Preparation and spectroscopic characterization of surface‐enriched (with active sites) polymer‐supported phase‐transfer catalysts and their efficiency in organic addition reactions: A kinetic study

We prepared two batches of surface‐enriched (with active sites) polymer‐supported phase‐transfer catalysts (SE‐PSPTC) by fixing the crosslinking monomer divinylbenzene (DVB) at 2% (first batch) and 6% (second batch) through a free‐radical suspension copolymerization method with vinylbenzyl chloride (VBC; 25%) as a functionality and with styrene (St) as a supporting monomer, followed by the quaternization of the resulting terpolymer beads with triethylamine. The enrichment of the active sites on the surfaces of the beads was accomplished by a surface‐grafting technique through the delayed addition of the functional monomer (VBC) to the partially polymerized copolymer beads of poly(St/DVB). To bring the active sites fully onto the surfaces, we prepared six different types of terpolymer beads in each batch by varying the partial polymerization time (PPT) of St/DVB—0 h [0 VBC (conventional)], 3 h (3 VBC), 6 h (6 VBC), 9 h (9 VBC), 12 h (12 VBC), and 15 h (15 VBC)—and then gradually adding the functional monomer (VBC) to the partially polymerized poly(St/DVB) system. The resulting terpolymer beads, containing different concentrations of pendant benzyl chloride (? CH₂Cl) on the surface in each batch, underwent facile quaternization [? CH₂N⁺(C₂H₅)₃Cl^?] with an increase in the PPT of St/DVB and remained constant at 12 VBC and 15 VBC. To asses the superiority of the catalysts according to the surface enrichment of the active sites, particularly between conventional (0 VBC) catalysts and other PPT‐based SE‐PSPTCs, we characterized all the catalysts by estimating the chloride‐ion concentration, by using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), EDAX, and ESCA, and by carrying out the dichlorocarbene addition to olefins. The chloride‐ion concentration by the Volhard method and the peak intensity of the C? N stretching absorbance concentration, that is, the quaternary onium group in the FTIR spectra of both batches, increased with the PPT of St/DVB in both batches of catalysts. In particular, the chloride concentration of a first‐batch catalyst of a representative mesh size (?120 + 140) had a twofold enhancement between the conventional catalyst (0 VBC; 1.88 m equiv g^?1) and 9 VBC/SE‐PSPTC (3.74 m equiv g^?1), although the same amount of the functional monomer was added in both preparations. These results showed the higher enrichment of the active site on the surface of 9 VBC, and the same trend was also maintained for second‐batch catalysts, regardless of the catalyst mesh size. SEM images of both batches showed that there was a higher concentration of nodules [due to the grafting of poly(VBC)] on the surfaces of the beads of 9 VBC/SE‐PSPTC and the aforementioned PPT catalysts than on the surfaces of the conventional catalysts (0 VBCs), which exhibited smooth surfaces (because of the simultaneous addition of all three monomers). This observation confirmed the enrichment of active sites on the surfaces. In the EDAX analysis, up to a depth of 0.5–1 μm, the surface chloride concentration increased from 0 VBC to 9 VBC/SE‐PSPTC and remained constant in 12 VBC and 15 VBC, first‐batch catalysts of a representative mesh size (?120 + 140). The same trend was also observed in second‐batch catalysts, indicating the enrichment of the onium group more on the surface in 9 VBC/SE‐PSPTCs. The ESCA analysis, to a depth of about 20–30Å, proved that the concentration of covalent chloride on the surface had increased from 0 VBC (15%) to 9 VBC/SE‐PSPTCs (29%) and remained constant thereafter in first‐batch catalyst; the trend was the same for second‐batch catalysts, also confirming the strong evidence of surface enrichment of the active sites. Similarly, the rate constants of different olefin addition reactions catalyzed by both batches of catalysts also increased from 0 VBC to 9 VBC and remained constant with 12 VBC and 15 VBC catalysts. The twofold increase of the rate constants, regardless of the olefins, for conventional catalysts to 9 VBC/SE‐PSPTCs confirmed the enrichment of the active sites on the surfaces. All these experimental observations proved that 50% of the active sites were successfully brought out from inside the poly(St/DVB) networks to the exterior surfaces, although same amount of VBC was added for the preparation of all the catalyst types. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 347–364, 2003     

Macroporous polystyrene-supported quaternary ammonium salt catalysts for the addition of carbon dioxide to glycidyl methacrylate

