Miniemulsion polymerization of styrene with a block copolymer surfactant

A series of miniemulsion systems based on styrene/azobisisobutyronitrile in the presence of poly(methyl methacrylate‐b‐2‐(dimethylamino)ethyl methacrylate) as a surfactant and hexadecane (HD) as a cosurfactant were developed. For comparison, a series of pseudoconventional emulsions also were carried out with the same procedure used for the aforementioned series but without the cosurfactant (HD). Both the droplet size and shelf life were also measured. Experimental results indicate that it is possible to slow the effect of Ostwald ripening and thereby produce a stable miniemulsion with the block copolymer as the surfactant and HD as the cosurfactant. In addition, the extent to which varying the surfactant concentration and copolymer composition could affect both the polymer particle size during the polymerization and the polymerization rate was examined. Variation in the polymer particle sizes during polymerization indicates that droplet and aqueous (micellar or both homogeneous) nucleation occurs in the miniemulsion polymerization. With the same concentration of the surfactant used in the miniemulsion polymerization, the polymerization rates of systems with M₁₂B₃₆ are faster than those of systems with M₁₂B₁₂. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1818–1827, 2000     

Viscoelasticity of a butadiene–styrene block copolymer

A commercial elastomeric block copolymer of butadiene (B) with styrene (A) is studied. A single chain of the material has the formula A-B-A. Differential thermal analysis studies show the presence of two transitions. The lower transformation temperature corresponds to the T_g of the butadiene chain segments, and the upper transformation temperature corresponds to the T_g of the styrene chain segments. The upper transition of the material is also studied by following the variation of the torsional modulus with temperature. This transition is found to be quite unusual. Our experiments show that the upper transformation of unstressed block copolymer samples is broad. The transition sharpens for samples which, prior to the modulus–temperature experiments, are stress-relaxed at high elongations. These observations (and those of the literature) suggest that the styrene and butadiene chain segments in the block copolymer aggregate in the solid state and give rise to two distinct transition phenomena. Our studies of the upper transformation suggest that stretching of the bulk material enhances the aggregation of the styrene chain segments. Pure polystyrene (A) blocks of the material are recovered by selective cleavage and fractionation experiments. The T_g of the pure polystyrene blocks is found to be similar to the value of the upper transition temperature of the copolymer. The ABA blocks copolymer is found also to undergo a stress-softening phenomenon analogous to that of reinforced rubber.     

Achieving high conversions in nitroxide-mediated living styrene miniemulsion polymerization

Nitroxide-mediated living radical polymerizations of styrene were run in miniemulsion. Using a modified miniemulsion process that does not require the use of a volatile costabilizer, near complete conversions could be achieved in 2-3 hours while preserving narrow molecular weight distributions and a high degree of chain livingness. Increased rates and final conversions were achieved by semi-batch addition of the nitroxide scavenger ascorbic acid.     

环氧乙烷与苯乙烯两亲性聚合物的合成

Graft eopolymer eontaining poly(ethylene oxide)side chains on a polystyrene backbone were acrylamided. The amide groups in the copolymers were ionized by using potassium naphthalene, and grafting was achieved by utilizing the amide anions as initiator sites for the polymerization of ethylene oxide at 70℃. The graft copolymers was characterized with respect to molecule weight and composition using NMR, IR, GPC, and DSC. GPC result from the graft copolymer sample suggested a narrow size distribution.     

Copolymerization of ethylene and styrene to a nearly-alternating crystalline copolymer

An almost alternating stereoregular copolymer can be obtained by copolymerizing ethylene and styrene with the catalyst ethylenebis(1-indenyl)zirconium dichloride activated by methylaluminoxane at −25°C. The regular microstructure pointed out by the NMR spectrum allows the copolymer to crystallize as shown by calorimetric and X-ray diffraction measurements.     

Photochemical Properties of Supramolecular Dyad with Pyrenylethenylquinoline as a Photochrome

Spectral and photochemical properties of a bichromophoric dyad with two photochromes, 2-[(2-(pyren-1-yl)ethenyl]quinoline (PEQ) bridged by ten methylene groups have been investigated. Stationary spectroscopy does not show substantial interaction between the PEQ groups in the dyad, but the appearance of another, more long-living component in the f luorescence decay kinetics indicates possible excimer formation. The formation of the chemically active excimer is also confirmed by the intramolecular [2+2] photocycloaddition reaction to give tetrasubstituted cyclobutane with two vicinal pyrene substituents. This reaction competes with trans–cis photoisomerization of the dyad. It has been proposed that the π-stacking interaction of two PEQ groups with a long system of π-bonds plays an important role in the excimer formation followed by the photocycloaddition reaction.     

Synthesis of a novel centipede-like copolymer of styrene and methyl methacrylate

A well-defined,A2B-type,centipede-like copolymer of styrene and methyl methacrylate(PS-PS-PMMA) was synthesized by the combination of living anionic polymerization and atom transfer radical polym-erization(ATRP) . The synthetic approach involves the coupling reaction of polystyrene(PS) backbone bearing 1,1-diphenylethene(DPE) pendant groups,produced by ATRP and Wittig reaction,with living polystyryllithium(PSLi) ,and subsequent polymerization of the resulting 1,1-diphenylmethyl anions with methy methacrylate. The centipede-like copolymer was characterized by 1H NMR,IR,SEC,SLS,and DSC measurements.     

