Synthetic Polymers from Sugar-Based Monomers

Chemically Recyclable Pseudo-Polysaccharides from Living Ring-Opening Polymerization of Glucurono-1,6-lactones

Recent advances in synthetic methods and monomer design have given access to precision carbohydrate polymers that extend beyond native polysaccharides. In this article, we present the synthesis of a class of chemically recyclable ester-linked pseudo-polysaccharides via the living anionic ring-opening polymerization of glucurono-1,6-lactones. Notably, the pseudo-polysaccharides exhibited defined chain-end groups, well-controlled molecular weights, and narrow molecular weight distributions, all hallmarks of living polymerization. Furthermore, we demonstrate that our approach is modular, as evidenced by tunable glass transition temperatures (Tg) and the ability to produce both amorphous and semicrystalline polymers by adjusting the monomer side chain structure. Lastly, we showcased the complete catalytic chemical recycling of these pseudo-polysaccharides back to the monomers. The flexibility of the polymerization and the recyclability of these pseudo-polysaccharides promote a sustainable circular economy while offering the potential to access polysaccharide-like materials with tunable thermal and mechanical properties.

Designing Degradable Polymers from Tricycloalkenes via Complete Cascade Metathesis Polymerization

Cascade metathesis polymerization has been developed as a promising method to synthesize complex but well-defined polymers from monomers containing multiple reactive functional groups. However, this approach has been limited to the monomers involving simple alkene/alkyne moieties or produced mainly non-degradable polymers. In this study, we demonstrate a complete cascade ring-opening/ring-closing metathesis polymerization (RORCMP) using various tricycloalkenes and two strategies for the efficient degradation. Through rational design of tricycloalkene monomers, the structure and reactivity relationship was explored. For example, tricycloalkenes with trans configuration in the central ring enabled faster and better selective cascade RORCMP than the corresponding cis isomers. Also, a 4-substituted cyclopentene moiety in the monomers significantly enhanced the overall cascade RORCMP performance, with the maximum turnover number (TON) reaching almost 10,000 and molecular weight up to 170 kg/mol using an amide-containing monomer. Furthermore, we achieved one-shot cascade multiple olefin metathesis polymerization using tricycloalkenes and a diacrylate, to produce new highly A,B-alternating copolymers with full degradability. Lastly, we successfully designed xylose-based tricycloalkenes to give well-defined polymers that underwent ultra-fast and complete degradation under mild conditions.

Embracing Sustainability: The World of Bio-Based Polymers in a Mini Review

The proliferation of polymer science and technology in recent decades has been remarkable, with synthetic polymers derived predominantly from petroleum-based sources dominating the market. However, concerns about their environmental impacts and the finite nature of fossil resources have sparked interest in sustainable alternatives. Bio-based polymers, derived from renewable sources such as plants and microbes, offer promise in addressing these challenges. This review provides an overview of bio-based polymers, discussing their production methods, properties, and potential applications. Specifically, it explores prominent examples including polylactic acid (PLA), polyhydroxyalkanoates (PHAs), and polyhydroxy polyamides (PHPAs). Despite their current limited market share, the growing awareness of environmental issues and advancements in technology are driving increased demand for bio-based polymers, positioning them as essential components in the transition towards a more sustainable future.

Simultaneous Formation of Polyhydroxyurethanes and Multicomponent Semi-IPN Hydrogels

This study introduces an efficient strategy for synthesizing polyhydroxyurethane-based multicomponent hydrogels with enhanced rheological properties. In a single-step process, 3D materials composed of Polymer 1 (PHU) and Polymer 2 (PVA or gelatin) were produced. Polymer 1, a crosslinked polyhydroxyurethane (PHU), grew within a colloidal solution of Polymer 2, forming an interconnected network. The synthesis of Polymer 1 utilized a Non-Isocyanate Polyurethane (NIPU) methodology based on the aminolysis of bis(cyclic carbonate) (bisCC) monomers derived from 1-thioglycerol and 1,2-dithioglycerol (monomers A and E, respectively). This method, applied for the first time in Semi-Interpenetrating Network (SIPN) formation, demonstrated exceptional orthogonality since the functional groups in Polymer 2 do not interfere with Polymer 1 formation. Optimizing PHU formation involved a 20-trial methodology, identifying influential variables such as polymer concentration, temperature, solvent (an aprotic and a protic solvent), and the organo-catalyst used [a thiourea derivative (TU) and 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU)]. The highest molecular weights were achieved under near-bulk polymerization conditions using TU-protic and DBU-aprotic as catalyst-solvent combinations. Monomer E-based PHU exhibited higher Mw¯ than monomer A-based PHU (34.1 kDa and 16.4 kDa, respectively). Applying the enhanced methodology to prepare 10 multicomponent hydrogels using PVA or gelatin as the polymer scaffold revealed superior rheological properties in PVA-based hydrogels, exhibiting solid-like gel behavior. Incorporating monomer E enhanced mechanical properties and elasticity (with loss tangent values of 0.09 and 0.14). SEM images unveiled distinct microstructures, including a sponge-like pattern in certain PVA-based hydrogels when monomer A was chosen, indicating the formation of highly superporous interpenetrated materials. In summary, this innovative approach presents a versatile methodology for obtaining advanced hydrogel-based systems with potential applications in various biomedical fields.

