Fluorinated Amphiphilic Block Copolymers: Combining Anionic Polymerization and Selective Polymer Modification

We report the preparation of novel fluorinated block copolymers using a two-step modification sequence. We first prepared model polyisoprene-poly-tert-butylmethacrylate block copolymers by anionic polymerization. Exposing these materials to difluorocarbene (generated by the thermolysis of hexafluoropropylene oxide) resulted in modification of the polyisoprene block to the corresponding difluorocyclopropane repeating unit without compromising the integrity of the poly-tert-butylmethacrylate block. Hydrolysis of the difluorocarbene-modified materials gave the corresponding difluorocarbene-modified polyisoprene-polymethacrylic acid diblock copolymers. These amphiphilic materials are expected to exhibit interesting self-assembly behavior in aqueous solution.     

Living Anionic Polymerization of tert‐Butyl Acrylate in a Flow Microreactor System and Its Applications to the Synthesis of Block Copolymers

Living anionic polymerization of tert‐butyl acrylate initiated by 1,1‐diphenylhexyllithium is conducted in a flow microreactor system in the presence of lithium chloride. A high degree of control over the molecular weight distribution is achieved under easily accessible conditions, for example at ?20 °C. The subsequent reaction of a reactive polymer chain end with an alkyl methacrylate in an integrated flow micoreactor system leads to the formation of a block copolymer with a narrow molecular weight distribution.

     

Anionic polymerization of acrylates. II. Polymerization of 2-ethylhexyl acrylate initiated by butyllithium/lithium-tert-butoxide system in tetrahydrofuran and its mixtures with toluene

The anionic polymerization of 2-ethylhexyl acrylate (EtHA) initiated with the complex butyllithium/lithium-tert-butoxide (BuLi/t-BuOLi) was investigated at ?60°C in a medium of various solvating power, i.e., in mixtures of toluene and tetrahydrofuran and in neat tetrahydrofuran. With increasing amount of THF in the mixture the attainable limiting conversion of polymerization decreases; the monomer can be polymerized quantitatively only in a toluene/THF mixture (9/1). Molecular weights of the polymers thus obtained, their distribution, and initiator efficiency are not appreciably affected by the polymerization medium. The molecular weight distribution of the products is medium-broad (M_w/M_n = 2–2.4), with a hint of bimodality. The ¹H-¹³C-NMR, and IR spectra suggest that during the polymerization there is neither any perceptible reesterification of the polymer with the alkoxide nor transmetalation of the monomer with the initiator. In a suitable medium, autotermination of propagation proceeds to a limited extent only, predominantly via intramolecular cyclization of propagating chains; in a medium with a higher content of polar THF, it prevails and terminates propagation before the polymerization of the monomer has been completed. © 1992 John Wiley & Sons, Inc.     

Modular Synthesis of Functional Block Copolymers

Summary: The free‐radical addition of ω‐functional mercaptans to the vinyl double bonds of 1,2‐polybutadiene‐block‐poly(ethylene oxide) copolymers was used for modular synthesis of well‐defined functional block copolymers. The modification reaction proceeds smoothly and yields quantitatively functionalized block copolymers (¹H NMR and FT‐IR spectroscopy) without disturbing the molecular‐weight distribution of the parent copolymer (PDI < 1.09, size exclusion chromatography).

The modular synthetic pathway towards the functional block copolymers reported here.     

Transparent inorganic/organic copolymers by the Sol-Gel process: Copolymers of tetraethyl orthosilicate (TEOS), vinyl triethoxysilane (VTES) and (meth)acrylate monomers

Vinyl triethoxysilane (VTES) and (meth)acrylate monomers were mixed to create covalently bonded inorganic/organic copolymers, with and without tetraethyl orthosilicate (TEOS). Vinyl groups underwent free radical polymerization along with copolymerization with (meth)acryl groups of the monomer. For the two-monomer system, (meth)acrylate monomer and VTES, polymerization resulted in mechanically strong copolymers with flexure strengths greater than 40 MPa. Three-component materials obtained by polymerization of (meth)acrylate monomer, VTES and TEOS were homogeneous, highly transparent, with flexure strengths similar to those for silica xerogels, about 20 Mpa.     

Synthesis of Block Copolymers with a Pentasilane Core

We report a new method for the synthesis of block copolymers with a pentasilane core by the polymerization of alkyl methacrylate monomers using the pentasilyl dianion as an initiator. The polymerization proceeded with living features and yielded the corresponding block copolymers with controlled molecular weights. The amphiphilic block copolymer was obtained by the polymer reaction, and it formed sphere‐like aggregates in MeOH/H₂O solution.

