Progress in Polymer Science最新文献

Underwater adhesion has been the focus of many recent developments motivated by potential biomedical applications. Although most literature on underwater adhesives has focused on strong covalent chemistries, soft materials based on weak molecular interactions have gained interest. Instead of relying on potentially toxic chemical crosslinking reactions to form covalent bonds, these materials are often sticky due to their soft, viscoelastic nature, in a similar manner to soft hydrophobic Pressure-Sensitive Adhesives (PSAs). In this review, we critically discuss the state-of-the-art in the design and characterization of soft viscoelastic coacervates and gels based on specific weak molecular interactions for underwater adhesion. From the perspectives of materials science and mechanics, we investigate the relationships between the composition and structure of these materials and their underwater viscoelastic and adhesive properties. An originality of our review lies in the analogies and comparisons we draw with PSAs as well-understood hydrophobic self-adhesive counterparts of the relatively hydrophilic underwater adhesives discussed here. Considering current literature, a criterion has been proposed to distinguish hydrophilic and hydrophobic adhesives. The insights from this review are condensed into detailed guidelines for the design of future soft underwater adhesives. We conclude the review with important open questions and the perspectives of the field.

Star polymers with well-defined molecular architectures have been widely studied in the last few decades. Of particular interest has been processing-structure-property relationships of star polymers in the thin film form and their potential applications in the field of biology and medicine. This review presents the state-of-the-art of research on nano- and microlayers of star polymers on solid substrates explored in the last two decades. We start the discussion with a short introduction to the general features of star polymers to introduce the reader to the subject. Subsequently, methods for the preparation of star polymer nano- and microlayers on solid surfaces and their resulting properties are discussed. Special emphasis will be given to the differences between the properties of layers obtained from star polymers and their linear analogues. The potential of star polymer nano- and microlayers to drive innovations in polymer technology will be illustrated with examples in areas such as antibacterial films, tissue engineering, or in systems delivering bioactive substances. Finally, a brief summary of challenges and future perspectives in the field of this interesting generation of polymeric materials is given.

Phosphorus-containing polymers have gained special attention during the past several years as a result of their fascinating properties and wide-ranging applications. The various stable bonding configurations of phosphorus atoms have enabled the synthesis of a large number of stable monomers and polymers with unique and interesting properties, such as improved organo-solubility, good thermal stability, mechanical robustness, and excellent transport characteristics. This in-depth review aims to give an overview of the synthesis and structural modification of various phosphorus-containing polymers and their uses in different membrane-based applications.

In the last decade, phosphorus-containing polymers such as polyimide, poly(arylene ether), poly(arylene thioether), poly(arylene ether sulfone), poly(phthalazinone ether), and polytriazole have been used as proton exchange membranes. Subsequently, these phosphorus-based polymers also emerged as an attractive class of polymers for proton exchange membranes due to the outstanding water retention capacity within the membranes as well as well-networked ionic channels for proton conduction, adhesive strength, and peroxide resistance. The incorporation of phosphorus atoms in polymeric materials has also emerged as one of the most effective methods for enhancing the refractive index of polymers. As a result, a large number of research works have been carried out on phosphorus-containing polymers for optical applications. In addition, phosphorus-based polymers have attracted interest in areas such as gas separation and flame retardance. Motivated by these recent developments, this article reviews the synthesis, classification, and structure-property-performance relationships of phosphorus-containing polymers and delineates recent advances in their application in areas such as proton exchange membranes, optoelectronics as well as gas separation applications.

We survey progress in the development of the processes for radical-promoted single-unit monomer insertion (SUMI) or reversible deactivation radical addition (RDRA), focussing on aminoxyl- [nitroxide-] mediated SUMI (NM-SUMI), reversible-addition-fragmentation chain transfer-SUMI (RAFT-SUMI) and atom-transfer radical addition (ATRA). Radical-promoted thiol-ene processes are also briefly discussed. We detail the strategies for achieving selectivity with respect to single unit insertion vs oligomerization and look critically at progress towards discrete oligomer synthesis by consecutive SUMI reactions. We examine the use of SUMI to install α-, ω- or mid-chain-functionality in RDRP-synthesized polymers. Finally, we examine the prospects for using radical-promoted SUMI in the synthesis of sequence-defined polymers where monomer placement is precisely defined to the level of the individual monomer units in the polymer chain.

