Renewability is not Enough: Recent Advances in the Sustainable Synthesis of Biomass-Derived Monomers and Polymers

Improving the Performance of Photoactive Terpene-Based Resin Formulations for Light-Based Additive Manufacturing

Photocurable liquid formulations have been a key research focus for the preparation of mechanically robust and thermally stable networks. However, the development of renewable resins to replace petroleum-based commodities presents a great challenge in the field. From this perspective, we disclose the design of photoactive resins based on terpenes and itaconic acid, both potentially naturally sourced, to prepare photosets with adjustable thermomechanical properties. Biobased perillyl itaconate (PerIt) was synthesized from renewable perillyl alcohol and itaconic anhydride via a scalable solvent-free method. Photoirradiation of PerIt in the presence of a multiarm thiol and photoinitiator led to the formation of networks over a range of compositions. Addition of nonmodified terpenes (perillyl alcohol, linalool, or limonene) as reactive diluents allowed for more facile preparation of photocured networks. Photosets within a wide range of properties were accessed, and these could be adjusted by varying diluent type and thiol stoichiometry. The resins showed rapid photocuring kinetics and the ability to form either brittle or elastic materials, with Young's modulus and strain at break ranging from 3.6 to 358 MPa and 15 to 367%, respectively, depending on the chemical composition of the resin. Glass transition temperatures (Tg) were influenced by thioether content, with temperatures ranging from 5 to 43 °C, and all photosets displayed good thermal resistance with Td,5% > 190 °C. Selected formulations containing PerIt and limonene demonstrated suitability for additive manufacturing technologies and high-resolution objects were printed via digital light processing (DLP). Overall, this work presents a simple and straightforward route to prepare renewable resins for rapid prototyping applications.

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.

Facile and Efficient Production of Biomass-Derived Isosorbide Dioxides via Epoxidation Using In situ-generated DMDO under Ultrasonication

Herein, we present a facile synthetic process for producing biomass-derived isosorbide (ISB) dioxides using dimethyl dioxirane (DMDO) as an efficient oxidizing agent, which was generated in situ from acetone and KHSO5 . To achieve high conversion and product yield, the KHSO5 concentration, KHSO5 flow rate, and reaction temperature were optimized. Under the optimal conditions, rapid and efficient epoxidation using the in situ-generated DMDO was observed under ultrasonication, yielding the desired product within 35 min at 0 °C. This study offers a convenient and efficient method for generating biomass-derived ISB building blocks, which have significant potential for the fabrication of bioplastics.

Recent advances in catalytic and non-catalytic epoxidation of terpenes: a pathway to bio-based polymers from waste biomass

Epoxides derived from waste biomass are a promising avenue for the production of bio-based polymers, including polyamides, polyesters, polyurethanes, and polycarbonates. This review article explores recent efforts to develop both catalytic and non-catalytic processes for the epoxidation of terpene, employing a variety of oxidizing agents and techniques for process intensification. Experimental investigations into the epoxidation of limonene have shown that these methods can be extended to other terpenes. To optimize the epoxidation of bio-based terpene, there is a need to develop continuous processes that address limitations in mass and heat transfer. This review discusses flow chemistry and innovative reactor designs as part of a multi-scale approach aimed at industrial transformation. These methods facilitate continuous processing, improve mixing, and either eliminate or reduce the need for solvents by enhancing heat transfer capabilities. Overall, the objective of this review is to contribute to the development of commercially viable processes for producing bio-based epoxides from waste biomass.

Structural Metamorphoses of d-Xylose Oxetane- and Carbonyl Sulfide-Based Polymers In Situ during Ring-Opening Copolymerizations

