Effect of amines on vinyl polymerization initiated by chromous acetate–alkyl halide systems

The radical polymerization of vinyl monomers initiated by Cr²⁺–RX in the presence of various amines was studied in DMF at 30°C. Polyamines able to form the chelate complex with Cr²⁺ accelerated the rate of polymerization of styrene in the following order: ethanolamine > triethylenetetramine > diethylenetriamine > ethylenediamine. However, aliphatic monoamine, hexamethylenediamine, and aromatic diamine did not have any effect on the polymerization. These results suggest that the effect of multidentate ligands may be associated with chelating effects which affect the electron transfer ability of the metal complex. An apparent activation energy of 8.2 kcal/mole for the polymerization of styrene was obtained in the presence of ethanolamine. With the Cr²⁺–CHCl₃ system, on addition of ethanolamine, the polymerization of methyl methacrylate was accelerated, and acrylonitrile and vinyl chloride, could be polymerized.     

Graft copolymerization of styrene on rubber containing halogen by chromous acetate

Graft copolymerization of styrene on rubber containing chlorine, e.g., chloroprene rubber (CR) and chlorosulfonated polyethylene (Hypalon), with chromous acetate (Cr²⁺) was carried out in DMF–THF mixed solvent at 50°C. From the kinetic study, the normal kinetic orders with respect to the concentration of initiator and monomer were obtained at low concentrations of CR, but the deviation from conventional first-order to second-order kinetics with respect to the monomer concentration was observed at high CR concentrations: R_p ∝ [CR]^1/2 [Cr₂₊]^1/2[styrene]¹ (at low CR concentration); R_p ∝ [CR]^1/2 [Cr₂₊]^1/2[styrene]¹ (at high CR concentration). This result was explained in terms of the high viscosity of the reaction medium due to the rubber contained in solution. An initiation site along the polymer chain was assumed from the graft copolymerization with three kinds of CR having different microstructures. The results of fractionation of obtained polymer showed that the graft efficiency was high but a large amount of gel was formed.     

New neutral Ni(II)- and Pd(II)-based initiators for polymerization of styrene

Neutral nickel and palladium σ-acetylide complexes [Ni(CCPh)₂(PBu₃)₂] and [Pd(CCPh)₂(PBu₃)₂] are novel initiators for the polymerization of styrene in CHCl₃ over a range of polymerization temperature from 40 to 60 °C. Between them, the nickel catalyst exhibited much higher activity than the palladium catalyst. The polystyrene obtained with Ni(II) initiator was a syndio-rich atactic polymer and its weight-average molecular weight reached 279 000. The mechanism of the polymerization was discussed and a radical mechanism was proposed.     

Polymerization of 1,3‐dienes with functional groups. II. Free‐radical polymerization of N‐(2‐methylene‐3‐butenoyl)piperidine

The free‐radical homopolymerization and copolymerization behavior of N‐(2‐methylene‐3‐butenoyl)piperidine was investigated. When the monomer was heated in bulk at 60 °C for 25 h without an initiator, about 30% of the monomer was consumed by the thermal polymerization and the Diels–Alder reaction. No such side reaction was observed when the polymerization was carried out in a benzene solution with 1 mol % 2,2′‐azobisisobutylonitrile (AIBN) as an initiator. The polymerization rate equation was found to be R_p ∝ [AIBN]^0.507[M]^1.04, and the overall activation energy of polymerization was calculated to be 89.5 kJ/mol. The microstructure of the resulting polymer was exclusively a 1,4‐structure that included both 1,4‐E and 1,4‐Z configurations. The copolymerizations of this monomer with styrene and/or chloroprene as comonomers were carried out in benzene solutions at 60 °C with AIBN as an initiator. In the copolymerization with styrene, the monomer reactivity ratios were r₁ = 6.10 and r₂ = 0.03, and the Q and e values were calculated to be 10.8 and 0.45, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1545–1552, 2003     

Initiation of the stereospecific polymerization of p-chlorophenylglycidyl and phenylglycidyl ethers by the Al(OiPr)3 + ZnEt2 (1:1) initiator system

The Al(OiPr)₃ + ZnEt₂ (1:1) system has been found to be an efficient initiator of the polymerization of phenylglycidyl ethers. About 40–60% of the polymer obtained was an isotactic polymer fraction (ca. 80% of iso diads). By using aluminum isopropoxide containing C¹⁴, the amount of linear polymer molecules terminated by isopropoxide groups was shown not to exceed 50%. IR spectrophotometric studies of the structure of the initiator system showed that its components form a complex compound by an exchange of substituents between the aluminum and zinc atoms.     