In the present study, the synthesis of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate (DOMA) from carbon dioxide and glycidyl methacrylate (GMA) was investigated in a semi-batch reactor using macroporous polystyrene beads containing pendant quaternary ammonium salt catalysts. The catalysts were prepared by partial copolymerization of styrene (ST) and divinylbenzene (DVB) with isooctyl alcohol, and then by copolymerization with vinylbenzyl chloride (VBC). Quaternization of the pendant chloromethyl groups was carried out by using trialkylamines. The catalytic activity of the macroporous polymer was influenced by VBC and isooctyl alcohol concentration, and by the structure of trialkylamine. A kinetic study was also carried out to better understand the reaction steps. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of well‐defined hairy polymer microspheres by precipitation polymerization and surface‐initiated atom transfer radical polymerization

A variety of polymer microspheres were successfully synthesized by the surface‐initiated atom transfer radical polymerization (SI‐ATRP) of monomers by using monodisperse polymer microsphere having benzyl halide moiety as a multifunctional polymeric initiator. First, a series of monodisperse polymer microsphere having benzyl chloride with variable monomer ratio (P(St‐DVB‐VBC)) were synthesized by the precipitation polymerization of styrene (St), divinylbenzene (DVB), and 4‐vinylbenzyl chloride (VBC). Next, hairy polymer microspheres were synthesized by the surface‐initiated ATRP of various monomers with P(St‐DVB‐VBC) microsphere as a multifunctional polymeric initiator. The hair length determined by the SEC analysis of free polymer was increased with the increase of M/I. These hairy polymer microspheres were characterized by SEM, FT‐IR, and Cl content measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1296–1304     

A hyper-cross-linked polystyrene with nano-pore structure

Chloromethylated polystyrene (CMPS) beads were prepared by suspension polymerization of vinylbenzyl chloride (VBC), divinylbenzene (DVB) and styrene (St) in the presence of porogen. The same feed volume ratio of DVB leads to similar cross-linking degree for all CMPS, but decreasing VBC content provided a progressively reduced content of chloromethyl groups in each CMPS. Hyper-cross-linked polystyrene (HCLPS) beads were obtained by post cross-linking reaction of CMPS in dichloroethane (DCE) containing Friedel-Crafts catalyst. The role of porogen and its influence on nano-pore structure of HCLPS were investigated. The results showed that different types of porogen had significant effect on the nano-pore structure of the final products, such as specific surface area, average pore size and total pore volume. Using the mixture of toluene and cyclohexanol as inner porogen can yield the highest specific surface area for HCLPS beads. Moreover, higher amount of VBC lead to greater specific surface area and total pore volume. It was therefore indicated that nano-pore structure of HCLPS can be controllably prepared via changing porogen type and VBC concentration. Finally, the unprecedented swelling capacity was found for the hyper-cross-linked species derived from different porogen types.     

Addition of Carbon Dioxide to Glycidyl Methacrylate over Polymer-Supported Quaternary Ammonium Salt Catalysts

In the present study, the synthesis of (2-oxo-1,3-dioxolan-4yl)methyl methacrylate from carbon dioxide and glycidyl methacrylate was investigated using polymer-immobilized quaternary ammonium salt catalysts. The catalysts were prepared by emulsion copolymerization of styrene, divinylbenzene and vinylbenzene chloride (VBC). The influence of partial polymerization time, VBC concentration, structure of the trialkyl amine and counter anion of quaternary salts on the catalytic behavior is discussed. The catalytic activity of the immobilized catalysts was maintained even up to 7 repeated experimental runs.     

Aminated polystyrene membranes for a fiber optic pH sensor based on reflectance changes accompanying polymer swelling

We have prepared toughened, porous, aminated polystyrene membranes that undergo an increase in reflectance as the pH increases from 6.8 to 8.0. Vinylbenzyl chloride (VBC) is copolymerized with divinylbenzene (DVB) in the presence of a toughening agent, Kraton G1652, a styrene-ethylene, butylene-styrene triblock copolymer, and a porogenic solvent, xylene/ dodecane. The optimum formulation for sensing is 2% DVB (mol DVB/mol VBC), 2% Kraton (g Kraton/g VBC) and 40% (v/v) 21 xylene: dodecane. Benzoyl peroxide is used as the initiator. The components are partially polymerized at 85 °C to a viscosity of 600–800 centipoise. The polymerization is then stopped by reducing the temperature. A drop of the partially polymerized solution is confined between two microscope slides and the polymerization reaction is completed. The resulting membrane is then swollen in 1,4-dioxan and reacted with diethanolamine. These membranes have been incorporated into a pH sensor based on changes in reflected intensity measured through a bifurcated bundle of twenty unbuffered 50/55 core/cladding glass-on-glass optical fibers with numerical apertures of 0.57. The resulting sensor is stable and requires inexpensive optical components, a red-emitting LED as the source and a silicon photodiode as the detector.     

