Macromolecules最新文献

Langevin dynamics simulations of double-knotted DNA molecules in a nanochannel reveal that the interactions between the two knots differ with the degree of channel confinement. In relatively wide channels, the two knots can intertwine with each other, forming a persistently intertwined knot. Moreover, the two knots can pass through each other in large channels. In contrast, for small channel sizes, the knots tend to remain separated, and their crossing is inhibited. The change in knot–knot interactions as the channel size decreases is rationalized through an analysis of the magnitude of the transverse fluctuations, which must be large enough to allow one knot to swell to accommodate the intertwined state.

A new versatile cyclic polymer platform for the design of advanced cyclic materials was prepared by combining ring-expansion metathesis polymerization (REMP) and click chemistry. Cyclic poly(norbornenyl azlactone) backbones were synthesized over an unprecedented length range with number-average degree of polymerization (DP_n) ranging from 25 to 1000. The cyclic topology was thoroughly characterized using ¹H NMR, size exclusion chromatography (SEC) with multiangle light scattering (MALS) and viscometer detection. Postpolymerization modification (PPM) of these scaffolds was carried out with amino-terminated mannoses using the click aminolysis of the azlactone moiety to prepare a library of multivalent cyclic glycopolymers. The binding inhibition of the resulting cyclic glycopolymers was assessed against a panel of model and biologically relevant lectins (Bc2L-A, FimH, langerin, DC-SIGN, and ConA). The cyclic carbohydrate-functionalized polynorbornenes exhibited high lectin-binding inhibitory potency in the biochip assay, surpassing their monovalent analogues by several orders of magnitude and competing strongly with their linear polymer analogues in terms of IC₅₀ values. Interestingly, the cyclic polymers also prevented the adhesion of Adherent-Invasive Escherichia coli implied in Crohn’s disease, to intestinal cells.

The fourth-generation oxazine ring-substituted polybenzoxazines have recently gained attention as promising high-performing thermosets. This work successfully investigates the role of the conjugated alkenyl moiety at the oxazine ring in influencing the course of polymerization with dual benefits: lowering the ring-opening polymerization (ROP) temperature and regulating the mass-loss phenomena. By employing biosourced precursors, viz., cinnamaldehyde and trans-4-stilbene carboxaldehyde, a facile methodology for monomer synthesis is demonstrated. The structural characterization of these benzoxazines is achieved using high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy, which indicate the successful inheritance of the reactive conjugated alkenyl functionalities into the oxazine ring-substituted benzoxazine monomers. The thermal behavior of the benzoxazine monomers is examined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to realize lowered ROP temperature (∼195 °C) and mass-loss (∼7%). Moreover, thermal polymerization and degradation kinetics, as well as relevant spectroscopic analyses, are performed to study the effect of the (conjugation vs extended conjugation) alkenyl functionality in determining the polymerization mechanisms of herein reported monomers. Prior to onset, ROP is observed to proceed via fragmentation, i.e., bond cleavage of the zwitterion intermediates and subsequent cycloaddition-adduct formation from in situ generated species. However, at a later stage, complete polymerization occurs through a more complex route, including the ROP of the oxazine ring and the participation of other adducts in the cross-linking process. The current strategy offers an intriguing avenue for modifying oxazine ring carbon centers with reactive functional organic skeletons, which may play an instrumental role in exploring potential high-temperature applications.

