Macromolecular Chemistry and Physics最新文献

Polyimide (PI) hollow microspheres possess lightweight and excellent thermal resistance, which are widely used in microreactors, catalysis, adsorption separation, high-temperature insulation, and so on. In this manuscript, PI hollow microspheres are fabricated by constructing a crosslinked structure combined with gradient heating. The formation of PI hollow microspheres includes gas nucleation, expansion, and imidization. The PI hollow microspheres size is controlled by adjusting polyester ammonium salts size, and microspheres size is distributed in 309–956 µm. PI hollow microspheres have lightweight, excellent heat resistance and carbonization performance, bulk density, initial decomposition temperature, and weight residue at 800 °C is 87.3–178.6 kg m⁻³, 533.6 °C and 59.8%. The PI hollow microspheres have potential applications in high-temperature resistant and multifunctional composite materials preparation. Moreover, this method is simple, efficient, and highly operable, which can be used for large-scale production of PI hollow microspheres.

In contemporary society, with its emphasis on environmental stewardship, the development of “green” (eco-friendly) inks is of paramount importance. These inks are utilized across a broad spectrum of applications, ranging from the printing of packaging material to the 3D printing of functional components. This study explores the synthesis of eco-friendly, biodegradable supramolecular polymer materials predicated on ureido-pyrimidinone (UPy). The subsequent formulation of these materials into functional inks is achieved by the incorporation of multi-walled carbon nanotubes (MWCNTs). These resultant inks exhibit outstanding photothermal conversion properties, robust electrical conductivity, intrinsic self-repair capabilities, and superior writability. Moreover, this research demonstrates the recyclability of MWCNTs within the ink matrix, exhibiting a recovery efficiency of ≈90%. Such a high recovery rate offers a novel perspective on the sustainable reuse of conductive fillers in polymer-based inks.

Dynamic mechanical spectroscopy is a common analysis for polymers. Rectangular specimens are usually used for measurement in the solid state due to their easy designing. However, in reason of the non-symmetric shape of sample, rectangular specimens do not experience linear stress on their all body, leading to overestimation of shear modulus. Corrections are required to determine the right shear modulus. In this present work, straight shear modulus determination is carried out using specimens with a cylindrical shape. The reliability of the technique is described on a biosourced polymer materials made of thermoplastic starch, plasticized by glycerol, choline chloride/urea mixture (ChCl/U), 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) and 1-ethyl-3-imidazolium acetate ([EMIM]Ac). The technique is shown to be particularly interesting to avoid any additional shaping of the specimens prior to measurements, that can be detrimental to their properties (evaporation, degradation). A comparison between cylinder and rectangular specimen has also been made to illustrate the interest of cylinder clamping on biosourced polymer material.

Current families of reversible photochemical reactions present challenges for light-controlled polymers of either photostationary states, which are common in photoinduced cycloaddition/cycloreversion reactions, or exclusively intramolecular bond changes, which characterize most photochromic units. In response to these challenges, here the concept of “proximal photocleavage” is presented, which combines photochemical crosslinking with a photocleavable linker, enabling a one-time bond formation/cleavage sequence. Proximal photocleavage methacrylate monomers comprising, in series along the pendant of the methacrylate, a coumarin unit for crosslinking and either a phenacyl or ortho-nitrobenzyl photocleavable group for decrosslinking are reported. The photophysical properties of these monomers and their statistical copolymers with methyl methacrylate are described, and wavelength selective crosslinking and de-crosslinking of thin polymer films are demonstrated.

Linear N-substituted polyacrylamides bearing tricarboxylic moieties pendant to the backbone are synthesized, and coordinative binding approach is developed to convert them into Gd³⁺/Eu³⁺-metallopolymers. Inner-sphere coordination of the lanthanide ions with the pendant chelating moieties, together with their outer-sphere stabilization by the randomly coiled backbone, are the reasons for peculiar water proton relaxation and luminescence properties of the metallopolymers obtained. Indeed, for Gd³⁺-metallopolymer, the values of longitudinal and transverse relaxivity (r₁ and r₂) are 50 and 60 mm⁻¹·s⁻¹, respectively, while for the Eu³⁺-counterpart, Eu³⁺-centered luminescence is significantly raised compared to Eu³⁺ aquaions. Coil-like conformation of the metallopolymer molecules undergoes a swelling at pH values above 5.0 as evidenced by transmission electron microscopy TEM and dynamic light scattering (DLS) data, which is followed by the changes in the Eu³⁺-centered luminescence and r₁₍₂₎-values of Gd³⁺/Eu³⁺-metallopolymers. The phosphates additives (adenosine monophosphoric acid (AMP), adenosine diphosphoric acid (ADP), HPO₄²⁻ and adenosine triphosphoric acid (ATP) induce well detectable changes in both water proton relaxation and luminescence of Gd³⁺/Eu³⁺-metallopolymers. The luminescent changes distinguish AMP from the other phosphates, while the changes in water proton relaxation are greater for HPO₄²⁻ and ATP compared to AMP and ADP. This study explains this by interplay of the effects associated with the formation of ternary phosphate-lanthanide-polymer complexes and stripping of lanthanide ions from the polymer molecules.

Nanostructures derived from structural polysaccharides, such as cellulose and chitin, are notable for their sustainability, lightweight properties, and superior mechanical attributes. The macroscopic performance of these materials largely depends on the orientation of nanostructures. This study explores the preferential orientation of chitinous nanofibers (NFs) within a thermoplastic polymer matrix (PM) comprising poly(N-vinylpyrrolidone) and glycerol, achieved through dry thermal stretching techniques. Altering the PM composition enables the modulation of the system's glass transition temperature (T_g). Chitin NFs are effectively dispersed within the PM, with their orientation enhanced by stretching at temperatures ≈30 °C above the T_g of the composites, resulting in an elongation at rupture (ε) of 105%. Under similar temperature conditions, composites with chitosan NFs show strong interactions with the PM, hindering the stretching process (ε = 10%). In contrast, composites with acetylated chitin NFs demonstrate increased stretchability (ε = 170%) but have insufficient interactions to stabilize their orientation. These interactions, identified as hydrogen bonds through FTIR, vary significantly based on the functional groups present on the NF surfaces. This variation is supported by DSC and dynamic mechanical analysis. Oriented ChNFs hold potential for bioactive applications.

The self-assembly and dynamics of amphiphilic diblock copolymers composed of densely grafted poly(oligo ethylene glycol methacrylate) (POEGMA) and poly(lauryl methacrylate) (PLMA) by means of calorimetry, small-angle X-ray scattering (SAXS), and dielectric spectroscopy are investigated. It is reported that the inherent immiscibility between the parent homopolymers, combined with the increased molar mass, results in strong segregation, maintained up to elevated temperatures (i.e., T = 423 K). SAXS reveals that well-separated POEGMA and PLMA domains self-assemble into spheres with bicontinuous cubic packing and in lamellar nanostructure in copolymers with respective compositions of 16 and 52 wt.% PLMA. This strong segregation enables the weak crystallization/melting of the short ethylene glycol chains. Additionally, molecular dynamics are investigated through isothermal dielectric and calorimetry measurements. The segmental dynamics (i.e., T_g-related) of POEGMA and PLMA closely resemble that found in respective homopolymers, implying heterogeneous dynamics. In the glassy state, the local motions of the POEGMA side chains predominantly govern the observed secondary processes in the copolymers. The results on the heterogeneous dynamics in the current amphiphilic diblock copolymers with the densely grafted architecture are compared and contrasted with copolymers having a bottle–brush architecture lacking the amphiphilic nature.