Quasiliving Carbocationic Polymerization. II. The Discovery: The α-Methylstyrene System

A detailed analysis of elementary reactions of carbocationic polymerization culminated in the prediction and subsequent experimental demonstration of quasiliving polymerization. Quasiliving polymers are formed in a system provided that the process of chain termination and chain transfer to monomer are absent or reversible, i.e., the propagating ability of the chain end is maintained throughout the experiment, and the molecular weight increases in proportion to the cumulative amount of monomer added. The chain end can be active (carbocation) or dormant (reactivable polymeric olefin or cation source). Chain transfer is suppressed by keeping the monomer concentration low. Quasiliving polymerizations are maintained by continuous slow feeding of dilute monomer to a charge containing the initiating or propagating species (quasiliving polymerization technique). A comprehensive kinetic scheme has been developed that describes quasiliving polymerization in quantitative terms. Quasiliving polymerization was demonstrated experimentally in the “H₂O”/BCl₃/α-methylstyrene and cumyl chloride/BCl₃/α-methylstyrene systems. M _n versus monomer input plots are linear over wide ranges, indicating quasiliving conditions, and poly(α-methylstyrenes) with M _n > 2 × 10⁵ have been obtained, Molecular weight distributions were found progressively to narrow and dispersion ratios M _w/M _n to decrease.     

Quasiliving Carbocationic Polymerization. XVI. Forced Ideal Terpolymerization of Styrene-α-Methylstyrene-lsobutylene

Forced ideal carbocationic terpolymerization of styrene/α-methylstyrene/isobutylene systems has been achieved by continuous addition of mixed monomer feeds to 2-chloro-2,4,4-trimethylpentane/TiCl₄ initiator/coinitiator charges dissolved in n-hexane/methylene chloride solvent mixtures. The compositions of terpolymers were uniform and identical to those of the feeds in the concentration ranges studied. The number-average molecular weights increased monotonously with the amounts of monomers consumed; however, pronounced chain transfer to monomer was evident. The microstructure of the products was investigated ¹³C-NMR spectroscopy. According to dual detector GPC, ¹³C-NMR and DSC data true terpolymers have formed.     

Vinyl Polymerization. CLXVII. Vinyl Polymerization Initiated with p-Methoxy p′-nitrobenzoyl Peroxide

It was described in the literature that p-methoxy-p′-nitrobenzoyl peroxide decomposed homolytically in benzene, but heterolytically in acetone. However, in the present study the polymerizations of styrene and acrylonitrile were found to proceed always through radical mechanism in benzene, dimethylformamide, or acetone. And in the above various solvents, the rate of polymerization was found to be almost equal.     

Polymerization of spiro-orthoesters—2. A kinetic approach

The polymerization behaviour of a typical spiro-orthoester, 2-Phenoxymethyl-1,4,6-trioxaspiro(4,4)-nonane, was investigated. The polymerization rate decreases abnormally with conversion; the effect is explained by a mechanism involving deactivation of the active centres by the polymer.     

Soluble Bimetallic Oxoalkoxide Catalysts. IV. Ring-Opening Polymerization of β-Propiolactone

Abstract

The polymerization of β-propiolactone by aluminum-zinc oxoalkoxides corresponding to the structure has been studied. The overall kinetics of the reaction follow a first current order in monomer and a first order in catalyst. Mechanistic studies also indicate that these initiators operate through selective acyl-oxygen cleavage of the lactone ring with insertion in the aluminum-oxygen bond. Moreover, the polymerization proceeds by a perfectly “living” process.     

Anionic Polymerization of α-Methylstyrene. IX. Nature of the Propagating Species

Abstract

The nature of the initiating and propagating species involved in the anionic polymerization of α-methylstyrene has been explored. The earlier hypothesis that multimodal GPC molecular weight distributions in polymers arise solely out of different reaction steps or different ion-pair mechanisms being involved has been modified for poly-α-methylstyrene. Multimodal GPC molecular weight distributions in poly-α-methylstyrene initiated with potassium at 25°C and polymerized at 25°C or higher in THF, p-dioxane, or cyclohexane as solvents have been ascribed to the presence of two different types of tetramers which grow simultaneously but at different rates, each responding to its own well-defined thermodynamic equilibrium and yielding dormant and living polymers. Reaction schemes describing the initiation (at 25°C) and propagation reactions (between -25 and 60°C) in the polymerization (in solution of THF as well as in bulk) of α-methylstyrene initiated with potassium-naphthalene, butyl-lithium, and butyllithium-tetramethylethylenediamine (TMEDA) have been presented. The role of coordinating agents naphthalene and TMEDA in changing irreversible propagations into reversible ones has been emphasized.     