Magnetic solid-phase extraction using magnetic hypercrosslinked polymer for rapid determination of illegal drugs in urine

A novel magnetic material Fe₃O₄/SiO₂/P(MAA‐co‐VBC‐co‐DVB) was prepared via the hypercrosslinking of its precursor which was produced via precipitation polymerization of methacrylic acid (MAA), vinylbenzyl chloride (VBC), and divinylbenzene (DVB) in the presence of Fe₃O₄/SiO₂ submicrospheres with the surface containing abundant reactive double bonds. The resultant sorbent was characterized by scan electron microscopy, N₂ adsorption, and Fourier transform infrared spectroscopy. It was found that this material had remarkable features such as large surface area (500 m²/g) and pore volume (0.32 cm³/g), as well as desirable chemical composition (including hydrophobic and ion‐exchange moieties). Taking advantages of the Fe₃O₄/SiO₂/P(MAA‐co‐VBC‐co‐DVB), a magnetic SPE (MSPE) coupled with capillary electrophoresis (CE) method was developed for the determination of illegal drugs in urine samples. The extraction time could be clearly shortened up to 3 min. The recoveries of these drug compounds were in the range of 84.0–123% with relative standard deviations ranging between 1.7 and 10.5%; the limit of detection was in the range of 4.0–6.0 μg/L. The proposed method is simple, effective, and low‐cost, and provides an accurate and sensitive detection platform for abused drug analysis.     

New Core-Shell Type Polymeric Supports Based on the Amberlite XAD-4 Adsorbent: A Novel Synthesis Procedure

The chloromethyl groups have been introduced into commercial S/DVB copolymer matrixes via interpenetrating polymer networks (IPN) synthesis. The procedure involves impregnation of the Amberlite XAD‐4 adsorbent, with use of the vinylbenzyl chloride (VBC) and divinylbenzene (DVB) monomers mixture, and suspension polymerization process. The syntheses were evaluated by FT‐IR spectra and SEM analyses and furthermore by chlorine content determination as well as characterization of porous structure by nitrogen adsorption at liquid nitrogen temperature. Designed synthesis approach allowed determining organic and water phases composition. Furthermore, impact of an excess of the organic phase removal method has been investigated. Basing on the obtained results it could be stated that the chloromethyl groups, derived from VBC monomer, were successfully introduced into the XAD‐4 structure. Captured SEM images revealed significant changes in the beads' surface morphology after polymerization processes. The presented studies reveal designed and executed synthesis processes, which involve the use of a proper water phase and excess of organic phase removal. Observed changes in the beads' morphology suggest that introduced functionalities are concentrated on the porous surface of the XAD‐4 adsorbent.     

Synthesis of Davankov‐type hypercrosslinked resins using different isomer compositions of vinylbenzyl chloride monomer,and application in the solid‐phase extraction of polar compounds

Two different gel‐type resins have been prepared by suspension polymerization using 2 wt % divinylbenzene (DVB) with either p‐vinylbenzyl chloride (pVBC) or a mixture of VBC isomers (～ 70% m‐; ～ 30% p‐). Significant difference in the chlorine content was observed, which was attributed to a more favored hydrolysis process when p‐VBC was used. The presence of hydroxyl groups has been confirmed by elemental microanalytical data and solid‐state ¹³C cross‐polarization/magic angle spinning (CP‐MAS) nuclear magnetic resonance (NMR) spectra. Hypercrosslinked resins were prepared from both gel‐type precursors by treatment with FeCl₃ in 1,2‐dichloroethane (DCE) at 80 °C. The resultant resins showed differences in specific surface area and degree of hydrophilicity. The performance of the hypercrosslinked resins was evaluated in solid‐phase extraction (SPE) of polar compounds, and better results were obtained for the hypercrosslinked resin prepared from p‐VBC that combines a relatively high specific surface area (908 m² g^?1) and somewhat higher oxygen content (3.96 wt % O). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1718–1728, 2005     