Polymers constructed from copolymerizations of carbohydrates with C1 feedstocks are promising targets that provide transformation of sustainably sourced building blocks into next-generation, environmentally degradable plastic materials. In this work, the initial intention was to expand beyond polycarbonates prepared by the copolymerization of oxetanes derived from d-xylose with CO2 and incorporate sulfur atoms through the establishment of monothiocarbonates that would provide the ability to modulate the backbone compositions and result in unique effects upon the chemical, physical, and mechanical properties. Therefore, the syntheses of poly(1,2-O-isopropylidene-α-d-xylofuranose monothiocarbonate)s were investigated by ring-opening copolymerizations of 3,5-anhydro-1,2-O-isopropylidene-α-d-xylofuranose with carbonyl sulfide (COS) facilitated by (salen)CrCl/cocatalyst systems. Unexpectedly, when copolymerization temperatures exceeded 40 °C, oxygen/sulfur exchange reactions occurred, causing in situ dynamic backbone restructuring through a series of inter-related and complex mechanistic pathways that transformed monothiocarbonate monomeric repeating units into carbonate and thioether dimeric repeating units. These backbone structural compositional transformations were investigated through a combination of Fourier transform infrared and nuclear magnetic resonance spectroscopic techniques and were demonstrated to be easily tuned via temperature and catalyst/cocatalyst stoichiometries. Furthermore, the regiochemistries of these d-xylose-based sulfur-containing polymers revealed that monothiocarbonate monomeric repeating units had a head-to-tail connectivity, while the carbonate and thioether dimeric repeating units had dual head-to-head and tail-to-tail connectivities. These sulfur-containing polymers exhibited enhanced thermal stabilities compared to their oxygen-containing polycarbonate analogues and revealed variations in the effects upon glass transition temperatures, demonstrating the effect of sulfur incorporation in the polymer backbone. These findings contribute to the advancement of sustainable polymer production by using feedstocks of natural origin coupled with COS.

Chemical Recycling Processes of Waste Polyethylene Terephthalate Using Solid Catalysts

Polyethylene terephthalate (PET) is a non-degradable single-use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform post-consumer PET into PET's building block chemicals. Non-catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, heterogeneous catalysts assisted depolymerization of post-consumer PET to monomers and other value-added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure-activity correlations are briefly outlined in each section. An outlook for future development is also presented.

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.

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.

Room Temperature Reduction of Titanium Tetrachloride-Activated Nitriles to Primary Amines with Ammonia-Borane

The reduction of a variety of aromatic and aliphatic nitriles, activated by a molar equivalent of titanium tetrachloride, has been achieved at room temperature using ammonia borane as a safe reductant. The corresponding methanamines were isolated in good to excellent yields following a simple acid-base workup.

Comparative hydrodynamic characterisation of two hydroxylated polymers based on α-pinene- or oleic acid-derived monomers for potential use as archaeological consolidants

The Oseberg Viking ship burial is one of the most extensive collections of Viking wooden artefacts ever excavated in Norway. In the early twentieth century, many of these artefacts were treated with alum in order to preserve them, inadvertently leading to their current degraded state. It is therefore crucial to develop new bioinspired polymers which could be used to conserve these artefacts and prevent further disintegration. Two hydroxylated polymers were synthesised (TPA6 and TPA7), using α-pinene- and oleic acid-derived monomers functionalised with an acrylate moiety. Characterisation using biomolecular hydrodynamics (analytical ultracentrifugation and high precision viscometry) has shown that these polymers have properties which would potentially make them good wood consolidants. Conformation analyses with the viscosity increment (ν) universal hydrodynamic parameter and ELLIPS1 software showed that both polymers had extended conformations, facilitating in situ networking when applied to wood. SEDFIT-MSTAR analyses of sedimentation equilibrium data indicates a weight average molar mass M_w of (3.9 ± 0.8) kDa and (4.2 ± 0.2) kDa for TPA6 and TPA7 respectively. Analyses with SEDFIT (sedimentation velocity) and MultiSig however revealed that TPA7 had a much greater homogeneity and a lower proportion of aggregation. These studies suggest that both these polymers-particularly TPA7-have characteristics suitable for wood consolidation, such as an optimal molar mass, conformation and a hydroxylated nature, making them interesting leads for further research.

Challenges of Green Production of 2,5-Furandicarboxylic Acid from Bio-Derived 5-Hydroxymethylfurfural: Overcoming Deactivation by Concomitant Amino Acids

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is highly attractive as FDCA is considered as substitute for the petrochemically derived terephthalic acid. There are only few reports on the direct use of unrefined HMF solutions from biomass resources and the influence of remaining constituents on the catalytic processes. In this work, the oxidation of HMF in a solution as obtained from hydrolysis and dehydration of saccharides in chicory roots was investigated without intermediate purification steps. The amount of base added to the solution was critical to increase the FDCA yield. Catalyst deactivation occurred and was attributed to poisoning by amino acids from the bio-source. A strong influence of amino acids on the catalytic activity was found for all supported Au, Pt, Pd, and Ru catalysts. A supported AuPd(2 : 1)/C alloy catalyst exhibited both superior catalytic activity and higher stability against deactivation by the critical amino acids.