Searching for Conjugates as New Structures for Antifungal Therapies

The progressive increase in fungal infections and the decrease in the effectiveness of current therapy explain research on new drugs. The synthesis of compounds with proven antifungal activity, favorable physicochemical and pharmacokinetic properties affecting their pharmaceutical availability and bioavailability, and limiting or eliminating side effects has become the goal of many studies. The publication describes the directions of searching for new compounds with antifungal activity, focusing on conjugates. The described modifications include, among others, azoles or amphotericin B in combination with fatty acids, polysaccharides, proteins, and synthetic polymers. The benefits of these combinations in terms of activity, mechanism of action, and bioavailability were indicated. The possibilities of creating or using nanoparticles, "umbrella" conjugates, siderophores (iron-chelating compounds), and monoclonal antibodies were also presented. Taking into account the role of vaccinations in prevention, the scope of research related to developing a vaccine protecting against fungal infections was also indicated.

Network-supported and adaptable binding efficacy for flexible and multi-functionalized chitosan/phenolic carbaldehyde hydrogels

A thoughtful strategy has been intended to control the hydrogel networking to assess the binding efficacy of multifunctional hydrogel. The processing of two distinct network-supported hydrogels has portrayed to express the operating interactions involved during co-existence with solvents, small molecules, biomolecules, etc. Herein, chitosan has separately functionalized in semisynthetic approaches with 4-hydroxyisopthalaldehyde (ChDA) and 2-hydroxybenzene-1,3,5-tricarbaldehyde (ChTA) to construct different gel networks. The disposition of gel networks ChDA adapts more flexible chain or spine, whereas ChTA possesses restricted movements within gel networks. The gel networks of hydrogels have a significant role in their distinct physical activities. Their gel-bonding elucidations have performed to establish the variation in mechanical, swelling photophysical properties, etc. Remarkable self-fluorescence behaviors are used as a tool for binding study. Distinctive gel networks and their flexibility have investigated against self-fluorescence, UV-Vis, and FTIR against small molecule, Boron trifluoride and biomolecule, and Bovine serum albumin. Hydrogel/BF3 shows variation in fluorescence due to the disposition of gel networks. Hydrogel/BSA quenching of fluorescence at three different temperatures provides the binding constant and Stern-Volmer quenching constant. Theoretical DFT and docking studies successfully established the flexibility against binding study. The controlling of cross-linking or functionalization is very crucial for the development of hydrogel-mediated applications.

Unraveling the Effect of Stereoisomerism on Mobility-Stretchability Properties of n-Type Semiconducting Polymers with Biobased Epimers as Conjugation Break Spacers

The development of intrinsically stretchable n-type semiconducting polymers has garnered much interest in recent years. In this study, three biobased dianhydrohexitol epimers of isosorbide (ISB), isomannide (IMN), and isoidide (IID), derived from cellulose, were incorporated into the backbone of a naphthalenediimide (NDI)-based n-type semiconducting polymer as conjugation break spacers (CBSs). Accordingly, three polymers were synthesized through the Migita-Kosugi-Stille coupling polymerization with NDI, bithiophene, and CBSs, and the mobility-stretchability properties of these polymers were investigated and compared with those of their analogues with conventional alkyl-based CBSs. Experimental results showed that the different configurations of these epimers in CBSs sufficiently modulate the melt entropies, surface aggregation, crystallographic parameters, chain entanglements, and mobility-stretchability properties. Comparable ductility and edge-on preferred stacking were observed in polymers with endo- or exo-configurations in IMN- and IID-based polymers. By contrast, ISB with endo-/exo-configurations exhibits an excellent chain-realigning capability, a reduced crack density, and a proceeding bimodal orientation under tensile strain. Therefore, the ISB-based polymer exhibits high orthogonal electron mobility retention of (53 and 56)% at 100% strain. This study is one of the few examples where biobased moieties are incorporated into semiconducting polymers as stress-relaxation units. Additionally, this is the first study to report on the effect of stereoisomerism of epimers on the morphology and mobility-stretchability properties of semiconducting polymers.

