Synthese,caracterisation et reactivite de polymeres porteurs de fonctions chloroformiates

Chemical modification of low molecular weight polymers having functional groups along the chain, can lead to new macromolecular compounds which direct synthesis cannot be studied by classical polymerization ways. Synthesis of polymers possessing chloroformate groups has been obtained by a double modification reaction of polydienes backbones. Reactivity of new functions has been used for fixation of various organic compounds on the macromolecular chain. On the resulting polymers, the organic products are linked by carbonate, urethane or thiolcarbonate bounds varying with the nature of starting molecules: alcohol, amine or thiol which has reacted on the chloroformate groups.     

Synthese de polyalcadienes monochloroformiates. Modification chimique par des alcool,amine et thiol

Some monofunctional polydienes with various extremities are obtained by chemical modification of ω-monochloroformate polymers. The chosen products are an alcohol, an amine and a thiol. The organic compounds are attached to the end of a macromolecular chain by a carbonate, a urethane or a thiolcarbonate link. The resulting polymers are characterized by i.r. and NMR analysis. These modification reactions of end groups may be used as model reactions for polymers having specific properties.     

Synthèse de polyalcadiènes à extrémités fonctionnelles chlorure d'acide—étude de la réactivité de ces fonctions terminales

Two types of chemical modification of polymers are considered: attachment of functional groups as end-groups for diene polymers and also reaction of these end-groups with diamines. The deactivation, by means of the di-acid chloride of ortho-phthalic acid, of living polybutadiene or living polyisoprene leads to polydienes with molecules having one or two acid chloride end-groups. Chemical modification of these end-groups by an aliphatic diamine leads either to a new polymer having amine end-groups or to a polycondensation causing a substantial increase in molecular weight, depending upon the conditions.     

Mechanochemical Synthesis of Stimuli Responsive Microgels

Mechanochemical approaches are widely used for the efficient, solvent-free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free-radical polymerization allows solvent- and initiator-free syntheses of structurally and morphologically well-defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end-groups.     

End-functionalized ROMP polymers for Biomedical Applications

We present two novel allyl-based terminating agents that can be used to end-functionalize living polymer chains obtained by ring-opening metathesis polymerization (ROMP) using Grubbs' third generation catalyst. Both terminating agents can be easily synthesized and yield ROMP polymers with stable, storable activated ester groups at the chain-end. These end-functionalized ROMP polymers are attractive building blocks for advanced polymeric materials, especially in the biomedical field. Dye-labeling and surface-coupling of antimicrobially active polymers using these end-groups were demonstrated.     

First example of N-heterocyclic carbenes as catalysts for living polymerization: organocatalytic ring-opening polymerization of cyclic esters

A novel metal-free, organocatalytic approach to living polymerization is presented. N-heterocyclic carbenes were employed as nucleophilic catalysts for the ring-opening polymerization (ROP) of cyclic ester monomers. The catalysts is used in combination with an initiator, such as an alcohol, which generates an alpha-end group bearing the ester from the initiating alcohol upon ring-opening and a hydroxyl functional omega-chain end that propagates the chain. This class of catalyst proved to be more reactive than tertiary amine and phosphine nucleophiles, producing narrowly dispersed polymers of predictable molecular weights at room temperature in 1-2 h. Catalysis with respect to both initiating alcohol and monomer was observed. Control of the alpha and omega end-groups was demonstrated with a pyrene-labeled initiator, allowing the preparation of well-defined macromolecular architectures. Analogous to the ROP of cyclic esters using biocatalysts, the polymeriztion pathway using the N-heterocyclic carbenes is believed to ensue through a monomer-activated mechanism.     

Living Polymers in Ionic and Radical Polymerizations: Recent Developments

The discovery of living polymers, that is, assemblies of polymer molecules formed by anionic polymerization which may grow without chain-breaking reaction and may react subsequently with other monomers and various reagents through their end-groups, has led to great progress in the knowledge of the mechanism of anionic polymerization and to the synthesis of a large variety of well-defined block copolymers, graft co-polymers, and polymers with functionalized end-groups. Since only a limited number of the current monomers are polymerizable by an anionic mechanism, many attempts have been made to obtain similar results by polymerizing other monomers by cationic, radical, and Ziegler polymerization. Systems making it possible to work at temperatures higher than those used for many anionic and most cationic polymerizations would be particularly interesting.     

Synthesis of Aminotelechelic Polymers with the Redox System TiCl3/NH2OH in the Hydrochloric Aqueous Phase. I. Polymerization Possibilities and Limits

Among recent progress in the field of macromolecular chemistry, of considerable interest has been the synthesis of α, ω-ordifunctional polymers. These polymers, called “telechelic” polymers, are interesting because many reactions are possible on their functional end-groups:     

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.     