The ladder-type benzimidazobenzophenanthroline (BBL) polymer is one of the most important and most studied n-type conducting polymers. It is also an organic mixed ion-electron conductor (OMIEC), which can undergo electrochemical switching in electrolyte solutions by accommodating opposite ions. The extensive morphological changes of the OMIEC material during operation affect the transport properties and, hence, the device performance. However, molecular insights into the dynamic structural changes during the electrochemical switching are limited, as they are difficult or impossible to access in experiments. The computational microscope based on molecular dynamics (MD) calculations can provide us with complete insights into the detailed dynamic morphological changes that are currently missing, to a large extent, for the BBL polymer. In the present study, using atomistic MD simulations, we obtained microscopic insights into the electrochemical switching of BBL film in two different electrolytes, namely, single-atom counterion K⁺ (potassium) in water and molecular counterion DMBI⁺ (dimethyl-3-butyl imidazolium) in chloroform. For both cases, the maximum crystallinity is found up to a moderate reduction level. Beyond that, ion intercalation initiates a structural phase transition and causes a decrease in the crystalline order of the film. At the higher reduction levels, the single-atom K⁺ counterions are stabilized within the lamellar stacked BBL chains; in contrast, the DMBI⁺ counterions with higher molecular weights are stabilized within the BBL π–π stacks, forming π–π stacking between BBL and DMBI⁺. Our findings substantiate how molecular dopants can improve the thermomechanical stability of the material and why smaller single-atom counterions are preferred for maintaining better crystallinity. The detailed microscopic insights into the morphological changes during the electrochemical switching of BBL film, which cannot be directly accessed experimentally, can definitely help design n-type OMIEC-based devices made of BBL.

Ion transport through membrane nanopores is pertinent to several applications, including water desalination and energy harvesting. We synthesized a series of polymerized ionic liquids (PILs) based on the 1-butyl-3-vinylimidazolium cation ([BVIM]⁺ with three different anions ([X]⁻: [TFSI]⁻, [BF₄]⁻, [PF₆]⁻). We explored how mixtures of the PIL with the corresponding IL (poly[BVIM]⁺[X]⁻/[BMIM]⁺[X]⁻) penetrate the nanopores. For this purpose, we employ ex situ reflection optical microscopy of the evolution of the imbibition length and in situ conductivity measurements by nanodielectric spectroscopy. The latter provides details of ion motion during and following imbibition. In the bulk, symmetric poly[BVIM]⁺[X]⁻/[BMIM]⁺[X]⁻ mixtures are locally heterogeneous, composed of nearly pure IL domains and mixed PIL/IL domains. When the mixture is placed on top self-ordered nanoporous aluminum oxide templates (AAO), the ionic liquid is dragged by capillary action into the pores. During imbibition the two components partially demix. At the end of the filling process the pores contain an excess of the IL and a minority of PIL chains. Subsequently we explored the effect of polymer adsorption and surface functionality on the kinetics of ion transport. The results suggest the possibility to separate a mixture of ionic compounds (IL and PIL in this case) by the difference in the imbibition kinetics of its constituent components. Applications of AAOs as separation membranes for ionic systems are discussed.

The urgent demand for more sustainable materials has led to significant research in the field of CO₂-based polymers. This work describes monomer synthesis, polymerization, and polymer properties of long chain terpenoid- and CO₂-based polycarbonates. Utilizing (R,R)-(salcy)-Co(III)Cl (Co(Salen)Cl) and bis(triphenylphosphine)iminium chloride ([PPN]Cl) as a binary catalytic system, high molar mass polymers (up to 46.4 kg mol^–1) were achieved with narrow dispersities (M_w/M_n < 1.13) via solvent-free bulk polymerization. Crucially, synthesis of these high molar mass polycarbonates necessitates a reactor design featuring low reactor/gas volumes, as well as CO₂ with very low content of water, a requirement that is independent of the specific monomer employed. For this reason, an extensive evaluation of reactor/gas volume and predrying of CO₂ was conducted to achieve narrow molar mass distributions. A glass transition temperature range between −43 and −29 °C was achieved by employing both saturated and unsaturated terpenoids. When combining various terpenoid-based monomers, an ideally random terpolymerization was observed, confirmed by offline ¹H NMR kinetics. The resulting copolymers characterized by double bonds in their polymer side chains are addressable for further postmodification reactions. Owing to their good thermal stability and low T_g values, the absence of cross-linking reactions and high molar masses, these flexible long chain terpenoid-based polycarbonates emerge as highly promising candidates for use as soft segments in thermoplastic elastomers.