Toward Economical and Sustainable Production of Renewable Plastic: Integrative System-Level Analyses

2,5-Furandicarboxylic acid (FDCA) is one of the promising renewable plastic monomers enabling to address several environmental issues, instead of petroleum-based terephthalic acid (TPA). In this study, an integrative process for the co-production of FDCA and furfural as well as activated carbon was developed, and the economic feasibility and environmental sustainability for the proposed process were evaluated. In the proposed process, there were major four catalytic conversion reactions: (1) hydrolysis of biomass to its derivatives (cellulose, hemicellulose, and lignin), (2) dehydration of hemicellulose to furfural, (3) dehydration of cellulose to 5-hydroxymethylfurfural (HMF), and (4) successive oxidation of HMF to FDCA. Particularly, a heat exchanger network coupled with a heat pump was established to minimize the utility consumption, thereby reducing 72 % of the heating requirement. Techno-economic analysis revealed that the minimum selling price of FDCA was $1380 ton^-1 , which is comparable to that of petroleum-based TPA ($1445 ton^-1 ). Uncertainty analysis using the Monte Carlo simulation method was employed to quantify the risk associated with the unforeseen market condition. From the life-cycle assessment, we observed that the proposed process is more environmentally sustainable than conventional TPA production in terms of climate change and fossil depletion metrics.

Bioderived 4D Printable Terpene Photopolymers from Limonene and β-Myrcene

Green manufacturing and reducing our cultural dependency on petrochemicals have been topics of growing interest in the past decade, particularly for three-dimensional (3D) printable photopolymers where often toxic solvents and reagents have been required. Here, a simple solvent-free, free-radical polymerization is utilized to homo- and copolymerize limonene and β-myrcene monomers to produce oligomeric photopolymers (M_n < 11 kDa) displaying Newtonian, low viscosities (∼10 Pa × s) suitable for thiol-ene photo-cross-linking, yielding photoset materials in a digital light processing (DLP)-type 3D printer. The resulting photosets display tunable thermomechanical properties (poly(limonene) displays elastic moduli exceeding 1 GPa) compared with previous works focusing on monomeric terpenes as well as four-dimensional (4D) shape memory behavior. The utility of such photopolymers for biomedical applications is briefly considered on the premise of the hydrophilic nature (measured by contact angle) as well as their cytocompatibility upon seeding films with macrophages. These terpene-derived, green 4D photopolymers are shown to have promising physical behaviors suitable for an array of manufacturing and 3D printing applications.

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.

Chemo-enzymatic functionalized sustainable cellulosic membranes: Impact of regional selectivity on ions capture and antifouling behavior

Most of the polymeric membranes synthesized for decentralization of polluted water use fossil-based components. Thus, there is an urgent need to create robust and tunable nano/micro materials for confidently designing efficient and selective polymeric water filters with guaranteed sustainability. We have chosen a robust high-grade microfibrillated cellulose (MFC) as the functional material and selectively tuned it via enzymatic catalysis, which led to the attachment of phosphate group at the C6 position, followed by esterification (fatty acid attachment at C2 and C3 carbon), which led to the increase in its antifouling properties. We have demonstrated the robustness of the functionalization by measuring the separation of various metal ions, and the antifouling properties by adding foulants, such as Bovine Serum Albumin (BSA) and cancerous cells to the test solutions. These prototype affinity MFC membranes represent the most promising type of next-generation high-performance filtration devices for a more sustainable society.

Well-organised two-dimensional self-assembly controlled by in situ formation of a Cu(II)-coordinated rufigallol derivative: a scanning tunnelling microscopy study

The two-dimensional self-assembly of rufigallol derivatives and their metal coordination were studied by scanning tunnelling microscopy. Ex situ Cu(II)-coordinated rufigallol derivatives exhibited columnar structures with some defects, whereas regular and linear structures were formed upon in situ metal coordination at solid/liquid interfaces.