Preparation of a Hyper‐cross‐linked Polymer Monolithic Column and Its Application to the Sensitive Determination of Genomic DNA Methylation

A hyper‐cross‐linked polymer monolithic column, poly(methacrylatoethyl trimethyl ammonium‐co‐vinylbenzene chloride‐co‐divinylbenzene) (MATE‐co‐VBC‐co‐DVB) with phenyl and quaternary ammonium groups was successfully prepared in the current study. The prepared monolith possesses large specific surface area, narrow mesopore size distribution and high column efficiency. The poly(MATE‐co‐VBC‐co‐DVB) monolithic column was demonstrated to have strong anion exchange/reversed‐phase (SAX/RP) mixed‐mode retention for analytes on capillary liquid chromatography (cLC). By using this monolithic column, we developed a rapid and sensitive method for the detection of DNA methylation. Our results showed that six nucleobases (adenine, guanine, cytosine, thymine, uracil, and 5‐methylcytosine (5‐mC)) can be baseline separated within 15 min by electrostatic repulsion and hydrophobic interactions between nucleobases and the monolithic stationary phase. The limit of detection (LOD, signal/noise=3) of 5‐mC is 0.014 pmol and endogenous 5‐mC can be distinctly detected by using only 10 ng genomic DNA, which is comparable to that obtained by mass spectrometry analysis. Furthermore, by using the method developed here, we found that DNA methylation inhibitor 5‐azacytidine (5‐aza‐C) and 5‐aza‐2′‐deoxycytidine (5‐aza‐CdR) could induce a significant decrease of genome‐wide DNA methylation in human lung carcinoma cells (A549) and cervical carcinoma cells (HeLa).     

Gold sorption on weak base anion exchangers with aminoguanidyl groups

Two resins with different matrices, both bearing aminoguanidyl ligands, were obtained and used for gold sorption from hydrochloric acidic and from alkali solutions. Resin 1 was a aminoguanidine derivative of poly(acrylonitril-co-vinyl acetat-co-divinyl benzene) terpolymer (AN/VA/DVB), (67:27:10 wt.%), and Resin 2 the same derivative of gel expanded poly(vinylbenzyl chloride-co-divinylbenzene) copolymer (VBC/DVB). The resins sorption capacity and sorption isotherms of both resins were determined for AuCl₄⁻ and Au(CN)₂⁻ anions. Resin 2 revealed the best sorption of gold from acidic and alkali solutions: 68 and 23 mg/g, respectively. The effect of the HCl concentration on AuCl₄⁻ removal from solution was investigated. Gold was recovered quantitatively from both resins using a 5% thiourea solution in 0.1 HCl. Both resins remained ability of multiple gold sorption and desorption under acidic conditions.     

Selective resins,synthesis and sorption for precious metals

Resins based on vinylbenzyl chloride (VBC) and divinylbenzene (DVB) copolymer were synthesised and used for preconcentration and separation of Au, Pt and Pd from hydrochloric acid solutions. Resulted resins show functionality concentration up to 5,8 mmol/g. The acidity and interference of other ions on the resins sorption were discussed. The sorption capacities of gold, platinum and palladium from hydrochloric solutions reaches to 85, 100 and 60 mg/g and distribution coefficients achieve 50 000 value. Recovery of noble metals revealed average of 60-98% from mulitcomponent solutions.     

Optimisation of polystyrene resin-supported Pt catalysts in room temperature, solvent-less, oct-l-ene hydrosilylation using methyldichlorosilane

Six precursor resins with systematic variation of porous parameters were prepared by suspension polymerisation using specific compositions of divinylbenzene, styrene vinylbenzyl chloride (VBC) and 2-ethylhexan-l-ol (a porogen). Surface areas from N(2) sorption and BET analysis were approximately 2-170 m(2)g-(1). The VBC content in each case was 38 mol% and these groups were aminated using the sodium salt of trimethylethylene diamine. Pt was introduced onto each resin at three different loadings (approximately 0.03, approximately 0.2 and approximately 0.4 mmol g-(1)) by appropriate manipulation of K(2)PtCl(6). The matrix of 18 resin-supported Pt complexes was then assessed for catalytic activity in the room temperature, solvent-less, hydrosilylation of oct-l-ene using methyldichlorosilane such that alkene: silane: Pt ratio was fixed at 2:1:1x10(-3). Though all the catalysts showed activity lower than that of homogeneous Speier s catalyst, most were sufficiently active to be potentially valuable heterogeneous catalysts in the laboratory, and indeed the plant. The most lightly loaded resins proved to be the least active. The remainder were recycled 5 times, and the best performers, the most highly loaded species, a further 5 times making 10 consecutive uses in all. A strong dependence on the porous structure of the resins was demonstrated with the activity rising systemically with the surface area. The two highest surface area highest loaded species displayed good activity even when used for the tenth time. The level of concurrent alkene isomerisation observed was very low throughout (<1%) making these heterogeneous species very selective as well as highly active. Overall the derived catalysts are excellent candidates for use in the research laboratory, and with further development could also be valuable in continuous processes.     