     

Anionic polymerization of acrylates. III. Polymerization of 2-ethylhexyl acrylate initiated by lithium-tert-butoxide

The polymerization of 2-ethylhexyl acrylate (EtHA) initiated with lithium-tert-butoxide (t-BuOLi) in tetrahydrofuran (THF) and in the temperature range between ?60 and 20°C was investigated. The reaction rate is distinctly temperature-dependent and at ?60°C is already very low, similarly to the polymerization of methacrylates. Molecular weights of the polymers thus formed, particularly at higher temperatures, are inversely proportional to conversion of the monomer due to the slow initiation reaction. This is documented by the low consumption of alkoxide even at long reaction times, which also depends on the reaction temperature. At higher temperatures the polymerization stops spontaneously, due to the greater extent of autotermination reactions. The weak initiating efficiency of the alkoxide decreases still more with decreasing concentration of the monomer during the polymerization, as confirmed by the concentration dependence of the reaction rate in toluene at ?20°C. The results suggest a negligible initiating effect of alkoxides in complex bases, particularly at lower polymerization temperatures. © 1992 John Wiley & Sons, Inc.     

Synthesis of Styrenic‐Terminated Methacrylate Macromonomers by Nitroanion‐Initiated Living Anionic Polymerization

N‐Isopropyl‐4‐vinylbenzylamine (PVBA) was synthesized and used as an initiator for the polymerization of methacrylates to synthesize macromonomers with terminal styrenic moieties. LiPVBA initiated a living polymerization and block copolymerization of methyl methacrylate, 2‐(N,N‐dimethylamino)ethyl methacrylate and tert‐butyl methacrylate and produced polymers having well‐controlled molecular weights and very low polydispersities (M̄_w/M̄_n < 1.1) in quantitative yield. ¹H NMR analysis revealed that the polymers contained terminal 4‐vinylbenzyl groups. The macromonomers were reactive in the copolymerization with styrene.     

Defined Poly[styrene‐block‐(ferrocenylmethyl methacrylate)] Diblock Copolymers via Living Anionic Polymerization

Ferrocenylmethyl methacrylate (FMMA) is one of the very few metallocene‐based monomers that are promising candidates for truly living anionic polymerization. Nevertheless, FMMA homopolymers with a narrow polydispersity, or block copolymerization studies that result in satisfying blocking efficiencies, are unknown so far. Here we describe a procedure that leads to highly regular FMMA‐based polymers for the first time, characterized by polydispersity indices (PDI) of less that 1.05 and very high blocking efficiencies (>95%) in sequential copolymerization with styrene. Some of the obtained poly[styrene‐block‐(ferrocenylmethyl methacrylate)]s show unusual microphase morphologies, presumably the consequence of high T_gs causing ‘frustrated’ non‐equilibrium states.

     

Block Copolymers in Emulsion and Dispersion Polymerization

Summary: This article deals with recent progress including the authors' work concerning the application of block copolymers as polymeric surfactants in heterophase polymerizations. The synthesis methods for preparing block copolymers by emulsion and dispersion techniques are outlined, with emphasis on recently developed controlled free radical polymerizations in aqueous media. Specific characteristics of amphiphilic block copolymers are described, for example, micellization and emulsifying effects. A general overview of emulsion and dispersion polymerization in an aqueous and organic medium with ionic and nonionic block copolymers is presented for the preparation of electrosteric and sterically stabilized latex particles. Typical examples of microemulsion, miniemulsion, oil‐in‐oil emulsion, and micellar polymerizations are provided. Current and potential developments of so‐called “hairy latexes”, inverse‐, multiple‐, and solid emulsions, as well as of nonaqueous polymeric dispersions are also discussed.

PS foam obtained by free radical polymerization of water‐in‐styrene, stabilized with a PS–PEO diblock copolymer.     

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.     

Organosilicon‐Assisted Transformation of Living Anionic into Living Cationic Polymerization

A novel method is described for transforming an anionic polymerization process into a cationic polymerization process assisted by organosilyl groups. The reaction of the p‐tolyldimethylsilyl end group of polystyrene and trifluoromethanesulfonic acid produced a silyl triflate end group that served as a macroinitiator for the living cationic polymerization of isobutyl vinyl ether. The Si O linkage in the block copolymers underwent specific cleavage by reaction with tetrabutylammonium fluoride.