Polyester synthesis based on 3-carene as renewable feedstock

Utilizing renewable feedstocks for the synthesis of biobased and preferrable biodegradable polyesters as substitute for fossile-based polymers remains one of the major challenges towards a sustainable polymer economy. One such...

Fatty Acids and their Derivatives as Renewable Platform Molecules for the Chemical Industry

Oils and fats of vegetable and animal origin remain an important renewable feedstock for the chemical industry. Their industrial use has increased during the last 10 years from 31 to 51 million tonnes annually. Remarkable achievements made in the field of oleochemistry in this timeframe are summarized herein, including the reduction of fatty esters to ethers, the selective oxidation and oxidative cleavage of C-C double bonds, the synthesis of alkyl-branched fatty compounds, the isomerizing hydroformylation and alkoxycarbonylation, and olefin metathesis. The use of oleochemicals for the synthesis of a great variety of polymeric materials has increased tremendously, too. In addition to lipases and phospholipases, other enzymes have found their way into biocatalytic oleochemistry. Important achievements have also generated new oil qualities in existing crop plants or by using microorganisms optimized by metabolic engineering.

Estrogenic activity of lignin-derivable alternatives to bisphenol A assessed via molecular docking simulations

Lignin-derivable bisphenols are potential alternatives to bisphenol A (BPA), a suspected endocrine disruptor; however, a greater understanding of structure–activity relationships (SARs) associated with such lignin-derivable building blocks is necessary to move replacement efforts forward. This study focuses on the prediction of bisphenol estrogenic activity (EA) to inform the design of potentially safer BPA alternatives. To achieve this goal, the binding affinities to estrogen receptor alpha (ERα) of lignin-derivable bisphenols were calculated via molecular docking simulations and correlated to median effective concentration (EC₅₀) values using an empirical correlation curve created from known EC₅₀ values and binding affinities of commercial (bis)phenols. Based on the correlation curve, lignin-derivable bisphenols with binding affinities weaker than ∼−6.0 kcal mol⁻¹ were expected to exhibit no EA, and further analysis suggested that having two methoxy groups on an aromatic ring of the bio-derivable bisphenol was largely responsible for the reduction in binding to ERα. Such dimethoxy aromatics are readily sourced from the depolymerization of hardwood biomass. Additionally, bulkier substituents on the bridging carbon of lignin-bisphenols, like diethyl or dimethoxy, were shown to weaken binding to ERα. And, as the bio-derivable aromatics maintain major structural similarities to BPA, the resultant polymeric materials should possess comparable/equivalent thermal (e.g., glass transition temperatures, thermal decomposition temperatures) and mechanical (e.g., tensile strength, modulus) properties to those of polymers derived from BPA. Hence, the SARs established in this work can facilitate the development of sustainable polymers that maintain the performance of existing BPA-based materials while simultaneously reducing estrogenic potential.

This article explores lignin-derivable bisphenols as alternatives to bisphenol A – a suspected endocrine disruptor – by investigating their structure-activity relationships with respect to estrogen receptor alpha via molecular docking.

Stereoretention in the Bulk ROP of l-Lactide Guided by a Thermally Stable Organocatalyst

Polylactide (PLA) has emerged as one of the most promising bio-based alternatives to petroleum-based plastics, mainly because it can be produced from the fermentation of naturally occurring sugars and because it can be industrially compostable. In spite of these benefits, the industrial ring-opening polymerization (ROP) of l-lactide (L-LA) still requires the use of highly active and thermally stable metal-based catalysts, which have raised some environmental concerns. While the excellent balance between activity and functional group compatibility of organic acid catalysts makes them some of the most suitable catalysts for the metal-free ROP of L-LA, the majority of these acids are highly volatile and subject to decomposition at high temperature, which limits their use under industrially relevant conditions. In this work we exploit the use of a nonstoichiometric acid–base organocatalyst to promote the solvent-free and metal-free ROP of L-LA at elevated temperatures in the absence of epimerization and transesterification. To do so, a stable acidic complex was prepared by mixing 4-(dimethylamino)pyridine (DMAP) with 2 equiv of methanesulfonic acid (MSA). Both experimental and computational results indicate that DMAP:MSA (1:2) not only is highly thermally stable but also promotes the retention of stereoregularity during the polymerization of L-LA, leading to PLLA with a molar mass of up to 40 kg mol^–1 and a chiral purity in excess of 98%. This result provides a new feature to exploit in organocatalyzed polymerization and in the design of new catalysts to facilitate the path to market.

