Polymeric materials under nanoconfinements have substantially deviated physical properties with respect to the bulk, especially glass transition temperature, physical aging, and crystallization behavior. Here we highlight the leading methods for creating various confinement systems. Upon these systems, recent advances on hard and soft confinement effect for glass transition, physical aging, mechanical properties and crystallization of polymers are reviewed in details. Furthermore, as nanoconfined systems in extreme conditions are experimentally inaccessible, simulation results describing confinement effect on such systems are also discussed.

A series of new bisphosphine-monoxide (BPMO) ligands based on benzothiophene backbone and the corresponding palladium complexes {к²-2-P(O)(Ph)₂-3-PR¹R²-C₈H₄S}PdMeCl {2a: R¹ = R² = Ph; 2b: R¹ = R² = 2-OMe-Ph; 2c: R¹ = R² = 2-CF₃-Ph; 2d: R¹ = Ph, R² = 2-(2′,6′-(OMe)₂C₆H₃)-C₆H₄} were synthesized and fully characterized by ¹H-, ¹³C-, ³¹P-, and 2D-NMR spectroscopy and single-crystal X-ray diffraction. In the presence of Na⁺B[3,5-(CF₃)₂C₆H₃]₄^– (NaBArF), these complexes showed very high activities (up to 2.0 × 10⁷ g·mol^–1·h^–1) for ethylene polymerization. More significantly, these catalysts enabled the copolymerization of ethylene with a broad scope of commercially available polar comonomers such as acrylates, acrylic acid, acrylonitrile, vinyltrialkoxysilane, allyl acetate, and long-chain 6-chloro-1-hexene to give functionalized polyethylene with reasonable catalytic activities (up to 10⁶ g·mol^–1·h^–1) and incorporations (up to 5.3 mol%). This contribution suggests that, besides the modulation of conventionally steric and electronic factors, the connectivity (at different linking positions) of BPMO (P,O) donors to the heteroaryl backbone also greatly influences the catalyst properties in terms of catalytic activity, polymer branching content, comonomer scope, and comonomer incorporation.

As a typical plant virus which has biocompatibility and high transfection efficiency, tobacco mosaic virus (TMV) has shown broad application potential in drug or gene delivery field. Elucidating its intracellular trafficking is of great importance in investigation of its cytotoxicity, targeting site, and delivery efficiency, and is advantageous to designing new TMV-based drug delivery systems with different targets. By taking advantage of the regulated pH value of different organelles in a mammalian cell, we exploit a pH detection strategy to investigate the intracellular trafficking pathway of TMV. Here, we report a single-wavelength excited ratiometric fluorescent pH probe. This probe is constructed by simultaneously coupling pH-sensitive fluorescein isothiocyanate (FITC) and pH-insensitive rhodamine B isothiocyanate (RBIRC) onto the inner surface of TMV. The fluorescence intensity ratio of FITC to RBITC excited at 488 nm responds specifically towards pH value over other interferential agents. By taking use of this single-wavelength excited ratiometric pH probe and confocal laser scanning microscopy, it is shown that the endocytosed TMV is located in a pH decreasing microenvironment and eventually enters lysosomes. This work may provide important guidance on construction of TMV-based nano carriers.

Electromagnetic interference (EMI) shielding materials are in great demand in electronic equipment and our surrounding environment to resist the increasing serious radiation pollution. Compared with their metal counterparts, conductive polymer composites (CPCs) have unique advantages of lightweight, corrosive resistance, low cost, and excellent processability, and are therefore an ideal choice for developing high-performance EMI shielding materials. However, CPCs based EMI shielding materials are limited to high filler loading, which caused poor mechanical properties and processability. Here, we demonstrate a facile and highly scalable approach to develop high-performance EMI shielding materials with low filler loading by using miscible poly(phenylene oxide)/polystyrene (PPO/PS) blend as the matrix. In contrast to PS/carbon nanotubes (CNTs) composites, PPO/PS/CNTs composites show much higher EMI shielding effectiveness caused by good dispersion of CNTs and highly interconnected conductive network. An excellent EMI shieling effectiveness of 23−25 dB is achieved for PPO/PS/10%CNTs composites with a thickness of only 375 μm, which is superior to most of reported polymer/CNTs composites prepared by melt-compounding. In addition, the results show that although absorption is the major shielding mechanism, the contribution of reflection is also important and closely related to the connectivity of conductive network, as well as the electrical conductivity of the CPCs.