Radiation-Induced,Solid-State Polymerization of Derivatives of Methacrylic Acid. XI. Aspects of the Polymerization of Methacrylic Acid by γ-Irradiation

Aspects of the radiation-induced polymerization of methacrylic acid in the crystalline state have been investigated and utilized to evaluate the mechanism of polymerization. In particular, results for post-irradiation polymerization at 0°C after radiation doses of 0.1 to 2.0 Mrad support the concepts of Lando and Semen that chain initiation essentially all commences at the same time, that chain propagation continues without termination, and that termination of nonpropagating radicals proceeds simultaneously.     

Electrochemical polymerization of dicarboxylic acids—IV. Polymerization of sebacic acid

The electrolysis of sebacic acid was investigated in methanol, methanol:pyridine (1:1) and methanol:acetonitrile (1:1). The various products were analyzed. In methanol, the major product was the oligomeric carboxylic acid fraction (55%) and the yield of oligomeric hydrocarbons and polymer was lower. With the other two solvents, the polymer was the major product. Four types of hydrocarbons were formed: n-alkane, 1-alkene, x-alkene (the position of the double bond is not known) and cycloalkane. The polymers obtained in all the solvents had the character of cross-linked and branched polyethylene, having ester and methoxy groups. These polymers did not suffer degradation during basic hydrolysis. In comparison with adipic acid, sebacic acid had more tendency to yield polymer and carboxylic acids than hydrocarbons.     

Carbocationic Polymerization in the Presence of Sterically Hindered Bases. V. The Polymerization of α-Methylstyrene by the “H2O”7BCI3 Initiating System

The influence of 2,6-di-tert-butylpyridine (DtBP) on the polymerization of α-methylstyrene (αMeSt) induced by the “H₂O”/BC1₃ initiating system in the -20 to ?60°C range has been studied in detail. Adventitious H₂O (“H₂O”) is the initiating cationogen and initiation most likely proceeds by a concerted route in the absence of free protons or the acid H^⊕BC1₃ OH^⊕ Polymerizations are extremely rapid and kinetic termination is absent (conversions are 100%) in the absence of DtBP. In the presence of DtBP, polymerizations are still very fast; however, conversions are reduced. Significantly, conversions increase with decreasing temperatures, which suggests the operational presence of terminative proton entrapment. Molecular weights increase with decreasing temperatures in the presence and absence of DtBP and the slopes of the linear Arrhenius plots (In [Mbar]_w versus 1/T) are parallel; the molecular weights obtained in the presence of DtBP are close to a factor of 10 higher than those produced in the absence of this hindered pyridine. The virtual identity of the slopes of Arrhenius plots indicates close similarity between the nature and rate of molecular-weight-determining events in the absence and presence of DtBP, i.e., k_p/k_tr,m and k_p/k_tr,G^⊕ DtBP profoundly affects molecular weight dispersity: [Mbar]_w/[Mbar]_n = 3.0–4.0 in the absence of DtBP whereas [Mbar]_w/[Mbar]_n = 1.5 -1.8 in the presence of DtBP. The number w of polymer molecules formed (yield/[Mbar]_n) in the absence of DtBP whereas [Mbar]_w/[Mbar]_n = 1.5–1.8 in presence of DtBP. The number of polymer molecules formed (yield/[Mbar]_n) = 1.5–1.8 in the presence of DtBp. The number of polymer molecules formed (yield/[Mbar]_n) in the absence of DtBP decreases with decreasing temperature while those formed in the presence of DtBP remain constant. According to Mayo, (1/[Mbar]_n versus 1/ [M] plots chain transfer to monomer in the peresence of DtBP is vey low (k_tr,m /k_p = 6.4 × 10^?4 and 2.8 × 10^?4 at ?30 and ?50°C) but not zero. Conceivably two kinds of chain transfer to monomer reactions may exist (direct and indirect) and only one (i.e., the indirect one) may be trappable by DtBP. The effect of [DtBP] on the percent converstion and [Mbar]_n was investigated: Above a fairly well defined [DtBP], neither conversions nor [Mbar]_n's were affected by [DtBP]. With increasing [DtBP] molecular weight dispersions rapidly decrease and [Mbar]_w [Mbar]_n's seem to level off at ～ 1.5 at relatively high [DtBP]. Changing the polarity of the solvent characteristically affects the mechanism of α MeSt polmerzation in the presence and absence of DtBP results in a strong increase in [Mbar]_w/[Mbar]_n (from ～ 1.5 to ～ 4.0), in the presence of DtBP [Mbar]_w/[Mbar]_n remains virtually unchanged at ～1.5.     

