Low‐Temperature Polymerization of Olefins in the Presence of Titanium Monoamidinate/MAO Catalyst

This paper reports the predominantly syndiotactic‐specific polymerization of propylene in the presence of titanium monoamidinate/methylaluminoxane (MAO) catalysts. The same catalysts, depending on the reaction conditions, also promote either predominantly 1,4‐cis or 1,4‐trans polymerization of 1,3‐butadiene and polymerization of styrene either to highly syndiotactic or to stereoirregular polymer. Some preliminary information about the features of propylene polyinsertion is also reported.

Expansion of the 20–24 ppm region of the ¹³C NMR spectrum of sample 2. The starred resonance at 21.75 ppm and the shoulders are not assigned.     

Quantitative Analysis of Dielectric Constants from EFM Images of Multicomponent Polymer Blends

Summary: A simple quantitative model for the analysis of EFM images of three‐ or more‐component polymer blends is applied to determine the dielectric constants of the blend constituents. The value of the dielectric constant of PIPA calculated from the EFM images of POMA‐PIPA‐APP blend is determined in good agreement with the literature value.

     

Preparation and Characterization of Acetoacetoxyethyl Methacrylate‐Based Gels

Novel polymeric gels have been prepared by radical copolymerization of acetoacetoxyethyl methacrylate (AAEM) and hydroxyethyl methacrylate (HEMA) in water‐ethanol medium. The influence of the HEMA:AAEM ratio and crosslinker concentration on properties of gels was studied. Independently on gel composition the maximum swelling was detected in chloroform. It was found that PAAEM gels possess phase transition temperature or upper critical solution temperature (UCST) in alcohol‐water solutions. UCST decreases in linear order from 75 to 10 °C when HEMA content in gel structure increases. The minimal UCST of AAEM/HEMA gels in binary alcohol‐water mixtures is shifted toward lower temperatures and lower alcohol concentrations when the alkyl chain of alcohol increases.

AAEM/HEMA gels prepared at different BIS concentrations (1:1 mol‐%, 2:2.5 mol‐%, 3:5 mol‐%).     

Synthesis of Di‐block Copolymers Containing Regioregular Poly(3‐hexylthiophene) and Poly(tetrahydrofuran) by a Combination of Grignard Metathesis and Cationic Polymerizations

Poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was synthesized by cationic ring‐opening polymerization of tetrahydrofuran (THF) using a poly(3‐hexylthiophene) macroinitiator. Poly(3‐hexylthiophene) macroinitiator used for the ring‐opening polymerization of THF was synthesized by reacting the hydroxypropyl end‐group with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. ¹H NMR spectroscopy and SEC data confirmed the formation of the di‐block copolymers. Field‐effect mobility of poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was measured in a thin‐film transistor configuration and was found to be 0.009 cm² · V^?1 · s^?1.

     

Photoinduced Polymerization of Thiophene Using Iodonium Salt

Summary: Thiophene was polymerized by means of UV irradiation using diphenyliodonium hexafluorophosphate as a photoinitiator. An initiation mechanism involving electron transfer from photochemically generated onium radical cations to thiophene was proposed. N‐Ethoxy‐2‐methylpyridinium hexafluorophosphate and triphenylsulfonium hexafluorophosphate were also found to be effective in facilitating the polymerization of thiophene. Polymerization is accompanied with the film formation on the surface of the reaction tube. The photochemically obtained polymers were characterized by FT‐IR, DSC, and SEM analyses and compared with those obtained by oxidative and electrochemical means. Electrical conductivities of the samples were measured by four‐probe technique.

Photograph of the polymerization mixture containing thiophene and iodonium salt in CH₂Cl₂ before (a), after 5 min of irradiation (b), and dried film (c).     

Synthesis and ATRP Activity of New TREN‐Based Ligands

Summary: Ligands suitable for atom transfer radical polymerization (ATRP) were prepared by the Michael addition of several acrylates (allyl, benzyl, butyl, 2‐ethylhexyl, and 3‐(dimethoxymethylsilyl)propyl acrylates) with tris(2‐aminoethyl)amine (TREN). These ligands, readily prepared from inexpensive precursors, were used for the preparation of catalyst complexes suitable for polymerization of (meth)acrylates and styrene, providing activity comparable to catalysts currently used for these monomers. Catalysts containing ligands with a dimethoxymethylsilyl substituent were examined for copper removal after the reaction mixture was contacted with silica gel.

