Macromolecules最新文献

The rational design of donor–acceptor (D–A) monomers enables control over porosity, electroactivity, and stability in conjugated microporous polymers (CMPs). Herein, we report the synthesis of five thiophene–benzothiadiazole-based monomers, four of them novel, and their polymerization via chemical (FeCl₃ oxidative) and electrochemical routes. Structural diversity was introduced through terthiophene regiochemistry (2,3- vs 2,4-substitution) and rigid, multibranched cores including benzene, spirobifluorene, and tetraphenylmethane. Chemically synthesized bulk CMPs exhibit specific surface areas of 81–591 m² g^–1, while electropolymerized films from planar monomers suffer pore collapse. In contrast, rigid three-dimensional monomers yield smooth, highly porous films with surface areas up to 318 m² g^–1. The rigid structure of SpTBTTh enables the formation of thin polymer films with smooth morphology while preserving high porosity. Combined with favorable energy level alignment, these characteristics highlight the potential of rigid D–A CMP films as active layers in organic photovoltaic architectures.

Crystallization in poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is strongly influenced by the thermal history. Additive-free P(3HB-co-5% 4HB) was biosynthesized, and melt memory domains were identified from DSC crystallization measurements after processing for 3 min at temperatures between 152 and 212 °C. A broad self-nucleation domain (∼20 °C) was confirmed by polarized optical microscopy, whereas complete melt memory erasure led to sparse nucleation and slow crystallization. Thermal degradation, already present at low processing temperatures, substantially reduced the molecular weight, which was shown to affect spherulite growth rates and overall crystallization behavior. When melt memory was evaluated after thermal history removal (3 min at T_DI) and recrystallization, the self-nucleation domain narrowed (∼10 °C). Increasing T_DI further weakened memory due to degradation-induced molecular weight reduction. These results demonstrate that meaningful crystallization studies of P(3HB-co-4HB) require careful optimization of processing temperatures to balance melt memory effects with molecular weight retention within the narrow thermal processing window of this copolymer.

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a widely used conducting polymer, whose conductivity can be enhanced by incorporation of specific chemical components, whereas diffusion of water into the material can reduce its conductivity. These changes are typically linked to morphological changes in lamella crystallite size, π–π stacking, chain orientation, and interlamella connectivity. However, an atomistic-level understanding of how specific chemical components influence these properties remains limited, particularly in relation to experimentally observed conductivity trends. In this study, molecular dynamics (MD) simulations are employed to investigate the effects of electrolytes, dopamine, and poly(ethylene glycol) 400 (PEG-400) on PEDOT:PSS morphology and relate the findings to experimental observations. All chemical components were found to screen electrostatic interactions between PEDOT and PSS, potentially affecting the conductivity. Dopamine tends to reduce conductivity by intercalating between PEDOT and PSS, disrupting interdomain connectivity. In contrast, PEG-400 enhances conductivity by improving interlamellar connectivity without altering PEDOT chain conformation, challenging conventional explanations and suggesting an alternative mechanism. CuCl₂ enhances conductivity via PEDOT conformational changes associated with partial PSS loss, whereas NaCl shows minimal morphological changes, in agreement with established explanations. Overall, MD simulations confirm the established trends, provide alternative insights, and challenge commonly accepted explanations, demonstrating their utility in validating, refining, and reinterpreting molecular mechanisms in complex polymer systems.

We demonstrate that long-chain branched polypropylene (LCB PP) exhibits pronounced melt memory above the equilibrium melting point due to topological constraints and gel-like structures that slow the relaxation of non-equilibrium chain states. These states, formed during synthesis and subsequent melt processing, act as self-nuclei in differential scanning calorimetry (DSC) experiments and persist beyond the conventional 5 min equilibration used in standard DSC protocols. The decay of self-nuclei, monitored via the isothermal crystallization rate, follows a power-law dependence with the equilibration time. This behavior agrees with diffusive relaxation of non-equilibrium clusters in a topologically complex environment. Morphological analyses show that self-nucleation produces nucleation densities (N_d) up to 10¹¹ cm^–3, which suppresses spherulitic growth and induces anisotropic lamellar textures. The self-nuclei are most effectively reduced in a prior solution treatment of the polymer, which decreases N_d and crystallization rate but also increases the viscoelastic relaxation time, demonstrating the link between melt structure and crystallization.

In this study, the chain end of a reversible addition–fragmentation chain transfer (RAFT) polymerization agent of poly(cyclohexene carbonate) (PCHC) was synthesized via the ring-opening copolymerization of CO₂ and cyclohexene oxide (CHO) by using s-dodecyl-s’-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (DDMAT) as a chain transfer agent. Various block copolymers of poly(cyclohexene carbonate)-b-poly(styrene-alt-N-(hydroxyphenyl)maleimide) (PCHC-b-PSHPMI) were subsequently synthesized by the RAFT copolymerization of styrene and N-(hydroxyphenyl)maleimide (HPMI) in the presence of azobis(isobutyronitrile) (AIBN), which were characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). DSC thermal analyses indicated that the single T_g values were observed for all PCHC-b-PSHPMI copolymers, indicating miscible behavior, and the T_g value was 194 °C for the PCHC-b-PSHPMI78 copolymer. One- and two-dimensional (2D) FTIR spectroscopy revealed that these PCHC-b-PSHPMI copolymers actually provide relatively weak intermolecular O–H···O═C hydrogen bonding, which was attenuated by the self-association of hydrogen bonding within the pure PCHC and pure PSHPMI segments. In the solid-state ¹³C NMR spectra, a pronounced chemical shift variation of the C–OH and C═O units of the PSHPMI segment and C═O units of the PCHC segment was also observed, which is attributable to the intermolecular hydrogen interactions in these PCHC-b-PSHPMI copolymers. Rotating-frame ¹H spin–lattice relaxation [T_1ρ(H)] analyses also indicated the complete miscible behavior of these block copolymers within the 2–3 nm length scale, and the relaxation times exhibited positive deviations from the linear predicted rule. These results suggest that the loose chain structure was formed because of the weaker intermolecular hydrogen bonding between the PCHC and PSHPMI segments in the block copolymers.

