An activated neodymium‐based catalyst for styrene polymerization

Coordination polymerization of styrene with a ternary catalyst system composed of catalyst neodymium tricarboxylate (Nd), co‐catalyst Al(i‐Bu)₃ (Al) and chlorinating agent trichloroethane (Cl) was carried out in cyclohexane. The effects of the catalyst system preparation procedure and of the reaction conditions on catalytic activity, molecular weight and molecular weight distribution of the resultant polymers were investigated. The catalytic activity depended mainly on the molar ratios of Al/Nd and of Cl/Nd and on the ageing temperature and polymerization temperature. High polymerization conversion and high catalytic activity could be obtained at high Al/Nd ratios and/or at high ageing temperature. The catalyst system exhibited high activity of 8.32 × 10⁴ g polystyrene (mol Nd h)^?1 at 50 °C. The molecular weight of the polymers obtained reached high weight‐average (M_w) values (M_w = 4.35 × 10⁵ g mol^?1) when Al/Nd = 8, but relatively low values (6000–11 000 g mol^?1) at high Al/Nd ratios. Copyright © 2005 Society of Chemical Industry     

Copolymerization of butadiene with styrene using a rare‐earth metal compound – dialkylmagnesium – halohydrocarbon catalytic system

Copolymerizations of butadiene (Bd) with styrene (St) were carried out with catalytic systems composed of a rare‐earth compound, Mg(n‐Bu)₂ (di‐n‐butyl magnesium) and halohydrocarbon. Of all the rare earth catalysts examined, Nd(P₅₀₇)₃–Mg(n‐Bu)₂–CHCl₃ showed a high activity in the copolymerization under certain conditions: [Bd] = [St] = 1.8 mol l^?1, [Nd] = 6.0 × 10^?3 mol l^?1, Mg/Nd = 10, Cl/Nd = 10 (molar ratio), ageing for 2 h, copolymerization at 50 °C for 6–20 h. The copolymer of butadiene and styrene obtained has a relatively high styrene content (10–30 mol%), cis‐1,4 content in butadiene unit (85–90%), and molecular weight ([η] = 0.8–1 dL g^?1). Monomer reactivity ratios were estimated to be r_Bd = 36 and r_St = 0.36 in the copolymerization. © 2002 Society of Chemical Industry     

Synthesis and mechanical properties of high impact polystyrene with in situ bulk polymerization toughened by one‐pot Nd‐based styrene–isoprene–butadiene terpolymer rubber

High impact polystyrene (HIPS) resins were obtained with in situ bulk polymerization toughened by styrene–isoprene–butadiene terpolymer rubber (SIBR). SIBR prepolymer was prepared through selective polymerization of styrene (St), isoprene (Ip), and butadiene (Bd) in St with [Nd]/[Al]/[Cl] catalyst. Nd‐based catalyst exhibited more favorable activity toward conjugated diene other than St, resulting in St solution of random SIBR with high cis‐1,4 stereoregularity and low St content, which was directly exposed to the free radical polymerization of St to generate HIPS. Effect of toughened rubber and the initiators [difunctional (D2) and trifunctional (T3)] were examined to attain HIPS possessing mechanical properties as follow: impact strength, 0.9–24.8 kJ/m²; tensile strength, 16.0–27.5 MPa; and elongation at break, 7.4–107.0%. Increasing SIBR matrix in HIPS improved the impact strength and decreased tensile strength. The fracture surface morphologies of HIPS specimens were studied by notched impact tests and scanning electron microscopy (SEM), illustrating that the incremental SIBR matrix presented synergistic toughening effect of crazing to enhance the ductile fracture behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43979.     

Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems

Styrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (M_w/M_n < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C¹ in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of Pst‐b‐PDMS‐b‐PSt copolymers by atom transfer radical polymerization

Polystyrene‐b‐poly(dimethylsiloxane)‐b‐polystyrene (Pst‐b‐PDMS‐b‐PSt) triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). Commercially available difunctional PDMS containing vinylsilyl terminal species was reacted with hydrogen bromide, resulting in the PDMS macroinitiators for the ATRP of styrene (St). The latter procedure was carried out at 130°C in a phenyl ether solution with CuCl and 4, 4′‐di (5‐nonyl)‐2,2′‐bipyridine (dNbpy) as the catalyzing system. By using this technique, triblock copolymers consisting of a PDMS center block and polystyrene terminal blocks were synthesized. The polymerization was controllable; ATRP of St from those macroinitiators showed linear increases in M_n with conversion. The block copolymers were characterized with IR and ¹H‐NMR. The effects of molecular weight of macroinitiators, macroinitiator concentration, catalyst concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3764–3770, 2004     

