Heterotelechelic Polymers by Ring‐Opening Metathesis and Regioselective Chain Transfer

Heterotelechelic polymers were synthesized by a kinetic telechelic ring‐opening metathesis polymerization method relying on the regioselective cross‐metathesis of the propagating Grubbs’ first‐generation catalyst with cinnamyl alcohol derivatives. This procedure allowed the synthesis of hetero‐bis‐end‐functional polymers in a one‐pot setup. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer. The end functional groups can be changed using different aromatically substituted cinnamyl alcohol derivatives. Different monomers were investigated and the presence of the functional groups was shown by NMR spectroscopy and MALDI‐ToF mass spectrometry. Labeling experiments with dyes were conducted to demonstrate the orthogonal addressability of both chain ends of the heterotelechelic polymers obtained.     

A Road Less Traveled to Functional Polymers: Epoxide Termination in Living Carbanionic Polymer Synthesis

Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end‐functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl‐modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.g., miktoarm star polymers) is summarized and potential applications as well as future perspectives are discussed.

     

Oxo-Thiolation of Cationically Polymerizable Alkenes Using Flow Microreactors

The present study describes the cationic oxo-thiolation of polymerizable alkenes by using highly reactive cationic species generated by anodic oxidation. These highly reactive cations were able to activate alkenes before their polymerization. Fast mixing in flow microreactors effectively controlled chemoselectivity, enabling higher reaction temperatures.     

Membrane Microreactors for the On-Demand Generation,Separation, and Reaction of Gases

The use of gases as reagents in organic synthesis can be very challenging, particularly at a laboratory scale. This Concept takes into account recent studies to make the case that gases can indeed be efficiently and safely formed from relatively inexpensive commercially available reagents for use in a wide range of organic transformations. In particular, we argue that the exploitation of continuous flow membrane reactors enables the effective separation of the chemistry necessary for gas formation from the chemistry for gas consumption, with these two stages often containing incompatible chemistry. The approach outlined eliminates the need to store and transport excessive amounts of potentially toxic, reactive or explosive gases. The on-demand generation, separation and reaction of a number of gases, including carbon monoxide, diazomethane, trifluoromethyl diazomethane, hydrogen cyanide, ammonia and formaldehyde, is discussed.     

Controlled Synthesis,Characterization and Application of Novel Functional Fluorinated Polymer By Metal-Free Anionic Polymerization

A well-defined block polymer, di-n-butyl ester terminated poly(2,2,3,4,4,4-hexafluorobutyl methacrylate (BTHFMA), was synthesized by the metal-free anionic polymerization. The tetrabutylammonium salt of di-n-butyl malonate was served as functional carbanionic initiator for the anionic polymerization of 2,2,3,4,4,4-hexafluorobutyl methacrylate in a controlled ‘living’ manner for the first time at ambient temperature. The chemical structure of this product was characterized by FT-IR, ¹H-NMR, and ¹³C-NMR. Gel permeation chromatography (GPC) results showed that the molecular weight of BTHFMA ranged from 1025 to 6582 and the molecular weight distributions were fairly narrow (Mw/Mn = 1.12–1.16). By blending the poly(methyl methacrylate-co-butyl acrylate) [P(MMA-co-BA)] with BTHFMA, we minimized the amount of the BTHFMA used while achieving a hydrophobic surface. The surface properties and compositions of the [P(MMA-co-BA)]/BTHFMA blend films were studied by contact angle and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the 5 wt% blends of BTHFMA could obviously increase hydrophobic ability of the blend with a high water contact angle (98.2^o) and low surface energy (24.2mN/m). XPS results indicated the fluorine mass content of the surface of the 5 wt% blend was up to 26.6%, which suggested BTHFMA enriched on the surface of the blend.     

Successive Synthesis of Regular and Asymmetric Star-Branched Polymers by Iterative Methodology Based on Living Anionic Polymerization Using Functionalized 1,1-Diphenylethylene Derivatives

In order to achieve the successive synthesis of star-branched polymers, we have developed a new iterative methodology which involves only three sets of the reactions in each iterative process: (a) a coupling reaction of a living anionic polymer with 1,1-bis(3-chloromethylphenyl)ethylene to prepare a DPE-chain-functionalized polymer, (b) an addition reaction of sec-BuLi to the DPE-chain-functionalized polymer, followed by treatment with 1-(4-(4-bromobutyl)phenyl)-1-phenylethylene to prepare a new DPE-chain-functionalized polymer whose DPE is separated by four methylene units from the main chain, and (c) a coupling reaction of 1,1-bis(3-chloromethylphenyl)ethylene with the polymer anion derived from the newly prepared DPE-chain-functionalized polymer and sec-BuLi. With this methodology, a series of well-defined 4-arm, 8-arm, and 16-arm regular star-branched polystyrenes as well as 4-arm A₂B₂, 8-arm A₄B₄, and 16-arm A₈B₈ asymmetric star-branched polymers comprising polystyrene and poly(α-methylstyrene) segments have been successively synthesized.     

