Polymer Chemistry最新文献

Block copolymer self-assembly in solution offers a versatile platform for designing nanostructures with tailored morphologies in aqueous environments. While morphology is commonly controlled by adjusting block ratios, kinetic trapping of nanostructures represents a powerful yet underexplored strategy to direct shape and structure formation, for example in biomedical applications. In this study, we investigate the self-assembly behavior of the amphiphilic block copolymer poly[(butyl acrylate)₅₀-co-(pyridyl disulfide ethyl acrylate)₅]-block-(poly ethylene oxide)₁₂₅-N₃ (P(BA₅₀-PDSA₅)-b-PEO₁₂₅-N₃) using a solvent switch method. The polymer features a neutral, biocompatible hydrophilic block and a hydrophobic block with a low glass transition temperature (T_g). By systematically varying the initial solvent composition (DMSO/acetone), polymer concentration (1, 4, 7 mg mL⁻¹), and water addition rate (1, 2, 4, 20 mL h⁻¹), we demonstrate precise control over nanoparticle morphology. DMSO content above 80% favored vesicle formation, while balanced DMSO/acetone mixtures stabilized worm-like micelles. Lower polymer concentration of 1 mg mL⁻¹ resulted in a decrease in the formation of non-spherical morphologies, and faster water addition rate of 4 mL h⁻¹ broadened the worm phase, indicating a strong influence of kinetics on the final morphology. Characterization via asymmetric flow field-flow fractionation (AF4), dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM) revealed sharp transitions and mixed phases, highlighting the sensitivity of the system to subtle assembly conditions. These findings provide mechanistic insights into morphology control and underscore the potential of kinetically guided self-assembly for designing shape-specific nanostructures, which is particularly relevant for biomedical applications where nanoparticle shape influences biodistribution, cellular uptake, and therapeutic efficacy.

The properties of biomacromolecules lead to the development of synthetic mimics to emulate their functions. In an earlier report, we presented L-pyroglutamic acid (PGA)-functionalized methacrylate-based polymers demonstrating a typical upper critical solution temperature (UCST)-type phase transition behavior and an intriguing liquid–liquid phase separation (LLPS) phenomenon in pure water, provided the degree of polymerization was restricted to 40 (P. Chowdhury, B. Saha, K. Bauri, B. S. Sumerlin and P. De, J. Am. Chem. Soc., 2024, 146, 21664–21676). In this contribution, PGA-based well-defined polymers with two different backbone structures (methacrylate and styrene) and varied chain lengths are synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Despite differences in backbone hydrophobicity, both polymers featured cosolvency phenomenon, as evident from the phase diagrams of ternary polymers/water/alcohol systems, and displayed sharp and reversible UCST-type transitions in water/alcohol solutions with negligible hysteresis. In addition, their phase transition temperature could be modulated in a wide temperature range from 10 to 80 °C by varying the molar mass, polymer concentration, the composition of the binary water/alcohol mixture, the identity of the alcohol, and also the nature and concentration of the foreign substances. Interestingly, the higher molar mass methacrylate polymers formed coacervate droplets that underwent macroscopic LLPS in a binary water/ethanol (80/20, vol/vol) mixture. Overall, this study advances the fundamental understanding of PGA-tethered uncharged, thermoresponsive homopolymers.

Conjugated polyarylenes with well-defined structures and functional properties are highly desirable for advanced materials, but their synthesis often requires harsh conditions or expensive catalysts. In this work, an efficient, transition-metal-free cyclization polymerization of aromatic diynes using dimethyl sulfoxide (DMSO) as both a solvent and a key reactant was developed. This polymerization is applicable to a wide range of aromatic diynes, producing a series of poly(m-terphenyl)s with high weight-average molecular weights (M_w up to 22 700) in moderate to high yields (up to 94%) at 130 °C under nitrogen in the presence of KOH/CH₃OH. The poly(m-terphenyl)s exhibited excellent thermal stability (T_d up to 367.7 °C) and morphological stability (T_m up to 252.5 °C). Moreover, the tetraphenylethylene (TPE)-containing poly(m-terphenyl)s display aggregation-enhanced emission (AEE) properties, and its aggregates could serve as a fluorescent probe for Fe³⁺ detection, showing high selectivity and sensitivity (limit of detection = 8.21 × 10⁻⁷ M) with a large Stern–Volmer quenching constant (49 970 M⁻¹). Therefore, this work not only expands the toolkit of alkyne-based polymerization but also provides a cost-effective strategy to convert low-cost industrial raw materials (DMSO) into functional conjugated polymers, holding great promise for chemical sensing applications.