Synthesis of 1,3‐benzodioxole end‐functionalized polymers via reversible addition–fragmentation chain transfer polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene was carried out in the presence of a novel RAFT reagent, bearing 1,3‐benzodioxole group, benzo [1,3]dioxole‐5‐carbodithioic acid benzo [1,3]dioxol‐5‐ylmethyl ester (BDCB), to prepare end‐functionalized polystyrene. The polymerization results showed that RAFT polymerization of styrene could be well controlled. Number–average molecular weight (M_n(GPC)) increased linearly with monomer conversion, and molecular weight distributions were narrow (M_w/M_n < 1.4). The successful reaction of chain extension and analysis of ¹H NMR spectra confirmed the existence of the functional 1,3‐benzodioxole group at the chain‐end of polystyrene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3535–3539, 2006     

The terpolymer of neodymium‐catalyzed styrene,isoprene, and butadiene: Efficient synthesis of integral rubber containing atactic styrene–styrene sequences and high Cis‐1,4 polyconjugated olefins

The present study focuses on the terpolymer of styrene (St), isoprene (Ip), and butadiene (Bd) synthesized together in cyclohexane at 70°C with neodymium (Nd) compound, alkylaluminum, and chlorinating agent (Cl) rare earth cocatalyst system. The resultants possessed atactic St–St sequences and high cis‐1,4 polyconjugated olefins in macromolecular chains besides controllable composition. The composition of the St–Ip–Bd terpolymers and molecular weight (M_w), molecular weight distribution (M_w/M_n) were controlled through the adjustment of Nd compound, alkylalumium, monomers feed ratio (St/Ip/Bd), and [Nd]/[monomers]. With the inventory rating of St raised from 15% to 55%, the content of St in the terpolymers got increased from 2% to 15%. And the content of the Ip segments and Bd segments in the terpolymers increased from 33% to 56% and from 28% to 54%, respectively, with the proportion of Ip/Bd varied from 1/2 to 2/1. As the [Nd]/[monomers] varied from 1.0 × 10^?3 to 5.0 × 10^?4, the molecular weight increased from 1.3 × 10⁴ to 2.7 × 10⁴. According to the proton nuclear magnetic resonance (¹H‐NMR) and ¹³C‐NMR, it was proved that both microstructures of polybutadiene segments and polyisoprene segments were high cis‐1,4‐configuration. A single glass‐transition temperature was observed in the differential scanning calorimetry curve. POLYM. ENG. SCI., 54:1858–1863, 2014. © 2013 Society of Plastics Engineers     

Synthesis of high molecular weight copolymer of styrene and butadiene bearing high 1,4‐cis butadiene unit from copolymerization with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with CpTiCl₃/methylaluminoxane (MAO) catalyst in the presence or absence of chloranil (CA) was investigated. The CpTiCl₃/MAO catalyst showed a high activity for the copolymerization of St with Bd. The 1,4‐cis contents in the Bd units for the copolymerization of St and Bd with the CpTiCl₃/MAO catalyst was observed, and the 1,4‐cis content was optimum at a MAO/Ti mole ratio of around 225. The effect of the polymerization temperature on the copolymerization was noted, as was the effect of the 1,4‐cis microstructure in the Bd units for the copolymerization of St and Bd. The addition of CA to the CpTiCl₃/MAO catalyst was found to influence the molecular weight of the copolymer. The high weight‐average molecular weight copolymer (M_w = ca. 50 × 10⁴) consisting of mainly a 1,4‐cis microstructure of Bd units (1,4‐cis = 80.0%) was obtained from the copolymerization with the CpTiCl₃/MAO catalyst in the presence of CA (CA/Ti mole ratio = 1) at 0°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2942–2946, 2003     

