Polymerisation in lyotropic liquid-crystalline phases of dioctadecyldimethylammonium bromide

The polymerisation of styrene in lyotropic liquid-crystalline (LC) phases of dioctadecyldimethylammonium bromide (DODAB) in water is explored. Amphiphile concentrations between 20 and 50 wt % are employed. The study is set out as a model study for polymerisation reactions in nonstabilised, nonfunctional bilayer systems. X-ray characterisation was used to assess the phase behaviour of the lyotropic mesophases before, during and after polymerisation. The DODAB/water system forms the lamellar phase within the concentration range considered. Addition of styrene to the lamellar phase of DODAB at an equimolar ratio induces a phase shift to a bicontinuous cubic phase at elevated temperatures near the phase-transition temperature. Upon polymerisation within this cubic phase, the phase structure is maintained if the system is kept at constant temperature; however, if the polymer/amphiphile phase is cooled, the lamellar phase, being typical of the DODAB/water system, is restored. It is concluded that, as a result of phase separation between the polymer and the amphiphile phase, the polymerisation in lyotropic LC phases does not provide a stable copy of the templating amphiphile phase. This is in analogy to the observations for polymerisations in other lyotropic phases. Received: 16 March 2000 Accepted: 1 July 2000     

The effect of 4-vinylcyclohexene on the degradation of polystyrene and on the polymerisation of styrene

It has previously been postulated that the inhibition of polystyrene degradation observed in the initial stages of the isothermal degradation of polystyrene-polybutadiene blends is partly due to reaction of polystyryl radicals with 4-vinylcyclohexene (4VCH) evolved from the polybutadiene. This hypothesis has been tested by examining the effect of small amounts of 4VCH on polystyrene degradation and on the free radical polymerisation of styrene. The results provide support for the hypothesis: there is an induction period in the degradation and the polymerisation is retarded. From molecular weight measurements on polymers made in the presence of various amounts of 4VCH, a chain transfer constant in styrene polymerisation at 60°C of 117 × 10^?5 has been calculated.     

Half-titanocenes for precise olefin polymerisation: effects of ligand substituents and some mechanistic aspects

Selected examples concerning effects of both cyclopentadienyl fragment (Cp') and anionic donor ligand (Y) in nonbridged modified half-titanocenes of the type, Cp'TiX(2)(Y) (X = halogen, alkyl), as new type of olefin polymerisation catalysts have been reviewed. These complexes displayed unique characteristics not only for ethylene (co)polymerisation but also for syndiospecific styrene polymerisation, ethylene/styrene copolymerisation; precise fine tuning of the ligand substituents plays an important role for the successful (co)polymerisation; a different mechanistic consideration for the syndiospecific styrene polymerisation, which can explain the copolymerisation behaviour in this catalysis, has also been introduced.     

First report of reversible addition-fragmentation chain transfer (RAFT) polymerisation in room temperature ionic liquids

The Reversible Addition-Fragmentation chain Transfer (RAFT) polymerisation of acrylates, methacrylates and styrene is reported for the first time in room temperature ionic liquids; the acrylate and methacrylate polymerisations show a living character and lead to well-characterised polymers, with narrow polydispersity (< 1.3); in the case of styrene, the insolubility of the polymer in the ionic liquids stops the polymerisation at an early stage.     

Effect of ligand substituents in olefin polymerisation by half-sandwich titanium complexes containing monoanionic iminoimidazolidide ligands-MAO catalyst systems

Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl(2)[1,3-R(2)(CH(2)N)(2)C=N] (1a-d) [R = Ph (a), 2,6-Me(2)C(6)H(3) (b), cyclohexyl (c), (t)Bu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation.     

Mathematical Analysis of the Formation of Molecule Sizes on a Spinning Disc Reactor

A mathematical analysis of the behaviour of the molecular weights of addition polymers during a polymerisation process is described. Spinning disc reactor (SDR) technology has been shown to yield significant improvements in terms of polymerisation rates whilst retaining close control of the molecular weights and the molecular weight distributions^[1,2]. However, understanding of the kinetics of the polymerisation process on a SDR remains unresolved. One of the questions to be addressed concerns the sizes of the macromolecules preferably formed during the polymerisation process. To address this question, a mathematical analysis of the observed trends in number and weight average molecular weight, monomer concentration and polydispersity during the polymerisation process on a SDR has been undertaken. To validate the results, experimental data obtained from benzoyl peroxide initiated free radical polymerisation of styrene on a SDR^[2] was used. It was concluded that most of the monomers consumed are in the growth of smaller size chains.     

