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Several current topics are introduced in this review, with particular attention to highly proton-conductive polymer thin films with organized structure and molecularly oriented structure. Organized structure and molecularly oriented structure are anticipated as more promising approaches than conventional less-molecular-ordered structure to elucidate mechanisms of high proton conduction and control proton conduction. This review introduces related polymer materials and molecular design using lyotropic liquid crystals and hydrogen bond networks for high proton conduction. It also outlines the use of substrate surfaces and external fields, such as pressure and centrifugal force, for organizing structures and molecularly oriented structures.

The creation of DMC-based biodegradable materials with excellent properties is a potential and sustainable option now that the industrial production of dimethyl carbonate (DMC) synthesis from carbon dioxide is commercially feasible. Herein, a series of kilogram-scale DMC-based biodegradable poly(butylene carbonate) (PBC) with distinct molecular weight gradients (number average molecular weight (Mn) varied from 23 to 67 kg/mol) were synthesized successfully through a facile melt polycondensation reaction using a 5 L stainless steel reactor. The microstructure of the polymers was confirmed by FTIR and 1H NMR. It was thoroughly discussed how molecular weight affected the physical performance of PBC, including thermal properties, rheological behaviors, mechanical characteristics, and degradation behaviors. The findings indicated that the molecular weight had significant influence on the physical characteristics of PBC. Especially, PBC with Mn greater than 46 kg/mol showed excellent mechanical strength and elongation at break with the values of 37.3 MPa and 559.1%, respectively. All the PBCs exhibited appreciable biodegradability under enzymatic degradation. In addition, as a novel and environmentally acceptable nucleating agent, magnesium mandelate (Mg(MdA)2) was introduced into PBC via melt blending. The non-isothermal behaviors and isothermal crystallization kinetics of the PBC/Mg(MdA)2 were specially forced. It was discovered that Mg(MdA)2 greatly accelerated both the non-isothermal and isothermal crystallization of PBC and exhibited a prominent nucleation activity on the crystallization of PBC. Moreover, the WAXD patterns of all the blend samples displayed the same distinctive peaks as neat PBC, proving that the structure of the PBC crystals had no modification with the addition of Mg(MdA)2. Accordingly, the current work proposed enlarged step-by-step synthesis of PBC material and physical modification which highlighted the technical feasibility of PBC industrial production and expansion of processing molding applications.

The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles.

We examined the agglomeration behavior of a suspension of SiO 2 nanoparticles with average dimensions of ∼15 nm in a solution of tetrahydrofuran and polydisperse poly(methyl methacrylate) (PMMA) with a weight-average molecular weight in the range of (0.3–31) × 10 4 . For PMMA with a critical molecular weight ( M c ) of ∼3 × 10 4 or larger, at which PMMA chains show effective entanglement, a critical polymer concentration ( C* ) was clearly observed. At C* , the dispersed SiO 2 nanoparticles came into contact with one another and rapidly agglomerated. C* increased with decreasing molecular weight. However, no clear C* was observed for PMMA ( M w : 0.3 × 10 4 ) with M c or lower molecular weights. The molecular weight dependence of the observed C* can be explained by the depletion effect, but the lack of a clear C* for low molecular weight PMMA cannot be explained with this theory. Because C* occurs in the vicinity of the critical concentration, at which the random coils in the solution come into contact with one another and begin to overlap, the entanglement of random coils is considered to be the driving force behind nanoparticle agglomeration. However, no C* was observed because effective entanglement does not occur for PMMA with M c or lower. The transmittance is suddenly diminished at a critical concentration C *, and the C * shifts to the higher value as the smaller molecular weight is employed and, especially in the case of M w of ca. 0.3 × 10 4 , C * was not found out up to ca. 50 wt%.

The dipole moment of poly(ethylene oxide) (PEO) and its dependence on molecular weight and temperature have been investigated by measuring the dielectric constant and the density of dilute PEO-benzene solutions in the temperature range from 25 to 55°C. The dipole moments of the polymers (μmolecule2 )1/2 , increased linearly with respect to the square root of the degree of polymerization n, which confirms the theoretical prediction that the long-range excluded volume interactions have little effect on the dipole moment of polymers such as PEO. The estimated value for diethyl ether μDE is 1.20D, according to the relationship between (μmolecule2 )1/2 and n1/2 for PEO oligomers,10,17 which leads to a C-O bond moment, mC-O , of 1.07 D. The averaged dipole moment per constitutional repeating unit (μ2 )1/2 for PEO polymers is 1.040 ± 0.002 [D] at 25°C. The following dipole moment ratio and the temperature coefficient were obtained for PEO in benzene: (μ2 )/m2 = 0.472 ± 0.002 (at 25°C) and d ln(μ2 )/dT = (2.11 ± 0.28) × 10-3 K-1 (25-45°C). The experimental results are compared with the conformational characteristics of PEO investigated by the rotational isomeric state (RIS) analyses by Abe et al. and Sasanuma et al.

