Macromolecular Chemistry and Physics最新文献

Polymer gas sorption and permeability are key parameters when choosing materials for applications from gas separation to food packaging. These parameters are naturally affected by the polymer chemistry, but also by the bulk morphology. In this work, the effect of chain folding (intramolecular) collapse on such properties is studied. While maintaining the same chemical composition, powders and films made from linear and folded chains are compared, indicating that chain folding affects only slightly the overall gas solubility in the polymer, but the diffusivity and permeability is changed very significantly. Measurements at different pressures provide clear support for well-behaved systems which are chemically similar but show very different properties, allowing for the decoupling of chemistry and properties.

Drugs with low water solubility comprise a significant proportion of pharmaceutical compounds. To control the release of these drugs, polymer thin-film formulations with a physical hydrophobic barrier layer do not provide ideal release profiles. In this study, polymer carriers with hydrophilic polyvinyl alcohol (PVA) as the barrier layer are developed, and investigated the effect of the PVA film thickness on the release of hydrophobic molecules. Instead of an aqueous system, an oil-based system is used to measure membrane permeability, and Nile Red is used as the hydrophobic model drug. PVA thin films are prepared with polycaprolactone as the supportive layer, which retained their permeability. In the limited thickness range investigated, PVA thin films exhibited thickness-dependent permeability toward the hydrophobic model drug.

Currently, recovery of organic solvents using eco-friendly methods is one of the primary industrial tasks. Separation of liquid media by pervaporation offers more advantages as compared to conventional purification methods, such as distillation, in view of low energy and resource consumption. This work is focused on the study of novel copolyamide with 2-pyridylquinoline-4,7-dicarboxylic acid moieties in the main chain and its metal-polymer complex in the form of dense films. At present, metal-polymer complexes are growing in importance among membranes. The analysis of mechanical and thermal properties of the films also supports their high operational characteristics. Comprehensive studies of the structure of the obtained films show that both samples have a rigid and dense structure, but the metal-polymer complex is characterized by an increased surface roughness. The hypothesis of supramolecular association between polymers and separated liquids (methanol and toluene) is confirmed by quantum chemical calculations. Transport properties of novel polymers in pervaporation of toluene/methanol mixtures are examined and compared with the literature data. Both polymer films demonstrate an outstanding selectivity toward toluene in the separation of binary mixtures. The developed films have higher values of total flux and separation factor as compared to the most of known membranes.

Smart windows can effectively balance the space temperature of buildings without compromising the essential functions of windows. However, conventional thermochromic windows have limited sunlight regulation capabilities and face challenges with switching as desired. Herein, A class of novel smart windows based on crystal hydrogels is introduced that achieve free switching between transparent (for heating) and opaque (for radiative cooling) states through thermal and mechanical stimuli. The crystal hydrogels are made from cross-linked polyacrylamide (PAM) and sodium acetate (NaAc). By optimizing the sodium acetate concentration and sample thickness, The combination of excellent cooling ability is achieved at the opaque state and good low-temperature stability at the transparent state in the hydrogels. Using the optimized hydrogel to prepare a smart window equipped with a heater and a mechanical trigger tip, the rapid on-demand transition between transparent and opaque states is demonstrated. The results indicate that the smart window lowers temperatures by up to 9.4 °C compared to ordinary windows and maintains stable emissivity and reflectivity even after 100 cycles due to its robust solar modulation capabilities. This technology provides new energy-saving solutions for smart buildings but also explores future applications of smart materials, showcasing innovative advantages and technical strengths in smart windows.