Nonionic latices in aqueous media

The rate of conversion of styrene into polystyrene by emulsion polymerisation has been investigated in the absence and in the presence of methoxy-polyethyleneglycol methacrylate, MeOPEGMA. The effect of adding MeOPEGMA at different stages of the polymerisation was also investigated. Additions at the beginning of the polymerisation and at the early stages gave a bimodal particle size distribution whereas late additions gave small particle size, monodisperse latices which were electrosterically stabilised. The latter materials were found to be colloidally stable to the addition of high concentrations of electrolyte and to freeze-thaw conditions.Part 3: Brit. Polymer J., 1987, 19:435     

Diffusion‐Controlled Particle Growth and its Effects on Nucleation in Stirred Emulsion Polymerisation Reactors

Summary: Particle formation and growth in the batch emulsion homo‐polymerisation of styrene and methyl methacrylate monomers under diffusion‐controlled conditions were studied. The polymerisations started with two stratified layers of a monomer and water containing an initiator and a surfactant, with the water layer being gently stirred. Because of limitations in monomer transport, the rate of particle growth was substantially reduced and as a result a large number of polymer particles formed.

Schematic presentation of the highly diffusion‐controlled polymerisation.     

Simultaneous enzymatic ring opening polymerisation and RAFT-mediated polymerisation in supercritical CO2

This report presents the first simultaneous, metal-free synthesis of block copolymers through combination of enzymatic ring-opening polymerisation of epsilon-caprolactone with RAFT-mediated controlled radical polymerisation of styrene.     

The dispersion polymerization of unsaturated monomers initiated by the macromonomeric initiator

The dispersion polymerizations of styrene (St) and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimer (PEO-MIM) in ethanol/water were investigated at 50, 60 and 80°C. The polymerisation rate vs. conversion dependence was described by with a maxim at the beginning of polymerisation. Polymerization was faster with MMA than with St. The limiting conversion was inversely proportional to temperature and was much more pronounced with St. The rate of polymerization increased with temperature. The overall initial activation energy increased with conversion and reached value ca. 25 kJ.mol⁻¹ for MMA and 50 kJ.mol⁻¹ for styrene at ca. 60% conversion. The particle size was observed to decrease with increasing the macroinimer concentration. The polymer dispersions were unstable and a large amount of coagulum appeared during the polymerisation especially in the styrene-containing reaction system.     

Tuning the active species from syndiospecific styrene polymerisation to ethylene/styrene copolymerisation by (aryloxo)(cyclopentadienyl)titanium complexes-MAO catalysts

Exclusive formation of poly(ethylene-co-styrene)s were observed by introduction of ethylene into the solution of syndiospecific styrene polymerisation using Cp'TiCl(2)(O-2,6-(i)Pr(2)C(6)H(3)) (Cp' = 1,2,4-Me(3)C(5)H(2), tert-BuC(5)H(4))-MAO catalysts without by-production of syndiotactic polystyrene, whereas the styrene polymerisation did not proceed when ethylene was removed from the reaction mixture of ethylene/styrene copolymerisation.     

Towards an easy access to amphiphilic rod-coil miktoarm star copolymers

Water-soluble stimuli-responsive AB2 miktoarm star copolymers were prepared by atom transfer radical polymerisation of styrene followed by chain-end modification, polymerisation of either gamma-benzyl-L-glutamate N-carboxyanhydride or tert-butylacrylate and a final step of hydrolysis.     

Analytical strategies for the quality assessment of recycled high-impact polystyrene: a combination of thermal analysis, vibrational spectroscopy, and chromatography

Various analytical techniques (thermal analysis, vibrational spectroscopy, and chromatographic analysis) were used in order to monitor the changes in polymeric properties of recycled high-impact polystyrene (HIPS) throughout mechanical recycling processes. Three key quality properties were defined and analysed; these were the degree of mixing (composition), the degree of degradation, and the presence of low molecular weight compounds. Polymeric contaminations of polyethylene (PE) and polypropylene (PP) were detected in some samples using differential scanning calorimetry (DSC). Vibrational spectroscopy showed the presence of oxidised parts of the polymeric chain and gave also an assessment of the microstructure of the polybutadiene phase in HIPS. The presence of low molecular weight compounds in the HIPS samples was demonstrated using microwave-assisted extraction followed by gas chromatography-mass spectrometry (GC-MS). Several volatile organic compounds (VOCs), residues from the polymerisation, additives, and contaminations were detected in the polymeric materials. Styrene was identified already in virgin HIPS; in addition, benzaldehyde, α-methylbenzenaldehyde, and acetophenone were detected in recycled HIPS. The presence of oxygenated derivates of styrene may be attributed to the oxidation of polystyrene (PS). Several styrene dimers were found in virgin and recycled HIPS; these are produced during polymerisation of styrene and retained in the polymeric matrix as polymerisation residues. The amount of these dimers was highest in virgin HIPS, which indicated that emission of these compounds may have occurred during the first life-time of the products. This paper demonstrates that a combination of different analytical strategies is necessary to obtain a detailed understanding of the quality of recycled HIPS.     