     

Grafting of Polystyrene onto Poly(butyl acrylate) and Polystyrene Backbones Using Functionalized Methacrylates

Summary: Grafting of terminal epoxide‐functionalized polystyrene onto poly[styrene‐co‐(2‐hydroxyethyl methacrylate)] or poly[(butyl acrylate)‐co‐(2‐hydroxyethyl methacrylate)] backbones was carried out by coupling reactions catalyzed by boron trifluoride. The functionalized backbones were prepared by free radical copolymerization of 2‐hydroxyethyl methacrylate (HEMA) with styrene or butyl acrylate. For the synthesis of terminal functionalized polymer chains a side reaction of the TEMPO‐mediated free radical polymerization of methacrylates could be used successfully to convert TEMPO‐terminated polymers into terminal epoxide‐functionalized polymers by the use of glycidyl methacrylate. The number of epoxide units attached to the backbone was directly related to the TEMPO concentration during the disproportionation reaction. Taking P(S‐co‐HEMA) as well as P(BuA‐co‐HEMA) backbones in coupling reactions with different epoxy‐functionalized polystyrenes in the presence of boron trifluoride, graft polymers with up to 7 and 37 side chains per backbone were produced.

Molecular weight distribution curves of a linking experiment between P(BuA‐co‐HEMA) backbones and epoxide‐functionalized polystyrene side chains.     

Synthesis and Dielectric Study of New Liquid‐crystalline Polysiloxanes Presenting a Thioether Spacer

Three new cyanobiphenyl polysiloxanes presenting long thioether spacers have been carried out. This type of spacer leads to very stable liquid‐crystalline polymers at room temperature and remove the crystallinity phenomenon. Dielectric analysis results show that the thioether spacer brings much more molecular flexibility to the system.

Example of an “interdigitated” structure observed by X‐ray analysis.     

Gas‐Phase Assisted Surface Polymerization of Vinyl Monomers with Fe‐Based Initiating Systems

Summary: Gas‐phase assisted surface polymerization (GASP) of methyl methacrylate (MMA) and styrene (St) was investigated with Fe‐based radical initiating systems, FeCl₂/2,2′‐bipyridine (Bpy)/methyl α‐bromophenylacetate (MBPA), etc. GASP with these initiating systems proceeded to produce corresponding polymers on substrate surfaces. The resulting PMMA had very high PDI values, suggesting an uncontrolled reaction. In an attempt to control the GASP, polymerization with a simple initiating system, Fe(0)/MBPA, was examined on Fe(0)‐metal surfaces, resulting in significant polymerization activity to produce high‐molecular‐weight PMMA. The results of time‐course tests on GASP of MMA and St suggested that a change had taken place to produce physically controlled propagation sites on the Fe(0) powder surfaces.

GASP schemes with a simple initiating system Fe(0)/MBPA.     

Ethylene Polymerization with Silica‐Supported Nickel‐Diimine Catalyst: Effect of Support and Polymerization Conditions on Catalyst Activity and Polymer Properties

Ethylene was polymerized using both homogeneous and modified methylaluminoxane (MMAO)‐treated silica supported nickel‐diimine catalysts (1,4‐bis(2,6‐diisopropylphenyl) acenaphthene diimine nickel(II ) dibromide) in a slurry semibatch reactor. The effects of catalyst support and polymerization conditions (ethylene pressure and reaction temperature) on catalyst activity and polymer properties were systematically investigated. The supported catalyst gave far lower activity than the homogeneous catalyst. The activities of both catalyst systems increased with polymerization temperature with a maximum at 40 °C. Compared with the homogeneous catalyst, the supported catalyst system produced polyethylene with a different microstructure. Due to steric effects, the supported catalyst system exhibited lower chain walking rates than the homogeneous catalyst, producing polymers with less branching content and, thus higher melting points. Depending on polymerization conditions, two active site populations were observed during polymerization using supported catalyst; one population remained fixed on the surface of the support, and the other was extracted from the support, exhibiting the same polymerization behavior as the homogeneous catalyst.