In addition to traditional rubber applications, 1,4-cis-polyisoprene (cis-PI) has been utilized in wearable electronics. While synthetic PI typically exhibits lower durability compared to natural rubber (NR), high-molecular-weight cis-PI compensates by offering improved mechanical properties and chemical resistance. The group proposes using a commercial cis-PI with high molecular weight of 250 000 g mol⁻¹ (PI_250K-C) grafted onto modified nanoparticle structures including silicon dioxide (mSiO₂), rutile titanium dioxide (mRTiO₂), and anatase titanium dioxide (mATiO₂) as an insulator in organic field effect transistors (OFETs) due to its naturally low dielectric constant. The nanoparticles are pretreated with a coupling agent to improve adhesion and prevent aggregation. Rubber composite films, designated X%-mY-PI_250K-C (where X = 10, 20, 30% and Y = mSiO₂, mRTiO₂, mATiO₂), are fabricated using sulfur vulcanization. The modified films demonstrate excellent mechanical stress (1.15 ± 0.1 MPa) and elasticity, enduring 50 loading–unloading cycles without residual strain. In contrast, rubber composites produced from simple blending show half the mechanical stress at 0.7 ± 0.3 MPa, which is attributed to nanoparticle agglomeration observed in SEM and EDX results. Additionally, mRTiO₂ nanoparticles significantly increase the dielectric constant of PI_250K-C from 2.12 to 12.93, enhancing electrical performance for TFT applications. This study underscores the effectiveness of the “grafting to” approach for producing robust rubber composites, highlighting the importance of nanoparticle selection and fabrication precision for stretchable organic electronics.

The effect of chain dispersity on the relative stability of Frank–Kasper (FK) phases self-assembled from diblock copolymers (DBCPs) is studied using self-consistent field theory applied to DBCPs with one disperse block obeying the Poisson or Schulz–Zimm distributions. The results demonstrate that the chain dispersity enhances the relative stability of the FK phases. For DBCPs with small conformational asymmetry, the FK $�\sigma$ phase can be stabilized by dispersity and the stability window of the FK phases widens with the increase of dispersity. For DBCPs with large conformational asymmetry, the Laves C14 and C15 phases, which are metastable in monodisperse DBCPs, can be stabilized by dispersity. An analysis of the spatial organization of polymers reveals that the enhanced stability of the FK phases originated from intra- and inter-domain segregation of chains with different lengths.

Protein-based optoelectronics faces two challenges to keep the performance of conventional technologies: stabilizing proteins through water-free fabrication methods and developing bio-friendly interfaces. In this context, bio-hybrid lighting, which integrates fluorescent protein (FP) based photon down-converting filters, represents an emerging concept toward ensuring a sustainable lighting sector. They promise to replace rare earth and/or toxic emitters applied for photon down-conversion in white commercial LEDs with FP-polymer color filters. A key component is a branched polyethylene oxide that stabilizes FPs in a water-less environment upon film forming. Recently sugar additives are successfully used as natural desiccation protectants against osmotic dehydration stress to further enhance FP stability by reinforcing intra-protein H-bonding. Herein, the glycosylation of the branched polymer is disclosed to stabilize FPs in coatings that resulted in 300-fold enhanced device stability due to a significant reduction of the heat generation and slow-down of the H-transfer-assisted emission deactivation process compared to reference polymer coatings. Thermal and spectroscopic techniques suggest that this finding is related to the higher crystallinity of the coatings and rigid environment provided by the glycosylated polymers. Overall, this work reinforces the use of sugars (additives or glycosylated polymers) to preserve the emission/thermal properties of FPs in water-less environments for optoelectronics.

As functional composite materials rapidly develop, the insufficient thermal conductivity of polymer materials to meet application requirements is becoming increasingly apparent. In this work, electrospinning is employed to prepare hydroxylated boron nitride nanosheet (OH-BNNSs)/water-based polyurethane (WPU)/polyvinyl alcohol (PVA) composite nanofiber membranes with good thermal conductivity. When the content of OH-BNNSs is 10 wt.%, the thermal conductivity of the OH-BNNS/PVA/WPU composite nanofiber membrane can reach 0.629 W (mK)⁻¹, with yield strength, ultimate tensile strength, and elastic modulus of ≈3.85, ≈5.87, and ≈35.22 MPa, respectively. The results indicate that the OH-BNNS/WPU/PVA composite nanofiber membrane exhibits good thermal conductivity and outstanding hydrophilicity. When the content of OH-BNNSs is appropriate, the composite membrane also demonstrates good mechanical properties, showing significant potential in the field of thermally conductive polymer materials.