Effect of stirring on cellulose graft copolymerization. IV. Grafting of styrene by initiator systems involving potassium persulfate

Dissolving pulp and its partially xanthated derivative were grafted with styrene, using either the Fe²⁺?K₂S₂O₈ redox system of potassium persulfate alone as initiators. The conversion of styrene to both copolymer and homopolymer was found to be influenced by agitator speed. The effect of stirring was much more pronounced with the xanthated substrate in that a welldefined conversion maximum was observed at the same agitation speed for both total polymer and copolymer. Grafting onto dissolving pulp with the redox initiator also showed a maximum, but a maximum total polymer and maximum copolymer were located at different agitator speeds. Grafting of styrene onto dissolving pulp initiated by potassium persulfate was almost independent of stirring in the 0–910 rpm range.     

Agitation requirement for synthesis of micron-sized monodisperse polymer particles in soap-free polymerization method

Single-stage polymerization recently proposed for producing micron-sized polymer particles in aqueous media by Gu, Inukai and Konno (2002) was carried out under the control of agitation with styrene monomer, an amphoteric initiator, 2,2′-azobis [N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate and a pH buffer NH₃/NH₄Cl at a monomer concentration of 1.1 kmol/m³ H₂O, an initiator concentration of 10 mol/m³ H₂O and a buffer concentration of [NH₃] = [NH₄Cl] = 10 mol/m³ H₂O. In the polymerizations, impeller speed was ranged from 300 to 500 rpm to satisfy complete dispersion of the monomer phase and not to introduce the gas phase from the free surface. Polymerization experiments under steady agitation indicated that impeller speed was an important factor for size distribution of polymer particles. An increase in impeller speed promoted particle coagulation during the polymerization to enlarge the average size of polymer particles but widen the size distribution. To produce polymer particles with narrow size distribution, stepwise reduction in impeller speed was examined in the polymerization experiments. It was demonstrated that this method was more effective than the steady agitation. The impeller speed reduction could produce highly monodisperse particles with an average size of 2 μm and a coefficient of variation of size distributions of 2.2% that was much smaller than typical monodispersity criterion of 10%.     

Tuning the Redox Chemistry of a Cr/SiO2 Phillips Catalyst for Controlling Activity,Induction Period and Polymer Properties

The Cr/SiO₂ Phillips catalyst has taken a central role in ethylene polymerization ever since its discovery in 1953. This catalyst is unique compared to other ethylene polymerization catalysts, since it is active without the addition of a metal-alkyl co-catalyst. However, metal-alkyls can be added for scavenging poisons, enhancing the catalyst activity, reducing the induction period and altering polymer characteristics. Despite extensive research into the working state of the catalyst, still no consensus has been reached. Here, we show that by varying the type of metal-alkyl co-catalyst and its amount, the Cr redox chemistry can be tailored, resulting in distinct catalyst activities, induction periods, and polymer characteristics. We have used in-situ UV-Vis-NIR diffuse reflectance spectroscopy (DRS) for studying the Cr oxidation state during the reduction by tri-ethyl borane (TEB) or tri-ethyl aluminum (TEAl) and during subsequent ethylene polymerization. The results show that TEB primarily acts as a reductant and reduces Cr⁶⁺ with subsequent ethylene polymerization resulting in rapid polyethylene formation. TEAl generated two types of Cr²⁺ sites, inaccessible Cr³⁺ sites and active Cr⁴⁺ sites. Subsequent addition of ethylene also revealed an increased reducibility of residual Cr⁶⁺ sites and resulted in rapid polyethylene formation. Our results demonstrate the possibility of controlling the reduction chemistry by adding the proper amount and type of metal-alkyl for obtaining desired catalyst activities and tailored polyethylene characteristics.     

Synthesis and radical polymerization of styrene derivative bearing kojic acid moieties

A styrene derivative ( 1 ) bearing kojic acid moieties was prepared by the base-catalyzed reaction of p-formylstyrene with kojic acid. Hydroxyl groups in 1 were subjected to acetylation. Although 1 did not undergo radical polymerization, the acetylated styrene derivative ( 2 ) showed good radical homo- and copolymerizability. For instance, a polymer having the number average molecular weight (M_n) of 60,000 was obtained in almost quantitative yield (97%) by the polymerization of 2 in chloroform (1.5 M) at 60°C for 36 h using α,α′-azobis(isobutyronitrile) (AIBN, 5 mol %) as an initiator. Under similar conditions, copolymers of 2 with styrene were also obtained in high yield. By partial deacetylation of the copolymer with a triethylamine catalyst, a copolymer containing α-hydroxyketone structures originated from kojic acid moieties was successfully regenerated. The deacetylated copolymer can be crosslinked by complexation with metal salts such as Al³⁺. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of Cr-MSU-1 and its catalytic application for oxidation of styrene