Ring-Opening Metathesis Polymerization of δ-Pinene: Well-Defined Polyolefins from Pine Sap

Well-controlled ring-opening metathesis polymerization (ROMP) of δ-pinene is reported. The monomer is produced through a facile, metal-free, three-step synthesis from highly abundant and sustainable α-pinene. Using Grubbs third-generation catalyst, δ-pinene undergoes ROMP to high conversion (>95%) with molar mass up to 70 kg mol^-1 and narrow dispersity (<1.2). A highly regioregular propagation mechanism was concluded by NMR spectroscopic analysis that revealed a head-to-tail (HT, >95%) microstructure and high trans content (>98%). Successful ROMP is corroborated with density functional theory calculations on δ-pinene's ring strain energy (∼35 kJ mol^-1). Poly(δ-pinene) has a high glass transition temperature (∼104 °C) and a unique chiral microstructure bearing gem-dimethylcyclobutane rings. Controlled ROMP also allowed the synthesis of block copolymers containing segments of poly(δ-pinene) and polynorbornene which are discussed. Finally, bulk polymerization of δ-pinene is possible, indicating a greener approach to these materials, albeit with some loss of control.

β-Pinene-Derived Polyesteramides and Their Blends: Advances in Their Upscaling, Processing, and Characterization

Terpene-based polyesteramides (PEAs) are sustainable and have a variety of favorable properties, making them suitable for a wide range of applications and for contribution to a much more sustainable polymer industry. This work focuses on the synthesis of the lactam from β-pinene and its copolymerization with ε-caprolactone. An important step in synthesizing β-pinene lactam is the oxidation of β-pinene to nopinone. To make the established oxidative cleavage more sustainable and efficient, the required amounts of Al₂ O₃ and KMnO₄ are significantly reduced by using H₂ SO₄ as a catalyst. For the Beckmann rearrangement various catalysts and co-reagents are screened. Among these, the reaction with tosyl chloride is found the most favorable. Subsequently, the chain lengths of the β-pinene-based PEAs are remarkably increased from 6000 g mol^-1 to more than 25 100 g mol^-1 by fine-tuning reaction time, temperature, and decreasing catalyst and initiator concentrations. Also, different catalysts for polymerization are tested. The resulting material shows melting temperatures of ≈55 °C and decomposition temperatures of 354 °C or higher. Processing via melt pressing or casting turned out to be quite difficult due to the polymer's brittleness. Furthermore, regarding biomedical applications, blends of PEA with polyethylene glycol were successfully prepared, yielding a more hydrophilic material.

Prospects of Using Biocatalysis for the Synthesis and Modification of Polymers

Trends in the dynamically developing application of biocatalysis for the synthesis and modification of polymers over the past 5 years are considered, with an emphasis on the production of biodegradable, biocompatible and functional polymeric materials oriented to medical applications. The possibilities of using enzymes not only as catalysts for polymerization but also for the preparation of monomers for polymerization or oligomers for block copolymerization are considered. Special attention is paid to the prospects and existing limitations of biocatalytic production of new synthetic biopolymers based on natural compounds and monomers from biomass, which can lead to a huge variety of functional biomaterials. The existing experience and perspectives for the integration of bio- and chemocatalysis in this area are discussed.