Nucleoside Analogs: A Review of Its Source and Separation Processes

Nucleoside analogs play a crucial role in the production of high-value antitumor and antimicrobial drugs. Currently, nucleoside analogs are mainly obtained through nucleic acid degradation, chemical synthesis, and biotransformation. However, these methods face several challenges, such as low concentration of the main product, the presence of complex matrices, and the generation of numerous by-products that significantly limit the development of new drugs and their pharmacological studies. Therefore, this work aims to summarize the universal separation methods of nucleoside analogs, including crystallization, high-performance liquid chromatography (HPLC), column chromatography, solvent extraction, and adsorption. The review also explores the application of molecular imprinting techniques (MITs) in enhancing the identification of the separation process. It compares existing studies reported on adsorbents of molecularly imprinted polymers (MIPs) for the separation of nucleoside analogs. The development of new methods for selective separation and purification of nucleosides is vital to improving the efficiency and quality of nucleoside production. It enables us to obtain nucleoside products that are essential for the development of antitumor and antiviral drugs. Additionally, these methods possess immense potential in the prevention and control of serious diseases, offering significant economic, social, and scientific benefits to the fields of environment, biomedical research, and clinical therapeutics.

Advances, challenges, and prospects for surgical suture materials

As one of the long-established and necessary medical devices, surgical sutures play an essentially important role in the closing and healing of damaged tissues and organs postoperatively. The recent advances in multiple disciplines, like materials science, engineering technology, and biomedicine, have facilitated the generation of various innovative surgical sutures with humanization and multi-functionalization. For instance, the application of numerous absorbable materials is assuredly a marvelous progression in terms of surgical sutures. Moreover, some fantastic results from recent laboratory research cannot be ignored either, ranging from the fiber generation to the suture structure, as well as the suture modification, functionalization, and even intellectualization. In this review, the suture materials, including natural or synthetic polymers, absorbable or non-absorbable polymers, and metal materials, were first introduced, and then their advantages and disadvantages were summarized. Then we introduced and discussed various fiber fabrication strategies for the production of surgical sutures. Noticeably, advanced nanofiber generation strategies were highlighted. This review further summarized a wide and diverse variety of suture structures and further discussed their different features. After that, we covered the advanced design and development of surgical sutures with multiple functionalizations, which mainly included surface coating technologies and direct drug-loading technologies. Meanwhile, the review highlighted some smart and intelligent sutures that can monitor the wound status in a real-time manner and provide on-demand therapies accordingly. Furthermore, some representative commercial sutures were also introduced and summarized. At the end of this review, we discussed the challenges and future prospects in the field of surgical sutures in depth. This review aims to provide a meaningful reference and guidance for the future design and fabrication of innovative surgical sutures. STATEMENT OF SIGNIFICANCE: This review article introduces the recent advances of surgical sutures, including material selection, fiber morphology, suture structure and construction, as well as suture modification, functionalization, and even intellectualization. Importantly, some innovative strategies for the construction of multifunctional sutures with predetermined biological properties are highlighted. Moreover, some important commercial suture products are systematically summarized and compared. This review also discusses the challenges and future prospects of advanced sutures in a deep manner. In all, this review is expected to arouse great interest from a broad group of readers in the fields of multifunctional biomaterials and regenerative medicine.

Synthesis and Biodegradability of Tartaric Acid-Based Poly(ester-thioether)s via Thiol-Ene Click Polymerization

Using scandium triflate [Sc(OTf)₃] as a catalyst, chemoselective esterification of tartaric acids by 3-butene-1-ol was performed, and we produced three dialkene monomers: l-di(3-butenyl) tartrate (BTA), d-BTA, and meso-BTA. Thiol-ene polyaddition of these dialkenyl tartrates and dithiols including 1,2-ethanedithiol (ED), ethylene bis(thioglycolate) (EBTG), and d,l-dithiothreitol (DTT) proceeded in toluene at 70 °C under nitrogen to give tartrate-containing poly(ester-thioether)s (M_n, (4.2-9.0) × 10³; molecular weight distribution (M_w/M_n), 1.6-2.5). In differential scanning calorimetry, the poly(ester-thioether)s showed single T_gs between -25 and -8 °C. In biochemical oxygen demand (BOD) tests using activated sludge, poly(l-BTA-alt-EBTG) and poly(l-BTA-alt-ED) showed 32 and 8% biodegradability, which is comparable to that of similar l-malate-containing poly(ester-thioether)s (23 and 13% biodegradation, respectively). Notably, we observed enantio and diastereo effects on biodegradation because poly(l-BTA-alt-EBTG), poly(d-BTA-alt-EBTG), and poly(meso-BTA-alt- EBTG) showed different degradation behaviors during the biodegradation test (BOD/theoretical oxygen demand (TOD) values after 28 days, 32, 70, and 43%, respectively). Our findings provide insights into the design of biomass-based biodegradable polymers containing chiral centers.

