DNA meets synthetic polymers--highly versatile hybrid materials

The combination of synthetic polymers and DNA has provided biologists, chemists and materials scientists with a fascinating new hybrid material. The challenges in preparing these molecular chimeras were overcome by different synthetic strategies that rely on coupling the nucleic acid moiety and the organic polymer in solution or on solid supports. The morphologies and functions of the bioorganic block copolymers can be controlled by the nature of the synthetic polymer segment as well as by the sequence composition and length of the DNA. Recent developments have expanded the scope and applications of these hybrid materials in a number of different areas including biology and medicine, as well as bio- and nanotechnology. Their usage ranges from gene delivery through to DNA detection to programmable nano-containers for DNA-templated organic reactions.     

Polythiophene-block-poly(phenyl isocyanide) copolymers: One-pot synthesis,properties and applications

Conjugated block copolymers have gained increasing interests in recent years. Development of a novel method for facile synthesis of conjugated block copolymers with desired structures and functions is greatly desired. In this mini review, we summarized the recent advances in one-pot synthesis of conjugated block copolymers containing π-conjugated polythiophene and helical polyisocyanide segments by using a nickel(Ⅱ) complex as single catalyst. The sequential living polymerization of the two monomers proceeded in a controlled manner, affording expected block copolymers in high yields with controlled molecular weights(Mns) and narrow molecular weight distributions(Mw/Mns). By using this method, a family of block copolymers with expected structure and tunable compositions can be facilely prepared. Introducing functional groups onto the pendant, these block copolymers can exhibit interesting self-assembly property, tunable light emission and multi-responsiveness.     

A “click” approach to ROMP block copolymers

Amphiphilic block copolymers can be conveniently prepared via convergent syntheses, allowing each individual polymer block to be prepared via the polymerization technique that gives the best architectural control. The convergent “click‐chemistry” route presented here, gives access to amphiphilic diblock copolymers prepared from a ring opening metathesis polymer and polyethylene glycol. Because of the high functional group tolerance of ruthenium carbene initiators, highly functional ring opening metathesis polymerization (ROMP) polymer blocks can be prepared. The described synthetic route allows the conjugation of these polymer blocks with other end‐functional polymers to give well‐defined and highly functional amphiphilic diblock copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2913–2921, 2008     

Polymer-DNA hybrids as electrochemical probes for the detection of DNA

The syntheses of several norbornene block copolymers containing oligonucleotide and ferrocenyl side chains and their use in the electrochemical detection of DNA are described. Two kinds of DNA-containing block copolymers with either ferrocenyl or dibromoferrocenyl groups were prepared via ring-opening metathesis polymerization (ROMP). Based on these two distinct ferrocene derivatives, a triblock copolymer labeling strategy was developed. With this strategy, the identity of DNA target can be determined by the E1/2s of the ferrocenyl moieties and the ratio of peak currents. These polymers exhibit predictable and tailorable electrochemical properties, high DNA duplex stability, and unusually sharp melting transitions, which are highly desirable characteristics for DNA detection applications. Significantly, single-base mismatches could be easily detected using two distinct block copolymers as dual-channel detection probes in an electrochemical DNA detection format.     

Investigation of polymer surfaces using scanning force microscopy (SFM) “a new direct look on old polymer problems”

In this contribution, the general concepts of force microscopy will be presented together with its application to polymer surfaces (Ref.1). Several examples will be presented to illustrate that force microscopy is a powerful and promising tool for investigation of (polymer) surfaces, such as the imaging of polymer single crystals and the surface structure of thin films of piezo- and pyroelectric block copolymers. Individual molecules were resolved in the case of polytetrafluoroethylene and double-stranded circular DNA, without any particular surface treatment.     

