Access to Hydroxy-Functionalized Polypropylene through Coordination Polymerization

Preparation of polyethylenes containing hydroxy groups has been already industrialized through radical copolymerization under harsh conditions followed by alcoholysis. By contrast, hydroxy-functionalized polypropylene has proven a rather challenging goal in polymer science. Propylene can't be polymerized through a radical mechanism, and its coordination copolymerization with polar monomers is frustrated by catalyst poisoning. Herein, we report a new strategy to reach this target. The coordination polymerization of allenes by rare-earth-metal precursors affords pure 1,2-regulated polyallenes, which are facilely transformed into poly(allyl alcohol) analogues by subsequent hydroboration/oxidation. Strikingly, the copolymerization of allenes and propylene gives unprecedented hydroxy-functionalized polypropylene after post-polymerization modification. Mechanistic elucidation by DFT simulation suggests kinetic rather than thermodynamic control.     

Synthesis of novel polymeric materials based on aliphatic polyesters by combination of different controlled polymerization methods

Combination of the living ring-opening polymerization (ROP) of ε-CL and lactides with the “controlled” free radical polymerization of styrene and methacrylic monomers is a versatile strategy for the synthesis of well-defined block and graft copolymers. In this respect, the dual “living” polymerization strategy in which two different functional groups on a single molecule used to initiate the two controlled mechanisms is particularly efficient. Combination of ROP and step-growth polymerization is another versatile methodology for the preparation of a large variety of new materials, e.g. polyimide nanofoams, polyester/silica hybrid materials and star and branched polyesters by dendritic initiation.     

Controlled Polymerization of Multivinyl Monomers: Formation of Cyclized/Knotted Single‐Chain Polymer Architectures

Seventy years ago, Flory and Stockmayer predicted that the polymerization of multivinyl monomers (MVMs) would inevitably lead to insoluble cross‐linked gel networks. Since then, the use of MVMs has largely been limited to as cross‐linking agents. More recently, however, polymerization strategies such as reversible deactivation radical polymerization (RDRP) have paved the way for the exploration of new possibilities in terms of both polymer architectures and functional capabilities. This Minireview provides historical context to the problem of polymerizing MVMs, before highlighting how RDRP has led to the formation of new cyclized/knotted polymer structures. Although the potential of such cyclized/knot polymer architectures is far from being fulfilled, some emerging applications are discussed.     

Cationic Polymerization: From Photoinitiation to Photocontrol

During the last 40 years, researchers investigating photoinitiated cationic polymerizations have delivered tremendous success in both industrial and academic settings. A myriad of photoinitiating systems have been developed, thus allowing polymerization of a broad array of monomers (e.g., epoxides, vinyl ethers, alkenes, cyclic ethers, and lactones) under practical, inexpensive, and environmentally benign conditions. More recently, owing to progress in photoredox catalysis, photocontrolled cationic polymerization has emerged as a means to precisely regulate polymer chain growth. This Minireview provides a concise historical perspective on cationic polymerization induced by light and discusses the latest advances in both photoinitiated and photocontrolled processes. The latter are exciting new directions for the field that will likely impact industries ranging from micropatterning to the synthesis of complex biomaterials and sequence‐controlled polymers.     

Control of polymer topology through transition-metal catalysis: synthesis of hyperbranched polymers by cobalt-mediated free radical polymerization

A novel approach was demonstrated for the synthesis of hyperbranched polymers by direct free radical polymerization of divinyl monomers controlled by a cobalt chain transfer catalyst (1). By controlling the competition between propagation and chain transfer with 1, the free radical polymerization of ethylene glycol dimethacrylate (3) afforded soluble hyperbranched polymers in one pot. The structure of the hyperbranched polymers was confirmed by (1)H and (13)C NMR. The molecular weight and intrinsic viscosity of the hyperbranched polymers were measured by matrix-assisted laser desorption ionization (MALDI) mass spectrometry and size exclusion chromatography (SEC) equipped with triple detectors. The intrinsic viscosities of the hyperbranched polymers are much lower than those of their linear analogues and do not show molecular weight dependence. The unique structure and properties of these hyperbranched polymers combined with the commercial availability of many divinyl monomers and the robustness of free radical polymerization make this new approach attractive for the preparation of new functional materials.     