A Novel Approach to Functionalization of Aryl Azides through the Generation and Reaction of Organolithium Species Bearing Masked Azides in Flow Microreactors

A novel straightforward method for aryl azides having functional groups based on generation and reactions of aryllithiums bearing a triazene group from polybromoarenes using flow microreactor systems was achieved. The present approach will serve as a powerful method in organolithium chemistry and open a new possibility in the synthesis of polyfunctional organic azides.     

Using Triethylborane to Manipulate Reactivity Ratios in Epoxide-Anhydride Copolymerization: Application to the Synthesis of Polyethers with Degradable Ester Functions

The anionic ring-opening copolymerization (ROCOP) of epoxides, namely of ethylene oxide (EO), with anhydrides (AH) generally produces strictly alternating copolymers. With triethylborane (TEB)-assisted ROCOP of EO with AH, statistical copolymers of high molar mass including ether and ester units could be obtained. In the presence of TEB, the reactivity ratio of EO (r_EO), which is normally equal to 0 in its absence, could be progressively raised to values lower than 1 or higher than 1. Conditions were even found to obtain r_EO equal or close to 1. Samples of P(EO-co-ester) with minimal compositional drift could be synthesized; upon basic degradation of their ester linkages, these samples afforded poly(ethylene oxide) (PEO) diol samples of narrow molar mass distribution. In other cases where r_EO were lower or higher than 1, the PEO diol samples eventually isolated after degradation exhibited a broader distribution of molar masses because of the compositional drift of initial P(EO-co-ester) samples.     

Synthesis of asymmetric star-branched polymers consisting of three or four different segments in composition by means of living anionic polymerization with a new dual-functionalized 1,1-bis(3-chloromethylphenyl)ethylene

A series of four-armed A₂BC, AB₂C, and ABC₂ asymmetric star-branched polymers with a three-component system, the A, B, and C segments of which are polystyrene, polyisoprene, and poly(4-trimethylsilylstyrene), respectively, have been successfully synthesized with a methodology based on living anionic polymerization with dual-functionalized 1,1-bis(3-chloromethylphenyl)ethylene ( 1 ). These star-branched polymers have well-defined architectures and precisely controlled chain lengths, as confirmed by size exclusion chromatography, ¹H and ¹³C NMR, vapor pressure osmometry, and static light scattering analyses. A simple and convenient one-pot process for star-branched polymer synthesis is an additional advantage of this methodology. One problem to be solved is that the synthetic route is limited in some cases by the inherently low reactivity of polyisoprenyllithium toward the 1,1-diphenylethylene functionality of in-chain-functionalized polymers. A new four-armed ABCD star-branched polymer, the A, B, C, and D segments of which are polyisoprene, poly(4-methoxystyrene), polystyrene, and poly(4-trimethylsilylstyrene), could also be synthesized through the extension of the methodology using 1 to a four-component system. The successful results strongly demonstrate the synthetic versatility and potential of this methodology for a wide variety of well-defined asymmetric star-branched polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4535–4547, 2004     

氧和正丁基锂引发的阴离子活性聚合物的反应

对氧和正丁基锂引发的阴离子活性聚合物反应的研究发展,反应产物中有基础分子量两倍的大分子物,而且大分子产物的含量与正丁基锂用量成正向关系,提出了可能的反应机理。     

Synthesis and cleavage of core‐labile poly(alkyl methacrylate) star polymers

Core‐cleavable star polymers were synthesized by the coupling of living anionic poly(alkyl methacrylate) arms with either dicumyl alcohol dimethacrylate (DCDMA) or 2,5‐dimethyl‐2,5‐hexanediol dimethacrylate (DHDMA). This synthetic methodology led to the formation of star polymers that exhibited high molecular weights and relatively narrow molecular weight distributions. The labile tertiary alkyl esters in the DCDMA and DHDMA star polymer cores were readily hydrolyzed under acidic conditions. High‐molecular‐weight star polymer cleavage led to well‐defined arm polymers with lower molecular weights. Hydrolysis was confirmed via ¹H NMR spectroscopy and gel permeation chromatography. Thermogravimetric analysis (TGA) of the star polymers demonstrated that the DCDMA and DHDMA star polymer cores also thermally degraded in the absence of acid catalysts at 185 and 220 °C, respectively, and the core‐cleavage temperatures were independent of the arm polymer composition. The difference in the core‐degradation temperatures was attributed to the increased reactivity of the DCDMA‐derived cores. TGA/mass spectrometry detected the evolution of the diene byproduct of the core degradation and confirmed the proposed degradation mechanism. The DCDMA monomer exhibited a higher degradation rate than DHDMA under identical reaction conditions because of the additional resonance stabilization of the liberated byproduct, which made it a more responsive cleavable coupling monomer than DHDMA. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3083–3093, 2003     