Hydroxyapatite-graft-poly(D-lactide) (HA-g-PDLA) was synthesized by ring-opening polymerization with HA as initiator and stannous octanoate (Sn(Oct)₂) as catalyst. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) results indicate that PDLA chains are successfully grafted onto HA particles by covalent bond. Under two different processing temperatures (190 and 230 °C), the effect of the grafted PDLA chains on the crystallization behavior of poly(L-lactide)/HA-g-PDLA (PLLA/HA-g-PDLA) composite was investigated in the current study, comparing to neat PLLA and its four composites (PLLA/HA, PLLA/HA-g-PLLA, PLLA/PDLA, and PLLA/HA/PDLA). The crystallization rate of PLLA/HA-g-PDLA composite is highly enhanced comparing to PLLA, PLLA/HA and PLLA/HA-g-PLLA composites in which there are no stereocomplex (SC) crystallites. In addition, when the processing temperature rises from 190 °C to 230 °C, the acceleration of PLLA crystallization in PLLA/HA-g-PDLA composite is not influenced so much as other composites containing SC crystallites, such as PLLA/HA/PDLA or PLLA/PDLA. The differential scanning calorimetry (DSC) results demonstrate that even without SC crystallites, the crystallization of PLLA can still be accelerated a lot in this composite. This may be related to the interaction between the grafted PDLA chains and the amorphous PLLA chains in PLLA/HA-g-PDLA composite. The isothermal crystallization kinetics studies indicate that the nature of nucleation and crystal growth of PLLA/HA-g-PDLA composite are more likely 3D crystalline growth with heterogeneous nucleation mode, which are different from PLLA or other composites. This investigation could shed new light on the application of PLLA/HA composites.

In this work, step-cycle tensile behavior of two bimodal polyethylene (PE) materials, a PE100 grade pipe material, XS10, and a PE100-RC (Resistant Crack) grade pipe material, XSC50, was comparatively investigated. By decomposing the strain into a recoverable part and an unrecoverable part, it was found that the deformation recovery capability of XSC50 during stretching was larger than that of XS10. Structural evolution characterized by in situ synchrotron small angle X-ray scattering indicated that the fragmentation of initial crystals in XSC50 occurred at lower strain than in XS10. Considering that XSC50 had relatively small lamellar thickness and similar crystallinity to XS10, we speculated that the larger deformation recovery capability of XSC50 during stretching probably derived from stronger entangled amorphous region caused by larger density of tie molecules and entanglements, which were usually regarded to have a significant influence on the slow crack growth (SCG) resistance of PE materials. As expected, the experimental result of strain hardening modulus test suggested that the deformation recovery capability during stretching was positively correlated with the SCG resistance for XS10 and XSC50 used in this work. The step-cycle tensile test had the potential to be developed into a supplement for comparison of SCG resistance of PE materials.

In this study, we investigate the motion of polymer segments in polymer/nanoparticle composites by varying nanoparticle (NP) volume fractions. By studying the probability distribution of segment displacement, segment trajectory, and the square displacement of segment, we find the intermittent motion of segments, accompanied with the coexistence of slow and fast segments in polymer nanocomposites (PNCs). The displacement distribution of segments exhibits an exponential tail, rather than a Gaussian form. The intermittent dynamics of chain segments is comprised of a long-range jump motion and a short-range localized motion, which is mediated by the weakly attractive interaction between NP and chain segment and the strong confinement induced by NPs. Meanwhile, the intermittent motion of chain segments can be described by the adsorption-desorption transition at low particle loading and confinement effect at high particle loading. These findings may provide important information for understanding the anomalous motion of polymer chains in the presence of NPs.

Eight 6FDA-TFDB polyimide (PI) samples with absolute molecular weights ranging from 1.25 × 10⁵ g·mol^–1 to 3.11 × 10⁵ g·mol^–1 are obtained by precipitation fractionation. Rheological experiments are conducted to determine the influence of molecular weight on the associating behavior of PI in N,N′-dimethylformamide (DMF) solutions in a broad volume fraction, including abnormal steady shear flow, solution heterogeneity, and scaling behavior. Abnormal flow behaviors, i.e., multi-region shear thinning and weak shear thickening, are studied, and these behaviors have not been reported in literature. The heterogeneity of PI/DMF solutions is examined by dynamic rheological test. By plotting η_sp versus ϕ/ϕ_η, four concentration regions of I–IV can be distinguished for all PI samples with various molecular weights. The scaling results in different concentration regions are in good agreement with the associative polymer theory proposed by Rubinstein and Semenov. The scaling exponents do not show molecular weight dependence in concentration regions I and II. In concentration regions III and IV, the scaling exponents change little when the molecular weight is below 242 k but increase when the molecular weight increases from 242 k to 311 k. This work can help us to understand polyimide solution properties from dilute to semidilute entangled solutions, and will guide the polyimide solution preparation for different processing.