Hyperpolarized δ-[1- 13C]gluconolactone imaging visualizes response to TERT or GABPB1 targeting therapy for glioblastoma

TERT promoter mutations are a hallmark of glioblastoma (GBM). Accordingly, TERT and GABPB1, a subunit of the upstream mutant TERT promoter transcription factor GABP, are being considered as promising therapeutic targets in GBM. We recently reported that the expression of TERT or GABP1 modulates flux via the pentose phosphate pathway (PPP). Here, we investigated whether 13C magnetic resonance spectroscopy (MRS) of hyperpolarized (HP) δ- [1-13C]gluconolactone can serve to image the reduction in PPP flux following TERT or GABPB1 silencing. We investigated two different human GBM cell lines stably expressing shRNAs targeting TERT or GABPB1, as well as doxycycline-inducible shTERT or shGABPB1cells. MRS studies were performed on live cells and in vivo tumors, and dynamic sets of 13C MR spectra were acquired following injection of HP δ-[1-13C]gluconolactone. HP 6-phosphogluconolactone (6PG), the product of δ-[1-13C]gluconolactone via the PPP, was significantly reduced in TERT or GABPB1-silenced cells or tumors compared to controls in all our models. Furthermore, a positive correlation between TERT expression and 6PG levels was observed. Our data indicate that HP δ-[1-13C]gluconolactone, an imaging tool with translational potential, could serve to monitor TERT expression and its silencing with therapies that target either TERT or GABPB1 in mutant TERT promoter GBM patients.

Glycopolymers Mediate Suicide Gene Therapy in ASGPR-Expressing Hepatocellular Carcinoma Cells in Tandem with Docetaxel

Cationic glycopolymers stand out as gene delivery nanosystems due to their inherent biocompatibility and high binding affinity to the asialoglycoprotein receptor (ASGPR), a target receptor overexpressed in hepatocellular carcinoma (HCC) cells. However, their synthesis procedure remains laborious and complex, with problems of solubilization and the need for protection/deprotection steps. Here, a mini-library of well-defined poly(2-aminoethyl methacrylate hydrochloride-co-poly(2-lactobionamidoethyl methacrylate) (PAMA-co-PLAMA) glycopolymers was synthesized by activators regenerated by electron transfer (ARGET) ATRP to develop an efficient gene delivery nanosystem. The glycoplexes generated had suitable physicochemical properties and showed high ASGPR specificity and high transfection efficiency. Moreover, the HSV-TK/GCV suicide gene therapy strategy, mediated by PAMA₁₄₄-co-PLAMA₁₉-based nanocarriers, resulted in high antitumor activity in 2D and 3D culture models of HCC, which was significantly enhanced by the combination with small amounts of docetaxel. Overall, our results demonstrated the potential of primary-amine polymethacrylate-containing-glycopolymers as HCC-targeted suicide gene delivery nanosystems and highlight the importance of combined strategies for HCC treatment.

Cross-Linking of Sugar-Derived Polyethers and Boronic Acids for Renewable, Self-Healing, and Single-Ion Conducting Organogel Polymer Electrolytes

This report describes the synthesis and characterization of organogels by reaction of a diol-containing polyether, derived from the sugar d-xylose, with 1,4-phenylenediboronic acid (PDBA). The cross-linked materials were analyzed by infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), scanning electron microscopy (FE-SEM), and rheology. The rheological material properties could be tuned: gel or viscoelastic behavior depended on the concentration of polymer, and mechanical stiffness increased with the amount of PDBA cross-linker. Organogels demonstrated self-healing capabilities and recovered their storage and loss moduli instantaneously after application and subsequent strain release. Lithiated organogels were synthesized through incorporation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into the cross-linked matrix. These lithium-borate polymer gels showed a high ionic conductivity value of up to 3.71 × 10^-3 S cm^-1 at 25 °C, high lithium transference numbers (t ₊ = 0.88-0.92), and electrochemical stability (4.51 V). The gels were compatible with lithium-metal electrodes, showing stable polarization profiles in plating/stripping tests. This system provides a promising platform for the production of self-healing gel polymer electrolytes (GPEs) derived from renewable feedstocks for battery applications.

Fully Bio-based Poly(ketal-ester)s by Ring-opening Polymerization of a Bicylcic Lactone from Glycerol and Levulinic Acid

