Biobased Plastics and Elastomers from Renewable Rosin via “Living” Ring-Opening Metathesis Polymerization

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.

Ring-Opening Metathesis Polymerization for the Synthesis of Terpenoid-Based Pressure-Sensitive Adhesives

Pressure-sensitive adhesives (PSAs) made from norbornene-functionalized terpenoid-based monomers are reported as a possible alternative to the conventional petrochemically based PSAs. For this, tetrahydrogeranyl, menthyl, and isobornyl norbornenate monomers, with a renewable carbon content up to 72%, are synthesized and copolymerized via ring-opening metathesis polymerization (ROMP) with cyclooctadiene and 5-norbornene-2-carboxylic acid. ROMP enables a much faster and controlled polymerization process in comparison to free radical polymerization techniques when targeting high molecular weights and therefore unlocks a potential to design a unique class of PSA materials. The moduli at bonding and debonding frequencies of the obtained PSAs are plotted in the Chang classification system and are used to predict their adhesive performance. Tack and peel measurements indicate that the terpenoid-based norbornenate formulations show similar adhesive properties in comparison to the previously investigated acrylic counterparts.

Synthesis of polar polynorbornenes with high dielectric relaxation strength as candidate materials for dielectric applications

Materials with high dielectric permittivity and dielectric relaxation strength are sought for thermal and pressure sensors and electrical energy generators. However, most polymers have either too low dielectric permittivity or are so polar that their glass transition temperature (T _g) is too high and thus decomposition and side reactions occur before an electric field can polarize the polar groups. Here, we use the power and versatility of ring-opening metathesis polymerization (ROMP) to synthesize polar polymers with high dielectric relaxation strength and T _g significantly below the decomposition temperature. We first synthesized six polar norbornene monomers by conventional esterification, which were then polymerized by ROMP using Grubbs first- and third-generation catalysts. The structure of the polynorbornenes obtained were verified by multinuclear NMR spectroscopy, molecular weights determined by gel permeation chromatography (GPC), and thermal properties evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, their dielectric permittivity, conductivity, and dielectric losses were measured at different temperatures and frequencies ranging between 0.1 and 10⁶ Hz.

Wood-Derived Functional Polymeric Materials

In recent years, tremendous efforts have been dedicated to developing wood-derived functional polymeric materials due to their distinctive properties, including environmental friendliness, renewability, and biodegradability. Thus, the uniqueness of the main components in wood (cellulose and lignin) has attracted enormous interest for both fundamental research and practical applications. Herein, the emerging field of wood-derived functional polymeric materials fabricated by means of macromolecular engineering is reviewed, covering the basic structures and properties of the main components, the design principle to utilize these main components, and the resulting wood-derived functional polymeric materials in terms of elastomers, hydrogels, aerogels, and nanoparticles. In detail, the natural features of wood components and their significant roles in the fabrication of materials are emphasized. Furthermore, the utilization of controlled/living polymerization, click chemistry, dynamic bonds chemistry, etc., for the modification is specifically discussed from the perspective of molecular design, together with their sequential assembly into different morphologies. The functionalities of wood-derived polymeric materials are mainly focused on self-healing and shape-memory abilities, adsorption, conduction, etc. Finally, the main challenges of wood-derived functional polymeric materials fabricated by macromolecular engineering are presented, as well as the potential solutions or directions to develop green and scalable wood-derived functional polymeric materials.

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.

Reduction of liquid terminated-carboxyl fluoroelastomers using NaBH4/SmCl3

Using a simple one-pot method, the reduction of liquid terminated-carboxyl fluoroelastomers (LTCFs) by sodium borohydride and samarium chloride (NaBH₄/SmCl₃) was successfully realized and liquid terminated-hydroxyl fluoroelastomers (LTHFs) were obtained. The structure and functional group content of LTCFs and LTHFs were analyzed by FTIR, ¹H-NMR, ¹⁹F-NMR and chemical titration. The results showed that –C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C– and carboxyl groups of LTCFs were reduced efficiently, the reduction rate reached 92% under optimum reaction conditions. Compared with other frequently-used metal chlorides, SmCl₃ with a high coordination number could increase the reduction activity of NaBH₄ more effectively and the reduction mechanism was explored.

A facile method using NaBH₄/SmCl₃ allows for reduction of liquid terminated-carboxyl fluoroelastomers (LTCFs) in excellent yields and provides an attractive potential scheme for the reduction of other carboxyl organic compounds.