Radical polymerization of monomers with functional groups such as carboxylic acid and amide moieties yields materials of significant technical importance. The reactions are mostly carried out in aqueous phase, which provides the additional advantage of using a cheap and benign solvent. In addition to varying monomer concentration, temperature and pressure, the kinetics and thus the polymer properties may be tuned by varying the degree of monomer ionization, by changing pH and ionic strength of the aqueous solution, and by addition of an organic cosolvent. These systems exhibit strong interactions via hydrogen bonds resulting in large effects on rate coefficients, even for propagation, which for long have been considered as almost insensitive towards solvent environment. The determination of rate coefficients in aqueous solution largely assists the understanding of the impact of intermolecular interactions on polymerization rate. Despite the enormous importance of polymers produced by radical polymerization in aqueous solution, the associated mechanism and the availability of accurate rate coefficients have been very limited. This situation has improved by applying pulsed-laser techniques, which enable the precise measurement of individual rate coefficients in aqueous solution as required for the simulation of radical polymerization processes.

This review primarily addresses the two most important rate coefficients, i.e., those for propagation and termination, with the diffusion-controlled termination step depending on radical chain length. Both rate coefficients have been studied over a wide range of reaction conditions. The enormous improvement in data quality reached by using methods such as pulsed-laser polymerization (PLP) – size-exclusion chromatography (SEC) and single pulse (SP) – PLP – electron paramagnetic resonance (EPR) spectroscopy is illustrated. Outlined are results for homopolymerizations of non-ionized monomers, subdivided into monomers which may or may not undergo backbiting. This reaction adds considerable complexity, as backbiting results in the formation of midchain radicals with reactivity differing largely from the one of chain-end radicals. The kinetic investigations have been extended to partially and fully ionized monomers. Examples are given of how the rate coefficients from PLP experiments are used to simulate polymerization kinetics and polymer properties of continuously-initiated systems. The review demonstrates that the basic kinetic concepts for conventional radical polymerization in organic media also apply towards polymerization of monomers in aqueous solution.

The encapsulation of biologically active ingredients (e.g., peptides, proteins, enzymes, drugs) into polymer particles is extensively used for drug delivery purposes. However, this strategy relies mainly on emulsification processes from preformed polymers, which leads to strong limitations such as low particle concentrations (typically a few wt%), poor active ingredient loadings, as well as a rather limited structural diversity of the polymers usually used. Conversely, polymerizations in dispersed media, which allow for the formation of scalable suspensions of (nano)particles during the polymerization process, have been advantageously used for the in situ encapsulation of active ingredients. In this review, the in situ encapsulation of active ingredients, such as peptides, proteins, enzymes or drugs, in polymer particles obtained by polymerization in dispersed media for potential biomedical applications, is covered. Their physical and chemical encapsulations were both considered as function of the polymerization technique used. Several polymerization and encapsulation parameters will be discussed in view of adjusting the drug loading and the encapsulation efficiency of the active agent considered.

The adsorption and transport of molecules or ions in the confined space of microporous materials often reveal properties not seen in either dense bulk or microporous materials. The unexpected behavior of confined polymers motivates their application in advanced technologies. While the majority of microporous materials consist of network/framework-type strong intermolecular connections, making the processing and roll-to-roll fabrication of these materials particularly challenging, there exists a special category of microporous polymers that are amorphous and can be solution-processed. They feature relatively weak intermolecular bond strength, low long-range order, and large free-volume elements due to frustrated polymer chain motion. However, it remains elusive to design and synthesize solution-processable amorphous microporous organic polymers for those working in the field of membrane separations and electrochemistry. The application of membranes derived from these polymers in processes beyond gas separations is also overlooked. Thus, we review the synthetic strategies toward solution-processable amorphous microporous organic polymers (SAMOPs), with a particular focus on the characteristics and the monomer/polymer structural features of each reaction. Computation-based materials design, including computational tools are introduced that can reveal the monomer/polymer rigidity, polymer chain packing, thereby the generation of free volume elements, and the pore architecture, to facilitate the design and identification of desirable polymers. On-polymer modification methodology that can afford standing-alone membranes with functional groups for applications beyond gas separation, especially targeting membrane-based electrochemical devices are subsequently covered. The molecular transport/ion in the sub-1-nm space provided by solution-processable amorphous microporous organic polymers are presented and the wide range application of membranes derived from these polymers is demonstrated. Finally, challenges, perspectives, and future research directions are discussed.