Macromolecular architecture control of fluorescent polymers presents an important approach to diverse self-assembled nanostructures and tailored functions. Herein, tetraphenylethylene (TPE) derivatives with different bromopropionate and hydroxyl functionalities were synthesized efficiently. Based on the single electron transfer living radical polymerization (SET-LRP) of oligo(ethylene glycol) methyl ether acrylate (OEGA) and the mechanistic transition to reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA), well-defined aggregation-induced emission (AIE)-active miktoarm star TPE-(POEGA)_n-(PBzMA)_4−n (n = 1–3) nanoassemblies were synthesized for the first time. The nanoassemblies were utilized as an ideal platform to probe the intricate interplay between macromolecular architecture, self-assembly behavior, and fluorescence properties. Results showed that the arm engineering (changing the respective arm numbers) of miktoarm star polymers can bring about drastic alterations in the self-assembled morphology and photoluminescence characteristics. This arises from the influences of macromolecular structure on molecular packing, intermolecular interactions and intramolecular motions. This work highlights the unique advantage of miktoarm star architecture design and has far-reaching implications for the rational design of high-performance intelligent fluorescence systems.

Epoxy resins (EPs) are widely used in adhesives, coatings, encapsulation materials, and high-performance composites due to their excellent overall properties, such as excellent bond strength, dimensional stability, chemical resistance, etc. However, EPs have the significant disadvantage of insufficient flame retardancy, which limits their applicability. At the same time, increasing environmental concerns, such as global warming and the depletion of oil resources, require the exploration of alternatives, especially bio-EPs derived from sustainable sources. This review presents the research progress on intrinsic flame-retardant EPs, including those based on phosphate esters, phosphaphenanthrene, and cyclotriphosphazene, as well as their underlying mechanisms. Subsequently, the synthetic routes, structures, and properties of several representative bio-based flame-retardant EPs, such as eugenol-based, cardanol-based, rosin-based, vegetable-oil-based, and vanillin-based, were introduced. Finally, the development of bio-based flame-retardant EPs is envisioned, which can be further studied in terms of expanding raw material choices, optimizing synthesis and processing methods, long-term stability, life cycle assessment, and sustainability analysis. This review is instructive for the research on the synthesis of bio-based EPs and their flame-retardant modification.

Developing simple and highly efficient organocatalytic systems for the ring-opening alternating copolymerization (ROAC) of epoxides and cyclic anhydrides remains a significant challenge. Herein, a simple phosphazenium salt, specifically tetrakis[tris(dimethylamino)phosphoranylidenamino]phosphonium chloride (P₅⁺Cl⁻), combined with triethylborane (BEt₃) as a cocatalyst, has been demonstrated to be an efficient binary catalytic system for the ROAC of epoxides and cyclic anhydrides. Promoted by the bulky P₅⁺ cation and the electrostatic effects arising from loosely associated cation–anion pairs in P₅⁺Cl⁻, the P₅⁺Cl⁻/BEt₃ binary system exhibited excellent catalytic performance, achieving the maximum turnover frequency (TOF) of 9800 h⁻¹ at 180 °C in the ROAC of cyclohexene oxide (CHO) and phthalic anhydride (PA). Moreover, the ROAC proceeded in a controlled manner, which was supported by kinetic studies, nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC) spectra, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis. The methodology produced polyester with a high molecular weight (M_n) of up to 103 kDa, which offered a rare example of poly(PA-alt-CHO) exceeding 100 kDa. A series of well-defined polyesters were synthesized by the coupling of various epoxides (CHO, PO, BO, ECH, AGE and SO) with PA using the P₅⁺Cl⁻/BEt₃ catalytic system.

In this study, poly(ethylene glycol)-based materials exhibiting pH-controllable and time-dependent lower critical solution temperature (LCST) were developed using glycidyl triazolyl polymers (GTPs) functionalized with tri(ethylene glycol) monomethyl ether (EG3) and carboxylic acid (COOH) side groups via a copper-free azide–alkyne cycloaddition reaction. The physical properties of the GTP-EG3 homopolymer and the GTP-EG3-co-COOH copolymer were characterized using NMR, IR, size exclusion chromatography, differential scanning calorimetry, and thermogravimetric analysis. The effects of copolymer composition, polymer concentration, ions in phosphate-buffered saline (PBS), and pH on LCST behavior were systematically investigated. PBS was found to promote aggregation of the GTP-EG3 homopolymer due to the salting-out effect described by the Hofmeister series. Since non-ionized COOH groups behave as hydrophobic moieties, the LCST decreased with increasing COOH content. Active control of LCST through pH variation was successfully demonstrated, revealing a linear relationship between LCST and the degree of COOH ionization. The equivalence point observed in the pH titration deviated from the theoretical value. Over time, this deviation gradually diminished. In connection with this phenomenon, a time-dependent change in LCST was also observed, even though no chemical reaction such as hydrolysis took place. The observed LCSTs ranged from 18 °C to 81 °C, encompassing the physiological temperature range.

