Progress in Polymer Science最新文献

Microbial infections endanger human health and life. Conventional antibiotics has saved countless human lives, however, is seriously challenged by the quick emergence of antibiotic-resistant pathogens. It is urgent to develop new types of antimicrobial agents to treat antibiotic-resistant microbial infections. Host defense peptides (HDPs) have broad-spectrum antimicrobial activity and low susceptibility to antimicrobial resistance, therefore, have been actively studied to develop promising antimicrobial agents. However, natural HDPs are structurally unstable due to their easy hydrolysis by proteases. Sequence-defined peptides have been explored as HDP mimics and have proven as promising candidates of antimicrobial drugs. Nevertheless, preparation of these HDP-mimicking peptides by solid-phase synthesis is time-consuming, expensive, and difficult for large scale synthesis. Assisted by the development of polymerization chemistry, polypeptides can be prepared in the form of amino acid polymers conveniently and at large scales using the polymerization strategy. Amino acid polymers, also known as poly(amino acid)s, have the same or similar backbone structure as natural peptides and have excellent biocompatibility. Several classes of such antimicrobial polymers have been explored as synthetic mimics of HDPs including α-amino acid polymers, β-amino acid polymers, peptoid polymers, amino acid hybrid polymers, and peptide mimicking polymers such as poly(2-oxazoline)s. To tune the biological activities and obtain the optimal antimicrobial polymers, key structure characteristics of HDPs are involved and investigated such as positive charges and the hydrophobic/hydrophilic amphiphilic structure. In this review, we provide an overview of research in the last decade about the design of HDP-mimicking antimicrobial amino acid polymers and beyond, including positive charge, amphiphilic structure, chain length, end group, hydrophilicity, stereochemistry, secondary structure, topology, self-assembly and backbone structure, as well as the major applications of antimicrobial amino acid polymers. Finally, we provide a perspective on the comparison between antimicrobial peptides and antimicrobial amino acid polymers, as well as some key challenges that still need to be addressed for possible clinical application of HDP-mimicking antimicrobial amino acid polymers.

Unlike natural macromolecules (e.g., nucleic acids and proteins) possessing precisely defined molar mass, chain sequence, chirality, and topology, synthetic polymers are typically featured with broad chain length distributions, inhomogeneous compositions, and undefined sequences. To bridge the wide gap between natural and synthetic polymers, sequence-defined polymers (SDPs) have gradually emerged and developed with precise chain length, sequence, tacticity, and topology, holding great promise to reach the same level of precision, complexity, and functionality of biopolymers. The emergence of SDPs confers an unparalleled opportunity to precisely regulate their primary structures, rational intrachain and interchain self-organization, and macroscopic properties, enabling the fundamental elucidation of structure-function relationships. This review aims to summarize recent progresses in the synthesis and advanced applications of emerging and booming SDPs. Some prospects are proposed towards future challenges and versatile promising developments of SDPs.

Lignocellulose has been extensively researched over the past decades in response to the growing global significance of renewable resources and environment-friendly materials. Hemicellulose is a large family of polysaccharides present in the primary and secondary cell walls of all land plants, fresh-water plants, and some seaweeds. It has gained significant attention in the development of hemicellulose-based functional polymeric materials owing to its distinct features such as environment-friendliness, renewability, and biodegradability. Recent studies have focused on the isolation, structural characterization, and chemical modification of hemicellulose and the preparation of hemicellulose-based materials. This review, comprehensively elaborates the preparation of hemicellulose-based functional polymeric materials via chemical modification, including the structures and properties of hemicellulose; design strategies for harnessing hemicellulose; and various forms of hemicellulose-based functional polymeric materials such as nanoparticles, films and coatings, hydrogels and aerogels, carbon quantum dots, porous carbons and catalysts. This review provides an update on hemicellulose-based functional materials, with a focus on their controlled-release, adsorption, biosensing, packaging, catalytic conversion, and electrode applications. Future perspectives on challenges and opportunities in the research field of hemicellulose are briefly highlighted.

Nature endows numerous organisms with the ability to realize their basic physiological activities through stimulus-responsive actuation. Inspired by these interesting biological structures, various biomimetic hydrogel actuators with excellent controllability, fast response, and toughness have been developed. Here, the principles of enabling stimulus-responsive behavior in polymer materials are first reviewed for the example of biological materials and subsequently recent progress in implementing stimuli-response behavior in bioinspired hydrogel actuators are being discussed. Particular emphasis is on the mechanisms underlying mechanical toughening of hydrogel actuators and its role in applications. The goal is to highlight recent progress, find the common threads, and discuss the fundamental differences to determine the current challenges and future directions for this field.

Semicrystalline polymers products usually adopt a crystallized form in their end-use environment. These crystallized polymers undergo various deformations under different external fields (e.g., stretching) from precursor processing, post treatment to final shape formation. Such deformation process is accompanied by multi-scale and multi-stage structural evolutions due to the complex hierarchical structures of crystallized polymers. These structural evolutions control over essential physical properties of semicrystalline polymers, which can be further developed towards high-performance industrial materials. A profound understanding of associated mechanisms is the critical key to interpret the complicated deformation process and to optimize the practical performances of polymer materials. The past reviews have more or less focused on one aspect of deformation while the multi-scale vision is lacking. Herein, this review brings a comprehensive presentation of strain-induced structural mechanics of crystallized polymers based on a multi-scale, multi-stage standpoint from the initiation of plasticity until failure. Important structural changes and associated mechanisms during the whole deformation process are systematically summarized, with particular attention paid to the crystal phase transition and crystal morphology evolution. Besides, the relationships between resulted microstructures and the essential end-use properties of crystallized polymers as well as their performances as common industrial materials are discussed. By summarizing the recent processes, this review is hoped to open up more aventunes for developing deformation-inspired sophisticated materials facing broader and interdisciplinary application fields.

The incorporation of heteroatom-containing weak bonds along polymer backbones has become a popular tool to accelerate degradation. Many methods have already been reported for the synthesis of degradable heteroatom-containing polymers based mainly on conventional step-growth polymerization and chain-growth ring-opening polymerization (ROP). In recent years, ring-opening metathesis polymerization (ROMP) has evolved as an emerging approach for the synthesis of various types of degradable polymers, from carbocyclic norbornene derivatives to heterocyclic olefin monomers. Classic ruthenium (Ru)-based catalysts exhibit not only high reactivity to C=C double bonds but also high tolerance to polar functional groups. Hence, a rich range of functional groups can be incorporated into cyclic olefin monomers and then transferred to the polymer backbones. This review covers the synthesis of the various heteroatom-containing degradable (co)polymers via ROMP, including poly(thio)acetals/polyketals, polyorthoesters, polyesters, polycarbonates, polyphosphoesters/polyphosphoamidates, poly(enol ether)s, poly(silyl ether)s, polydisulfides, polyketones, polyacylsilanes, polyamides, and polyureas, as well as their degradable mechanisms under different conditions. The review also highlights applications in tissue engineering and medicine.

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.