Macromolecules最新文献

Aromatic poly(dithioacetal)s (PDTAs) are functional optical polymers with high refractive indices (n_D ∼ 1.7), colorlessness, and chemical recyclability, although the high flexibility of the dithioacetal unit has resulted in poor glass transition temperatures (T_g < 100 °C). In this study, we present a rational approach to improving the T_g and transparency of PDTAs by introducing polar S=O-containing side chains to leverage intermolecular dipole–dipole interactions. PDTAs with 4-(methylsulfonyl)phenyl (SO₂MePh) side groups, in particular, exhibit much improved T_g (up to 133 °C) and transparency (%T ≥ 98) while retaining their high refractive indices (n_D = 1.72–1.74) compared to methylthio-containing PDTAs. Density measurements revealed that introducing S=O groups into PDTA side chains induces sulfone-bonding interactions that lead to denser interchain packing in the bulk, thereby enhancing thermostability. Strikingly, combining SO₂MePh side chains and a rigid, polarizable biphenyl unit in the PDTA scaffold increases T_g by up to 177 °C while maintaining a comparably high refractive index (n_D = 1.74). Overall, these findings demonstrate the role of polar S=O groups in aromatic PDTAs as a key structure that balances thermal stability, transparency, and high-refractive-index properties.

Polypeptide-based block copolymers are promising platforms for creating hierarchical nanostructures because their secondary structures can direct mesoscale self-assembly. This study investigates how polypeptide chain length and thermal annealing govern the hierarchical organization of poly(ethylene glycol)-b-poly(ε-benzyloxycarbonyl-l-lysine) (PEG-b-PZLL) thin films. Combined FTIR, AFM, AFM-IR, and synchrotron GIWAXS/GISAXS analyses reveal that PZLL segments predominantly form α-helical conformations that assemble into hexagonally packed domains with nearly constant lattice parameters across compositions. Increasing the PZLL degree of polymerization stabilizes the α-helical structure, promotes preferential in-plane orientation of cylindrical domains, and enables the formation of long-range ordered fibrillar morphologies, whereas short PZLL chains partially transform into β-sheet structures during film formation and after high-temperature annealing. These findings establish a direct relationship between the secondary structure, orientational ordering, and mesoscale morphology in self-assembled polypeptide block copolymer films.

We study how confinement affects topology and conformations in flexible and semiflexible slit-confined polymer melts of varying thickness h. The knotting probability exhibits a maximum at intermediate thicknesses near the bulk radius of gyration h ≈ R_g,bulk, vanishes at small h, and approaches bulk values for large h. While knotting is enhanced close to boundaries, the entanglement length increases monotonically and conformations become increasingly flattened. A layer-resolved analysis of structural and topological properties allows us to reconstruct the explicit thickness dependencies by integrating layer-resolved properties of a thick slit.

Fluorescent polymers enable precise modulation of photophysical properties through controlled chain architecture; however, systematic decoupling of intrachain and interchain fluorescence contributions remains a significant challenge. Here, non-conjugated polynorbornene (pNB) is employed as a model backbone to investigate how chromophore planarity and degree of polymerization (DP) govern fluorescence mechanisms. Three homopolymers—pNBAn (planar anthracene), pNBDPQ (non-planar diphenyl quinoline), and pNBTPE (AIE-active tetraphenylethylene)—were synthesized via living ROMP (Ð ≤ 1.30, DP = 10–300). DLS confirmed single-chain morphology under all dilute-solution conditions, ruling out large-interchain aggregation. pNBAn exhibits progressive fluorescence quenching with increasing DP via intrachain entanglement; pNBDPQ undergoes a DP-dependent 76 nm emission red-shift with an isosbestic point in chloroform, attributed to chromophore planarization within entangled single chains; and pNBTPE displays DP-amplified AIE upon water addition, with π-stacking confirmed by HR-TEM. These findings establish both polymer DP and chromophore planarity as the key structural parameters governing intrachain fluorescence mechanisms in non-conjugated pNB systems.

Accessing complex morphologies in polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers at high PEO volume fractions is often hindered by PEO crystallization and relatively weak segregation strength. Here, we report an anomalous thermotropic transition from hexagonally packed cylinders (HEX) to a double gyroid (DG) network in PEO-rich PS-b-PEO/ionic liquid (IL) blends, where a strongly PEO-selective IL suppresses crystallization, swells the PEO domains, and increases the effective segregation strength (χ_eff) with increasing IL concentration. At low temperatures, strong PEO-IL hydrogen-bonding interactions promote anisotropic conformations of the PEO blocks and stabilize a frustrated HEX morphology under vitrified PS domains. Upon heating above the glass transition temperature of the PS block (T_g,PS), increased segmental mobility enables chain relaxation, while possible weakening of directional PEO-IL interactions may further reduce the tendency toward locally constrained chain extension. The swollen PEO/IL domain is consequently accommodated through an increase in the interfacial area per chain (Σ) and reduced chain stretching. The cylindrical geometry cannot accommodate this enlarged Σ without imposing severe packing constraints on the PS domains. The system therefore undergoes a HEX→DG transition, wherein the bicontinuous DG morphology redistributes interfacial area and chain conformations in three dimensions to relieve packing frustration under incompressibility. The DG structure can be kinetically trapped upon cooling, resulting in a robust three-dimensional ion-conducting network that exhibits higher conductivity than the cylindrical and lamellar phases.