In Situ Hetero End‐Functionalized Polythiophene and Subsequent “Click” Chemistry With DNA

It is demonstrated that bifunctionalized polythiophenes involving thiol and azide end‐functional groups can be synthesized by chain‐growth Suzuki‐Miyaura type polymerization. The bifunctionalized polythiophenes are successfully characterized by 1H NMR, gel permeation chromatography (GPC), and matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF). Furthermore, the azide end‐group reacts with DNA via “click chemistry” to form a polythiophene/DNA hybrid structure, which is characterized by ESI‐MS. The described synthetic approaches will lead to the synthesis of novel multi‐block copolymers as well as biomolecule‐based conjugated polymer structures.     

Double‐Hydrophilic Block Copolymers: Synthesis and Application as Novel Surfactants and Crystal Growth Modifiers

Double‐hydrophilic block copolymers are a new class of amphiphilic molecules of rapidly increasing importance with unique and fascinating properties potentially connecting materials science, pharmacy, biochemistry and polymer science. Characteristic of these polymers is their application in aqueous environments and that amphiphilicity is just induced in the presence of a substrate or by temperature and pH changes, respectively. Their chemical structure may be tuned for a wide range of applications covering as different aspects as stabilization of colloids, crystal growth modification, induced micelle formation, polyelectrolyte complexing towards novel drug carrier systems. As the potential of this novel polymer class is relatively unexplored yet, it can be expected that more applications will arise due to the possibility to adapt the chemical structure to either the desired substrate in contact with water or the stimulus for the induction of structural changes. This review describes the synthetic strategies towards these AB block copolymers, as well as their applications.     

New developments in the synthesis of block and graft copolymers via anionic and cationic methods

Ionic living polymerization methods are well suited for the synthesis of macromolecules of known structure, molecular weight and composition, and exhibiting low fluctuations in composition and in molecular weight. They were the first to allow the synthesis of well characterized block and graft copolymers. The present paper discusses a number of recent developments concerning these syntheses based on anionic or cationic living polymerization.     

Mass spectrometric imaging of synthetic polymers

The analysis of synthetic polymers represents today an important part of polymer science to determine their physical properties and to optimize the performance of polymeric materials for block copolymers as well as blend systems. The characterization can easily and rapidly be performed by mass spectrometry. In particular, the film formation of a synthetic polymer is of interest in material research and quality control, which can be determined by employing mass spectrometric imaging (MSI) using secondary ion mass spectrometry (SIMS) or matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. MALDI-MSI has been rapidly improved for the analysis of tissue cross-sections due to its soft ionization and accessible m/z range, which both also play an important role in polymer science. On the other hand, SIMS-MSI enables a sub-micrometer molecular spatial resolution, which is limited in MALDI-MSI due to the spatial resolution capabilities of the laser desorption process. The aim of the present contribution is to summarize recent advances in both imaging techniques for the analysis of synthetic polymers and to highlight their capabilities to correlate several imaging modalities in future applications.     

Theoretical aspects of small-angle neutron scattering from multiphase polymers

A molecular theory for small-angle neutron scattering from polymer mixtures is reviewed and extended to consider multiphase polymer systems such as block copolymers and their blends with homopolymers. Methods are developed for the isolation of scattering functions for individual components in these blends. These methods rely on two contrast-matching techniques: the concept of “composition matching,” where a mixture of deuterium-labeled and protonated species is used to match the contrast of a third component; and the synthesis of “phase-matched” block copolymers, where the contrast of the block copolymer sequences are matched. Methods are discussed specifically for the isolation of single chain and single sequence scattering functions for diblock and triblock copolymers, their blends with homopolymers, and star copolymers.     

Orthogonally Self‐Assembled Multifunctional Block Copolymers

We report the synthesis of telechelic poly(norbornene) and poly(cyclooctene) homopolymers by ring‐opening metathesis polymerization (ROMP) and their subsequent functionalization and block copolymer formation based on noncovalent interactions. Whereas all the poly(norbornene)s contain either a metal complex or a hydrogen‐bonding moiety along the polymer side‐chains, together with a single hydrogen‐bonding‐based molecular recognition moiety at one terminal end of the polymer chain. These homopolymers allow for the formation of side‐chain‐functionalized AB and ABA block copolymers through self‐assembly. The orthogonal natures of all side‐ and main‐chain self‐assembly events were demonstrated by ¹H NMR spectroscopy and isothermal titration calorimetry. The resulting fully functionalized block copolymers are the first copolymers combining both side‐ and main‐chain self‐assembly, thereby providing a high degree of control over copolymer functionalization and architecture and bringing synthetic materials one step closer to the dynamic self‐assembly structures found in nature.     