Polymerization of α-Methylstyrene with Potassium as Initiator. VII. Thermal Decomposition of the Reaction Products

The polymerization of α-methylstyrene, initiated with high concentrations of potassium in tetrahydrofuran and in p-dioxane or with a butyllithium-tetramethylethylenediamine complex in bulk, was carried out at temperatures above 25°C. The resulting products comprising varying proportions of both low (D + A of [Mbar]w = 2.0 to 4.0 × 10³) and high (B + C of [Mbar]W > 20.0 × 10³) molecular weight components were subjected to 50 min isothermal treatments at different temperatures. The poly-α-methylstyrene samples, prepared under the above mentioned solvent-conditions, which had similar proportions of components D + A and B + C, as characterized by gel permeation chromatography and nuclear magnetic resonance showed that their thermal stability decreased with the following order of solvent-conditions: Bulk > p-dioxane > THF. A comparison of the decomposition results obtained with polymers made up of components D + A and B + C and those made up exclusively of component B + C showed that the percent weight-loss and the decrease in molecular weight associated with the latter component B + C is more pronounced when the low molecular weight component D + A is present.     

Polymer-Supported Lewis Acid Catalysts. II. Cationic Polymerization of α-Methylstyrene with Polystyrene-Gallium Trichloride Complex as Initiator

The polymerization of α-methylstyrene catalyzed by a polymer-supported Lewis acid catalyst, polystyrene-gallium trichloride complex, is described. The kinetic equation of the cationic polymerization is R_p = k˙C_ms˙C_cat , and the apparent activation energy is 20.9 kJ/mol. The effect of different solvents on the polymerization rate is quite pronounced; for example, the polymerization rate decreased in the following order in the three solvents: CH₂ ClCH₂ Cl < CH₂ Cl₂ < CCl₄. High molecular weight poly(α-methylstyrene) (T_g = 185°C) could be obtained at room temperature. The mechanism of the polymerization is also discussed.     

Donor-Acceptor Complexes in Copolymerization. XVIII. Alternating Diene–Dienophile Copolymers. 1. Conjugated Diene–Maleic Anhydride Copolymers through Radical-Catalyzed Polymerization

The copolymerization of isoprene, butadiene, and other conjugated dienes with maleic anhydride was readily initiated in polar solvents by conventional free radical catalysts, including peroxides, hydroperoxides, and azobisisobutyronitrile, at high concentrations or at temperatures at which the catalyst had a half-life of 1 hr or less and the total reaction time was 0.5-1 hr. Decreasing the reaction temperature or the rate of catalyst addition resulted in increased yields of Diels-Alder adduct and decreased yields of copolymer. The molecular weight decreased as the temperature increased. Dioxane and tetrahydrofuran peroxides, obtained by the passage of oxygen or UV irradiation in air, also initiated the copolymerization. The soluble diene-maleic anhydride copolymers were equimolar and alternating, had [n] 0.1-6 (cyclohexanone) and contained 75-95% 1,4 structure according to ozonolysis, titration with IC1 and NMR. The IR spectrum of the butadiene–maleic anhydride copolymer indicated 75-95% cis-1,4, 5-20% trans-1,4 and 0-5% 1,2-vinyl unsaturation. The proposed mechanism of polymerization involves a donor-acceptor (diene-dienophile) interaction generating a ground-state charge transfer complex which is readily converted to the cyclic adduct. Under the influence of radicals the ground-state complex is transformed into an excited complex which undergoes polymerization. High concentrations of radicals are necessary to generate polymerizable excited complexes in competition with adduct formation.     