Synthesis of the block copolymer of styrene and 1-butene with a novel supported Ti-catalyst

The present investigation deals with sequential block copolymerization of styrene and 1-butene with a novel MgCl₂-supported TiCl₄ catalyst modified with a rare earth compound NdCl_x(OR)_y (SN-1 catalyst), which was developed in our laboratory. The catalytic activities are 1300–2500 g/g·Ti·h. Analyses of copolymers with solvent extraction, ¹³C-NMR, WAXD, GPC, and DSC was performed. The results indicate that the SN-1 catalyst selectively gave crystalline diblock copolymers of isotactic polystyrene and isotactic poly(1-butene), with the styrene unit content of 30–60 mol %. © 1996 John Wiley & Sons, Inc.     

Phase separation conditions for solutions of styrene copolymer with elastomer in a mixture of two monomers

This paper is concerned with incompatibility in the system styrene copolymer-elastomer-mixture of two monomers and its dependence on elastomer concentration and on composition of the styrene copolymers. At higher concentrations of SBR and of MMA in MS copolymers, there is less compatibility of MS and SBR polymers in SBR-MS-St + MMA systems. The compatibility of SBR and MS in St + MMA solutions is generally greater than for SBR and SAN in St + AN solutions. The compatibility of SBR-SAN-St + AN systems is less affected by concentrations of SBR and of AN in SAN than the compatibility of SBR-MS-St + MMA systems on the concentrations of SBR and of MMA in MS.     

Photodegradation of carbon monoxide–styrene copolymer in benzene and formation of block copolymer with methyl methacrylate

Photodegradation of carbon monoxide–styrene copolymer in benzene was investigated. In relation to the average number of main-chain scissions per macromolecule versus photoirradiation time, the straight line did not pass through the origin. This phenomenon was attributed to the presence of a labile bond from the carbonyl group in the main chain, in accordance with the results of Cameron and Lawrence which were found in the study of photodegradation of thermally polymerized polystyrene. In utilization of photodegradative behavior in carbon monoxide–styrene copolymer, a block copolymer of styrene with methyl methacrylate was prepared and was ascertained by precipitated fractionation, elementary analysis, and turbidimetry.     

Surface engineering of styrene/PEGylated‐fluoroalkyl styrene block copolymer thin films

A series of diblock copolymers prepared from styrenic monomers was synthesized using atom transfer radical polymerization. One block was derived from styrene, whereas the second block was prepared from a styrene modified with an amphiphilic PEGylated‐fluoroalkyl side chain. The surface properties of the resulting polymer films were carefully characterized using dynamic contact angle, XPS, and NEXAFS measurements. The polymer morphology was investigated using atomic force microscope and GISAXS studies. The block copolymers possess surfaces dominated by the fluorinated unit in the dry state and a distinct phase separated microstructure in the thin film. The microstructure of these polymers is strongly influenced by the thin film structure in which it is investigated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 267–284, 2009     

苯乙烯一氧化碳高聚物的合成与表征

阳离子钯-配体催化剂的的存在下,一氧化碳与烯烃的均相共聚形成新型环保材料聚酮,共聚单体一氧化碳价格低廉,生成的共聚物主链上存在具有反应活性的羰基官能团,与烯烃均聚物比较,具有光降解性能以及生物降解性能,     

Synthesis and characterization of star-comb styrene/butadiene copolymer

<正>A novel star-comb styrene/butadiene copolymer(SC-SBC) was synthesized by anionic polymerization and grafting reaction with epoxidized star liquid polybutadiene(ESPB) as coupling agent.The overall shape of the star-comb macromolecules can be altered by changing the molecular weight and number of the side chain.The molecular parameters and mechanical properties of the SC-SBC resins were investigated.The notched izod impact strength of the SC-SBC resins are excellent and reach as high as to 239 J/m.     

Coating of poly(styrene-co-divinylbenzene) beads with copolymer of styrene and divinylbenzene

The production of beads with cross-link density varying from the centre to the surface is described.     

Preparation of styrene/acrylonitrile copolymer microspheres and their composites with metal particles

 Monodispersed poly(styrene-co-acrylonitrile) [P(St-co-AN)] microspheres were prepared by emulsifier-free emulsion copolymerization of St with AN. Fourier transform IR spectroscopy and elemental analysis were used to measure the content of AN in the poly(St-co-AN) microspheres. X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of an AN unit on the surface of the microspheres. The combined results of the elemental analysis and the XPS measurements showed that the copolymer on the surface of the P(St-co-AN) particles was rich in AN compared with that in the interior of the particles. P(St-co-AN)–metal composite particles were prepared by chemical metal deposition. The addition of nickel could improve the distribution of cobalt on surface of the polymer microspheres. The preparation of polymer–bimetal composite particles was tried. Transmission electron microscopy and XRD were used to study the distribution and structure of the deposited metal particles. Received: 30 June 1999/Accepted in revised form: 16 September 1999