A fully renewable bio-based bicyclic lactone containing a five-membered cyclic ketal moiety, 7-methyl-3,8,10-trioxabicyclo[5.2.1]decan-4-one (TOD), was synthesized through a two-step acid-catalyzed process from glycerol and levulinic acid. The ring-opening polymerization (ROP) of TOD at 30°C with benzyl alcohol (BnOH) as the initiator and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst can afford high molar mass PTOD with a cis-2.4-disubstitued 2-methyl 1,3-dioxolane moiety in its repeating unit. PTOD is an amorphous polymer with a glass transition temperature (T_g ) of 13°C. It can be hydrolyzed into structurally defined small molecules under acidic or basic conditions by the selective cleavage of either the cyclic ketal or the ester linkage respectively. The TBD-catalyzed copolymerization of L-lactide (L-LA) and TOD at -20°C was investigated. It was confirmed that L-LA polymerized quickly with racemization to form PLA, followed by a slow incorporation of TOD into the formed PLA chains via transesterification. By varying the feed ratios of L-LA to TOD, a series of random copolymers (PLA-co-PTOD) with different TOD incorporation ratios and tunable T_g s were obtained. Under acidic conditions, PLA-co-PTOD degrades much faster than PLA via the selective cleavage of the cyclic ketal linkages. This work provides insights for the development of more sustainable and acid-accelerated degradable alternatives to aliphatic polyesters.

Synthesizing Polyurethane Using Isosorbide in Primary Alcohol Form, and Its Biocompatibility Properties

Isosorbide is a bio-based renewable resource that has been utilized as a stiffness component in the synthesis of novel polymers. Modified isosorbide-based bis(2-hydroxyethyl)isosorbide (BHIS) has favorable structural features, such as fused bicyclic rings and a primary hydroxyl function with improved reactivity to polymerization when compared to isosorbide itself. Polyurethane series (PBH PU series) using polycarbonate diol (PCD) and bis(2-hydroxyethyl)isosorbide (BHIS) were polymerized through a simple, one-shot polymerization without a catalyst using various ratios of BHIS, PCD, and hexamethylene diisocyanate (HDI). The synthesized BHIS and PUs were characterized using proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), and mechanical testing. To determine the feasibility of using these PUs as biomedical materials, we investigated the effects of their BHIS content on PBH PU series physical and mechanical properties. The PBH PU series has excellent elasticity, with a breaking strain ranging from 686.55 to 984.69% at a 33.26 to 63.87 MPa tensile stress. The material showed superb biocompatibility with its high adhesion and proliferation in the bone marrow cells. Given their outstanding mechanical properties and biocompatibility, the polymerized bio-based PUs can contribute toward various applications in the medical field.

Chemical vapor deposition of carbohydrate-based polymers: a proof of concept study

The aim of this work is to investigate if vinyl-modified carbohydrate compounds are suitable monomers for thin film polymerization via chemical vapor deposition in a proof-of-concept study. Synthetic carbohydrate-based polymers are explored as biodegradable, biocompatible, and biorenewable materials. A thin film of synthetic polymers bearing sugar residues can also offer a good surface for cell attachment, and thus might be applied in biomaterials and tissue engineering. The possibility of having such thin film deposited from the vapor phase would ease the implementation in complex device architectures. For a proof-of-concept study, sugar vinyl compound monomers are synthesized starting from methyl α-d-glucopyranoside and polymerized by initiated chemical vapor deposition (iCVD) leading to a thin polymer layer on a Si-substrate. Thus, a successful vapor polymerization of the sugar compounds could be demonstrated. Infrared spectroscopy shows that no unwanted crosslinking reactions take place during the vapor deposition. The solubility of the polymers in water was observed in situ by spectroscopic ellipsometry.

Graphical abstract

Bio-based monomers for amide-containing sustainable polymers

The field of sustainable polymers from renewable feedstocks is a fast-reviving field after the decades-long domination of petroleum-based polymers. Amide-containing polymers exhibit a wide range of properties depending on the type of amide (primary, secondary, and tertiary), amide density, and other molecular structural parameters (co-existing groups, molecular weight, and topology). Engineering amide groups into sustainable polymers via the "monomer approach" is an industrially proven strategy, while bio-based monomers are of enormous importance to bridge the gap between renewable sources and amide-containing sustainable polymers (AmSPs). This feature article aims at conceptualizing the monomer-design philosophy behind most of the reported AmSPs and is organized by discussing di-functional monomers for step-growth polymerization, cyclic monomers for ring-opening polymerization and amide-containing monomers for chain-growth polymerization. We also give a perspective on AmSPs with respect to monomer design and performance enhancement.

Sustainable cycloaliphatic polyurethanes: from synthesis to applications

Polyurethanes (PUs) are a versatile and major polymer family, mainly produced via polyaddition between polyols and polyisocyanates. A large variety of fossil-based building blocks is commonly used to develop a wide range of macromolecular architectures with specific properties. Due to environmental concerns, legislation, rarefaction of some petrol fractions and price fluctuation, sustainable feedstocks are attracting significant attention, e.g., plastic waste and biobased resources from biomass. Consequently, various sustainable building blocks are available to develop new renewable macromolecular architectures such as aromatics, linear aliphatics and cycloaliphatics. Meanwhile, the relationship between the chemical structures of these building blocks and properties of the final PUs can be determined. For instance, aromatic building blocks are remarkable to endow materials with rigidity, hydrophobicity, fire resistance, chemical and thermal stability, whereas acyclic aliphatics endow them with oxidation and UV light resistance, flexibility and transparency. Cycloaliphatics are very interesting as they combine most of the advantages of linear aliphatic and aromatic compounds. This original and unique review presents a comprehensive overview of the synthesis of sustainable cycloaliphatic PUs using various renewable products such as biobased terpenes, carbohydrates, fatty acids and cholesterol and/or plastic waste. Herein, we summarize the chemical modification of the main sustainable cycloaliphatic feedstocks, synthesis of PUs using these building blocks and their corresponding properties and subsequently present their major applications in hot-topic fields, including building, transportation, packaging and biomedicine.