Supramolecular polymers are, in broad brushstrokes, self-assembled structures built up from small building blocks via the use of noncovalent interactions. In favorable cases, supramolecular polymers embody the best features of covalent polymers while displaying unique reversibility, responsiveness, adaptiveness, and stability. This has made them of interest across a wide variety of fields, from molecular devices to sensors, drug delivery, cell recognition, and environmentally friendly materials systems. This review is concerned with the determinants that underlie supramolecular polymer construction, specifically the driving forces that have been exploited to create them. To date, nearly the full range of known noncovalent interactions (e.g., hydrogen-bonding, electrostatic interactions, charge transfer effects, and metal coordination, among others) has been exploited to create supramolecular polymers. Typically, one or more types of interactions is used to link appropriately designed monomers. The choice of noncovalent interaction can have a significant influence on the structure and function of the resulting supramolecular polymers. Understanding the connections between the forces responsible for the assembly of supramolecular polymers and their properties provides the foundation for further advances in this fast-moving field. Given the above, this review will discuss recent progress in the rapidly advancing field of supramolecular polymers organized by the types of underlying interactions. An overview of future challenges and opportunities for supramolecular polymers, including their formation, characterization, and applications, is also provided.

The macroscopic functions and properties of conjugated polymers depend on their microcosmic morphology and microstructure in the solid state. However, such morphology and microstructure from molecules to solid states are complicated. Therefore, it is a significant challenge to reveal the relationship among molecular structures to the complex microstructure and finally to device functions. This review focuses on the formation, behavior, and evolution of solution-state aggregation of conjugated polymers, which can influence and even determine the solid-state morphology and microstructure, ultimately clarifying the relationship between the microstructure and the properties of conjugated polymers. The critical role of solution-state aggregation is highlighted from a theoretical understanding of molecular interactions between polymer chains (conjugated backbones and/or flexible side chains) and solvent molecules. We highlight the recent progress on high-performance polymer-based devices through the solution-state aggregation strategy. Furthermore, we summarize the challenges and essential research direction on the solution-state aggregation, which will be addressed and established in the future. Therefore, an in-depth understanding of polymer aggregation will advance the development of high-performance conjugated polymers in various functional devices.

Poly(amino ester)s (PAEs) refer to a class of synthetic polymers characterized by repeating units in the backbone having tertiary amines and ester bonds, and bringing together the inherent biodegradability of polyesters and the rich tunable functionalities provided by tertiary amines. The presence of tertiary amines allows the introduction of various pendant groups, leading to diverse PAE material and properties, such as biodegradability, biocompatibility, water-solubility, stimulus-responsiveness (pH or temperature), etc. To date, PAEs are evolving into a new class of biodegradable polymer materials independent of aliphatic polyesters and have been widely used in various biomedical fields, such as gene delivery, drug delivery, bioimaging agents, etc. In addition, a new family of PAEs, namely N-acylated PAEs, with the same pendant carbonyl groups as poly(2-oxazoline)s, is expected to develop into new biopolymer platforms similar to polypeptoids and polyoxazolines. This review comprehensively summarizes the synthesis methods of PAEs, including polycondensation (PCD), Michael addition polymerization (MAP), spontaneous zwitterionic copolymerization (SZWIP), and ring-opening polymerization (ROP).