     

Design and Synthesis of Functionalized Styrene-Butadiene Copolymers by Means of Living Anionic Polymerization

Styrene-butadiene copolymers (SBR) end-functionalized with dimethylamino groups at the initiating and terminating chain-ends were successfully synthesized by a one-step methodology based on living anionic polymerization using 1-(4-dimethylaminophenyl)-1-phenylethylene. The expected structures of the resulting copolymers were confirmed by ¹H-NMR, SEC, and SLS analyses, titration, and model reactions. Furthermore, the possible synthesis of tri-functionalized styrene-butadiene copolymer with dimethylamino groups in a chain by extending the methodology is described.     

Polymerization shrinkage of (meth)acrylate determined by reflective laser beam scanning

The real‐time study of the shrinkage during UV‐curing of (meth)acrylate monomers is limited due to the very fast curing rate, their thin sample geometry (<100 μm), and low viscosity. We report a reflective laser scanning system for direct measurement of UV‐curing shrinkage. A low‐power laser beam at a wavelength of 650 nm, different from the polymerization wavelength (395 nm), was used. This noncontact method of measurement makes it possible to analyze the thin liquid monomer with a very low shrinkage (measuring accuracy 0.02 μm), and very fast curing rate (fast sampling speed of 50 KHz). Eight different kinds of UV monomers were tested using 2–5 mg specimens, and the shrinkage process was examined. The results proved that this new method was accurate and precise, and could be applied to different kinds of (meth)acrylates. Furthermore, the shrinkage capability of acrylic double bonds was determined as 23.98 mL/mol using this novel method. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Synthesis of Rod-Coil Block Copolymers using Two Controlled Polymerization Techniques

A double-headed initiator was synthesized yielding two functional groups for the initiation of the nickel mediated ring-opening polymerization of γ-benzyl-L -glutamate-N-carboxyanhydride and controlled radical polymerization of vinyl monomers via ATRP or NMP. Well-defined block copolymers combining polypeptides and synthetic polymers were obtained.     

Design and Implementation of a Reactor Setup for Combinatorial Anionic Synthesis of Block Copolymer Series with Well‐Defined Compositions

We present a combinatorial approach to the synthesis of block copolymer series by anionic polymerization, utilizing a specially designed reactor setup. The setup features one main reactor and three secondary reactors to carry out anionic polymerizations on laboratory‐scale quantities at low temperatures. The implementation was demonstrated with three series of AB‐ and ABC‐block copolymers with identical A‐ and AB‐blocks, respectively. The B‐block in AB‐diblock copolymers and the C‐block in ABC‐triblock copolymers can be varied with respect to block length or chemical constitution. Well‐defined series of block copolymers are useful for advanced optimization of functional block copolymers in nanotechnology applications.

     

新型手性聚（甲基）丙烯酸酯类聚合物的合成与表征

手性聚丙烯酸酯;新型手性聚（甲基）丙烯酸酯类聚合物的合成与表征     

Synthesis of Dendritic-Linear Block Copolymers by Atom Transfer Radical Polymerization

Polymers and copolymers with complex, yet well-defined architectures are drawing significant attentions in the search for materials with excellent properties. Of these macromolecular structures, dendritic-linear block copolymers consisting of covalently bound linear and dendritic segments have shown interesting solution, solid-state, and interfacial properties. As a novel polymerization approach, atom transfer radical polymerization (ATRP) has been attracting increasing interest recently, sin…     

Synthesis of Block Copolymers by Combination of Atom Transfer Radical Polymerization and Visible Light‐Induced Free Radical Promoted Cationic Polymerization

A new synthetic approach for the preparation of block copolymers by mechanistic transformation from atom transfer radical polymerization (ATRP) to visible light‐induced free radical promoted cationic polymerization is described. A series of halide end‐functionalized polystyrenes with different molecular weights synthesized by ATRP were utilized as macro‐coinitiators in dimanganese decacarbonyl [Mn₂(CO)₁₀] mediated free radical promoted cationic photopolymerization of cyclohexene oxide or isobutyl vinyl ether. Precursor polymers and corresponding block copolymers were characterized by spectral, chromatographic, and thermal analyses.     

基团转移聚合合成PMMA—PEA—PAN嵌段共聚物的研究

丙烯酸系橡胶的综合性能仅次于氟橡胶,成本较低,若制成可重复加工的热塑性弹性体则更有价值。前人曾用阴离子聚合法进行过合成试验,均因副反应太多等原因而未能获得满意的结果。基团转移聚合(GTP)是八十年代建立的合成高分子新方法,在室温下进行“活性聚合”是其重要特征。本文利用GTP方法、单官能团引发剂,仅通过适当控制加料次序和时机就合成了软段居中的三元共聚物,为合成全丙烯酸系热塑弹性体奠定了基础。