Click Step-Growth Polymerization and E/Z Stereochemistry Using Nucleophilic Thiol-yne/-ene Reactions: Applying Old Concepts for Practical Sustainable (Bio)Materials

Polymer sustainability is synonymous with "bioderived polymers" and the zeitgeist of "using renewable feedstocks". However, this sentiment does not adequately encompass the requirements of sustainability in polymers. In addition to recycling considerations and mechanical performance, following green chemistry principles also needs to be maximized to improve the sustainability of polymer synthesis. The synthetic cost (i.e., maximizing atom economy, reducing chemical hazards, and lowering energy requirements) of producing polymers should be viewed as equally important to the monomer source (biomass vs petrol platform chemicals). Therefore, combining the use of renewable feedstocks with efficient syntheses and green chemistry principles is imperative to delivering truly sustainable polymers. The high efficiency, atom economy, and single reaction trajectories that define click chemistry reactions position them as ideal chemical approaches to synthesize polymers in a sustainable manner while simultaneously expanding the structural scope of accessible polymers from sustainably sourced chemicals.Click step-growth polymerization using the thiol-yne Michael addition, a reaction first reported over a century ago, has emerged as an extremely mild and atom-efficient pathway to yield high-performance polymers with controllable E/Z stereochemistry along the polymer backbone. Building on studies of aromatic thiol-yne polymers, around 10 years ago our group began investigating the thiol-yne reaction for the stereocontrolled synthesis of alkene-containing aliphatic polyesters. Our early studies established a convenient path to high-molecular-weight (>100 kDa) E-rich or Z-rich step-growth polymers by judiciously changing the catalyst and/or reaction solvent. This method has since been adapted to synthesize fast-degrading polyesters, high-performance polyamides, and resilient hydrogel biomaterials. Across several systems, we have observed dramatic differences in material properties among polymers with different alkene stereochemistry.We have also explored the analogous thiol-ene Michael reaction to create high-performance poly(ester-urethanes) with precise E/Z stereochemistry. In contrast to the stereoselective thiol-yne polymerization, here the use of monomers with predefined E/Z (geometric) isomerism (arising from either alkenes or the planar rigidity of ring units) affords polymers with total control over stereochemistry. This advancement has enabled the synthesis of tough, degradable materials that are derived from sustainable monomer feedstocks. Employing isomers of sugar-derived isohexides, bicyclic rigid-rings possessing geometric isomerism, led to degradable polymers with fundamentally opposing mechanical behavior (i.e., plastic vs elastic) simply by adjusting the stereochemistry of the isohexide.In this Account, we feature our investigation of thiol-yne/-ene click step-growth polymers and efforts to establish structure-property relationships toward degradable materials with practical mechanical performance in the context of sustainable polymers and/or biomaterials. We have paid attention to installing and controlling geometric isomerism by using these click reactions, an overarching objective of our work in this research area. The exquisite control of geometric isomerism that is possible within polymer backbones, as enabled by convenient click chemistry reactions, showcases a powerful approach to creating multipurpose degradable polymers.

Ultra-Tough Elastomers from Stereochemistry-Directed Hydrogen Bonding in Isosorbide-Based Polymers

The remarkable elasticity and tensile strength found in natural elastomers are challenging to mimic. Synthetic elastomers typically feature covalently cross-linked networks (rubbers), but this hinders their reprocessability. Physical cross-linking via hydrogen bonding or ordered crystallite domains can afford reprocessable elastomers, but often at the cost of performance. Herein, we report the synthesis of ultra-tough, reprocessable elastomers based on linear alternating polymers. The incorporation of a rigid isohexide adjacent to urethane moieties affords elastomers with exceptional strain hardening, strain rate dependent behavior, and high optical clarity. Distinct differences were observed between isomannide and isosorbide-based elastomers where the latter displays superior tensile strength and strain recovery. These phenomena are attributed to the regiochemical irregularities in the polymers arising from their distinct stereochemistry and respective inter-chain hydrogen bonding.

