ACS Macro Letters最新文献

Here, we identify sterically exposed bromothiophene C–Brbonds in diketopyrrolopyrrole (DPP) monomers as monomer-level structuralwarning signs for hidden homocoupling defects in Migita–Stille-derivedDPP–dithienylethene (DTE) polymers. High-temperature ¹H NMR analysis revealed 11% DPP–DPP and 10% DTE–DTElinkages in a Stille-derived polymer represented by an alternatingDPP–DTE repeat unit, whereas a locally hexyl-substituted structuralcomparator contained <1% and approximately 1%, respectively. Matchedsmall-molecule Stille reactions reproduced the same substrate-dependentordering in every catalyst system directly compared. Under Pd/P(o-tolyl)₃ conditions, lowering the temperaturedecreased cross-coupling selectivity for the exposed substrate, butnot the locally substituted analogue, thereby highlighting the elevatedhomocoupling susceptibility of exposed C–Br sites. Comparisonof the homocoupling-rich Stille-derived polymer with a low-homocouplingSuzuki–Miyaura reference revealed distinct optical/electronicproperties, thin-film organization, and transistor characteristics.These findings underscore the need to verify polymer linkage sequencesexperimentally rather than infer them from formally drawn repeat unitsor general expectations regarding coupling selectivity.

We combine dielectric and viscoelastic measurements withnovelstatistical mechanical theories to establish and understand strongdecoupling of cation activated dynamics from the polymer segmentalrelaxation in polymerized ionic liquids. Weakly ion-dependent (Li,Na, K) apparent power laws with fractional exponents between the twocharacteristic time scales (ionic and segmental) are observed andpredicted in the supercooled regime. The ratio of segmental to ionrelaxation times grows in a strongly non-Arrhenius manner with cooling.However, at high (fast) enough temperature (segmental relaxation),the theory predicts that decoupling continuously vanishes, and a linearWalden-like proportionality between the two relaxation times is recovered.The theoretical analysis spans 20 decades in time, including the glassstate. The mechanistic key to the rich dynamics is the extent to whichion-activated barrier crossing is coupled with in-cage local polymerdynamical fluctuations that facilitate ion hopping.

Most terpene-derived polymers reported to date are amorphousresins,elastomers, or cross-linked networks. Here we report a crystalline isotactic polyterpenoid, poly(4,8-dimethyl-1,7-nonadiene)(PDMND), synthesized from naturally abundant citronellal using a pyridylamidohafnium catalyst. Temperature-dependent WAXD reveals that PDMND adoptsan isotactic-polypropylene-like (3/1) helical backbonewith an axial repeat of ca. 6.6 Å. Unlike conventional semicrystallinepolyolefins, the densely populated, nonlinear terpenoid side groupsprohibit chain folding and promote the packing of fully extended bottlebrush-likerigid rods. DSC, WAXD, FTIR, and rheological analyses reveal reversibleorder–disorder transitions from an ordered cylindrical-rodcrystal to a side-chain-disordered phase and further to a nematic-likecrystalline state before melting. This work expands terpene-derivedpolymers from amorphous materials to crystalline stereoregular polyolefinswith unusual bottlebrush-rod packing.

Domain spacing in block copolymers is typically limitedby polymercontour length. Here, we report anomalously large domain spacing instrongly segregated linear–bottlebrush diblock copolymers.Using transmission electron microscopy and small-angle X-ray scattering,we show that the bridging distance between neighboring linear domainsexceeds the bottlebrush backbone contour length. Notably, the excesslength matches that previously observed in linear–bottlebrush–lineartriblock copolymers, despite the inability of diblocks to form physicalnetworks. This agreement rules out network formation as the originof the anomaly. We propose that the penetration of linear segmentsinto the bottlebrush domain relieves side chain packing frustrationand increases the effective bottlebrush domain size. These findingsreveal a previously unrecognized mechanism for generating domain spacingbeyond contour-length limits and suggest that molecular architecturecan be used to program large length scales in nanostructured softmaterials.

Copolymerizationis widely used to combine functional moietiesin antimicrobial polymers, assuming their activities are retainedafter covalent integration. Here, we show that covalent integrationcan instead attenuate antibacterial membrane-perturbation activityin cationic polymethacrylates. Using quaternary ammonium- and sulfonium-containingpolymers as model systems, we compared homopolymers, physical mixtures,and random and block copolymers. Rifampicin potentiation against Escherichia coli was used as a functional readout. Althoughthe quaternary ammonium homopolymer enhanced rifampicin activity by1024-fold, this effect was largely lost after copolymerization, withboth random and block copolymers exhibiting only 2–4-fold potentiationdespite identical compositions. In contrast, physical mixtures retainedthe activity of the highly potent component. Mechanistically, copolymerarchitectures preserved membrane binding but restricted postadsorptioninterfacial organization, thereby reducing interfacial dissipationand membrane depolarization. These findings demonstrate that identicalcomposition does not guarantee preservation of functional output aftercopolymerization, highlighting the importance of intrachain organizationin antimicrobial polymer design.