High capacity organic monoliths for the simultaneous application to biopolymer chromatography and the separation of small molecules

A method for controlling the mesoporous structure of monolithic organic copolymers is presented by systematic variation in polymerisation time, employing poly(p-methylstyrene-co-1,2-(p-vinylphenyl)ethane) (MS/BVPE) as a representative styrene system. Decreasing the time of polymerisation introduces a considerable fraction of mesopores (up to 20% of the total pore volume), while keeping the support permeability reasonable high (～1.3 × 10^?14 m²). Monolith structures, prepared in such a manner, enable efficient (typically around 70,000 plates/m) and fast separation of low-molecular-weight compounds, whereas their performance towards biopolymers is comparable to column supports, fabricated according to typically used protocols (polymerisation time >12 h and thus monomer conversion >98%). The polymerisation time is hence a valuable tool to tailor the fraction of support flow-channels, macropores as well as mesopores, which is shown dramatically to influence the chromatographic separation characteristics of the respective column. This way, the preferred applicability of organic (styrene) monolithic copolymers can be extended to the separation of small molecules beyond biopolymer chromatography.     

Synthesis and styrene polymerisation catalysis of eta5- and eta1-pyrrolyl-ligated cationic rare earth metal aminobenzyl complexes

The cationic rare earth metal aminobenzyl complexes bearing mono(pyrrolyl) ligands are synthesised and structurally characterised, and the coordination mode of the pyrrolyl ligands is found to show significant influence on the polymerisation of styrene.     

Four-coordinate iron complexes bearing alpha-diimine ligands: efficient catalysts for atom transfer radical polymerisation (ATRP)

Four-coordinate iron(II) complexes bearing alpha-diimine ligands with alkyl substituents are shown to be efficient catalysts for the well-controlled atom transfer radical polymerisation of styrene; catalysts containing aryldiimine ligands support competitive beta-hydrogen chain transfer processes.     

Radical polymerisation of styrene in porous coordination polymers

The first radical polymerisation of styrene in porous coordination polymers has been carried out, providing stable propagating radicals (living radicals), and a specific space effect of the host frameworks on the monomer reactivity is demonstrated.     

Poly(ethylene glycol) as solvent for transition metal mediated living radical polymerisation

The use of poly(ethylene glycol)(PEG) with low molecular weights as a novel solvent for the transition metal mediated radical polymerisation of methyl methacrylate and styrene is reported. The utilisation of PEG leads to polymerisation kinetics that differ from those observed with more traditional organic solvents. Moreover, the amount of residual copper catalyst in the product is greatly reduced by precipitation of the polymer in ethanol.     

Living radical copolymerization of styrene/maleic anhydride

Styrene/maleic anhydride (MA) copolymerization was carried out using benzoyl peroxide (BPO) and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO). Styrene/MA copolymerization proceeded faster and yielded higher molecular weight products compared to styrene homopolymerization. When styrene/MA copolymerization was approximated to follow the first‐order kinetics, the apparent activation energy appeared to be lower than that corresponding to styrene homopolymerization. Molecular weight of products from isothermal copolymerization of styrene/MA increased linearly with the conversion. However products from the copolymerization at different temperatures had molecular weight deviating from the linear relationship indicating that the copolymerization did not follow the perfect living polymerization characteristics. During the copolymerization, MA was preferentially consumed by styrene/MA random copolymerization and then polymerization of practically pure styrene continued to produce copolymers with styrene‐co‐MA block and styrene‐rich block. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2239–2244, 2000     

Evaluation of solubility parameters during polymerisation of amine‐cured epoxy resins

A new procedure for the calculation of solubility parameter evolution during polymerisation has been developed for amine‐cured epoxy systems, which allows quantitative thermodynamic modelling of chemically induced phase separation (CIPS). Solubility parameters calculation, chemical analysis based on near infrared spectroscopy and curing kinetics results obtained by differential scanning calorimetry will allow to model the evolution of the Flory–Huggins interaction parameter in amine‐cured epoxy blends. The resin system investigated was based on a diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with isophorone diamine (IPD) blended with various reactive epoxydised dendritic hyperbranched polymer modifiers (HBP), yielding a CIPS‐controlled morphology. The analysis showed the evolution of the different contributions to the solubility parameters to follow the polymerisation kinetics. The dispersive contribution had the highest value at all stages of polymerisation, but the hydrogen and polar contributions showed the largest variation. By evaluating the dynamic evolution of the solubility parameter components, the Flory–Huggins interaction parameter in the epoxy resin‐hyperbranched polymer blends has been modelled as a function of time. This procedure, combined with thermodynamic modelling, will enable to predict phase diagrams in CIPS thermosetting blends quantitatively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1883–1892, 2000