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalyst for selective oxidation of toluene to benzoic acid with H2O2

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalysts were developed for the selective oxidation of toluene to benzoic acid in the presence of H₂O₂. The influence of the DVB content on the capacity of immobilized Fe(III) and on the catalytic activities of the polymeric complexes was investigated. The extent of Fe(III) uptake by the copolymers varied slightly with the concentration of DVB. The catalytic activities generally increase with increasing degree of crosslinker from 2 to 10% and decrease further with increasing the DVB content. Under the optimal conditions (80 °C, 6 h), the catalyst containing 10% DVB was found to be highly efficient in conversion of toluene to benzoic acid with 90% conversion and 96% selectivity.     

Synthesis of insoluble polystyrene‐supported flavins and their catalysis in aerobic reduction of olefins

2′,4′‐p‐Vinylbenzylideneriboflavin ( 2′,4′‐PVBRFl ) was prepared as a flavin‐containing monomer and copolymerized with divinylbenzene and styrene or its p‐substituted derivatives such as 4‐acetoxystyrene, 4‐vinylbenzyl alcohol, and 4‐vinylbenzoic acid to give the corresponding non‐functionalized and functionalized PS‐DVB‐supported flavins PS(H)‐DVB‐Fl , PS(OAc)‐DVB‐Fl , PS(CH₂OH)‐DVB‐Fl , and PS(COOH)‐DVB‐Fl , respectively. PS(OH)‐DVB‐Fl was also prepared by hydrolysis of PS(OAc)‐DVB‐Fl under basic conditions. These novel flavin‐containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)‐DVB‐Fl , and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)‐DVB‐Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)‐DVB‐Fl and PS(COOH)‐DVB‐Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non‐supported flavin catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1706–1713     

In-column “click” preparation of hydrophobic organic monolithic stationary phases for protein separation

Two types of macroporous organic polymer monoliths based on glycidyl methacrylate (GMA), 4-vinylbenzyl chloride (VBC) and divinylbenzene (DVB) were prepared inside stainless-steel tubes. Azide functionalities were firstly introduced on the surfaces of poly(GMA-co-DVB) and poly(VBC-co-DVB) monoliths to provide reactive sites for click chemistry. With the application of copper(I)-catalyzed (3 + 2) azide-alkyne cycloaddition, an in-column click-modification approach for covalent attachment of long alkyl chains onto polymer monoliths was developed. The column morphology and surface chemistry of the fabricated monolithic columns were characterized by the scanning electron microscopy, mercury intrusion porosimeter, Fourier transform infrared spectroscopy, and elemental analyses, respectively. The chromatographic performances of the “clicked” stationary phases were demonstrated with the high separation efficiency for a variety of proteins within 4 min.     

磁性聚苯乙烯-氯甲基苯乙烯材料的合成及其对蒽的吸附性能研究

采用4-氯甲基苯乙烯(VBC)为单体,二乙烯基苯为交联剂(DVB),以磁性γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)修饰硅胶微球为核,在偶氮二异丁腈(AIBN)引发下,以甲苯和聚乙二醇2000的混合溶液(质量比1∶2)为联合致孔剂,原位聚合制备了磁性聚苯乙烯-氯甲基苯乙烯材料(Fe3O4@Si O2@DVBVBC)。通过傅立叶红外光谱(FT-IR)、X-射线衍射(XRD)和氮气物理吸附对该材料的结构和组成特性进行了表征。以蒽为考察对象,对制备材料的吸附性能进行了考察,发现单体和交联剂的质量比对材料的吸附能力影响较大。当单体和交联剂的质量比为1∶4时,对蒽的吸附性能最佳。材料的孔结构会影响吸附平衡时间。制备的材料对蒽能够在30 min内达到吸附平衡且吸附率达95%。该材料对多环芳烃化合物的吸附主要依靠疏水作用。吸附动力学研究表明,材料对蒽的吸附性能对准一级动力学方程具有较好的拟合程度。采用2 mL乙腈涡旋15 min可将99%的蒽洗脱下来。     

