Synthesis of an amphiphilic styrenic block copolymer: Polycondensation of dichloromethane and low molecular weight poly(ethylene glycol) in the presence of hydroxypropylated polystyrene‐block‐polybutadiene

An amphiphilic styrenic block copolymer, polystyrene‐block‐polybutadiene‐block‐poly[oxymethylene‐alt‐oligo(oxyethylene)] (PS‐b‐PB‐b‐POME), was synthesized through a polycondensation reaction of low molecular weight poly(ethylene glycol) and dichloromethane in the presence of hydroxypropylated polystyrene‐block‐polybutadiene (PS‐b‐PB‐OH) used as a monofunctional chain‐capping reagent. PS‐b‐PB‐OH was in turn prepared via an anionic synthesis of PS‐b‐PB followed by oxetane capping and methanol quenching. Although PS‐b‐PB‐OH has insignificant hydrophilicity, PS‐b‐PB‐b‐POME containing both the hydrophobic PS‐b‐PB segment and the hydrophilic POME segment had an improved emulsifying capability and effectively decreased the interfacial tension between water and toluene. The hydrophile–lipophile balance value of this amphiphilic PS‐b‐PB‐b‐POME copolymer, consisting of 86 wt % of the POME segment and 14 wt % of the PS‐b‐PB segment, was 17.2. The molecular weight of the copolymer molecule was determined by gel permeation chromatography–multi‐angle laser light scattering, and the microstructure was analyzed using ¹H NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2625–2632, 2001     

Reactions of polystyryllithiums and model lithium carbanions with 9,10‐bis(halomethyl)anthracenes

The direct and nearly quantitative incorporation of 9,10‐anthracenylidene (AN) chromophores into polystyrene occurred via the reaction of polystyryllithium (PSLi) with 9,10‐bis(chloromethyl)anthracene (BCMA) at ?78 °C in tetrahydrofuran (THF)/ hexane containing between 30 and 40 vol % hexane. Although the reaction of PSLi and BCMA or 9,10‐bis(bromomethyl)anthracene (BBMA) in THF at ?78 °C gave nearly quantitative coupling, typically only 30–50% AN incorporation was observed, as determined by ultraviolet–visible spectrometry. Model coupling reactions of 3,3‐dimethyl‐1,1‐diphenyl‐1‐lithiobutane, (1,1,2,2‐tetramethyl)propylcyclopentadienyllithium, 9‐methylfluorenyllithium, and triphenylmethyllithium with BCMA or BBMA at ?78 °C in THF in nearly all cases gave several AN‐containing coupling products. This was consistent with lithium–halogen exchange leading to the linking of multiple AN groups. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3121–3129, 2001     

Syntheses of amphiphilic block copolymers by living cationic polymerization of vinyl ethers and their selective solvent‐induced physical gelation

Amphiphilic diblock copolymers were prepared by the living cationic polymerization of vinyl ethers in the presence of added bases, and their selective solvent‐induced physical gelation behavior was investigated. The block copolymerization of 2‐phenoxyethyl vinyl ether (PhOVE) and 2‐methoxyethyl vinyl ether (MOVE) was carried out in the presence of ethyl acetate with Et_1.5AlCl_1.5 in toluene at 0 °C. Despite the rate difference, diblock copolymers with a very narrow molecular weight distribution were obtained, quantitatively. By adding the selective solvent, water, to the acetone solution of the diblock copolymer, PhOVE₂₀₀‐b‐MOVE₄₀₀, physical gelation occurred suddenly and the system ceased to flow, maintaining transparency. Viscoelastic measurements and transmission electron microscopic observations were performed to examine the characteristic gelation behavior and structure of the obtained gels. Various gelation conditions and physical gelation by other amphiphilic block copolymers were also designed on the basis of the solubility of each block segment. Further, new forms of physical gelation, accompanied by the solubilization of immiscible organic compounds, were achieved using similar diblock copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3190–3197, 2001     

Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short‐chain alcohols

Styrene microemulsion polymerizations with different short‐chain alcohols [n‐C_iH_2i+1OH (C_iOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50–70 °C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C₆OH > C₄OH > C₅OH. This was related to the differences in the water solubility of C_iOH and the structure of the oil–water interface. The feasibility of using a water‐insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (C_iOH), the SPS concentration, and the initiator type (oil‐soluble 2,2′‐azobisisobutyronitrile versus water‐soluble SPS). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199–3210, 2001     

Copolymerization of propylene with various higher α‐olefins using silica‐supported rac‐Me2Si(Ind)2ZrCl2

The copolymerization of propylene with 1‐hexene, 1‐octene, 1‐decene, and 1‐dodecene was carried out with silica‐supported rac‐Me₂Si(Ind)₂ZrCl₂ as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one‐half to one‐eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with α‐olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294–3303, 2001     

Synthesis and characterization of new soluble poly(amide‐imide)s derived from 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane

A series of new soluble poly(amide‐imide)s were prepared from the diimide‐dicarboxylic acid 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane with various diamines by direct polycondensation in N‐methyl‐2‐pyrrolidinone containing CaCl₂ with triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.52–0.86 dL · g^?1. The poly(amide‐imide)s showed an amorphous nature and were readily soluble in various solvents, such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, and cyclohexanone. Tough and flexible films were obtained through casting from DMAc solutions. These polymer films had tensile strengths of 71–107 MPa and a tensile modulus range of 1.6–2.7 GPa. The glass‐transition temperatures of the polymers were determined by a differential scanning calorimetry method, and they ranged from 242 to 279 °C. These polymers were fairly stable up to a temperature around or above 400 °C, and they lost 10% of their weight from 480 to 536 °C and 486 to 537 °C in nitrogen and air, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3498–3504, 2001     

Differentiation of α‐COOH from β‐COOH in aspartic acids by N‐phosphorylation

The biomimic reactions of N‐phosphoryl amino acids, which involved intramolecular penta‐coordinate phosphoric‐carboxylic mixed anhydrides, are very important in the study of many biochemical processes. The reactivity difference between the α‐COOH group and β‐COOH in phosphoryl amino acids was studied by experiments and theoretical calculations. It was found that the α‐COOH group, and not β‐COOH, was involved in the ester exchange on phosphorus in experiment. From MNDO calculations, the energy of the penta‐coordinate phosphoric intermediate containing five‐member ring from α‐COOH was 35 kJ/mol lower than that of the six‐member one from β‐COOH. This result was in agreement with that predicted by HF/6‐31G** and B3LYP/6‐31G** calculations. Theoretical three‐dimensional potential energy surface for the intermediates predicted that the transition states 4 and 5 involving α‐COOH or β‐COOH group had energy barriers of ΔE=175.8 kJ?mol^?1 and 210.4 kJ?mol^?1, respectively. So the α‐COOH could be differentiated from β‐COOH intramolecularly in aspartic acids by N‐phosphorylation. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 41–51, 2001     

Dichloro(2,2′‐diamino‐4,4′‐bi‐1,3‐thiazole‐N3,N3′)copper(II)

The title complex, [CuCl₂(C₆H₆N₄S₂)], has a flattened tetrahedral coordination. The Cu^II atom is located on a twofold rotation axis and is coordinated by two N atoms from a chelating 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and by two Cl atoms. Intramolecular hydrogen bonding exists between the amino groups of the 2,2′‐di­amino‐4,4′‐bi‐1,3‐thia­zole ligand and the Cl atoms. The intermolecular separation of 3.425 (1) Å between parallel bi­thia­zole rings suggests there is a π–π interaction between them.     

3,9‐Bis(dicyanomethylene)‐2,4,8,10‐tetrathiaspiro[5.5]undecane

The title compound, 2,2′‐(2,4,8,10‐tetra­thia­spiro­[5.5]­undec­ane‐3,9‐diyl­idene)­bis­(propane­di­nitrile), C₁₃H₈N₄S₄, has been designed and synthesized for use as a potential new organic molecular electronic material. The spiro‐annulated structure has twofold symmetry and is formed by two equal push–pull ethyl­ene units, with the cyclo­alkyl­thio groups as electron donors and the cyano groups as electron acceptors. The intermolecular S?N non‐bonded separation within a layer in the lattice is 3.296 (6) Å, indicating a strong intermolecular interaction between the cyano groups and the S atoms, while the S atoms in two neighbouring mol­ecules have a shortest S?S contact of 3.449 (3) Å. In addition, attractive C—H?N and C—H?S interactions bridge adjacent mol­ecules either within a layer or between layers. In short, these four types of intermolecular interactions combine to form an extended three‐dimensional network in the lattice, resulting in a highly ordered array of molecular packing.     

O‐Ethyl and O‐methyl N‐(2,3,4,6‐tetra‐O‐acetyl‐β‐d‐glucopyranosyl)thiocarbamate

In both the title structures, O‐ethyl N‐(2,3,4,6‐tetra‐O‐acetyl‐β‐d ‐gluco­pyran­osyl)­thio­carbam­ate, C₁₇H₂₅NO₁₀S, and O‐methyl N‐(2,3,4,6‐tetra‐O‐acetyl‐β‐d ‐gluco­pyran­osyl)­thiocar­bam­ate, C₁₆H₂₃NO₁₀S, the hexo­pyran­osyl ring adopts the ⁴C₁ conformation. All the ring substituents are in equatorial positions. The acetoxy­methyl group is in a gauche–gauche conformation. The S atom is in a synperi­planar conformation, while the C—N—C—O linkage is antiperiplanar. N—H?O intermolecular hydrogen bonds link the mol­ecules into infinite chains and these are connected by C—H?O interactions.