Synthesis of arborescent styrene homopolymers and copolymers from epoxidized substrates

The synthesis of arborescent styrenic homopolymers and copolymers was achieved by anionic polymerization and grafting. Styrene and p‐(3‐butenyl)styrene were first copolymerized using sec‐butyllithium in toluene, to generate a linear copolymer with a weight‐average molecular weight M_w = 4000 and M_w/M_n = 1.05. The pendant double bonds of the copolymer were then epoxidized with m‐chloroperbenzoic acid. A comb‐branched (or arborescent generation G0) copolymer was obtained by coupling the epoxidized substrate with living styrene‐p‐(3‐butenyl)styrene copolymer chains with M_w ≈ 5000 in a toluene/tetrahydrofuran mixture. Further cycles of epoxidation and coupling reactions while maintaining M_w ≈ 5000 for the side chains yielded arborescent copolymers of generations G1–G3. A series of arborescent styrene homopolymers was also obtained by grafting M_w ≈ 5000 polystyrene side chains onto the linear and G0–G2 copolymer substrates. Size exclusion chromatography measurements showed that the graft polymers have low polydispersity indices (M_w/M_n = 1.02–1.15) and molecular weights increasing geometrically over successive generations. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

生物催化在高分子合成中的应用

生物催化剂已被越来越多地用于高分子学中,产生了许多新的反应、工艺和商业用途.酶和全细胞工艺都引起了众多关注,生物催化剂的立体选择性是它们的主要优势之一,新的或改良的方法层出不穷.生物催化的进程主要集中在几个方面上:聚合反应、聚合物修饰反应、聚合物降解反应以及单体和低聚物的合成.在这篇文章中,我们总结了生物催化在高分子合成中的最新应用.     

功能彩色高分子合成技术进展

本文通过实例对功能彩色高分子的合成方法以及每种合成方法的原理、特点、发展历史和可实行性作了较详细的综述。     

含噻二唑环的阴离子聚合引发剂在合成双官能团聚氧化乙烯中的应用

以氧化乙烯开环聚合为探针反应,考察了含噻二唑环的新型阴离子聚合引发剂(TDZ-K)的引发活性。反应在非均相中进行,分别用甲醇和甲基丙烯酰氯封端,得含双官能团的氧化乙烯聚合产物,其结构经IR,1H NMR,UV,VPO和GPC表征。加入乙酰丙酮,18-冠-6及PEO作助剂,有助于提高TDZ-K的引发活性。     

Generation and Reaction of Carbamoyl Anions in Flow: Applications in the Three‐Component Synthesis of Functionalized α‐Ketoamides

Using a flow microreactor system, carbamoyllithium compounds were successfully generated and used for reactions with electrophiles to give various amides, including α‐ketoamides. The present method could be applied to the three‐component synthesis of functionalized α‐ketoamides using a carbamoyllithium compound, methyl chloroformate, and a functionalized organolithium reagent.     

Synthesis and polymerizability of CN monomers

The synthesis and polymerizability of imine C?N monomers is surveyed. The investigated imines were either far more reactive than similarly substituted C?C or C?O monomers, or too stable to polymerize. Imines with electron‐attracting substituents on N favor polymerization by anionic mechanism, but led only to low molecular weight polymers. Imines with a donor substituent on N, such as N‐arylmethyleneimines, polymerized by cationic or anionic mechanism. 1‐ and 2‐Aza‐1,3‐butadienes were also rather unstable and polymerized to oligomers. The symmetrically substituted 2,3‐diaza‐1,3‐butadienes could be purified and polymerized successfully using anionic initiators, resulting in both 1,4‐ and 1,2‐structures in the polymer backbone, depending on the substituents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Functional polymers by living anionic polymerization

The application of living anionic polymerization techniques for the functionalization of polymers and block copolymers is reviewed. The attachment of functional groups to polymeric chains of predetermined lengths and narrow molecular weight distributions is described. Carboxyls, hydroxyls, amines, halogens, double bonds, and many other functional groups can be placed at one or two ends in the center or evenly spaced along polymeric chains. Subsequent transformations of the functional groups further contribute to the versatility of such treatments. General methods based on the use, as terminators, of substituted haloalkanes, as well as the addition of living polymers or their initiators to diphenylethylenes, substituted with appropriate functional groups or molecules, are discussed. Another approach, based on the living polymerization of monomers with protected functional groups, is also discussed. It has been used for the preparation of polymers and copolymers with evenly spaced functional groups. The combination of living anionic polymerization techniques with controlled radical and cationic polymerizations is also described. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2116–2133, 2002