Polymer Chemistry最新文献

The full potential of sequence-defined macromolecules remains unexplored, hindered by the difficulty of synthesizing sufficient amounts for the investigation of the properties of such uniform structures and their derived materials. Herein, we report the bidirectional synthesis and thermal behavior analysis of sequence-defined oligourethanes. The synthesis was conducted on a large scale (up to 50 grams) using a straightforward protocol, yielding uniform macromolecules as validated by NMR, ESI-MS and SEC. With this approach, a library of uniform oligourethanes (up to the octamers) was produced using two structural units: a hydrogen-bonding carbamate and a methyl-substituted alternative structure. By varying the chain length, monomer sequence and functionality, we were able to perform a systematic study of the impact of hydrogen bonding on the thermal properties of polyurethanes. Thermal analysis of the discrete oligomers using DSC revealed that both the molecular weight and microstructure significantly affect the glass transition and melting temperatures. TGA measurements also revealed differences in the thermal stability of the oligomers, underscoring the significance of the primary structure of polyurethanes. Additionally, the influence of the terminal groups on the degradation pathway was assessed via pyrolysis-GC-MS, which specifically highlighted the increased thermal stability in the absence of hydroxyl end groups. This work shows the interest of using sequence-defined synthetic macromolecules for the elucidation of structure–property relationships and thereby facilitates their fine-tuning towards specific material applications.

Addition and correction for ‘Limonene as a renewable unsaturated hydrocarbon solvent for living anionic polymerization of β-myrcene’ by Akhil Dev et al., Polym. Chem. 2021, 12, 3084–3087; https://doi.org/10.1039/d1py00570g.

The biomedical field is increasingly utilizing organic semiconducting materials, driving interest in the green synthesis of conjugated polymers from biomass-derived monomers. This study introduces an efficient C–H arylation method to synthesize furan-based conjugated polymers using oligofurans as building blocks. The resulting polymers exhibit excellent solubility and photostability, and as photosensitizers, they can generate singlet oxygen under both light and ultrasound excitation, effectively eradicating bacteria. Notably, long oligofurans demonstrate greater reactivity than individual furan monomers, which is crucial for producing high-molecular-weight furan-based conjugated polymers via direct C–H arylation. Moreover, adjusting the length of the oligofuran building blocks enables the tuning of the polymers’ bandgaps across the visible to near-infrared regions. This work presents a promising eco-friendly synthesis strategy for developing furan-based conjugated polymers with tailored properties for biomedical applications.

Late transition metal-catalyzed ethylene chain-walking polymerization offers a remarkably convenient method for synthesizing hyperbranched polyethylene. In this study, we created a series of pyridine-imine Ni(II) complexes with axially flexible cycloalkyl substituents, tailored for the production of hyperbranched oligoethylene oils (HBOEOs). These complexes exhibited moderate activity in HBOEO synthesis, reaching rates of up to 4.90 × 10⁵ g mol⁻¹ h⁻¹. The resulting products exhibited low molecular weights (325–523 g mol⁻¹) and high branching densities (110–167/1000C). NMR analysis verified their diverse branching structures, with a significant proportion of hyperbranched motifs. Notably, the activity, structure, and properties of the HBOEOs produced by the catalytic system were significantly influenced by alterations in the catalyst structure and oligomerization conditions. Specifically, when compared to rigid phenyl substituents, flexible cycloalkyl substituents proved more effective in promoting the catalytic system to produce HBOEOs with a higher degree of branching and improved liquefaction properties.

Cationic polymerisation of β-pinene (βP) via earth abundant catalysis has been investigated as a route to low molar mass poly(β-pinene) (PBP) for surfactant applications. As a ‘greener’ alternative to the often hazardous and poorly abundant Lewis acid catalysts reported for the cationic polymerisation of βP, imidazolium-based Lewis acid ionic liquids have been used as catalysts for the polymerisation, yielding polymers of up to M_n = 2560 g mol⁻¹. Iron(III) chloride (FeCl₃) proved to be an effective catalyst for the transformation in a scaled-up, industrially applicable polymerisation resulting in polymers of slightly higher molar mass (M_n = 5680 g mol⁻¹). Supercritical carbon dioxide (scCO₂) proved to be an effective solvent for the purification of the polymers on a large scale, efficiently removing unreacted monomer and solvent. The unsaturated nature of the polymer has been exploited via post-polymerisation functionalisation reactions (epoxidation/hydrolysis and radical thiol–ene), endowing the polymers with hydrophilic groups. The functionalised PBPs were fully characterised, demonstrating variations in thermal properties compared to the unfunctionalised polymer. Finally, with careful balancing of the amphiphilicity, the functionalised polymers were shown to stabilise oil/water emulsions for up to two weeks, demonstrating the potential of these bioderived materials in several surfactant applications.

Poly(trimethylene 2,5-furandicarboxylate) (PTF) is an emergent biobased polymer potentially able to outperform the fossil-based poly(ethylene terephthalate) counterpart. In this work, computational chemistry and vibrational spectroscopy tools are combined to elucidate the conformational preferences of PTF in both crystalline and amorphous regions. This approach departs from previous studies and leads to a new proposal for the crystal structure of this significant biobased polymer. In crystalline domains, PTF chains take on a helical conformation due to the gauche–gauche kinks present in 1,3-propanediol (PDO) segments, while 2,5-furandicarboxylate (FDCA) moieties adopt the syn–syn motif. Similarly to its counterparts, poly(ethylene 2,5-furandicarboxylate) (PEF) and poly(butylene 2,5-furandicarboxylate) (PBF), syn–syn FDCA units allow the formation of a vast array of C–H⋯O contacts between furanic hydrogens and adjacent carbonyl moieties. The proposed crystal structure of PTF consists of two-dimensional sheets of chains connected by C–H⋯O bonds, which are stacked upon one another forming π–π interactions among furanic rings. A thorough vibrational analysis of PTF's infrared and inelastic neutron scattering intensity profiles, with identification of vibrational modes sensitive to conformation and degree of crystallinity, sets a blueprint for future studies employing vibrational spectroscopy techniques.

Polymers based on 1,3-diene monomers play a pivotal role in many commercial elastomers and thermoplastic elastomers. This perspective summarizes the state of the art and recent developments in the living anionic polymerization of dienes, permitting to finely tune the properties of the resulting polymers. An emphasis is placed on novel biobased diene monomers (myrcene, farnesene, etc.) and polymerization solvents, which bear promise for more sustainable elastomers in the future. Furthermore, statistical copolymerization of dienes with vinyl monomers and the in situ monitoring of monomer gradients and formation of tapered di- and triblock copolymers due to disparate reactivity ratios is also reviewed. Thermoplastic elastomers based on tri- and multiblock architectures as well as recently reported diene-based polymer architectures are discussed as well. A summary of current challenges and future options for carbanionic diene polymerization concludes this short review article.