ROMPI-CDSA: ring-opening metathesis polymerization-induced crystallization-driven self-assembly of metallo-block copolymers

Polymerization-induced self-assembly (PISA) and crystallization-driven self-assembly (CDSA) are among the most prevailing methods for block copolymer self-assembly. Taking the merits of scalability of PISA and dimension control of CDSA, we report one-pot synchronous PISA and CDSA via ring-opening metathesis polymerization (ROMP) to prepare nano-objects based on a crystalline poly(ruthenocene) motif. We denote this self-assembly methodology as ROMPI-CDSA to enable a simple, yet robust approach for the preparation of functional nanomaterials.

Using α-Pinene-Modified Triethoxysilane as the New Cross-Linking Agent To Improve the Silicone Rubber Properties

α-Pinene-modified triethoxysilane (α-PTES) was synthesized by hydrosilylation in the presence of Karstedt's catalyst. The structure of α-PTES was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Under the catalysis of an organotin catalyst, α-PTES, which was the cross-linking agent, and the hydroxy-terminated poly(dimethylsiloxane) matrix were utilized to prepare the room-temperature vulcanized silicone rubber. Morphology, thermal performance, and mechanical properties of the modified silicone rubber were investigated by scanning electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis, and a universal testing machine. Because of the strong rigidity of the ring structure of α-pinene, the thermal and mechanical properties of modified silicone rubber were improved greatly than those of the silicone rubber, and the cross-linking agent of which was methyltriethoxysilane. Results showed that the tensile strength and the break at elongation increased by 69.2 and 125%, respectively, and they are nearly doubled compared to the unmodified silicone rubber.

Advances in Rosin-Based Chemicals: The Latest Recipes, Applications and Future Trends

A comprehensive review of the publications about rosin-based chemicals has been compiled. Rosin, or colophony, is a natural, abundant, cheap and non-toxic raw material which can be easily modified to obtain numerous useful products, which makes it an excellent subject of innovative research, attracting growing interest in recent years. The last extensive review in this research area was published in 2008, so the current article contains the most promising, repeatable achievements in synthesis of rosin-derived chemicals, published in scientific literature from 2008 to 2018. The first part of the review includes low/medium molecule weight compounds: Especially intermediates, resins, monomers, curing agents, surfactants, medications and biocides. The second part is about macromolecules: mainly elastomers, polymers for biomedical applications, coatings, adhesives, surfactants, sorbents, organosilicons and polysaccharides. In conclusion, a critical evaluation of the publications in terms of data completeness has been carried out with an indication of the most promising directions of rosin-based chemicals development.

Polyethylene Grafted Silica Nanoparticles Prepared via Surface-Initiated ROMP

Polyethylene and nanosilica represent the most ubiquitous commodity plastic and nanocomposite filler, respectively. Despite their potential utility, few examples exist in the literature of successfully combining these two materials to form polyethylene nanocomposites. Synthesizing well-defined polyethylene grafted to a surface is a significant challenge in the nanocomposites community. Presented here is a synthetic approach toward polyethylene grafted nanoparticles with controllable graft density and molecular weight of the grafted polymer. The variably grafted nanoparticles were then incorporated into a commercial high density polyethylene matrix. The synthesis, characterization, and challenges in making these materials are discussed.

Designing Rosin-Based Plasticizers: Effect of Differently Branched Chains on Plasticization Performance and Solvent Resistance of Flexible Poly(vinyl chloride) Films

In the present study, we report a strategy to prepare rosin-based plasticizers with differently branched chains, which have the same benzene ring and similar alkane structure compared to phthalate plasticizers. Castor oil methyl ester, cardanol, and triethyl citrate were reacted with the chemical structure of rosin-based plasticizers. Rosin-based plasticizers with differently branched chains as alternative plasticizers for preparing phthalate-free flexible poly(vinyl chloride) films. All rosin-based plasticizers exhibited more excellent solvent extraction performance than phthalate plasticizers in four different solvents. The plasticizing efficiency of rosin-based plasticizers containing triethyl citrate groups reached 85.5%. The relationships between plasticizing efficiency, thermal stability, solvent resistance, tensile properties, and relative molecular mass of the branched chains of rosin-based plasticizers were investigated.

A facile approach to thermomechanically enhanced fatty acid-containing bioplastics using metal–ligand coordination

Dynamic metal–ligand coordination creates physical crosslinking and thus improves chain entanglements for enhancing the thermomechanical properties of biobased polymers.