An Approximate Kinetic Treatment of Slow‐Initiated Living Polymerization. I. First‐Order Initiation and Propagation

A new method for deriving the initiation rate constant for a slowinitiated living polymerization process in which all reactions are first order with respect to all participants is presented. The method is based upon an approximate analytical solution of the set of differential equations modeling this class of processes. The solution is found by asymptotic expansion of the unknown functions, using a dimensionless parameter which characterizes the process.     

Synthesis and Characterization of Star-branched Polyisobutylene by Combination of Anionic Polymerization and Cationic Polymerization

The construction of polymer materials with controlled compositions, topologies, and functionalities has been the enduring focus in current research1,2. Among them, star polymers have been extensively studied for a long time, due to their markedly lower so…     

Modification of Montmorillonite through Intercalative Polymerization

Montmorillonite(MMT) was modified through intercalative polymerization of phenol and formaldehyde catalyzed by oxalic acid.The modified montmorillonite was delaminated at large,as demonstrated by XRD and TEM studies,It can disperse easily in epoxy resion to from exfoliated nanocomposites.The nanoscale silicate platelets dispersed in water can be metallized by silver deposition.     

Anionic Polymerization Behavior of α-Methylene-N-methylpyrrolidone

Anionic polymerization of α-methylene-N-methylpyrrolidone ( MMP ) was carried out in THF at −78∼0 °C with diphenylmethylpotassium (Ph₂CHK) and with diphenylmethyllithium (Ph₂CHLi) in the presence of Lewis acidic diethylzinc (Et₂Zn). Poly( MMP )s possessing predicted molecular weights based on the molar ratios between monomer and initiators and narrow molecular weight distributions (M_w/M_n < 1.1) were obtained in quantitative yields. It was demonstrated that the propagating chain end of poly( MMP ) was stable at −30 °C to form the polymers with well-defined chain structures. From the polymerizations at the various temperatures ranging from −50 to −30 °C, the apparent rate constant and the activation energy of the polymerization were estimated as follows: ln k = −6.93 × 10³/T + 25.7 and 57 ± 5 kJ mol⁻¹, respectively.     

Polymerization by phase transfer catalysis—5. Polycarbonates from diphenols with aromatic side groups

Polycarbonates were synthesized from phosgene and three different diphenols under phase transfer conditions, using quarternary ammonium and phosphonium salts and dichloromethane as solvent. The polycarbonates were characterized by i.r. and ¹H-NMR; the molecular weights were estimated from inherent viscosity measurements. The influences of the catalysts and the structure of the diphenol were studied; both exert an important effect on the molecular weights. The hydrolysis of the polycarbonates was studied by the variation of the η_inh values, the polymer undergoes a hydrolytic process in the organic phase, influenced by the catalysts, according to their structure.     

Polymerization of p -triethylstannyl-α-methylstyrene

Summary Polymerization of p-triethylstannyl--methylstyrene was studied under 6000 atm pressure in the presence of various initiators. Polymers were isolated and their elemental composition and properties were determined.     

Polymerization Mechanism of α-Linear Olefin

The density functional theory on the level of B3LYP/6-31G was empolyed to study the chain growth mechanism in polymerization process of α-linear olefin in TiCl₃/AlEt₂Cl catalytic system to synthesize drag reduction agent. Full parameter optimization without symmetryrestrictions for reactants, products, the possible transition states, and intermediates wascalculated. Vibration frequency was analyzed for all of stagnation points on the potential energy surface at the same theoretical level. The internal reaction coordinate was calculated from the transition states to reactants and products respectively. The results showed as flloes:(i) Coordination compounds were formed on the optimum configuration of TiCl₃/AlEt₂Cl.(ii) The transition states were formed. The energy di?erence between transition states and the coordination compounds was 40.687 kJ/mol. (iii) Double bond opened and Ti-C(4) bond fractured, and the polymerization was completed. The calculation results also showedthat the chain growth mechanism did not essentially change with the increase of carbon atom number of α-linear olefin. From the relationship between polymerization activation energy and carbon atom number of the α-linear olefin, it can be seen that the α-linear olefin monomers with 6-10 carbon atoms had low activation energy and wide range. It was optimum to synthesize drag reduction agent by polymerization.