Access to Hydroxy‐Functionalized Polypropylene through Coordination Polymerization

Preparation of polyethylenes containing hydroxy groups has been already industrialized through radical copolymerization under harsh conditions followed by alcoholysis. By contrast, hydroxy‐functionalized polypropylene has proven a rather challenging goal in polymer science. Propylene can't be polymerized through a radical mechanism, and its coordination copolymerization with polar monomers is frustrated by catalyst poisoning. Herein, we report a new strategy to reach this target. The coordination polymerization of allenes by rare‐earth‐metal precursors affords pure 1,2‐regulated polyallenes, which are facilely transformed into poly(allyl alcohol) analogues by subsequent hydroboration/oxidation. Strikingly, the copolymerization of allenes and propylene gives unprecedented hydroxy‐functionalized polypropylene after post‐polymerization modification. Mechanistic elucidation by DFT simulation suggests kinetic rather than thermodynamic control.     

Biomolecular Densely Grafted Brush Polymers: Oligonucleotides,Oligosaccharides and Oligopeptides

In this Minireview, we describe synthetic polymers densely functionalized with sequence-defined biomolecular sidechains. We focus on synthetic brush polymers of oligonucleotides, oligosaccharides, and oligopeptides, prepared via graft-through polymerization from biomolecule functionalized monomers. The resulting structures are brush polymers wherein a biomolecular graft is positioned at each monomer backbone unit. We describe key synthetic milestones, identify synthetic opportunities, and highlight recent advances in the field, including biological applications.     

Photochemical Reactions in Self‐Assembled Organic Monolayers Characterized by using Scanning Tunneling Microscopy

Research on the supramolecular self‐assembly behavior at interfaces is of great importance to improving the performance of nanodevices that are based on optical functional materials. In this Minireview, several photoinduced isomerization and polymerization reactions in self‐assembled organic monolayers on surfaces are discussed. Typical organic molecules contain azobenzene, alkynyl, or olefins groups. The feature surface base is a highly oriented pyrolytic graphite (HOPG) surface or a gold surface. Scanning tunneling microscopy (STM) is used as a strong tool to characterize new species’ structures before and after illumination.     

Synthesis of Functional Polymers by Post‐Polymerization Modification

Post‐polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional‐group tolerance, and the orthogonality of the post‐polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post‐polymerization modification of these precursors into functional polymers.     

Polymethacrylate monolithic columns for capillary liquid chromatography

In recent years, continuous separation media have attracted considerable attention because of the advantages they offer over packed columns. This research resulted in two useful monolithic material types, the first based on modified silica gel and the second on organic polymers. This work attempts to review advances in the development, characterization, and applications of monolithic columns based on synthetic polymers in capillary chromatography, with the main focus on monolithic beds prepared from methacrylate-ester based monomers. The polymerization conditions used in the production of polymethacrylate monolithic capillary columns are surveyed, with attention being paid to the concentrations of monomers, porogen solvents, and polymerization initiators as the system variables used to control the porous and hydrodynamic properties of the monolithic media. The simplicity of their preparation as well as the possibilities of controlling of their porous properties and surface chemistries are the main benefits of the polymer monolithic capillary columns in comparison to capillary columns packed with particulate materials. The application areas considered in this review concern mainly separations in reversed-phase chromatography, ion-exchange chromatography, hydrophobic and hydrophilic interaction modes; enzyme immobilization and sample preparation in the capillary chromatography format are also addressed.     

Electro-selective interconversion of living cationic and radical polymerizations

Orchestrating conflicting polymerization mechanisms in a single polymerization process through one external stimulus is a prerequisite to achieve in-situ selective synthesis of different monomers. Here we report an electrochemically controlled mechanism transformation that enables selective activation of living cationic or radical polymerization via an alternating voltage and dual electrocatalysts. Using identical mixed-monomer condition, a variety of desired block copolymer structures, including diblock, multiblock, random, and tapered copolymers can be obtained by simply varying the periods or phases of the alternating potential. Moreover, merging this electro-interconverted polymerization with a flow-chemistry technique can streamline preparation of functional polymer materials with complex multiblock structure. This study would offer a new vision on large-scale electrochemical synthesis of sequence-defined polymers.     

含多面低聚倍半硅氧烷新型杂化聚合物的合成

基于多面低聚倍半硅氧烷（POSS）的杂化聚合物是近年发展起来的一类新型有机/无机杂化材料,性能独特,应用前景广阔。本文综述了含POSS新型杂化聚合物的合成研究进展,涉及自由基溶液聚合、可控活性聚合、开环易位聚合、缩聚和配位聚合。     

Synthetic Approaches to Trifluoromethoxy‐Substituted Compounds

Because of the unique properties of the trifluoromethoxy group, molecules bearing this moiety will find applications in various fields, particularly in the life sciences. However, despite the great interest in this functional group, only a small number of trifluoromethoxylated molecules are currently synthetically accessible. Over the last few years, several innovative and promising strategies for the synthesis of trifluoromethoxylated compounds have been described. This Minireview discusses these existing methods with a particular focus on more recent advances.     