Chromium-containing mesoporous silica material Cr-MSU-1 was synthesized using lauryl alcohol-polyoxyethylene (23) ether as templating agent under the neutral pH condition by two-step method. The sample was characterized by XRD, TEM, FT-IR, UV-Vis, ESR, ICP-AES and N₂ adsorption. Its catalytic performance for oxidation of styrene was studied. Effects of the solvent used, the styrene/H₂O₂ mole ratio and the reaction temperature and time on the oxidation of styrene over the Cr-MSU-1 catalyst were examined. The results indicate that Cr ions have been successfully incorporated into the framework of MSU-1 and the Cr-MSU-1 material has a uniform worm-like holes mesoporous structure. After Cr-MSU-1 is calcined, most of Cr³⁺ is oxidized to Cr⁵⁺ and Cr⁶⁺ in tetrahedral coordination and no extra-framework Cr₂O₃ is formed. The Cr-MSU-1 catalyst is highly active for the selective oxidation of styrene and the main reaction products over Cr-MSU-1 are benzaldehyde and phenylacetaldehyde. Its catalytic performance remains stable within five repeated runs and no leaching is noticed for this chromium-based catalyst.     

Noncoordinating anions in carbocationic polymerization

The initiation and catalysis of isobutylene polymerization from several new metallocene and nonmetallocene initiator-catalysts that contain the noncoordinating anions (NCA), B(C₆F₅)₄⁻ and RB(C₆F₆)₃⁻, is reported. Application of these initiator-catalysts is extended to styrenics and vinyl ethers. The NCA does not contribute to termination and can be used in low concentrations compared with conventional Lewis acids. These qualities provide for isobutylene polymerizations that yield low M_n oligomers or high M_n polymer, dependent upon the initiator and polymerization conditions. Mechanistic aspects of initiation, transfer and termination as well as the participation of adventitious water are considered for each class of initiator-catalyst. The influence of the NCA on the stereoregularity of cationic styrene polymerization is also considered. NCAs do not cause the stereospecific carbocationic polymerization of styrene. We suggest that under conditions not conducive to carbocationic polymerization, NCA/metallocenes mediate the coordination polymerization of styrene. © 1997 John Wiley & Sons, Inc.     

Radical and cationic polymerizations of 3‐ethyl‐3‐methacryloyloxymethyloxetane

3‐Ethyl‐3‐methacryloyloxymethyloxetane (EMO) was easily polymerized by dimethyl 2,2′‐azobisisobutyrate (MAIB) as the radical initiator through the opening of the vinyl group. The initial polymerization rate (R_p) at 50 °C in benzene was given by R_p = k[MAIB]^0.55 [EMO]^1.2. The overall activation energy of the polymerization was estimated to be 87 kJ/mol. The number‐average molecular weight (M?_n) of the resulting poly(EMO)s was in the range of 1–3.3 × 10⁵. The polymerization system was found to involve electron spin resonance (ESR) observable propagating poly(EMO) radicals under practical polymerization conditions. ESR‐determined rate constants of propagation (k_p) and termination (k_t) at 60 °C are 120 and 2.41 × 10⁵ L/mol s, respectively—much lower than those of the usual methacrylate esters such as methyl methacrylate and glycidyl methacrylate. The radical copolymerization of EMO (M₁) with styrene (M₂) at 60 °C gave the following copolymerization parameters: r₁ = 0.53, r₂ = 0.43, Q₁ = 0.87, and e₁ = +0.42. EMO was also observed to be polymerized by BF₃OEt₂ as the cationic initiator through the opening of the oxetane ring. The M?_n of the resulting polymer was in the range of 650–3100. The cationic polymerization of radically formed poly(EMO) provided a crosslinked polymer showing distinguishably different thermal behaviors from those of the radical and cationic poly(EMO)s. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1269–1279, 2001     

The effect of solvents and organic acids on the p-doping behaviors of poly(3′,4′-Ethylenedioxy-2,2′:5′,2″-terthiophene)

Poly(3??,4??-Ethylenedioxy-2,2??:5??,2??-terthiophene) was synthesized by chemical oxidative polymerization of 3??,4??-Ethylenedioxy-2,2??:5??,2??-terthiophene using FeCl₃ as an oxidant. The resulting polymer was characterized by FTIR and ¹H NMR. p-doping behaviors of substituted polyterthiophene with different organic sulfonic acids (methanesulfonic acid, p-toluene sulfonic acid, and ??-naphthalene sulfonic acid) in different solvents (CH₃CN, CHCl₃, THF and DMF) were studied by UV-VIS spectroscopy. The results from structural characterizations showed that the ??,????-bonding predominates in polyterthiophene. The spectroscopic changes in UV-VIS showed that ??-naphthalene sulfonic acid was an efficient doping acid for polymer while varying the solvents. Meanwhile, CH₃CN showed a high efficiency for p-doping of polyterthiophene while varying the doping acids.     