Polymerization of styrene using novel bispyrazolylimine dinickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with a series of bispyrazolylimine dinickel (II) complexes of bis‐2‐(C₃HN₂(R₁)₂‐3,5)(C(R₂) = N(C₆H₃(CH₃)₂‐2,6)Ni₂Br₄ (complex 1 : R₁ = CH₃, R₂ = Ph; complex 2 : R₁ = CH₃, R₂ = 2,4,6‐trimethylphenyl; complex 3 : R₁ = R₂ = Ph; complex 4 : R₁ = Ph, R₂ = 2,4,6‐trimethylphenyl) in the presence of methylaluminoxane (MAO) was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time, and catalyst concentration on catalytic activity and molecular weight of the polystyrene were investigated in detail. The influence of the bulkiness of the substituents on polymerization activity was also studied. All of the four catalytic systems exhibited high activity (up to 10.50 × 10⁵ gPS/(mol Ni h)) for styrene polymerization and provide polystyrene with moderate to low molecular weights (M_w = 4.76 × 10⁴–0.71 × 10⁴ g/mol) and narrower molecular weight distributions about 2. The obtained polystyrene was characterized by means of FTIR, ¹H‐NMR, and ¹³C‐NMR techniques. The results indicated that the polystyrene was atactic polymer. The analysis of the end groups of polystyrene indicated that styrene polymerization with bispyrazolylimine dinickel complexes/MAO catalytic systems proceeded through a coordination mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis and characterization of poly(n‐butyl methacrylate)‐b‐polystyrene diblock copolymers by atom transfer radical emulsion polymerization

Poly(n‐butyl methacrylate) (PBMA)‐b‐polystyrene (PSt) diblock copolymers were synthesized by emulsion atom transfer radical polymerization (ATRP). PBMA macroinitiators that contained alkyl bromide end groups were obtained by the emulsion ATRP of n‐butyl methacrylate with BrCH₃CHCOOC₂H₅ as the initiator; these were used to initiate the ATRP of styrene (St). The latter procedure was carried out at 85°C with CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipyridine as the catalyst and polyoxyethylene(23) lauryl ether as the surfactant. With this technique, PBMA‐b‐PSt diblock copolymers were synthesized. The polymerization was nearly controlled; the ATRP of St from the macroinitiators showed linear increases in number‐average molecular weight with conversion. The block copolymers were characterized with IR spectroscopy, ¹H‐NMR, and differential scanning calorimetry. The effects of the molecular weight of the macroinitiators, macroinitiator concentration, catalyst concentration, surfactant concentration, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP are also reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2123–2129, 2005     

α‐Bis and α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polymers by atom transfer radical polymerization using 1,1‐bis[(4‐dimethylamino)phenyl]ethylene as tertiary diamine initiator precursor and functionalizing agent

The quantitative syntheses of α‐bis and α,ω‐tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1‐diphenylethylene derivative, 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1‐bromoethyl)benzene with 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number‐average molecular weight (M_n) and narrow molecular weight distribution (M_w/M_n) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non‐aqueous titration measurements. Copyright © 2012 Society of Chemical Industry     

Styrene–butadiene block copolymer with high cis‐1,4 microstructure

The sequential block copolymerization of styrene (St) and butadiene (Bd) was carried out with an activated rare earth catalyst composed of catalyst neodymium tricarboxylate (Nd), cocatalyst Al(i‐Bu)₃ (Al), and chlorinating agent (Cl). The microstructure, composition, and morphology of the copolymer were characterized by FTIR, ¹H NMR, ¹³C NMR, and TEM. The results show that styrene–butadiene diblock copolymer with high cis‐1,4 microstructure of butadiene units (～ 97 mol %) was synthesized. The cis‐selectivity for Bd units was almost independent on the content of styrene units in the copolymer ranging from 18.1 mol % to 29.8 mol %. The phase‐separated morphology of polystyrene (PS) domains of about 40 nm tethered by the elastomeric polybutadiene (PB) segments is observed. The PS‐b‐cis‐PB copolymer could be used as an effective compatilizer for noncompatilized binary PS/cis‐PB blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of poly(styrene‐b‐2‐hydroxyethyl acrylate) block copolymer using reverse iodine transfer polymerization

