SYNTHESIS AND CHARACTERIZATION OF WATER-SOLUBLE BLOCK COPOLYMERS WITH AN END-TAGGED NAPHTHALENE PROBE

Water-soluble A-B block copolymers of 2-perfluoroethyl-2-oxazoline or 2-pentyl-2-oxazoline as hydrophobic monomers and 2-methyl-2-oxazoline as hydrophilic monomer were prepared by means of the living cationic ring-opening polymerization. The polymerization was initiated with N-methyl-2-(1-naphthyl)-2-oxazolinium trifluoromethanesulfonate as fluorescence label followed by sequential addition of the hydrophobic and the hydrophilic monomer. The polymerization was monitored by ¹H NMR spectroscopy and gel permeation chromatography (GPC) measurements. The results revealed that fluorophilic block copolymers can be prepared by this method while lipohilic block copolymers are not accessible by this monomer sequence. Micelle formation of the fluorophilic block copolymers in aqueous solution was studied by means of steady-state fluorescence spectroscopy which confirmed strong intermolecular excimer formation of the terminal bounded naphthalene moiety. In chloroform as a good solvent for both blocks, only monomer fluorescence could be observed.     

Ring‐Opening Metathesis Polymerization in Aqueous Media Using a Macroinitiator Approach

Water‐soluble and amphiphilic polymers are of great interest to industry and academia, as they can be used in applications such as biomaterials and drug delivery. Whilst ring‐opening metathesis polymerization (ROMP) is a fast and functional group tolerant methodology for the synthesis of a wide range of polymers, its full potential for the synthesis of water‐soluble polymers has yet to be realized. To address this, we report a general strategy for the synthesis of block copolymers in aqueous milieu using a commercially available ROMP catalyst and a macroinitiator approach. This allows for excellent control in the preparation of block copolymers in water. If the second monomer is chosen such that it forms a water‐insoluble polymer, polymerization‐induced self‐assembly (PISA) occurs and a variety of self‐assembled nano‐object morphologies can be accessed.     

开环易位聚合合成瓶刷聚合物

瓶刷聚合物是一类具有独特侧链结构的梳形聚合物。功能性瓶刷聚合物在光子晶体、表面活性剂、医药载体、防污涂层以及智能材料等领域具有良好的应用价值。通过开环易位聚合合成瓶刷聚合物的方法具有合成步骤简单、聚合物接枝密度高和侧链组成均一等优点,在控制聚合物组成、分子量和分散性等方面具有显著优势。本文基于开环易位聚合,简述了合成瓶刷均聚物以及嵌段型、混合型和核-壳型三种类型的瓶刷共聚物的方法,并介绍了合成精确结构的瓶刷聚合物的新进展。     

Microwave-assisted synthesis and micellization behavior of soy-based copoly(2-oxazoline)s

Polymers based on renewable resources are promising candidates for replacing common organic polymers, and thus, for reducing oil consumption. In this contribution we report the microwave-assisted synthesis of block and statistical copolymers from 2-ethyl-2-oxazoline and 2-“soy alkyl”-2-oxazoline via a cationic ring-opening polymerization mechanism. The synthesized copolymers were characterized by gel permeation chromatography and ¹H-NMR spectroscopy. The micellization of these amphiphilic copolymers was investigated by dynamic light scattering and atomic force microscopy to examine the effect of hydrophobic block length and monomer distribution on the resulting micellar characteristics.     

可溶液加工的聚(多金属氧簇降冰片烯)和聚(己酸降冰片烯)嵌段和无规共聚物的合成及催化功能的研究

将一种可有机功能化的Wells-Dawson POM与降冰片烯相连接,制备了多金属氧簇降冰片烯单体.再利用活性可控的开环易位聚合方法(ROMP),在Grubbs 3~(rd)催化剂的作用下,合成了聚(多金属氧簇降冰片烯)-聚(己酸降冰片烯)的杂化嵌段和无规共聚物(H-CPs),分别简写为Poly(POM)_m-b-Poly(COOH)_n和Poly(POM)_m-r-Poly(COOH)_n.采用~1H-NMR、~(31)P-NMR和FTIR等方法对共聚物结构进行表征,确认我们成功地合成了由共价键连接这2种单体形成的H-CPs.最后,利用带有光散射和红外探测器的凝胶渗透色谱(SEC)测定聚合物的绝对分子量和分子量分布,证明所得到的H-CPs不仅分子量可控,而且分子量分布系数较窄.最后,研究了H-CPs催化氧化四氢噻吩(THT)成环丁亚砜(THTO)反应,结果表明,相比于聚(多金属氧簇)的均聚物(Poly(POM)),H-CPs的催化活性有所下降,原因是POM催化剂含量较低以及H-CPs在催化介质中溶解性的差异.     