Studies on the hydrolytic polymerization of chromium (III) ion: IX. Revision of graphical method for the reaction in the presence of maleic acid by computer

The hydrolytic polymerization of Cr²⁺ in the presence of maleic acid was studied by equilibrium pH method at 60°C and constant ionic strength. Both maleic acid and Cr³⁺ are of three different concentrations: 0.006, 0.008, 0.01 mol·L^?1. The state of Cr³⁺ in aqueous solution were determined by graphical method and pqr analysis. The following species were found (CrA)^+, Cr-(OH)A and Cr₂(OH)₂A₂. The results by graphical method were revised by computer calculation with data of about fifty experimental points. Hydrolysis constants of all species were obtained with good fitting. It is obvious that the results obtained by program LEMIT are more accurate than those by graphical method. Mechanism of Cr³⁺ polymerization in the presence of maleic acid is also discussed.     

Stereocontrol during the radical polymerization of methyl methacrylates with combined Lewis acids: Aluminium trichloride (AlCl3) and iron dichloride tetrahydrate

The radical polymerization of methyl methacrylate (MMA) was carried out in the presence of combined Lewis acids of the AlCl₃-FeCl₂ system. Compared with the polymerization produced in the presence of single Lewis acids, AlCl₃ or FeCl₂, the MMA polymerization in the presence of AlCl₃-FeCl₂ composite in CHCl₃ or 1-butanol produced a polymer with a higher isotacticity and in toluene produced a polymer with a much higher isotacticity (mm = 50%). The molecular weight and polydispersity of PMMA in the presence of Lewis acids were similar with those in the absence of Lewis acids, although Lewis acids decelerate the polymerization of MMA. The effects of the Lewis acids were greater in a solvent with a lower polarity. A possible stereocontrol mechanism of the polymerization was proposed. The Lewis acid composite of AlCl₃-FeCl₂ readily formed a complex with growing species. These complexes possessed apparent bulkiness that changes the direction of monomer addition to the growing radical center.     

Metal-ion recognition-competitive bulk liquid membrane transport of transition and post-transition metal cations using a thioether donor acyclic ionophore

The competitive bulk liquid membrane transport of Cr³⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺ and Pb²⁺ metal cations with a new synthetic sulfur donor acyclic ligand (pseudo-cyclic ionophore), i.e. 1-(2-[(2-hydroxy-3-phenoxypropyl)sulfanyl]ethylsulfanyl)-3-phenoxy-2-propanol; (C₂₀H₂₆O₄S₂), was examined using some organic solvents as membranes. The membrane solvents include: chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE), dichloromethane (DCM), nitrobenzene (NB), chloroform-nitrobenzene (CHCl₃-NB) and chloroform-dichloromethane (CHCl₃-DCM) binary mixtures. The transport process was driven by a back flux of protons, maintained by the buffering the source and receiving phases with pH 5 and 3, respectively. The aqueous source phase consisted of a buffer solution (CH₃COOH/CH₃COONa) at pH = 5 and containing an equimolar mixture of these seven metal cations. The organic phase contained the acyclic ligand, as an ionophore and the receiving phase consisted of a buffer solution (HCOOH/HCOONa) at pH = 3. For these systems that displayed transport behaviour, sole selectivity for Ag⁺ cation was observed under the employed experimental conditions in this investigation. The amount of Ag⁺ transported follows the trend: 1,2-DCE > CHCl₃ > DCM > NB in the bulk liquid membrane studies. The transport of the metal cations in CHCl₃-NB and CHCl₃-DCM binary solvents is sensitive to the solvent composition. The influence of the stearic acid, palmitic acid and oleic acid in the membrane phase on the ion transport was also investigated.     

