplastic Elastomers

Thermoplastic elastomers (TPEs) composed of ABA block polymers exhibit a wide variety of properties and are easily processable as they contain physical, rather than chemical, cross-links. Poly(γ-methyl-ε-caprolactone) (PγMCL) is an amorphous polymer with a low entanglement molar mass (M_e = 2.9 kg mol^-1), making it a suitable choice for tough elastomers. Incorporating PγMCL as the midblock with polylactide (PLA) end blocks (f_LA = 0.17) results in TPEs with high stresses and elongations at break (σ_B = 24 ± 2 MPa and ε_B = 1029 ± 20%, respectively) and low levels of hysteresis. The use of isotactic PLA as the end blocks (f_LLA = 0.17) increases the strength and toughness of the material (σ_B = 30 ± 4 MPa, ε_B = 988 ± 30%) due to its semicrystalline nature. This study aims to demonstrate how the outstanding properties in these sustainable materials are a result of the entanglements, glass transition temperature, segment-segment interaction parameter, and crystallinity, resulting in comparable properties to the commercially relevant styrene-based TPEs.

Mechanical properties and state of miscibility in poly(racD,L-lactide-co-glycolide)/(L-lactide-co-ε-caprolactone) blends

Polymers based on lactic acid (PLA) are a very promising category of biopolymers. As they are multi-stimuli responsive, can, in many ways, positively interact with the host, stimulating the innate reparative machinery of the human body. Since biopolymers for medical applications are subject to restrictive regulations, blending stands out as an effective method for obtaining tailored properties within a reduced time to market if compared to synthesis. Hence, in this study a set of PDLGA/PLCL blends was obtained by means of thermoplastic techniques and then further characterized. Evaluation techniques include GPC, NMR, DSC, tensile testing and SEM. Although mixtures proved to be immiscible, a full range of tensile properties was achieved. Observation of the surfaces of fracture provided visual evidence of the deformation mechanisms that occurred during the tensile tests which in the end led to failure. Interpretation of the thermal events based on molecular characterization parameters revealed phase separation, crystallization and plasticisation mechanisms that are relevant to any potential applications based on mechanical performance and shape memory behaviour.