Preparation and properties of room temperature vulcanized silicone rubber based on rosin-grafted polydimethylsiloxane

Rosin-grafted polydimethylsiloxane (RGSO) was prepared via ring-opening reaction of glycidyl ester of rosin acid (ER) with hydroxy-terminated amino polydimethylsiloxane (PDMS). The structure of RGSO was confirmed by ¹H and ¹³C NMR spectroscopy. The effects of ER on relative molecular weight and rheological properties of RGSO were studied by gel permeation chromatography and rotational rheometry. Then, room temperature vulcanized (RTV) silicone rubber modified with rosin was prepared using RGSO, hydroxy-terminated PDMS, tetraethoxysilane, and organotin catalyst. The structures and properties of RTV silicone rubbers were studied by scanning electron microscopy, thermogravimetric analysis, a universal testing machine and dynamic mechanical analysis. The rosin-modified silicone rubber showed remarkably improved thermal and mechanical properties. Temperatures corresponding to 10% weight loss and maximum rate of weight loss increased by 66 °C and 177 °C, respectively. Moreover, the tensile strength and elongation at break increased by 138% and 113%. The role of rosin structure in improvement of properties is discussed.

Rosin-grafted polydimethylsiloxane (RGSO) was prepared via ring-opening reaction of glycidyl ester of rosin acid (ER) with hydroxy-terminated amino polydimethylsiloxane (PDMS).

Sustainable Elastomers from Renewable Biomass

Sustainable elastomers have undergone explosive growth in recent years, partly due to the resurgence of biobased materials prepared from renewable natural resources. However, mounting challenges still prevail: How can the chemical compositions and macromolecular architectures of sustainable polymers be controlled and broadened? How can their processability and recyclability be enabled? How can they compete with petroleum-based counterparts in both cost and performance? Molecular-biomass-derived polymers, such as polymyrcene, polymenthide, and poly(ε-decalactone), have been employed for constructing thermoplastic elastomers (TPEs). Plant oils are widely used for fabricating thermoset elastomers. We use abundant biomass, such as plant oils, cellulose, rosin acids, and lignin, to develop elastomers covering a wide range of structure-property relationships in the hope of delivering better performance. In this Account, recent progress in preparing monomers and TPEs from biomass is first reviewed. ABA triblock copolymer TPEs were obtained with a soft middle block containing a soybean-oil-based monomer and hard outer blocks containing styrene. In addition, a combination of biobased monomers from rosin acids and soybean oil was formulated to prepare triblock copolymer TPEs. Together with the above-mentioned approaches based on block copolymers, multigraft copolymers with a soft backbone and rigid side chains are recognized as the first-generation and second-generation TPEs, respectively. It has been recently demonstrated that multigraft copolymers with a rigid backbone and elastic side chains can also be used as a novel architecture of TPEs. Natural polymers, such as cellulose and lignin, are utilized as a stiff, macromolecular backbone. Cellulose/lignin graft copolymers with side chains containing a copolymer of methyl methacrylate and butyl acrylate exhibited excellent elastic properties. Cellulose graft copolymers with biomass-derived polymers as side chains were further explored to enhance the overall sustainability. Isoprene polymers were grafted from a cellulosic backbone to afford Cell-g-polyisoprene copolymers. Via cross-linking of these graft copolymers, human-skin-mimic elastomers and high resilient elastomers with a well-defined network structure were achieved. The mechanical properties of these resilient elastomers could be finely controlled by tuning the cellulose content. As isoprene can be produced by engineering of microorganisms, these elastomers could be a renewable alternative to petroleum products. In summary, triblock copolymer and graft copolymer TPEs with biomass components, skin-mimic elastomers, high resilient biobased elastomers, and engineering of macromolecular architectures for elastomers are discussed. These approaches and design provide us knowledge on the potential to make sustainable elastomers for various applications to compete with petroleum-based counterparts.

Alternating and regioregular copolymers with high refractive index from COS and biomass-derived epoxides

The catalytic synthesis of well-defined COS- and biomass-derived copolymer with a high refractive index is described.

Stereochemical effects on the mechanical and viscoelastic properties of renewable polyurethanes derived from isohexides and hydroxymethylfurfural

Biomass-derived polyurethanes were synthesized using 2,5-bishydroxymethylfuran (BHMF) and diisocyanate functionalized isohexides, isosorbide bis(3-isocyanatopropanoate) (ISBIP) and isomannide bis(3-isocyanatopropanoate) (IMBIP), at varying feed ratios.