Solvent-Free Chemical Recycling of Polymethacrylates made by ATRP and RAFT polymerization: High-Yielding Depolymerization at Low Temperatures

Although controlled radical polymerization is an excellent tool to make precision polymeric materials, reversal of the process to retrieve the starting monomer is far less explored despite the significance of chemical recycling. Here, we investigate the bulk depolymerization of RAFT and ATRP-synthesized polymers under identical conditions. RAFT-synthesized polymers undergo a relatively low-temperature solvent-free depolymerization back to monomer thanks to the partial in situ transformation of the RAFT end-group to macromonomer. Instead, ATRP-synthesized polymers can only depolymerize at significantly higher temperatures (>350 °C) through random backbone scission. To aid a more complete depolymerization at even lower temperatures, we performed a facile and quantitative end-group modification strategy in which both ATRP and RAFT end-groups were successfully converted to macromonomers. The macromonomers triggered a lower temperature bulk depolymerization with an onset at 150 °C yielding up to 90 % of monomer regeneration. The versatility of the methodology was demonstrated by a scalable depolymerization (≈10 g of starting polymer) retrieving 84 % of the starting monomer intact which could be subsequently used for further polymerization. This work presents a new low-energy approach for depolymerizing controlled radical polymers and creates many future opportunities as high-yielding, solvent-free and scalable depolymerization methods are sought.     

Postpolymerization modification of poly(pentafluorophenyl methacrylate): Synthesis of a diverse water‐soluble polymer library

This article explores the feasibility of poly(pentafluorophenyl methacrylate) (PPFMA) prepared by reversible addition fragmentation chain transfer (RAFT) polymerization as a platform for the preparation of diverse libraries of functional polymers via postpolymerization modification with primary amines. Experiments with a broad range of functional amines and PPFMA precursors of different molecular weights indicated that the postpolymerization modification reaction proceeds with good to excellent conversion for a diverse variety of functional amines and is essentially independent of the PPFMA precursor molecular weight. The RAFT end group, which was well preserved throughout the polymerization, is cleaved during postpolymerization modification to generate a thiol end group that provides possibilities for further orthogonal chain‐end modification reactions. The degree of postpolymerization modification can be controlled by varying the relative amount of primary amine that is used and random polymethacrylamide copolymers can be prepared via a one‐pot/two‐step sequential addition procedure. Cytotoxicity experiments revealed that the postpolymerization modification strategy does not lead to any additional toxicity compared with the corresponding polymer obtained via direct polymerization, which makes this approach also of interest for the synthesis of biologically active polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4332–4345, 2009     

Novel polymeric platform produced by photodegradation-induced rearrangement for a multifunctional negative photoresist

Herein, a series of polymers containing the photosensitive 2-dinitro-benzenemethanol carbonate (DNBC) was developed by click polymerization. Due to the unique photochemical cleavage recombination behavior of DNBC, these polymers were used as negative photoresists to create micropatterns. Furthermore, the photochemical behaviors of DNBC were studied by nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC). According the results, we speculated that the photochemical reaction of DNBC involved an initial chemical bond-breaking process and a subsequent recombination process. Importantly, by extending the aldehyde to a branched-chain structure, reactive patterns were developed by film preparation. Clickable amine functional molecules could be grafted upon the substrates by surface modification. Surface modification of reactive patterns with fluorescent amines gave a multifunctional pattern with tunable properties confirmed by scanning electron microscopy (SEM) and confocal fluorescence microscopy.     

Click Chemistry in Functional Aliphatic Polycarbonates

Click chemistry, one of the most important methods in conjugation, plays an extremely significant role in the synthesis of functional aliphatic polycarbonates, which are a group of biodegradable polymers containing carbonate bonds in their main chains. To date, more than 75 articles have been reported on the topic of click chemistry in functional aliphatic polycarbonates. However, these efforts have not yet been highlighted. Six categories of click reactions (alkyne‐azide reaction, thiol‐ene reaction, Michael addition, epoxy‐amine/thiol reaction, Diels‐Alder reaction, and imine formation) that have been afforded for further post‐polymerization modification of polycarbonates are reviewed. Through this review, a comprehensive understanding of functional aliphatic polycarbonates aims to afford insight on the design of polycarbonates for further post‐polymerization modification via click chemistry and the expectation of the practical application.     