Electroclinic properties of chiral smectic a liquid crystalline polymers and block copolymers

The scope for the synthesis and investigation of chiral smectic A liquid crystalline (LC) polymers and block copolymers is discussed. LC block copolymers can combine the molecular order of liquid crystals and the supramolecular order typical of block copolymers, thus allowing to attain information on mesomorphic responses in restricted geometries. We present a general overview on several aspects of the syntheses and properties of LC block copolymers, specifically those obtained by starting from azomacroinitiators. These materials can exhibit an electroclinic effect, that is an electrically induced molecular tilt, which is characterized by a linear dependence on the applied field and a very fast response time in the paraelectric smectic A phase. The current progress in their potential application in electrooptics is outlined.     

Biorecognizable polymers: Structure-properties relationship

The biocompatibility of polymers depends on their chemical composition, as well as physical and physico-chemical structure. However, biocompatibility is not an intrinsic polymer property since it relates to a particular localization of the polymer in the living organism. Any foreign macromolecule may be recognized by the living organism as “non-self”. The degree of recognition can be altered by modification of the structure of macromolecules or biomaterial surfaces. Modification of biomacromolecules (e.g., enzymes¹) or biomaterial surfaces with hydrophilic polymers, e.g., poly(ethylene oxide²) or other semitelechelic hydrophilic macromolecules³ has been shown to minimize biorecognition. On the other hand, to achieve specific recognition by cell receptors and/or antigens, complementary structures have to be incorporated as a part of the polymer structure^{4, 5}. The biorecognition of fluorescently labeled N-(2-hydroxypropyl)-methacrylamide copolymers containing side-chains terminated in acylated galactosamine by Hep G2 cells on the cellular and subcellular levels can be visualized by confocal fluorescence microscopy. The recognition of modified water soluble macromolecules strongly depends on their solution properties⁶. Incorporation of stimuli sensitive moieties into copolymer side-chains permits to control recognition by external stimuli, e.g., irradiation^{7, 8}, resulting in the change of the copolymer conformation. On the other hand, the biorecognition of unsoluble (crosslinked) copolymers depends mainly on their surface structure. The rationale for the structure modification of synthetic copolymers to regulate biorecognition will be reviewed. The principles will be described for the interaction of synthetic polymers with enzymes⁹, cell surface receptors and/or antigens^{10, 11}, lectins of the gastrointestinal tract^{12, 13}, and immobilized lectins¹⁴.     

Mechanistic and Synthetic Aspects of Atom Transfer Radical Polymerization

Abstract

Mechanistic and synthetic aspects of atom transfer radical polymerization (ATRP) are reviewed. This controlled/“living” system polymerizes many monomers including styrenes, (meth)acrylates, acrylonitrile and dienes. The halogen end groups can be converted to other functional groups such as amines and azides. In addition to producing well-defined linear homopolymers, statistical copolymers, block copolymers, and gradient copolymers, ATRP can be used to synthesize graft and hyperbranched copolymers through copolymerization with functionalized monomers. Selection of appropriate conditions for ATRP depends on targeted molecular weight and degree of polymer chain end-functionality and includes considering the monomer(s) to be polymerized, initiator structure/reactivity, amount of catalyst/deactivator used, halogen end-group used, and temperature.     