Developing high-performance polyurethane (PU) elastomers requires overcoming the inherent trade-off between strength and toughness through precise control of the microphase separation morphology. Advances in nanostructure control and nondestructive microstructural detection are therefore essential. Herein, we report a hyperbranched PU elastomer (PU-HPAE_x) synthesized using hyperbranched poly(amino ester) (HPAE) as a dual-function macromonomer that acts simultaneously as a chain extender and a nonconventional fluorescent probe. The hyperbranched architecture creates a three-dimensional network enriched with high-density sacrificial hydrogen bonds (H-bonds) and a well-defined microphase-separated morphology, resulting in exceptional strength (65.80 MPa), elongation (1031.70%), and toughness (185.3 MJ m^–3)─overcoming classical strength–toughness conflicts. In addition, the hyperbranched topology promotes efficient cluster-triggered emission (CTE) via through-space conjugation (TSC), endowing PU-HPAE_x with exceptionally strong fluorescence (quantum yield 11.16%). Critically, HPAE serves as an intrinsic fluorescent probe, enabling in situ visualization of micrometer-scale phase separation and its dynamic evolution, thereby providing key insights into the morphology–performance relationship. Furthermore, HPAE exhibits stimuli-responsive fluorescence under both mechanical strain and humidity, highlighting its potential application in smart sensing. By leveraging topological structure regulation, this work successfully establishes a novel strategy for fluorescent PU elastomers that integrates high performance with nondestructive visualization of microphase morphology.

We investigate the coupled evolution of heterogeneous strain, crystallinity, and stress fields in natural rubber (NR) sheets containing a circular hole during uniaxial stretching, with a focus on how strain-induced crystallization (SIC) influences local stress concentration at structural discontinuities. By high-resolution digital image correlation, an empirical strain-crystallinity relationship and a hyperelasticity analysis firmly grounded in stress–strain data obtained under diverse deformation modes, we quantitatvely map the spatial distributions of strain, SIC, and stress in the extreme vicinity (≈0.2 mm) of the defect. Local strain concentration at the lateral hole edges triggers pronounced SIC, resulting in strong stiffening and a stress concentration factor (K_t*) as high as 4.5─significantly exceeding classical elastic predictions. Upon further stretching, K_t* plateaus, eventually as SIC develops in the far-field region, promoting a more homogeneous stress distribution. The SIC-induced stiffening also generates a highly anisotropic stress field near the hole edges due to preferential reinforcement along the crystalline orientation. The localized SIC causes characteristic hole-shape evolution, where the hole becomes increasingly elongated along the stretching axis compared with the fully amorphous state. These findings elucidate the fundamental interplay between SIC and local stress concentration in elastomers with structural discontinuities and provide mechanistic insights for designing defect-tolerant, high-toughness rubber materials.

The controlled preparation of stimulus-responsive soft nanomaterials, especially those with anisotropic nanostructures, has attracted wide attention. Herein, a series of N-(2-(6-(4-(diphenylamino)phenyl)-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)ethyl)acrylamide (TNAA, n = 0, 1, 2, 3, or 4)-containing luminescent monomers with an adjustable flexible spacer length are randomly copolymerized with N-isopropylacrylamide (NIPAM) to afford thermoresponsive polymers with a tunable cloud point temperature (CP) and fluorescence emission. By adjusting the molar ratio of TNAA to NIPAM, the CP of the polymers can be regulated from 49.1 ± 0.7 to 26.0 ± 0.8 °C, while the emission wavelength is controlled from 598 to 633 nm as the length of the flexible spacer shortens. Density functional theory calculation results verify that as the length of flexible spacers increases, the path for intramolecular electron transfer becomes longer. It induces an elevation in the energy required for electrons to transfer from the highest occupied molecular orbital to the lowest unoccupied molecular orbital, leading to the increase in the energy gap. Importantly, nanobowls with controlled diameter, opening size, and inherited thermoresponsive and tunable fluorescence properties are formed by self-assembly. As the temperature increases from below the CP of the polymer to 60 °C, the hydrophilic-to-hydrophobic transition of PNIPAM segments occurs, leading to the enhancement of the hydrophobic interactions and a more compact aggregation of the polymer chains. Consequently, the nanobowls also change from their original loose and porous structure to a relatively dense state. Overall, thermoresponsive luminescent nanobowls with controlled dimensions and fluorescence properties are achieved by manipulating the spacer length between fluorophores and the polymer backbone.