Degradable polymer nanoparticles are attracting increasing interest for applications in cargo-release and imaging, as well as offering degradable alternatives to non-degradable nanoparticles used in various commodity applications. One promising approach is the utilisation of photo-degradable polymers such as poly(vinyl ketones). Here we report the ethanolic dispersion and aqueous emulsion polymerisation-induced self-assembly (PISA) of phenyl vinyl ketone (PVK) using a linear polyethylene glycol macromolecular reversible addition–fragmentation chain transfer (RAFT) agent (PEG5K-TTC) to produce UV-light degradable block copolymer (PEG5k-b-PPVK) nanoparticles. We demonstrate that photo-RAFT PISA in ethanol produces well-defined PEG5k-b-PPVK spherical nanoparticles (D_z = 36–101 nm) with high monomer conversions in 2 h. These nanoparticles were found to readily degrade under UV-light irradiation, and in natural sunlight, with a substantial loss in molar mass (26 to 1 kg mol⁻¹). SAXS and TEM studies demonstrated that degradation in ethanol led to a complete loss of the nanoparticle structure. However, upon degradation in water, the particle structure was maintained, although chain degradation occurred as well; presumably because the formed hydrophobic PPVK fragments remain assembled in the hydrophobic particle core due to their insolubility in water. Aqueous emulsion thermal and photo-RAFT PISA of PVK were also studied to produce degradable aqueous diblock copolymer latexes. Utilisation of a photo-RAFT polymerisation procedure led to unwanted side reactions attributed to the production of light-generated monomer radicals, which can initiate a free-radical polymerisation within the monomer droplets. However, utilisation of a classical thermal-RAFT polymerisation avoided this competing initiation and generated well-controlled PEG-b-PPVK diblock copolymers. Lastly, the possibility to copolymerise styrene with PVK through an aqueous emulsion PISA was also demonstrated. All aqueous latexes also showed significant polymer degradation when irradiated with UV-light. This work demonstrates how UV-degradable diblock copolymer nanoparticles can be efficiently synthesised via PISA in both ethanol and water.

Chain extenders, usually small aliphatic diols, play a great role in thermoplastic polyurethanes (TPUs) by forming hard segments and increasing the molecular weight. In this study, two chain extenders, N,N-bis(2-hydroxyethyl)urea (MEA–DMC, containing a urea group) and N-(2-hydroxyethyl)-O-(2-hydroxyethyl)carbamate (MEA–EC, containing a single carbamate group), are synthesized to examine their effects on the resulting TPUs with the chain extender 1,4-butanediol (BDO) as a control. Specifically, the TPUs are prepared by reacting the extenders with a prepolymer composed of poly(tetramethylene glycol) (PTMG, M_n = 2000) and methylene-bis(4-cyclohexylisocyanate) (HMDI). The results show that the tensile strength and elongation at break of TPU-MEA-DMC-1, TPU-MEA-EC-1 and TPU-BDO-1 are 22.7 MPa, 12.0 MPa, and 8.2 MPa and 1400%, 1600% and 1200%, respectively. The influences of chain extender content, the molar ratio of NCO/OH (R-value), and prepolymer molecular weight on the properties of the as-prepared TPUs are also studied. The tensile strength of TPU-MEA-DMC is in the range of 22.7 MPa to 50.5 MPa, and that of TPU-MEA-EC is in the range of 12.0 MPa to 34.7 MPa, respectively. These improvements are primarily attributed to the presence of urea/urethane in the chain extenders or the hard segment density. Urea groups (two hydrogen-bond donors (–NH–)) or carbamate groups (one hydrogen-bond donor (–NH–)) enhance hydrogen-bonding density within the polymer, thus reinforcing its mechanical properties. Moreover, DSC analysis shows that TPU-MEA-DMC exhibits a PTMG cold crystallization exotherm near −25 °C, which weakens and shifts to higher temperatures with more hard segments or lower prepolymer molecular weight.

Coacervates have emerged as promising systems for achieving dynamic compartmentalization. In particular, synthetic polymeric complex coacervates represent a well-established class. However, they often disassemble at high ionic strength condition due to charge screening effects. In contrast, simple coacervates, which form via phase separation of a single polymer species, serve as complementary systems that can exist under such conditions. Despite this advantage, the design and understanding of synthetic simple coacervates remains limited. Here, we report the thermoresponsive simple coacervation behavior of synthetic copolymers compose of lower critical solution temperature (LCST)-type and hydrophilic monomers. Through systematic investigations, we revealed that a wide variety of combinations of LCST-type monomers and hydrophilic monomers enables thermoresponsive simple coacervation in water in the presence of salts. Our findings provide a guideline for designing thermoresponsive simple coacervate systems based on synthetic LCST-type copolymers. We also highlight the importance of carefully characterizing the microphases that emerge upon phase separation of thermoresponsive copolymers under each specific usage condition.