A bulk Poly(vinyl alcohol)/ZIF-8 (PVA/ZIF-8) porous composite with aligned porous structure was prepared by ice-templating method. The microstructure of PVA/ZIF-8 porous composites was characterized by scanning electron microscopy (SEM). The results showed that the composites had regular pore structure and ZIF-8 nanoparticles were evenly distributed on the skeleton of PVA. X-ray diffraction (XRD) test results showed that the crystalline structure of ZIF-8 was well preserved in the composites. The specific surface area of the composite was characterized by nitrogen adsorption/desorption test. The specific surface area of the composite was up to 1160 m²·g^–1. PVA/ZIF-8 porous composites could also support a certain weight with almost no volume shrinkage. The carbon dioxide adsorption quantity of the composite was up to 11.3 cm³·g^–1, proving that PVA/ZIF-8 porous composite has a good application prospect in the field of carbon dioxide adsorption.

Proton conductivity of proton exchange membranes (PEMs) strongly relies on microscopic morphology, which can be modulated by engineering the distribution of ionic groups. Herein, poly(arylene ether)s with densely distributed allyl functionalities are polymerized from a tetra-allyl bisphenol A monomer. The subsequent thiol-ene addition with sodium 3-mercapto-1-propanesulfonate yields comb-shaped sulfonated fluorinated poly(arylene ether)s (SFPAEs) with ion exchange capacities (IECs) ranging from 1.29 mmol·g⁻¹ to 1.78 mmol·g⁻¹. These SFPAEs exhibit superior proton conductivity over the whole temperature range, which is attributed to the enhanced hydrophilic/hydrophobic phase separation as evidenced by small angle X-ray scattering characterizations. The SFPAE-4-40 with an IEC of 1.78 mmol·g⁻¹ shows the largest proton conductivity of 93 mS·cm⁻¹ at room temperature under fully hydrated condition, higher than that of Nafion 212. Furthermore, the vanadium redox flow battery (VRFB) assembled with SFPAE-4-40 separator exhibits higher energy efficiency than the VRFB assembled with Nafion 212.

The role of mold temperature on the morphology and properties of rotational shearing polyethylene (PE) pipes was studied via a self-developed rotational shear system (RSS). The result indicated that when the mold temperature was 150 °C, the hoop tensile strength and Vicat softening temperature were enhanced rapidly, which were 383.6% and 137.9% higher than those of the conventional PE pipes, respectively. Morphology and crystal structure studies by SEM and DSC revealed that once the rotational shear was applied, the shish-kebab structure began to appear. With the increase of the mold temperature, due to the relaxation of most of the oriented molecular chains, the preservation of shish-kebab structure became difficult. When the mold temperature was 190 °C, only the inner layer of the pipes, where the cooling rate was the largest, could preserve the shish-kebab structure. According to WAXD, there was less shish structure, and the growth of kebab was distorted in the inner layer of the pipes at 210 °C. The result of SAXS suggested that the length of shish changed most within the temperature range from 170 °C to 190 °C. The results of DSC and WAXD showed less change in crystallinity and degree of orientation between the two temperatures. It can be concluded that the reduction of shish length leads to a decrease in mechanical properties and heat-resistance.

Using a hybrid simulation approach that combines a finite difference method with a Brownian dynamics, we investigated the motion of charged polymers. Owing to the fact that polymer-solution systems often contain a large number of particles and the charged polymer chains are in a state of random motion, it is a time-consuming task to calculate the electrostatic interaction of the system. Accordingly, we propose a new strategy to shorten the CPU time by reducing the iteration area. Our simulation results illustrate the effect of preset parameters on CPU time and accuracy, and demonstrate the feasibility of the “local iteration” method. Importantly, we find that the increase in the number of charged beads has no significant influence on the time of global iterations and local iterations. For a number of 80 × 80 × 80 grids, when the relative error is controlled below 1.5%, the computational efficiency is increased by 8.7 times in the case that contains 500 charged beads. In addition, for a number of 100 × 100 × 100 grids with 100 charged beads, the computational efficiency can be increased up to 12 times. Our work provides new insights for the optimization of iterative algorithms in special problems.