Complexities of Regioselective Ring-Opening vs Transcarbonylation-Driven Structural Metamorphosis during Organocatalytic Polymerizations of Five-Membered Cyclic Carbonate Glucose Monomers

Rigorous investigations of the organobase-catalyzed ring-opening polymerizations (ROPs) of a series of five-membered cyclic carbonate monomers derived from glucose revealed that competing transcarbonylation reactions scrambled the regiochemistries of the polycarbonate backbones. Regioirregular poly(2,3-α-d-glucose carbonate) backbone connectivities were afforded by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed ROPs of three monomers having different cyclic acetal protecting groups through the 4- and 6-positions. Small molecule studies conducted upon isolated unimers and dimers indicated a preference for Cx-O2 vs Cx-O3 bond cleavage from tetrahedral intermediates along the pathways of addition-elimination mechanisms when the reactions were performed at room temperature. Furthermore, treatment of isolated 3-unimer or 2-unimer, having the carbonate linkage in the 3- or 2-position as obtained from either Cx-O2 or Cx-O3 bond cleavage, respectively, gave the same 74:26 (3-unimer:2-unimer) ratio, confirming the occurrence of transcarbonylation reactions with a preference for 3-unimer vs. 2-unimer formation in the presence of organobase catalyst at room temperature. In contrast, unimer preparation at -78 °C favored Cx-O3 bond cleavage to afford a majority of 2-unimer, presumably due to a lack of transcarbonylation side reactions. Computational studies supported the experimental findings, enhancing fundamental understanding of the regiochemistry resulting from the ring-opening and subsequent transcarbonylation reactions during ROP of glucose carbonates. These findings are expected to guide the development of advanced carbohydrate-derived polymer materials by an initial monomer design via side chain acetal protecting groups, with the ability to evolve the properties further through later-stage structural metamorphosis.

Sugar-Based Polymers with Stereochemistry-Dependent Degradability and Mechanical Properties

Stereochemistry in polymers can be used as an effective tool to control the mechanical and physical properties of the resulting materials. Typically, though, in synthetic polymers, differences among polymer stereoisomers leads to incremental property variation, i.e., no changes to the baseline plastic or elastic behavior. Here we show that stereochemical differences in sugar-based monomers yield a family of nonsegmented, alternating polyurethanes that can be either strong amorphous thermoplastic elastomers with properties that exceed most cross-linked rubbers or robust, semicrystalline thermoplastics with properties comparable to commercial plastics. The stereochemical differences in the monomers direct distinct intra- and interchain supramolecular hydrogen-bonding interactions in the bulk materials to define their behavior. The chemical similarity among these isohexide-based polymers enables both statistical copolymerization and blending, which each afford independent control over degradability and mechanical properties. The modular molecular design of the polymers provides an opportunity to create a family of materials with divergent properties that possess inherently built degradability and outstanding mechanical performance.

Valorization of Spent Coffee Grounds as Precursors for Biopolymers and Composite Production

Spent coffee grounds (SCG) are a current subject in many works since coffee is the second most consumed beverage worldwide; however, coffee generates a high amount of waste (SCG) and can cause environmental problems if not discarded properly. Therefore, several studies on SCG valorization have been published, highlighting its waste as a valuable resource for different applications, such as biofuel, energy, biopolymer precursors, and composite production. This review provides an overview of the works using SCG as biopolymer precursors and for polymer composite production. SCG are rich in carbohydrates, lipids, proteins, and minerals. In particular, carbohydrates (polysaccharides) can be extracted and fermented to synthesize lactic acid, succinic acid, or polyhydroxyalkanoate (PHA). On the other hand, it is possible to extract the coffee oil and to synthesize PHA from lipids. Moreover, SCG have been successfully used as a filler for composite production using different polymer matrices. The results show the reasonable mechanical, thermal, and rheological properties of SCG to support their applications, from food packaging to the automotive industry.

Biomedical applications of carbohydrate-based polyurethane: From biosynthesis to degradation

The foremost common natural polymers are carbohydrate-based polymers or polysaccharides, having a long chain of monosaccharide or disaccharide units linked together via a glycosidic linkage to form a complex structure. There are several uses of carbohydrate-based polymers in biomedical sector due to its attractive features including less toxicity, biocompatibility, biodegradability, high reactivity, availability, and relatively inexpensive. The aim of our study was to explore the synthetic approaches for the preparation of numerous carbohydrate-based polyurethanes (PUs) and their wide range of pharmaceutical and biomedical applications. The data summarized in this study shows that the addition of carbohydrates in the structural skeleton of PUs not only improve their suitability but also effect the applicability for employing them in biological applications. Carbohydrate-based units are incorporated into the PUs, which is the most convenient method for the synthesis of novel biocompatible and biodegradable carbohydrate-based PUs to use in various biomedical applications.

Pathway to fully-renewable biobased polyesters derived from HMF and phenols

Building on previous work where 5-hydroxymethylfurfural (HMF) was selectively functionalized by etherification with phenols, we demonstrated that the oxidized versions of these HMF ethers can be converted to functionalized δ-hexalactones...