稀土络合催化苯乙烯均聚及其与二乙烯苯共聚

应用稀土化合物:环烷酸钕Nd(naph)_3和二(2-乙基己基)磷酸钕Nd·(P_(204)_3分别与三异丁基铝Al(i-Bu)_3组成络合催化剂引发苯乙烯均聚及其与二乙烯苯共聚。适宜的聚合温度为50℃:[Nd]=3×10~(-5)mol/ml;[M]=3×10~(-3)mol/ml;Al/Nd=10(摩尔比),并且催化剂按以下次序配制:钕化合物→溶剂→苯乙烯→三异丁基铝,苯乙烯的转化率在90％以上。溶剂种类及聚合条件不同,制得的聚苯乙烯可为白色或黄色粉末状无定形聚合物,分子量几百至上万。聚合体系中添加PeCl_3能抑制黄色产生。在共聚反应中,二乙烯苯比苯乙烯显示较高的反应活性。     

Synthesis of graft copolymers with polyisobutylene branch chains

<正>The copolymerization of 4-vinylbenzyl chloride(VBC) and vinyl acetate(VAC) was carried out in toluene at 75℃via radical polymerization using 2,2'-azo-bis-(isobutyronitrile)(AIBN) as an initiator.The random copolymers of poly(4-vinylbenzyl chloride-co-vinyl acetate)(P(VBC-co-VAC)) with number average molecular weight(M_n) from 2000 to 6900,relatively narrow molecular weight distribution(MWD,M_w/M_n ca.2.0) and with different copolymer composition of 4-vinylbenzyl chloride(VBC) from 17 mol%to 62 mol%could be obtained.The P(VBC-co-VAC) copolymers with an average number of 7 to 13 initiating sites of benzyl chloride per macromolecule could be used for the cationic polymerization of isobutylene(IB).The cationic polymerizations of IB were further conducted by using P(VBC-co-VAC) copolymers as macroinitiators in conjunction with TiCl_4 at -40℃in CH_2Cl_2.The effects of VBC/TiCl_4(molar ratio) on monomer conversion,M_n and MWD of the resultant copolymers were investigated under 3 sets of conditions.It is found that P(VBC-co-VAC)-g-PIB copolymers with relatively narrow MWD(M_w/M_n ca.2.0) and with terminal tert-chlorine functional groups in branched PIB chains could be successfully synthesized when VBC/TiCl_4(molar ratio) was set in the range from 0.10 to 1.12.The unimodal GPC curve of the P(VBC-co-VAC)-g-PIB copolymers by RI detector was almost in harmony with the GPC curve by UV detector.The TEM image of the P(VBC-co-VAC)-g-PIB copolymer stained by RuO indicated that the copolymer formed a two-phase morphology with P(VBC-co-VAC)-rich domains of 20-100 nm in size tethered by PIB branch segments.     

Polystyrene with dendritic branching by convergent living anionic polymerization. II. Approach using vinylbenzyl chloride

Vinylbenzyl chloride (VBC) has been used as a coupling agent in Convergent Living Anionic Polymerization to produce polymers with dendritic branching. The slow addition of a stoichiometric amount of VBC to living polystyrene chains allows the coupling to proceed through macromonomer formation followed by vinyl addition. Changing the reaction conditions produced two types of structures. Star‐shaped polymers with a hyperbranched core were made by the continuous slow addition of VBC alone, and chain‐extended hyperbranched structures with varied molecular weight between branch points were produced by the slow addition of VBC mixed with different amounts of styrene monomer. The extent of growth of the two different types of structures ranged from 2.4 to 2.6 generations for the case of VBC added alone, corresponding to an average of 5.3 to 6.1 arms attached to the hyperbranched core, and from 3.2 to 4.2 generations for polymers produced from the addition of VBC mixed with styrene. Relatively low polydispersities were obtained for all samples. The highly branched nature of the polymers was reflected in the low intrinsic viscosity relative to linear polystyrene and in the dependence of glass‐transition temperature on the molecular weight relative to the number of end groups. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4289–4298, 2000