Reverse iodine transfer polymerizations (RITP) of 2‐h‐ydroxyethyl acrylate (HEA) were performed in N,N‐dimethylformamide at 75°C using AIBN as initiator. Poly(2‐hydroxyethyl acrylate) (PHEA) with M_n = 3300 g mol^?1 and M_w/M_n <1.5 were obtained. Homopolymerization of styrene in RITP was also carried out under similar conditions using toluene as solvent. The resulting iodo‐polystyrene (PS‐I) with (M_{n, SEC} = 607 g mol^?1, polydispersity index (PDI) = 1.31) was used as a macroinitiator for the synthesis of amphiphilic block copolymers based on HEA with controlled well‐defined structure. Poly(styrene‐b‐2‐hydroxyethyl acrylate) (PS‐b‐PHEA) with M_n = 13,000 g mol^?1 and polydispersity index (M_w/M_n) = 1.4 was obtained, copolymer composition was characterized using ¹H‐NMR and FTIR, whereas SEC and gradient HPLC were used to confirm the formation of block copolymer and the living character of polymer chains. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Graft copolymerization of thiophene onto polystyrene synthesized via nitroxide‐mediated polymerization and its polymer − clay nanocomposite

A new strategy for graft copolymerization of thiophene onto a polystyrene (PSt) backbone by a multi‐step process is suggested and the effects of an organoclay on the final properties of the graft copolymer sample are described. For this purpose, first poly(styrene‐co‐4‐chloromethyl styrene) [P(St‐co‐CMSt)] was synthesized via nitroxide‐mediated polymerization. Afterwards, the chlorine groups of P(St‐co‐CMSt) were converted to thiophene groups using the Kumada cross‐coupling reaction and thiophene‐functionalized PSt multicenter macromonomer (ThPStM) was synthesized. The graft copolymerization of thiophene monomers onto PSt was initiated by oxidized thiophene groups in the PSt chains after addition of ferric chloride (FeCl₃), an oxidative catalyst for polythiophene synthesis, and FeCl₃‐doped polythiophene was chemically grafted onto PSt chains via oxidation polymerization. The graft copolymer obtained was characterized by ¹H NMR and Fourier transform infrared spectroscopy, and its electroactivity behavior was verified under cyclic voltammetric conditions. Finally, PSt‐g‐PTh/montmorillonite nanocomposite was prepared by a solution intercalation method. The level of dispersion of organoclay and the microstructure of the resulting nanocomposite were probed by means of XRD and transmission electron microscopy. It was found that the addition of only a small amount of organoclay (5 wt%) was enough to improve the thermal stabilities of the nanocomposite.© 2013 Society of Chemical Industry     

Nitroxide‐mediated ‘living’ free radical synthesis of novel rod–coil diblock copolymers with polystyrene and mesogen‐jacketed liquid‐crystal polymer segments

The synthesis of rod–coil diblock copolymers with narrow polydispersity was achieved for the first time by TEMPO‐mediated ‘living’ free radical polymerization of styrene and 2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene. The block architecture of the two diblock copolymers thus prepared, MPCS‐block‐St (5400/2400) and MPCS‐block‐St (10 800/8700), was confirmed by GPC, ¹H and ¹³C NMR and DSC studies. The liquid‐crystalline behaviour of the copolymers was studied by DSC and polarized optical microscope. It was observed that both copolymers showed two distinct glass transitions, corresponding to polystyrene and poly(‐2,5‐bis[(4‐methoxyphenyl)oxycarbonyl]styrene). Above the glass transition temperature of rigid block, liquid‐crystalline phase was formed. The clearing point of the phase is higher than the polymer decomposition temperature. © 2000 Society of Chemical Industry     

Synthesis and characterization of PBMA‐b‐PSt‐b‐PBMA triblock copolymers by atom transfer radical emulsion polymerization

Poly(n‐butyl methacrylate)‐b‐polystyrene‐b‐poly(n‐butyl methacrylate) (PBMA‐b‐PSt‐b‐PBMA) triblock copolymers were successfully synthesized by emulsion atom transfer radical polymerization (ATRP). Difunctional polystyrene (PSt) macroinitiators that contained alkyl chloride end‐groups were prepared by ATRP of styrene (St) with CCl₄ as initiator and were used to initiate the ATRP of butyl methacrylate (BMA). The latter procedure was carried out at 85°C with CuCl/4,4′‐di (5‐nonyl)‐2,2′‐bipyridine (dNbpy) as catalyst and polyoxyethylene (23) lauryl ether (Brij35) as surfactant. Using this technique, triblock copolymers consisting of a PSt center block and PBMA terminal blocks were synthesized. The polymerization was nearly controlled, ATRP of St from those macroinitiators showed linear increases in the number average molecular weight (Mn) with conversion. The block copolymers were characterized with infrared (IR) spectroscopy, hydrogen‐1 nuclear magnetic resonance (¹HNMR), and differential scanning calorimetry (DSC). The effects of the molecular weight of macroinitiators, concentration of macroinitiator, catalyst, emulsion, and temperature on the polymerization were also investigated. Thermodynamic data and activation parameters for the ATRP were also reported. POLYM. ENG. SCI., 45:1508–1514, 2005. © 2005 Society of Plastics Engineers     