活性阴离子聚合及其单体的研究进展

适用于活性阴离子聚合的单体拓展研究是有关活性阴离子聚合的一项重要的研究工作.本文重点介绍了近十年在活性阴离子聚合领域出现的新型单体的结构设计、合成及其聚合过程的研究进展.文中涉及到的新型单体主要包括非(弱)极性类单体、极性单体及其它单体.进一步细分,非(弱)极性类单体分为苯乙烯衍生物类单体和丁二烯衍生物类单体,极性单体中含有丙烯酸酯类单体、丙烯酰胺类单体、氯乙烯以及N-乙烯基咔唑,其它单体包括异氰酸酯类、烯酮类以及杂环类单体.最后本文对上述这些新型单体中的一些单体用于复杂大分子拓扑结构的设计合成情况也作了简要介绍.     

Early Transition Metal Catalysis for Olefin–Polar Monomer Copolymerization

Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentially upgrading polyolefins for advanced, value‐added applications. The metal catalyst‐mediated copolymerization of non‐polar olefins with polar comonomers represents the seemingly most straightforward, atom‐ and energy‐efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)‐catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, largely associated with the Lewis basicity of the polar co‐monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this Minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechanistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them.     

(Co)polymerization of metal-containing monomers as a way of MMC synthesis

The principal advances and problems of the synthesis, of poly-, co- and graft- polymerization of metal-containing monomers (MCM) are analysed. The MCMs are classified on the type of the metal bond with the organic part of the molecule, viz. MCM with σ-, nv-, and π-bonds. The effect of a transition metal on both the polymerization and on the properties of the products formed is of special interest. The basic fields of application of metal-containing polymers have been summed up.     

A One Pot,One Step Method for the Preparation of Clickable Hydrogels by Photoinitiated Polymerization

Current preparation methods for hydrogels based on redox or photopolymerization of water soluble monomers are simple to use, and flexible, but have the drawback of requiring additional modification steps for tuning or introducing properties for specific purposes. We have devised a simple and rapid synthetic strategy to prepare hydrogels possessing reactive sites to incorporate any molecules of interest by “Click Chemistry”. The strategy is based on the use of propargyl acrylamide (PAm) as comonomer together with acrylamide (AAm) and N,N′‐methylene bisacrylamide (BAAm) as crosslinker in photoinitiated polymerization. With the selective reactivity of photochemically generated free radicals towards acrylic function of PAm, hydrogels with clickable acetylene groups can be prepared in one pot, one step manner. Based on the acetylene functionality, any molecule possessing azide groups can be conjugated onto hydrogel by “Click Chemistry” as demonstrated on the example of fluoroscent azide functional pyrene.     

Synthesis,characterization, and polymerization of propenyl ether analogues

A series of aromatic monomers bearing cationically polymerizable propenyl groups were prepared and characterized using the readily available starting materials: isoeugenol and o-allyl phenol. Monomers with both propenyl and vinyl ether functional groups were also synthesized by the reaction of these starting materials with chloroethyl vinyl ether. The reactivity of the resulting monomers in photoinitiated cationic polymerization was studied using differential scanning photocalorimetry and photogel point measurements. Their thermal properties were determined using thermogravimetric analysis. © 1994 John Wiley & Sons, Inc.     

Two-Dimensional Polymer Networks Locking on Inorganic Nanoparticles

Two-dimensional polymers (2DPs), single-layer networks of covalently linked monomers, show perspectives as membranes and in electronics. However, 2D polymerization of monomers in orthogonal directions limited the formation of 2DPs on nanoparticles (NPs) with high surface curvatures. Here we propose a high-curvature 2D polymerization to form a single-layer 2DP network as a non-contacting ligand on the surface of NPs for their stabilization and functionalization. The high-curvature 2D polymerization of amphiphilic Gemini monomers was conducted in situ on surfaces of NPs with various sizes, shapes, and materials, forming highly cross-linked 2DPs. Selective etching of core–shell NPs led to 2DPs as a non-contact ligand of yolk-shell structures with excellent shape retention and high NP-surface accessibility. In addition, by copolymerization, the 2DP ligands can covalently link to other functional molecules. This work promotes the development of 2DPs on NPs for their functional modification.