Separation and characterization of functional poly(n-butyl acrylate) by critical liquid chromatography

The separation of functional poly(n-butyl acrylate) (PnBA) polymers based on the number of end-groups under critical liquid chromatography (LC) conditions has been studied using a bare-silica column. The (near-) critical solvent compositions for non-, mono-, and difunctional (telechelic) carboxyl-PnBAs were determined in normal-phase LC, using mixtures of acetonitrile, acetic (or formic) acid, and dichloromethane of varying composition. Some formic or acetic acid had to be added to the mobile phase to elute PnBA polymers with carboxyl end-groups. The critical solvent compositions obtained were not exactly the same for non-, mono-, and difunctional PnBA polymers. These were unusual experimental observation, but they were in agreement with theoretic predictions. Nevertheless, low-molecular-mass PnBA samples were successfully separated according to the carboxyl functionality at (near-) critical conditions. With the aid of mass spectrometry (MS), the (near-) critical separation of low-molecular-mass PnBA polymers was confirmed to be mainly based on the carboxyl functionality. Calibration curves for evaporative light-scattering detection (ELSD) were used for quantitative analysis of carboxyl-functional PnBA polymers. The results proved that nearly ideal functionalities (average number of carboxyl end-groups per molecule up to 1.99) were achieved for telechelic PnBAs prepared by one-step reversible addition-fragmentation chain-transfer (RAFT) polymerization of PnBA.     

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.     

基于巯基点击反应与RAFT聚合的功能性聚合物合成

可逆加成-裂解链转移聚合(RAFT)由于单体适用面广、聚合条件温和、不受聚合方法的限制等特性, 已经成为活性合成聚合物的有效手段之一。点击化学(click chemistry)由于具有良好的选择性、模块性以及官能团耐受性等特点迅速成为许多研究领域,如药物、聚合物、功能材料等合成的有力工具,同时涌现出了多种基于巯基的点击反应。本文综述了近年来基于巯基的点击反应, 如巯基-烯、巯基-炔、巯基-异氰酸酯、巯基-环氧化物以及巯基-卤代烃等新型点击反应与RAFT聚合相结合在功能性聚合物的制备和修饰中的应用, 相信这两种手段的结合将在其中发挥积极的作用。     

Polymerisation de monomeres a structures biologiques

Fixation of biological compounds (cholesterol and testosterone) on (2-hydroxyethyl)methacrylate has been realized by a carbonate linkage. These new monomers have been characterized by N.M.R. and i.r.; they have been polymerized by a radical process. Resulting homopolymers have been analysed and compared with polymers bearing similar active compounds, previously synthesized by chemical modification of poly (2-hydroxyethyl)methacrylate.     

Spray-Coating of Catalytically Active MOF–Polythiourea through Postsynthetic Polymerization

A UiO-66-NCS MOF was formed by postsynthetic modification of UiO-66-NH₂. The UiO-66-NCS MOFs displays a circa 20-fold increase in activity against the chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate (DMNP) compared to UiO-66-NH₂, making it the most active MOF materials using a validated high-throughput screening. The −NCS functional groups provide reactive handles for postsynthetic polymerization of the MOFs into functional materials. These MOFs can be tethered to amine-terminated polypropylene polymers (Jeffamines) through a facile room-temperature synthesis with no byproducts. The MOFs are then crosslinked into a MOF–polythiourea (MOF–PTU) composite material, maintaining the catalytic properties of the MOF and the flexibility of the polymer. This MOF–PTU hybrid material was spray-coated onto Nyco textile fibers, displaying excellent adhesion to the fiber surface. The spray-coated fibers were screened for the degradation of DMNP and showed durable catalytic reactivity.     

Microwave-assisted one-pot three-component polymerization of alkynes,aldehydes and amines toward amino-functionalized optoelectronic polymers

We present a microwave-assisted one-pot polymerization with three-components of alkynes, aldehydes and amines for the synthesis of new amino-functionalized optoelectronic polymers. The polymerization of diynes(1a-1c), dialdehydes(2a and 2b) and dibenzylamine catalyzed by InCl_3 was carried out smoothly within 1h under microwave radiation, yielding four soluble polymers with high molecular weights. The resulting polymers P1 and P2 could be easily dissolved in alcohol and thus utilized as the cathode interlayer for polymer solar cells(PSCs). Compared with the control device, the PSCs with P1 and P2 as the cathode interlayer and PTB7-Th:PC_(71)BM as the photoactive layer exhibited significantly higher power conversion efficiencies(PCEs) of 9.49% and 9.16%, respectively. These results suggest that this polycoupling reaction is an efficient approach to construct three-component polymers for the practical applications.     

Synthesis and characterization of α,ω-dichloro-polymethylphenylsilane

The synthesis of a functional polysilane, α,ω-dichloro-polymethylphenylsilane (α,ω-dichloro-PMPS), based on the Wurtz-type reductive coupling, has been considered. A study of some reaction parameters shows that both yield and molecular weight distribution of α,ω-dichloro-PMPS can be greatly influenced by the work-up conditions, reaction time, monomer concentration and temperature during the initiation of the polymerization. By varying the synthesis conditions, different ratios of high and low molecular weight fractions were obtained. Samples of different molecular weight were isolated by fractional precipitation of the crude polymers. The chlorine-end functionalization was confirmed by ²⁹Si NMR spectroscopy and the concentration of end-groups was quantitatively determined by elemental analysis of chlorine.