Terpene polyacrylate TPA5 shows favorable molecular hydrodynamic properties as a potential bioinspired archaeological wood consolidant

There is currently a pressing need for the development of novel bioinspired consolidants for waterlogged, archaeological wood. Bioinspired materials possess many advantages, such as biocompatibility and sustainability, which makes them ideal to use in this capacity. Based on this, a polyhydroxylated monomer was synthesised from α-pinene, a sustainable terpene feedstock derived from pine trees, and used to prepare a low molar mass polymer TPA5 through free radical polymerisation. This polymer was extensively characterised by NMR spectroscopy (chemical composition) and molecular hydrodynamics, primarily using analytical ultracentrifugation reinforced by gel filtration chromatography and viscometry, in order to investigate whether it would be suitable for wood consolidation purposes. Sedimentation equilibrium indicated a weight average molar mass M_w of (4.3 ± 0.2) kDa, with minimal concentration dependence. Further analysis with MULTISIG revealed a broad distribution of molar masses and this heterogeneity was further confirmed by sedimentation velocity. Conformation analyses with the Perrin P and viscosity increment ν universal hydrodynamic parameters indicated that the polymer had an elongated shape, with both factors giving consistent results and a consensus axial ratio of ~ 4.5. These collective properties-hydrogen bonding potential enhanced by an elongated shape, together with a small injectable molar mass-suggest this polymer is worthy of further consideration as a potential consolidant.

Heterodinuclear catalysts Zn(ii)/M and Mg(ii)/M, where M = Na(i), Ca(ii) or Cd(ii), for phthalic anhydride/cyclohexene oxide ring opening copolymerisation

A series of heterodinuclear catalysts, coordinated by a Schiff base ligand, for ring opening copolymerisation of phthalic anhydride/cyclohexene oxide, highlight the best metal combinations for fast and selective catalysis.

Terpenoid-derived conjugated dienes with exo-methylene and a 6-membered ring: high cationic reactivity, regioselective living cationic polymerization, and random and block copolymerization with vinyl ethers

Biobased exo-methylene-conjugated dienes underwent regioselective living cationic polymerization to result in well-defined homo- and copolymers with good thermal properties.

Investigating the effect of α-pinene on the ROMP of δ-pinene

Ring opening metathesis polymerization of δ-pinene with varying amounts of α-pinene is explored.

Degradability, thermal stability, and high thermal properties in spiro polycycloacetals partially derived from lignin

Spiro polycycloacetals were synthesized from vanillin and syringaldehyde, along with high-performance co-monomers, exhibiting high glass transition temperatures and thermal stabilities, and rapid rates of hydrolysis in acidic solutions.

Biobased Polymers via Radical Homopolymerization and Copolymerization of a Series of Terpenoid-Derived Conjugated Dienes with exo-Methylene and 6-Membered Ring

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, such as methyl acrylate (MA), acrylonitrile (AN), methyl methacrylate (MMA), and styrene (St), resulting in copolymers with comparable incorporation ratios of bio-based cyclic conjugated monomer units ranging from 40 to 60 mol% at a 1:1 feed ratio. The monomer reactivity ratios when using AN as a comonomer were close to 0, whereas those with St were approximately 0.5 to 1, indicating that these diene monomers can be considered electron-rich monomers. Reversible addition fragmentation chain-transfer (RAFT) copolymerizations with MA, AN, MMA, and St were all successful when using S-cumyl-S'-butyl trithiocarbonate (CBTC) as the RAFT agent resulting in copolymers with controlled molecular weights. The copolymers obtained with AN, MMA, or St showed glass transition temperatures (Tg) similar to those of common vinyl polymers (Tg ~ 100 °C), indicating that biobased cyclic structures were successfully incorporated into commodity polymers without losing good thermal properties.

Biobased Cycloolefin Polymers: Carvone-Derived Cyclic Conjugated Diene with Reactive exo-Methylene Group for Regioselective and Stereospecific Living Cationic Polymerization

Carvone, a naturally abundant chiral cyclic α,β-unsaturated carbonyl compound, was chemically transformed into cyclic exo-methylene conjugated dienes. The exo-methylene group had high reactivity in cationic polymerization and was efficiently polymerized in a controlled manner via regioselective 1,4-conjugated additions using initiating systems effective for living cationic polymerization of vinyl ethers. The obtained polymers with 1,3-cyclohexenyl units and tetra-substituted olefins in the main chain showed high glass transition temperatures over 110 °C. The chiral monomer underwent stereospecific polymerization to result in polymers with low solubility and weak packing of the rigid main chain in the lamellar layers. The racemic mixture resulted in soluble amorphous polymers, which were subsequently hydrogenated into cycloolefin polymers with enhanced thermal properties.