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.     

Synthesis of fluorinated polymers via ROMP: a review

This review is concerned with the work conducted in the Durham group during the last twenty years. It is specifically concerned with ROMP of fluorinated monomers with classical and well-defined initiators, with the synthesis of stereoregular polymers, block and stereoblock copolymers.     

Solid-phase synthesis of polymers using the ring-opening metathesis polymerization

We report a general method for the solid-phase synthesis of polymers via the ring-opening metathesis polymerization (ROMP). The method involves polymerization in solution to form a block copolymer, immobilization of the polymer via reaction of one block with a resin-bound functional group, modification of the other block, and liberation of the polymer from the resin. We demonstrated the utility of this approach by generating a block copolymer with an N-hydroxysuccinimidyl ester-substituted block (for on-resin functionalization) and a maleimide-substituted block (for conjugation to the resin). We showed that the Diels-Alder reaction can be employed to immobilize the polymers and that amines of diverse structure can be used to modify the resin-bound polymers. The reversibility of the furan-maleimide Diels-Alder adduct was exploited to liberate the polymer from the support. Specifically, treatment of the resin with cyclopentadiene resulted in complete polymer release. The resulting polymers are functional: they were as potent in assays with the lectin concanavalin A as polymers generated by traditional solution routes. We anticipate that this method can be used for the rapid synthesis of diverse polymers via ROMP.     

Catalytic Living Ring Opening Metathesis Polymerisation: The Importance of Ring Strain in Chain Transfer Agents

A recently developed catalytic living ring opening metathesis polymerisation (ROMP) was investigated using a series of reversible chain transfer agents (CTA) carrying either cyclopentene or cyclohexene rings, differing only in ring strain. All cyclopentene derivatives examined showed significantly faster reaction rates than the corresponding cyclohexene derivatives. This resulted in lower molecular weight dispersities and better control of the molecular weight for the cyclopentene compared to the cyclohexene CTAs. Both Grubbs’ second and third generation catalysts could be employed in catalytic living ROMP using cyclopentene CTA derivatives. The kinetics of different CTAs were studied, block copolymers were synthesised and residual ruthenium quantified by ICP‐OES. All polymers were fully characterised by NMR, GPC and MALDI‐ToF mass spectrometry. The new cyclopentene CTAs are readily synthesised in a few straightforward steps and provide faster reaction kinetics than all previously reported reversible CTAs.     

Poly(arylenevinylene)s through Ring‐Opening Metathesis Polymerization of an Unsymmetrical Donor‐Acceptor Cyclophane

Reported are well‐defined donor‐acceptor alternating copolymers prepared using ring‐opening metathesis polymerization (ROMP). Unsymmetrical cyclophanedienes comprising electron‐donating (4‐methoxy‐1‐(2‐ethylhexyl)oxy)benzene (MEH) and electron‐accepting benzothiadiazole (BT) rings were synthesized from the corresponding [3.3]dithiaparacyclophanes. ROMP of the strained unsymmetrical and “electronically‐ambiguous” cyclophanedienes proceeded in a controlled manner in the presence of either Hoveyda–Grubbs II or Grubbs II initiator in wake of both steric and electronic encumbrance. The resulting polymers, comprising alternating BT and MEH‐PPV units, are achieved in molecular weights exceeding 20k with ? values ranging from 1.1–1.4. The living nature of the polymerization is verified through the formation of rod‐coil and rod‐rod block copolymers. Our strategy to develop previously unrealized polymers from functional building blocks featuring a locked‐in D‐A unit is significant in a field striving to achieve well‐defined and sequence‐specific materials.     

Precise synthesis of poly(macromonomer)s containing sugars by repetitive ring-opening metathesis polymerisation

Various poly(macromonomer)s containing sugars have been prepared by ROMP of norbornene macromonomers substituted with ROMP block copolymers containing acetal-protected sugars as the side chain, which upon removal of the protecting group affords a novel amphiphilic architecture.     

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.     