Biodegradable copolyesters based on a “soft” isohexide building block with tunable viscoelasticity and self-adhesiveness

PBIA copolyesters synthesised using a novel glycosylated monomer (IIDMC) have faster degradation and tunable self-adhesiveness.

Lacerda T. Monomers and Macromolecular Materials from Renewable Resources: State of the Art and Perspectives

A progressively increasing concern about the environmental impacts of the whole polymer industry has boosted the design of less aggressive technologies that allow for the maximum use of carbon atoms, and reduced dependence on the fossil platform. Progresses related to the former approach are mostly based on the concept of the circular economy, which aims at a thorough use of raw materials, from production to disposal. The latter, however, has been considered a priority nowadays, as short-term biological processes can efficiently provide a myriad of chemicals for the polymer industry. Polymers from renewable resources are widely established in research and technology facilities from all over the world, and a broader consolidation of such materials is expected in a near future. Herein, an up-to-date overview of the most recent and relevant contributions dedicated to the production of monomers and polymers from biomass is presented. We provide some basic issues related to the preparation of polymers from renewable resources to discuss ongoing strategies that can be used to achieve original polymers and systems thereof.

Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Single-crystal-to-single-crystal synthesis of a pseudostarch via topochemical azide-alkyne cycloaddition polymerization

There is high demand for polysaccharide-mimics as enzyme-stable substitutes for polysaccharides for various applications. Circumventing the problems associated with the solution-phase synthesis of such polymers, we report here the synthesis of a crystalline polysaccharide-mimic by topochemical polymerization. By crystal engineering, we designed a topochemically reactive crystal of a glucose-mimicking monomer decorated with azide and alkyne units. In the crystal, the monomers arrange in head-to-tail fashion with their azide and alkyne groups in a ready-to-react antiparallel geometry, suitable for their topochemical azide-alkyne cycloaddition (TAAC) reaction. On heating the crystals, these pre-organized monomer molecules undergo regiospecific TAAC polymerization, yielding 1,4-triazolyl-linked pseudopolysaccharide (pseudostarch) in a single-crystal-to-single-crystal manner. This crystalline pseudostarch shows better thermal stability than its amorphous form and many natural polysaccharides.

Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO₂ and CH₄) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

Efficient Bulky Organo-Zinc Scorpionates for the Stereoselective Production of Poly(rac-lactide)s

The direct reaction of the highly sterically demanding acetamidinate-based NNN'-scorpionate protioligand Hphbp^tamd [Hphbp^tamd = N,N'-di-p-tolylbis(3,5-di-tertbutylpyrazole-1-yl)acetamidine] with one equiv. of ZnMe₂ proceeds in high yield to the mononuclear alkyl zinc complex [ZnMe(κ³-phbp^tamd)] (1). Alternatively, the treatment of the corresponding lithium precursor [Li(phbp^tamd)(THF)] with ZnCl₂ yielded the halide complex [ZnCl(κ³-phbptamd)] (2). The X-ray crystal structure of 1 confirmed unambiguously a mononuclear entity in these complexes, with the zinc centre arranged with a pseudotetrahedral environment and the scorpionate ligand in a κ³-coordination mode. Interestingly, the inexpensive, low-toxic and easily prepared complexes 1 and 2 resulted in highly efficient catalysts for the ring-opening polymerisation of lactides, a sustainable bio-resourced process industrially demanded. Thus, complex 1 behaved as a single-component robust initiator for the living and immortal ROP of rac-lactide under very mild conditions after a few hours, reaching a TOF value up to 5520 h^-1 under bulk conditions. Preliminary kinetic studies revealed apparent zero-order dependence on monomer concentration in the absence of a cocatalyst. The PLA materials produced exhibited narrow dispersity values, good agreement between the experimental M_n values and monomer/benzyl alcohol ratios, as well as enhanced levels of heteroselectivity, reaching P_s values up to 0.74.

Thermally Remendable Polyurethane Network Cross-Linked via Reversible Diels-Alder Reaction

We prepared a series of thermally remendable and recyclable polyurethanes crosslinked via reversible furan-maleimide Diels-Alder reaction based on TDI end-caped branched Voranol 3138 terminated with difurfurylamine and 4,4'-bis(maleimido)diphenylmethane (BMI). We showed that Young modulus strongly depends on BMI content (from 8 to 250 MPa) that allows us to obtain materials of different elasticity as simple as varying BMI content. The ability of DA and retro-DA reactions between furan and maleimide to reversibly bind material components was investigated by NMR spectroscopy, differential scanning calorimetry, and recycle testing. All polymers obtained demonstrated high strengths and could be recovering without significant loss in mechanical properties for at least five reprocessing cycles.