Macromolecular Chemistry and Physics最新文献

Despite extensive research, the stabilization mechanism of mesomorphic isotactic polypropylene (iPP) at room temperature has not been elucidated completely. To address this issue, nanoscale structural information is indispensable. In this study, mesomorphic-α phase transition is studied with synchrotron wide-angle diffraction and small-angle X-ray scattering. It is found that during phase transition, the mobile amorphous content remained unchanged, while rigid amorphous fraction (RAF) decreased constantly, accompanied by an increase in long period. Assuming that the increase in long period is induced by the extension of the rigid amorphous coil (RAC), the thickness of RAF (R_RAF) is estimated, which is found to be 2.2 nm. This value is greater than the length of b axis in α crystal cell, which can be the reason that folded-chain iPP clusters in mesomorphic iPP cannot approach closer to form α crystal at room temperature. Besides, with R_RAF, the thickness of smectic layer is estimated, which is found to be 0.9 nm. At this thickness, bulk-free energy cannot compensate for the folded-surface free energy, which can be the other reason that mesomorphic iPP chains cannot transit into α crystal at room temperature. The information obtained in this study is favorable for understanding the stabilization mechanism of mesomorphic iPP.

Front Cover: In article 2400180 by Achilleas Pipertzis, Athanasios Skandalis, Stergios Pispas, and George Floudas, the nanophase separation in amphiphilic diblock copolymers with a densely grafted macromolecular architecture, was shown to drive heterogeneous dynamics as evidenced by small-angle X-ray scattering, differential scanning calorimetry, and dielectric spectroscopy.

Photo-ATRP technique has garnered significant attention due to its multitude of advantages, including its ability to be conducted under mild reaction conditions, user-friendly nature, and exceptional efficiency in polymerization. The heterogeneous photocatalysts not only exhibit exceptional quantum efficiency, but also possess a versatile bandgap that can be finely adjusted to accommodate a wide range of absorption wavelengths within the visible light spectrum, thereby emphasizing their potential for efficient recovery and reuse. The utilization of a variety of heterogeneous photocatalysts in photo-ATRP presents notable benefits for numerous applications, such as the lack of any remaining substances, simplicity in usage, and potential for reuse. This review focuses on recent progress in photo-ATRP utilizing a wide variety of heterogeneous photocatalysts, encompassing metal semiconductor nanoparticles, quantum dot, upconversion nanoparticles, metal–organic frameworks, covalent–organic frameworks, conjugated microporous polymers, hypercrosslinked polymer, and carbon-based materials.

Polymer networks have emerged as materials with widespread application, including their use in drug delivery, catalysis, and flexible electronics. They have traditionally been derived from organic building blocks using well-developed reaction types. Advances in main group synthetic chemistry have opened the door for the production of new polymer networks, including those containing phosphorus atoms that offer the traits of Lewis basic phosphorus centers. Here, the radical-catalyzed phosphane-ene reaction is used to prepare (co)polymer networks from iBuPH₂, trivinyltriptycene (TVT), and 1,3,5-triallyl-1,3,5-triazine-2,4,6-trione (TTT), which are the first of their type to include TVT. Networks rich in TVT exhibited greater thermal stability and reduced network mobility compared to those rich in TTT. Despite the rigidity, 3D, and internal free volume associated with the triptycene units present in TVT-rich networks, their swellability is similar to networks rich in TTT indicating that the presence of phosphines may be a dominating factor in the respective structure-property relationships.

Strain sensors from conducting polymer hydrogel have been widely employed in various wearable devices, electronic skins, and biomedical applications. These sensors provide outstanding flexibility and high sensitivity by integrating conducting polymer with hydrogels, making them particularly suitable for monitoring human motion and physiological signals like heart rate or muscle activity. Despite their extensive application potential, conducting polymer hydrogel face several technical challenges in practical use, including poor mechanical properties, lack of long-term stability, and difficulty in customizable design. This work introduces a method for fabricating a multipedal strain sensor using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/polyvinyl alcohol (PVA) dimethyl sulfoxide (DMSO)hydrogels through screen printing and demonstrates its application in human motion monitoring. The multipedal strain sensor demonstrates a low Young's modulus (200 kPa), high stretchability (400%), and excellent mechanical cyclic stability (3000 cycles). Furthermore, this strain sensor is further applied to detect human movements such as chewing, smiling, fist clenching, arm bending, and carotid pulse monitoring. Comparative analysis between the multipedal-designed sensor and the non-designed sensor highlights the enhanced sensing capabilities of the multipedal sensor. The design of this multipedal sensor holds the potential to broaden the design concepts for strain sensors and offers new insights for wearable devices and electronic skins.

In this study, a flexible sensor is successfully fabricated using self-healing nanocomposite hydrogels for monitoring human movement. The eco-friendly cellulose nanocrystals (CNCs) are used as nano-reinforcing materials, and the mechanical properties and self-healing efficiency of the materials are improved. The self-healing efficiency of hydrogels are realized by introducing a variety of reversible non-covalent interactions such as hydrogen bonding, borax chelation, and metal coordination. Notably, the mechanical strength and self-healing efficiency of these nanocomposite hydrogels can reach 2.8 MPa and 89.9%, respectively. Importantly, these self-healing nanocomposite hydrogels have been widely used in wearable flexible sensors to achieve high sensitivity to large-scale human movement. It is of great significance to design functional materials with good biocompatibility, sensitivity, and mechanical strength for wearable sensors.

Termination kinetics of radical polymerization of N-vinyl formamide (NVF) in aqueous solution has been measured via SP–PLP–NIR, i.e., single pulse (SP) initiation of pulsed laser polymerization (PLP) in conjunction with microsecond time-resolved near-infrared (NIR) detection of monomer concentration. Experiments are performed at initial NVF weight fractions from 0.20 up to bulk NVF, at monomer conversions up to 40%, and at temperatures from 40 to 70 °C as well as pressures from 500 to 2500 bar. Applying high pressure improves signal-to-noise quality. Data obtained upon pressure variation allow for extrapolation toward ambient pressure. The primary quantity from SP–PLP–NIR is k_p/<k_t>, i.e., the ratio of propagation rate coefficient, k_p, to apparent chain-length-averaged termination rate coefficient, <k_t>. With k_p being available from literature, k_p/<k_t> yields <k_t>. This quantity is relevant for modeling polymerization rate and polymer properties. Termination in the initial polymerization period turns out to be controlled by segmental diffusion and, at higher degrees of monomer conversion up to 40%, by translational diffusion.

Front Cover: Reactively processed multilayered films comprising PBAT nanocomposites not only achieve improved oxygen barrier and dimensional stability at high temperatures but also achieve a higher biodegradation than the neat PBAT film with a similar thickness. The soil–compost mixture after biodegradation of the films is nontoxic. Therefore, the reactively processed composite is a sustainable polymeric material with superior properties and may find packaging or biomedical applications where existing materials cannot be recycled. More details can be found in the article 2400067 by Suprakas Sinha Ray and co-workers.