Underwater adhesives are critical for marine engineeringand biomedicalapplications, but face challenges in their bonding strength and processingcomplexity. Inspired by mussel foot proteins, catechol-based curingagents (D-A and D-C) were successfully synthesized via a one-stepcondensation reaction, while monophenol-based curing agents (D-L andD-P) were prepared as the control groups. The D-C curing system exhibitedsuperior performance, demonstrating an exceptionally low curing activationenergy of 38.29 kJ/mol (27.70% lower than that of D-P), an ultrahighunderwater adhesion strength exceeding 15 MPa on stainless steel substrates(125.89% improvement over D-P), and an antidispersion behavior withcomplete flow cessation within 30 min of underwater application. Byintegrating multiscale characterization techniques (SFG spectroscopy,DFT calculations, AIMD simulations, and XPS), we systematically elucidatedthe multisynergistic adhesion mechanism of the D-C system. The resultsreveal a highly cooperative water displacement, interfacial bonding,and bulk network locking mechanism that collectively governs the superiorunderwater adhesion performance.

Rearranging hydrogels are used for applications thatrequire tailoredcontrol of solid- and liquid-like properties. These applications necessitatepinpointing the phase transition, where a sample-spanning structureis formed or broken. To characterize the mechanical properties atthe phase transition, we use time-cure superposition (TCS), whichsuperimposes rheological properties as a function of increasing extentsof gelation or degradation, p. We generally use reactiontime to estimate p. However, dynamic materials undergonetwork rearrangements, which invalidates this assumption. In thiswork, we characterize the rheology of a rearranging hydrogel duringdegradation using multiple particle tracking microrheology (MPT).The logarithmic slope of the particle mean-squared displacements,α, is used to estimate p instead of time, becauseα is directly related to the cross-link density, ρ, andis independent of time. This reformulation identifies the phase transitionunambiguously and more precisely, expanding the scope of the techniqueto quantify phase transitions in these types of hydrogels.

Nonviral polymeric vectors offer a tunable platform fornucleicacid delivery, yet formulation variables beyond polymer structureremain underexplored. Here, we systematically investigate the roleof stock solvent in shaping gene delivery performance using end-cappedhighly branched poly(amino ester) (HPAE) vectors. By combining a structuredexperimental design with an interpretable machine learning framework,we reveal that transfection efficiency is primarily governed by polymerfeatures, while solvent properties modulate performance through strongpolymer–solvent interactions. Descriptor-level analysis identifieskey molecular features associated with high-performing formulations,highlighting the importance of polymer size, charge density, and hydrophobic–polarbalance. Selected polymer–solvent combinations enable efficientCFTR protein restoration in cystic fibrosis disease cells and achieverobust in vivo transgene expression following systemicadministration in mice. Overall, this work establishes stock solventas a critical and tunable formulation parameter and provides a data-drivenframework for optimizing polymeric gene delivery systems.

Theefficient release of semiconducting single-walledcarbon nanotubes(s-SWCNTs) from conjugated polymer wrappers via photoisomerizationunder light stimuli is attractive but has not been achieved yet andremains challenging. Herein, we report a photoisomerization polymerof PFDD-CS, by incorporating a cyano-styrene linker featuring a twistedconjugate structure. It can undergo only the desired trans-to-cis photoisomerization, but not the normal photocyclizationnor photoaddition for cyano-styrene derivatives. Particularly, itcan even occur in situ successfully on the nanotube surface underlight stimuli, facilitating the release of bare s-SWCNTs. Experimentalresults revealed that the twisted conjugate structure of the initial trans-form contributes to the mobility on the surface ofs-SWCNTs, while the significant conformational differences betweenthe trans- and cis-isomers facilitatepolymer detachment and bare s-SWCNT release. This work provides amild, light-triggered strategy for obtaining pure nanotubes and advancesthe development of stimuli-responsive polymers for nanomaterials processing.

Postpolymerization modification of polyolefins enablesdirect introductionof functionality into high-volume, low-cost commodity materials, affordingaccess to functional materials that are otherwise challenging to synthesizedirectly from monomers. However, traditional postpolymerization modificationstrategies result in randomly distributed functionalization alongthe polyolefin backbone, which can disrupt crystallinity and degradethe thermomechanical properties of the derived polymers. Crystallite-templatedpostpolymerization functionalization has recently emerged as a promisingstrategy to overcome these limitations, yet existing approaches oftenrequire specially prepared semicrystalline gels. Here, we report aswelling-assisted postpolymerization functionalization strategy thatdirectly leverages the semicrystalline morphology of melt-processedpolyolefins. In this process, the chemical reagents are selectivelyintroduced to the amorphous phase of polymers for a targeted functionalizationreaction at elevated temperatures. The resulting functionalized polyolefinslargely retain the melting temperature and crystallinity of theirunmodified counterparts across multiple grafting monomers, highlightinga practical and versatile platform for producing functional polyolefinswith a preserved semicrystalline microstructure and bulk propertiesdirectly from commercial feedstocks.