Preparation magnetite core/coated with polystyrene shell hybrid materials via redox interfacial‐initiated emulsion polymerization

In this article, we describe a novel redox interfacial‐initiated micro‐emulsion polymerization (RIEP) to prepare hollow polystyrene microspheres with magnetite nanoparticles (MPs) core and polystyrene (PS) shell (MPs‐PS) under ambient pressure. The emulsion was constituted water‐based magnetic ferro‐fluid as dispersing phase and organic solvent and styrene (St) as continuous phase. Cumene hydroperoxide (CHPO)/iron (II) sulfates (FS) as the redox initiation system, the water‐soluble FS acted as the reducing component and the oil‐soluble CHPO as the oxidant component of the redox initiation system. Therefore, the primary radicals are produced mainly at the oil/water interface to initiate the polymerization of styrene to form polymer shell. The final products thoroughly characterized by X‐ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, field‐emission scanning electron microscopy, thermogravimetric analysis, dynamic light scattering, and X‐ray photoelectron spectroscopy, which showed the formation of hollow magnetite/polystyrene nanocomposite microspheres. Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer. The saturation magnetization (M_s), remanent magnetization (M_r) and coercivity (H_c) is 30 emu/g, 15 emu/g and 370 Oe, respectively. The results revealed that the hybrid materials microspheres were super‐paramagnetic. POLYM. COMPOS., 31:1846–1852, 2010. © 2010 Society of Plastics Engineers     

Synthesis of well‐defined polystyrene by radical polymerization using 1,1,2,2‐tetraphenyl‐1,2‐ethanediol/feCl3/PPh3 initiation system

Well‐defined polystyrenes with an α‐hydrogen atom and an ω‐chlorine atom end groups and narrow polydispersity (M_n = 2500–4200, M_w/M_n = 1.29–1.48) have been synthesized by a free radical polymerization process using a 1,1,2,2‐tetraphenyl‐1,2‐ethanediol (TPED)/FeCl₃/PPh₃ initiation system. The end groups were monitored by ¹H nuclear magnetic resonance spectroscopy. When the polymerization of styrenes in bulk carried out at 120°C and the ratio of [St]₀ : [TPED]₀ : [FeCl₃]₀ : [PPh₃]₀ was 200 : 1 : 4 : 12, the polymerization exhibited some living/controlled radical polymerization characteristics. The polymerization mechanism was proposed proceeding via a reverse atom transfer radical polymerization (ATRP). Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed chain extension polymerization in the presence of CuCl/2,2′‐bipyridine catalyst system via a conventional ATRP process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1607–1613, 2000     

Polymerization of 1,3‐dienes containing functional groups: 8. Free‐radical polymerization of 2‐triethoxysilyl‐ 1,3‐butadiene

The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (R_p) was found to be R_p = k[AIBN]^0.5[ 1 ]^1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol^?1. The monomer reactivity ratios in copolymerization with styrene were r ₁ = 2.65 and r_st = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry     

Molecular architectures of four‐arm star‐shaped styrene‐butadiene copolymer

To understand the molecular architectures of styrene‐butadiene four‐arm star (SBS) copolymers, a size exclusion chromatography combined with laser light scattering (SEC‐LLS) has been used to determine their weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^1/2), and a new method for the establishment of the Mark‐Houwink equation from one sample has been developed. Based on the Flory viscosity theory, we successfully have reduced the 〈S²〉^1/2 values of numberless fractions estimated from many experimental points in the SEC chromatogram to intrinsic viscosities ([η]). For the first time, the dependences of 〈S²〉^1/2 and [η] on M_w for the four‐arm star SBS in tetrahydrofuran at 25°C were found, respectively, to be 〈S²〉^1/2 = 2.62 × 10^?2 M (nm) and [η] = 3.68 × 10^?2 M (mL/g) in the M_w range from 1.4 × 10⁵ to 3.0 × 10⁵. From data of [η] and 〈S²〉^1/2 for linear and star SBS, we have obtained the information about the branching, namely, the ratios (g and g′) of 〈S²〉 and [η] for star SBS to that of the linear SBS of the same molecular weight, which agree with theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 961–965, 2005