聚合物微观结构对聚合物电解质膜性能的影响

聚合物的微观结构是设计具有优异的电化学性能的聚合物电解质膜(PEMs)的基础.在电解质膜中,相分离结构形成的离子簇和离子通道可以影响膜在高温低湿度条件下的离子传导和水的传输,这种结构形成的形貌也可以影响膜的吸水率、溶胀度、碱稳定性等性能.近几年来,人们对于具有微观相分离形貌的PEMs的合成和形貌开展了很多研究.本文主要...     

Recent advances in the study of biopolymers

In describing some of the macromolecular characteristics of the nucleic acids, particularly DNA, and of representative proteins, the following aspects are discussed: computer-assisted modeling as a useful tool for depicting the three-dimensional structures and macromolecular characteristics of biopolymers; conformational flexibility in biopolymers; parameters determining protein recognition; and the importance of the three-dimensional structure of antibodies, enzymes, receptors, ion channels, and proteins interacting with nucleic acids, in determining their characteristic biological functions. Many of the problems raised by molecular biologists concerning the mode of action of biopolymers could be tackled by polymer chemists, because of their experience in dealing theoretically as well as experimentally with synthetic and native high molecular weight compounds.     

活性聚合法合成结构精确的含氟嵌段共聚物

结构精确的含氟嵌段共聚物具有优异而独特的化学和物理性能,有广阔的应用前景,因此受到广泛的关注.含氟嵌段共聚物可分为两类,一类是侧基含氟嵌段共聚物,另一类是主链含氟嵌段共聚物.活性聚合为嵌段共聚物的合成提供了最为重要的方法,利用它可以合成结构精确、分子量可控、分子量分布窄的嵌段共聚物.根据单体的反应特性选择不同的聚合方法,可以得到不同的含氟嵌段共聚物.本文主要综述了近几年利用各种活性聚合方法合成结构精确的含氟嵌段共聚物方面的进展.     

Enzymatic Synthesis of Organic‐Polymer‐Grafted DNA

To create bioorganic hybrid materials, interdisciplinary work in the fields of chemistry, biology and materials science is conducted. DNA block copolymers are promising hybrid materials due to the combination of properties intrinsic to both the polymer and the nucleic acid blocks. Until now, the coupling of DNA and organic polymers has been exercised post‐synthetically in solution or on solid support. Herein, we report the first enzyme‐catalysed synthesis of DNA–organic polymer chimeras. For this purpose, four novel 2′‐deoxyuridine triphosphates carrying polymer‐like moieties linked to the nucleobase were synthesised. Linear polyethylene glycol monomethyl ethers of different sizes ( 1 ) and branched polyamido dendrons with varying terminal groups ( 2 ) were chosen as building blocks. We investigated the ability of DNA polymerases to accept the copolymers in comparison to the natural substrate and showed, through primer extensions, polymerase chain reactions and rolling circle amplification, that these building blocks could serve as a surrogate for the natural thymidine. By this method, DNA hybrid materials with high molecular weight, modification density, and defined structure are accessible.     

甲壳型液晶高分子研究进展与展望

简要介绍了甲壳型液晶高分子的模型理论, 概述了当前国内外对甲壳型液晶高分子设计、 液晶相态、 性质及基于甲壳型液晶高分子的嵌段共聚物体系的设计和自组装性质等研究进展, 展望了今后的研究方向.     

硅氧烷基聚合物电解质*

聚合物锂离子电池的核心技术是研制高离子传导率、适宜机械性能以及化学和电化学性能稳定的聚合物电解质材料。在众多寻求高性能聚合物电解质的研究工作中,由于硅氧烷基聚合物电解质具有灵活多样的分子结构设计、易于合成实施、优异的电化学性能和室温电导率等特点,一直是人们关注的热点领域。本文综述了近年来新型硅氧烷基聚合物电解质的设计与合成的研究工作,重点介绍了采用聚硅氧烷嵌段、接枝聚合物通过共混、互穿网络结构、交联网络结构以及无机-有机复合等方法开展的相关聚合物电解质的研究工作。同时也介绍了聚硅氧烷电解质的研究方法和基于聚硅氧烷电解质的应用研究进展。