DSC thermograms for polyethylene produced with homogeneous and supported catalysts at an ethylene pressure of 50 psig (3.45 · 10⁵ Pa) and reaction temperature 40 °C.     

Face‐to‐Face Alignment of Porphyrin/Fullerene Nanowires Linked by Axial Metal Coordination

A general approach to construct one‐dimensional face‐to‐face alignment of porphyrin/fullerene nanowires has been developed. This system uses extended trans‐dihydroxotin(IV) porphyrin and trans‐dicarboxylate‐substituted [60]fullerenoacetic diacid compounds. The nanowires are arranged in regular one‐dimensional linear arrays with lengths in the range 50–300 nm. In the nanowires, each fullerene unit is axially coordinated to the central metal ion of a Sn(IV) porphyrin unit via Sn‐carboxylate coordination and forms a face‐to‐face aligned structure. The synthesis and the hierarchical structure of nanowires have been investigated. They could have potential applications for photoelectronic devices, organic solar cells and so on.

     

Fabrication of Conjugated Polymer Supramolecules in Electrospun Micro/Nanofibers

A combination of top‐down (electrospinning for fabrication of high surface area micro/nanofibers) and bottom‐up (creation of supramolecular structures through self‐assembly processes in fiber) approaches has enabled the generation of conjugated polymer‐embedded fibers. The efficiency of fiber formation, encapsulated with colorimetric, and fluorogenic conjugated polydiacetylene supramolecules, was dependent on electrospinning conditions, such as concentration, molecular weight, type of matrix polymer, and solvent. In general, electrospinning of a chloroform solution containing 1.6 wt.‐% of a diacetylene monomer and 4 wt.‐% PEO of molecular weight 300 000 g · mol^?1 followed by 254 nm UV irradiation resulted in clean formation of polydiacetylene‐embedded fibers. In addition, UV irradiation during electrospinning can be used for in situ and continuous generation of polydiacetylenes‐encapsulated fibers.

     

Synthesis and Characterization of New Acrylate and Methacrylate Monomers with Pendant Pyridine Groups

To overcome some drawbacks of polyvinylpyridines, new monomers of acrylate and methacrylate type with pendant pyridine groups i.e., 4‐(3‐methacryloylpropyl)pyridine 1a and 4‐(3‐acryloylpropyl)pyridine 1b were successfully prepared, although it turned out to be challenging work to synthesize the acrylate monomer 1b . First polymerization studies showed that the new monomers could be polymerized easily by atom transfer radical polymerization (ATRP). The new polymers show excellent characteristics, such as very good solubility, low glass‐transition temperature, and easy quaternization.

Design and structure of new monomers 1a and 1b .     

Synthesis of High‐Molecular Weight Polymers Based on N,N‐Diallyl‐N‐Methylamine

High‐molecular weight polymers, namely poly(N,N‐diallyl‐N‐methylammonium trifluoroacetate) and poly(N,N‐diallyl‐N‐methylamine), were prepared by radical polymerization of N,N‐diallyl‐N‐methylamine in aqueous solution in the presence of an equimolar amount of trifluoroacetic acid and by polymerization of the newly synthesized equimolecular salt N,N‐diallyl‐N‐methylammonium trifluoroacetate in gentle conditions. We have established that chain termination is controlled by the bimolecular mechanism and that degradative chain transfer to monomer transforms into effective chain transfer (see Scheme). The possibility of controlling the polymerization rate and molecular weight of polymers is demonstrated. The mechanisms of the observed phenomena are discussed.

     

Novel Phosphorous‐Containing Aromatic Polyethers – Synthesis and Characterization

Summary: The synthesis of novel phosphorous‐containing aromatic polyethers P‐PEEK and P‐PSU, based on poly(ether ether ketone)s (PEEK) and poly(ether sulfone)s (PSU) was carried out successfully by using phosphorous‐containing aromatic diols instead of bisphenol A in the usual synthesis procedure. The molecular weights of the P‐PEEKs and P‐PSUs obtained reflect both the influence of the different halogen components used and the lower thermal stabilities of the phosphorous‐containing diols compared to bisphenol A. However, polymers with sufficient molecular weights could be obtained, having interestingly high T_gs, high thermal stabilities as well as modified flame retardance properties depending on the diol type incorporated.