The existing synthesis methods of cyclodextrin (CD) polyrotaxanes (PRs) are generally tedious and low-yield. Herein, we report an efficient synthesis strategy for α-, β-, and γ-CD PRs. A Diels–Alder (DA) reaction between 9-anthracenemethanol and maleimide was used as the capping reaction since the adduct was large enough to lock α- and β-CDs and the reaction could be catalyzed by CDs, achieving high yields in aqueous medium under mild conditions. For the synthesis of γ-CD PRs, we introduced maleimide-modified second-generation polylysine dendrons at both ends of the polymer axle to slow the dethreading during the capping reaction and increase the number of the end-capping groups. Through the microwave-assistant retro-DA reaction, we synthesized α-, β-, and γ-CD molecular tubes with desirable yields. We further expanded the strategy to the synthesis of β-CD rotaxane-based molecular shuttles and achieved fluorescence modulation using the light-driven shuttle movement of the CD ring along the axle.

Bottlebrush poly(propylene carbonate) (PPC) was synthesized with defined molecular dimensions in order to understand their relationship to viscoelastic properties. Chain-transfer polymerization of propylene oxide with CO₂ using a tethered binuclear cobalt(III) salen catalyst afforded norbornene maleimide end-functionalized PPCs that yielded bottlebrush polymers through subsequent ring-opening metathesis polymerization. A series of PPC bottlebrushes were synthesized with varied side-chain (6 < N_sc < 198) and backbone lengths (100 < N_bb < 1,000). Several bottlebrushes were synthesized wherein the maleimide backbone was entangled or unentangled and/or PPC side-chains were entangled as evidenced by the material’s plateau modulus measured by small amplitude oscillatory frequency sweeps. The brushes’ rubbery moduli ranged from 29 to 485 kPa depending on the dimensions and volume fraction of PPC. As the dimensions of the backbone and side-chain were varied, the material densities and plateau moduli were used to calculate the bottlebrush crowding factor in order to demonstrate that the materials behave as backbone-extended bottlebrushes and not as densely grafted combs. The PPC side-chains could be depolymerized through a chain-end backbiting reaction to yield propylene carbonate or thermally cross-linked through transcarbonation reactions of the side-chains.

In this work, we synthesize a series of linear-comb block copolymers, polystyrene-b-poly(polyethylene glycol methyl ether acrylate) (PS–PPEGMEA), and study the microphase separation mechanism by LiTFSI-doping. The increasing salt concentration promotes the microphase separation of PS–PPEGMEA and also deflects the phase transition boundaries to the lower PPEGMEA volume fraction. We reveal that the effective interaction parameter exhibits a linear to nonlinear dependence on increasing salt concentration and is eventually weakened by the formation of ion clusters at high salt concentration. We further quantify the conformational asymmetry of PS–PPEGMEA by theoretical analysis and point out that the limit of the order–order transition boundaries is defined by strong segregation theory. Therefore, electrostatic interaction and conformational asymmetry jointly determine the microphase separation of PS–PPEGMEA block copolymer electrolytes. This study provides a fundamental understanding of the phase behaviors of salt-doped linear-comb block copolymers and suggests experimental strategies to modulate their nanostructures, which could be very useful for developing novel solid polymer electrolytes.

Delving into effective polymerization systems to maximize the porosity of hyper-cross-linked polymers (HCPs) is highly favorable for simultaneously improving their high-pressure methane storage and delivery capacities. In the present work, a mixed-solvent knitting strategy was introduced to construct hierarchical polymer architectures at room temperature using dichloromethane (DCM) and dichloroethane (DCE) as dual external cross-linkers. A strong correlation exists between the textural properties of these polymers and their structural expanding/shrinking variations, showing a smooth transition from a highly microporous network to a hierarchical porous framework. Especially, HCP-MS-3 knitted by the mixed solvents of 1:1 volume ratio of DCM to DCE has an impressive high pore volume of 2.72 cm³ g^–1, surpassing almost all previously reported HCPs, which not only exhibits an excellent gravimetric methane storage capacity up to 0.429 g g^–1 at 273 K but also shows an effective methane delivery rate of nearly 90% from 5 to 100 bar. This simple and efficient mixed-solvent knitting strategy contributes a promising approach for the rational design of highly porous HCPs as low-cost and high-capacity methane adsorbents, which is highly desired for practical methane storage applications.