The dynamic shear properties of molecularly-thin films of unfunctionalized and end-functionalized (telechelic) Fomblin-Z perfluoropolyalkylether (PFPAE) melts with number-average molecular weight Mn≈ 3000−4000 g,mol-1 have been studied at shear rates of 10-2−105 s-1 at normal pressures of 1 and 3 MPa. The shear responses are compared to measurements on end-functionalized polymers of the same chemical composition but lower molecular weight, Mn≈ 2000 g,mol-1. The predominantly elastic response and high shear moduli of the confined film of unfunctionalized polymer, Fomblin Z03, suggest that it forms a structure likely to solidify already at low pressure. Its lubricating properties are less favorable than the ones found for hydroxyl- (DOL) and piperonyl-terminated Fomblin-Z (AM2001, AM3001), where associated molecules form a structure less prone to solidification under confinement. The thickness of the compressed films of the end-functionalized polymers increased more strongly with molecular weight than as Mn0.5. The shear moduli were found to be larger, the higher the molecular weight, indicating slower relaxations. At a normal pressure of 3 MPa, these films solidified and displayed stick–slip as seen already at 1 MPa in the Z03 film. The limiting shear stress of the unfunctionalized Z03, σ > 3 MPa, exceeded by an order of magnitude the limiting shear stress of all of the end-functionalized polymers. The limiting shear stress of the hydroxyl-terminated polymer was larger than that of the piperonyl-terminated polymer.

The electrical conductivity of polyaniline doped with camphor sulfonic acid (PAn-CSA) was studied. The results indicate that there is a critical temperature (Tc) and the temperature dependence of PAn-CSA conductivity shows metallic and semiconductor characteristics above and belowTc, respectively. The higher the molecular weight of PAn, the lower theTc. The conductivity was enhanced remarkably when PAn-CSA film was stretched, its room temperature conductivity is up to 750 S/cm when elogonation is 60%; however,Tc was independent of elongation.

Developing a high-performance donor polymer is critical for achieving efficient non-fullerene organic solar cells (OSCs). Currently, most high-efficiency OSCs are based on a donor polymer named PM6, unfortunately, whose performance is highly sensitive to its molecular weight and thus has significant batch-to-batch variations. Here we report a donor polymer (named PM1) based on a random ternary polymerization strategy that enables highly efficient non-fullerene OSCs with efficiencies reaching 17.6%. Importantly, the PM1 polymer exhibits excellent batch-to-batch reproducibility. By including 20% of a weak electron-withdrawing thiophene-thiazolothiazole (TTz) into the PM6 polymer backbone, the resulting polymer (PM1) can maintain the positive effects (such as downshifted energy level and reduced miscibility) while minimize the negative ones (including reduced temperature-dependent aggregation property). With higher performance and greater synthesis reproducibility, the PM1 polymer has the promise to become the work-horse material for the non-fullerene OSC community. The batch reproducibility of polymer donor materials limits the performance of polymer solar cells. Here Wu et al. develop a polymer donor PM1 by random terpolymerization strategy with a high efficiency of 17.6% in the device and excellent batch-to-batch reproducibility.

The glass transition is a long-standing unsolved problem in materials science. For polymers, our understanding of glass formation is particularly poor because of the added complexity of chain connectivity and flexibility; structural relaxation of polymers thus involves a complex interplay between intramolecular and intermolecular cooperativity. Here, we study how the glass-transition temperatureTgvaries with molecular weightMfor different polymer chemistries and chain flexibilities. We find thatTg(M)is controlled by the average mass (or volume) per conformational degree of freedom and that a “local” molecular relaxation (involving a few conformers) controls the larger-scale cooperativeαrelaxation responsible forTg. We propose that dynamic facilitation where a local relaxation facilitates adjacent relaxations, leading to hierarchical dynamics, can explain our observations, including logarithmicTg(M)dependences. Our study provides a new understanding of molecular relaxations and the glass transition in polymers, which paves the way for predictive design of polymers based on monomer-scale metrics.

Residual stress is an intrinsic property of semicrystalline plastics such as polypropylene and polyethylene. However, there is no fundamental understanding of the role intrinsic residual stress plays in the generation of plastic pollutants that threaten the environment and human health. Here, we show that the processing-induced compressive residual stress typically found in polypropylene and polyethylene plastics forces internal nano and microscale segregation of low molecular weight (MW) amorphous polymer droplets onto the plastic’s surface. Squeeze flow simulations reveal this stress-driven volumetric flow is consistent with that of a Bingham plastic material, with a temperature-dependent threshold yield stress. We confirm that flow is thermally activated and stress dependent, with a reduced energy barrier at higher compressive stresses. Transfer of surface segregated droplets into water generates amorphous polymer micropollutants (APMPs) that are denatured, with structure and composition different from that of traditional polycrystalline microplastics. Studies with water-containing plastic bottles show that the highly compressed bottle neck and mouth regions are predominantly responsible for the release of APMPs. Our findings reveal a stress-induced mechanism of plastic degradation and underscore the need to modify current plastic processing technologies to reduce residual stress levels and suppress phase separation of low MW APMPs in plastics. Residual stresses are pervasive in most modern plastics. Here, the authors show that they promote the migration of low-molecular-weight amorphous polymer and additives from bulk plastics and release micropollutants into water.