Synthesis of macrocyclic polystyrene-polydimethylsiloxane block copolymers

A series of macrocyclic polystyrene (PS)-polydimethylsiloxane (PDMS) block copolymers and similar block copolymers was synthesized by sequential polymerization of styrene and hexamethyl cyclotrisiloxane (D₃) initiated by a difunctional anionic initiator in THF at −78° followed by coupling with Cl₂SiMe₂ in very dilute (10⁻⁵ – 10⁻⁶ M) solutions. Total molecular weights ranged from about 2–85 × 10³. The formation of monodisperse macrocyclic block copolymers was indicated by the lower (15–30%) hydrodynamic volume of the rings compared to that of the linear block copolymers. Carbon-13 and ²⁹Si NMR likewise supported the absence of linear polymer in the macrocyclic block copolymer. The behavior of second virial coefficient A₂ of the rings and the linears versus temperature was examined by static light scattering in cyclohexane. Below 20° the A₂ for the linear polymer goes negative while that for the cycle remains positive. Dynamic light scattering (DLS) as a function of temperature also reflects that the cyclic polymers remain well solvated even down to 12°C. The DLS autocorrelation functions for the linear triblock however demonstrate the onset of aggregation and phase separation as the temperature is reduced below 20°C.     

Polymerization of 1,3‐dienes with functional groups. III. Free‐radical polymerization of N,N‐diethyl‐2‐methylene‐3‐butenamide

Free‐radical homo‐ and copolymerization behavior of N,N‐diethyl‐2‐methylene‐3‐butenamide (DEA) was investigated. When the monomer was heated in bulk at 60 °C for 25 h without initiator, rubbery, solid gel was formed by the thermal polymerization. No such reaction was observed when the polymerization was carried out in 2 mol/L of benzene solution with with 1 mol % of azobisisobutyronitrile (AIBN) as an initiator. The polymerization rate (R_p) equation was R_p ∝ [DEA]^1.1[AIBN]^0.51, and the overall activation energy of polymerization was calculated 84.1 kJ/mol. The microstructure of the resulting polymer was exclusively a 1,4‐structure where both 1,4‐E and 1,4‐Z structures were included. From the product analysis of the telomerization with tert‐butylmercaptan as a telogen, the modes of monomer addition were estimated to be both 1,4‐ and 4,1‐addition. The copolymerizations of this monomer with styrene and/or chloroprene as comonomers were also carried out in benzene solution at 60 °C. In the copolymerization with styrene, the monomer reactivity ratios obtained were r₁ = 5.83 and r₂ = 0.05, and the Q and e values were Q = 8.4 and e = 0.33, respectively. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 999–1007, 2004     

Synthesis of well‐defined naphthalene and photo‐labile group‐labeled polystyrene via ATRP

The atom transfer radical polymerizations of styrene were successfully carried out in bulk and solution, respectively, at 115 °C, with a novel photoiniferter reagent, (1‐naphthyl)methyl N,N‐diethyldithiocarbamate (NMDC), as an initiator in the presence of copper (I) bromide and N,N,N′,N″,N″‐pentamethyldiethylenetriamine. The results showed that NMDC was an effective initiator with high initiation efficiency for ATRP of St. The polymerization rate was first‐order with respect to the monomer concentration and the molecular weights of the obtained polystyrene (PS) increased linearly with the monomer conversion, with very narrow molecular weight distributions (M_w/M_n = 1.07–1.29). The functionalized naphthalene‐labeled PS bearing N,N‐(diethylamino)dithiocarbamoyl group which was confirmed by ¹H NMR analysis, and chain extension of the PS exhibited fluorescence and ultraviolet absorption in chloroform (CHCl₃). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 510–518, 2006     

Oxidation polymerization of a charge‐transfer complex of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene with 7,7,8,8‐tetracyanoquinodimethane

A π‐conjugated poly(α‐dithienylen‐dithiafulvene) ( 2 ) was obtained by the oxidation polymerization of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene ( 1 ) as a dithiafulvene monomer derived from 4‐(2‐thienyl)‐1,2,3‐thiadiazole. When a solution of 1 in CHCl₃ was added to a stirred solution of FeCl₃ in CHCl₃, only the low‐molecular‐weight product 2 was obtained. The mixture was stirred for 15 h with an N₂ flow. The polymerization at higher temperatures resulted in polymers with large insoluble fractions. A higher molecular weight polymer was obtained by the oxidation polymerization of a charge‐transfer complex of 1 with 7,7,8,8‐tetracyanoquinodimethane (compound 3 ). In contrast to 2 , polymer 4 was readily soluble in dimethyl sulfoxide, dimethylformamide, and acetone and partially soluble in tetrahydrofuran and methanol and had a larger molecular weight (peak top molecular weight = 37,000). The conductivity of polymer 4 was 3 orders of magnitude larger than that of polymer 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6592–6598, 2005