Comparison of the molecular weights of the synthesized P‐polyethers.     

Towards Highly Substituted Starburst Macromolecular Semiconductors: Microwave Synthesis,Spectroscopy and Electrochemical Properties

As part of a strategy to explore highly functionalized macromolecular semiconductors, a series of highly substituted twelve‐armed macromolecules F1CzTr‐F3CzTr consisting of truxene, 9‐phenylcarbazole and oligofluorene units were synthesized. To accomplish the synthesis of twelve‐armed targets, a high yield microwave enhanced synthesis method for direct twelve‐fold Suzuki couplings was developed. The resulting materials exhibited high purity and good monodispersity (PDI 1.01–1.03). The molecular weight of the compound F3CzTr achieved 14 266 g · mol^?1, representing one of the largest well‐defined starburst conjugated molecules. The thermal, photophysical and electrochemical properties were investigated.

     

Characterization of Water‐Dispersible n‐Type Poly(benzimidazobenzophenanthroline) Derivatives

Novel water dispersible poly(benzimidazobenzophenanthroline) polymers functionalized with poly(ethylene oxide) (BBL:PEO) have been investigated by cyclic voltammetry, in situ UV‐vis spectroscopy and atomic force microscopy. The cyclic voltammograms recorded during n‐doping indicate that the drop coated BBL:PEO films retain their properties despite functionalization. A small influence of the PEO side chains on redox properties of the investigated polymers was found, diminishing however after annealing. During spectroscopic experiments structural changes connected with polymer charging were observed (in accordance with a two electron transfer process). The functionalization of BBL with PEO side chains provided an easy processing method to obtain smooth and reproducible polymer films.

     

Functional Thin Polymer Films at High Pressure

Summary: A new thin‐film characterization setup was created based on the combination of a surface plasmon spectrometer with an electrochemical cell operated under high pressure of up to 200 MPa and at temperatures up to 120 °C. The examples given to document its performance include photoisomerization studies with poly(methyl methacrylate) (PMMA) films partly derivatized with disperse red (DR1), as well as, a preliminary account of the electropolymerization of EDOT under pressure and the assessment of the redox properties of the resulting thin PEDOT films.

Sketch of the high‐pressure electrochemistry surface plasmon cell.     

Atom Transfer Radical Polymerization Using Multidentate Amine Ligands Supported on Soluble Hyperbranched Polyglycidol

Summary: Controlled polymerization of styrene in toluene was achieved by atom transfer radical polymerization (ATRP) using hyperbranched polyglycidol‐supported multidentate amine ligands/Cu^IBr catalyst systems. These catalyst systems with nanoscopic dimensions were more active than the corresponding low‐molecular‐weight ligands. The controlled/living nature of the polymerization is supported by linear first order plots (ln[M]_o/[M] versus time) and a linear increase of versus conversion as well as low polydispersity. Similar controlled polymerization of methyl methacrylate was possible in acetonitrile. Up to 97% of total copper used for polymerization could be removed from the polymer by simple precipitation in methanol and filtration.

Molecular weight characteristics for styrene polymerization using PG‐triamine as a ligand.     

Synthesis of Polyacrylonitrile‐block‐Polystyrene Copolymers by Atom Transfer Radical Polymerization

Summary: The synthesis of polyacrylonitrile‐block‐polystyrene (PAN‐b‐PS) copolymers by atom transfer radical polymerization (ATRP) is reported. Chain extension of bromine terminated PAN macroinitiators with styrene was performed using a CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system and 2‐cyanopyridine as a solvent. The first‐order kinetic plots of styrene consumption showed a significant curvature, indicating a progressive decrease in the concentration of active species during copolymerization. The loss of the bromide end group was mainly ascribed to the elimination of HBr, as shown by ¹H NMR spectroscopy. By varying the molar ratio of either the catalyst or the monomer to the initiator, a series of PAN‐b‐PS copolymers were prepared, with polydispersities as low as 1.3, and molar compositions ranging from 8.6/91.4 to 35.5/64.5.

¹H NMR spectra of PAN‐b‐PS in DMF‐d₇ at 80 °C.