Analysis of polystyrene-b-polyisoprene copolymers by coupling of liquid chromatography at critical conditions to NMR at critical conditions of polystyrene and polyisoprene

For the investigation of the molecular heterogeneity of polystyrene-b-polyisoprene block copolymers, a chromatographic separation method, namely liquid chromatography at critical conditions was developed. This method was coupled on-line with (1)H-NMR(where NMR stands for nuclear magnetic resonance) for the comprehensive analysis of the polystyrene-b-polyisoprene copolymers. The copolymers were synthesized by two different methods: sequential living anionic polymerization and coupling of living precursor blocks. While (1)H-NMR allows just for the analysis of the bulk chemical composition of the block copolymers, the coupling with liquid chromatography at critical conditions provides selective molar mass information on the polystyrene and polyisoprene blocks within the copolymers. The polyisoprene block molar mass is determined by operating at chromatographic conditions corresponding to the critical point of adsorption of polystyrene and size exclusion chromatography mode for polyisoprene. The molar mass of the polystyrene block is determined by operating at the critical conditions of polyisoprene. In addition to the molar mass of each block of the copolymers, the chemical composition distribution of the block copolymers was determined. By using the coupling of liquid chromatography at critical conditions to (1)H-NMR, one can also detect the homopolymers formed during synthesis. Finally the microstructure of the polyisoprene block in the copolymers was evaluated as a function of molar mass.     

Crystalline-crystalline block copolymers of regioregular poly(3-hexylthiophene) and polyethylene by ring-opening metathesis polymerization

Block copolymers of regioregular poly(3-hexylthiophene) (P3HT) and polyethylene (PE) were synthesized through the chain transfer of olefin-terminated P3HT in the presence of cyclooctene via ring-opening metathesis polymerization (ROMP). Subsequent hydrogenation of the poly(cyclooctene) block yielded high molecular weight, crystalline-crystalline P3HT-PE block copolymers, which are thermally stable and resistant to solvents under ambient conditions. These copolymers were characterized by 1H NMR, DSC, and WAXS and represent the first materials of a class of crystalline-crystalline semiconducting-insulating block copolymers.     

A modular approach toward block copolymers

A novel methodology for the formation of block copolymers has been developed that combines ring-opening metathesis polymerization (ROMP) with functional chain-transfer agents (CTAs) and self-assembly. Telechelic homopolymers of cyclooctene derivatives end-functionalized with hydrogen-bonding or metal-coordination sites are formed through the combination of ROMP with a corresponding functional CTA. These telechelic homopolymers are fashioned with a high control over molecular weight and without the need for post-polymerization procedures. The homopolymers undergo fast and efficient self-assembly with their complement homopolymer or small molecule analogue to form block-copolymer architectures. The block copolymers show equivalent association constants as their small molecule analogues described in the literature, regardless of size or nature of the complementary unit or the polymer side chain.     

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.     

An All‐ROMP Route to Graft Copolymers

A new versatile synthesis strategy for macromonomers has been developed that uses the living ring‐opening metathesis polymerization (ROMP) with commercial Grubbs first generation ruthenium initiators. Homopolymers as well as diblock copolymers were end‐functionalized with norbornene derivatives to serve as macromonomers. The graft copolymerization of the macromonomers was also carried out employing ROMP. Well‐defined and highly functional graft copolymers are accessible by this new synthetic route.

     

Ring-Opening Metathesis Polymerization-Derived Materials for Separation Science,Heterogeneous Catalysis and Tissue Engineering

Summary: The chemistry of ring-opening metathesis polymerization- (ROMP) derived monolithic materials is summarized. Since ROMP triggered by well-defined transition metal alkylidenes is a living polymerization method, it allows for the controlled and highly reproducible synthesis of monolithic media in terms of total porosity, pore size distribution and specific surface area. In addition, the high functionality tolerance of ROMP allows for creating monolithic supports with an unprecedented diversity in terms of functional groups that may be introduced. Selected applications in the areas of separation science, heterogeneous catalysis and tissue engineering are presented and discussed within the context of ROMP.     

Synthesis of hybrid block copolymers via integrated ring-opening metathesis polymerization and polymerization of NCA

Linear hybrid block copolymers with well controlled molecular weights and narrow polydispersities were synthesized via ring-opening metathesis polymerization (ROMP) followed by ring-opening polymerization of amino acid N-carboxyanhydrides.     

Conducting Block Copolymer Nanowires Containing Regioregular Poly(3‐Hexylthiophene) and Polystyrene

Grignard Metathesis polymerization (GRIM) for the synthesis of regioregular poly(3‐alkylthiophenes) proceeds via a “living” chain growth mechanism. Due to the “living” nature of this polymerization regioregular poly(3‐alkylthiophenes) with predetermined molecular weight, narrow molecular weight distributions and desired chain end functionality are now readily available. Allyl terminated poly(3‐hexylthiophene) was successfully used as a precursor for the synthesis of di‐block copolymers containing polystyrene. The addition of “living” poly(styryl)lithium to the allyl terminated regioregular poly(3‐hexylthiophene) generated the di‐block copolymer. Poly(3‐hexylthiophene)‐b‐polystyrene was also synthesized by atom transfer radical polymerization. Integration of poly(3‐hexylthiophene) in di‐block copolymers with polystyrene leads to the formation of nanowire morphology and self‐ordered conducting nanostructured materials.