Ring-opening polymerization of α,β-disubstituted oxiranes by α-methoxyphenylmethylium hexachloroantimonate

α-Methoxyphenylmethylium hexachloroantimonate was used as a novel initiator for the polymerization of α,β-disubstituted oxiranes such as cyclohexene oxide (CHO) and 2-butene oxide (trans and cis) (2-BO) at ?78°C with dichloromethane or dichloromethane-toluene mixtures as solvents. The CHO polymerization mixture became turbid and the polymer precipitated in dichloromethane. The CHO polymerization proceed quantitatively in dichloromethane–toluene mixtures. The molecular weight distribution of polyCHO obtained was bimodal regardless of the solvent used. The polymerization of trans-2-BO was heterogeneous in both dichloromethane and dichloromethane–toluene mixture. The polymerization mixtures of cis-2-BO were transparent but reached a limit yield which was less than the polymer yield of trans-2-BO. Furthermore, the microstructure of the poly2-BOs were analyzed by Vandenberg's method and the results confirmed Vandenberg's finding that inversion of configuration occurs in the propagation step.     

Mechanism of Ziegler-Natta polymerization of propylene and α-d-propylene

Rates of propylene homopolymerization and α-d-propylene-propylene copolymerization were determined by using constant-pressure polymerization conditions. It could be demonstrated that the rate of propylene homopolymerization was constant under the conditions used. However, the initial rate of copolymerization was faster and decreased with time to the rate obtained for propylene homopolymerizations. The higher initial copolymerization rate was attributed to the stabilization of potentially active centers in solution when the deuterated monomer was present. These active centers are assumed to be formed by reactions of tetravalent titanium with monomer. These active centers, which are formed in solution, are said to be destroyed by isotopically controlled reactions, i. e., abstraction of the hydrogen or the α-deuterium atom from these monomer-alkylated species in solution or at the interface. These active centers are believed to be adsorbed and/or chemisorbed onto the precipitated catalyst surface and to be responsible for a polymer of considerably lower steric order. This scheme predicts a stereoregular polymer of high molecular weight produced by polymerization on a Ti(III) surface and a largely amorphous polymer of lower molecular weight produced by adsorbed and/or chemisorbed species. This prediction was verified by fractionation of the deuterated polymers into crystalline and amorphous portions.     

Cationic polymerization of α-methylstyrene oxide

The polymerization of α-Methyl Styrene Oxide initiated by trityl hexachloroantimonate is reported upon. Data is presented on side reactions, percent yield and molecular weight of polymer produced in the polymerization.     

Synthesis of novel α,α′,β-trisubstituted β-lactones

A concise and efficient synthesis of α,α′,β-trisubstituted β-lactones is presented. These novel lactones are easily obtained in five steps and will be dedicated to anionic ring opening polymerization.     

Photoinitiated cationic polymerization of limonene 1,2‐oxide and α‐pinene oxide

Limonene 1,2‐oxide (LMO) and α‐pinene oxide (α‐PO) are two high reactivity biorenewable monomers that undergo facile photoinitiated cationic ring‐opening polymerizations using both diaryliodonium salt and triarylsufonium salt photoinitiators. Comparative studies showed that α‐PO is more reactive than LMO, and this is because it undergoes a simultaneous double ring‐opening reaction involving both the epoxide group and the cyclobutane ring. It was also observed that α‐PO also undergoes more undesirable side reactions than LMO. The greatest utility of these two monomers is projected to be as reactive diluents in crosslinking photocopolymerizations with multifunctional epoxide and oxetane monomers. Prototype copolymerization studies with several difunctional monomers showed that LMO and α‐PO were effective in increasing the reaction rates and shortening the induction periods of photopolymerizations of these monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Cationic polymerization of γ-methyl- and α-methylphenylallene

The cationic polymerizations of γ-methylphenylallene ( 1 ) and α-methylphenylallene ( 2 ) were carried out with some Lewis acids at 25 and 0°C in dichloromethane to obtain the corresponding polymers through allyl cations, respectively. Tin (IV) chloride was found to be an effective catalyst for the cationic polymerization of both allenes 1 and 2 compared with other Lewis acids. Thus, in the polymerization of 1 , methanol-insoluble polymer was only obtained using Tin (IV) chloride, and M?_n of methanol-insoluble polymer obtained by Tin (IV) chloride was the highest in the polymerization of 2 . From the analysis of ¹H- and ¹³C-NMR spectra of the obtained polymers, the polymer from 1 consisted of two kinds of units polymerized by each double bonds of allene 1 , whereas the polymer from 2 consisted of only one unit polymerized by terminal double bond of allene 2 . Moreover, effect of solvent on the cationic polymerizations of 1 and 2 were discussed.     

γ-Ray-induced polymerization of α-haloacrylic acids

The γ-ray induced polymerizations of α-chloroacrylic acid, mp 66°C, and α-bromo-acrylic acid, mp 72°C, were investigated in the temperature range from 35°C to 85°C. An analysis of polymerization kinetics was made, and results were similar to those reported in the literature for other vinyl monomers. On heating of the polymer obtained, elimination of hydrogen halide takes place, and intramolecular lactone formation is observed. The rate of lactone formation of poly(α-chloroacrylic acid) obtained in the solid-state polymerization was found to be higher than that in the liquid state, because a highly isotactic configuration of polymers, tends to be formed in the solid-state polymerization, and elimination of hydrogen chloride is facilitated with an isotactic 5₂ helix structure.     

Block copolymerization. VIII. Anionic polymerization of α-pyrrolidone by polystyrene initiator

Polystyrene with N-acyl pyrrolidone groups at both ends was prepared by radical polymerization with 4,4′-azobis(pyrrolidone 4-cyanovalerate). With this polystyrene as the initiator, the anionic polymerization of α-pyrrolidone was carried out, to give the well-defined ABA-type block copolymers of α-pyrrolidone and styrene. The obtained copolymers were characterized by their composition, reduced viscosity, and initiation efficiency. Initiation efficiency was sufficiently high, and the stepwise propagation process was verified so far as the polymerization time was not so long. The results of the polymerization in a high-vacuum system were compared with those in a low-vacuum system, and some differences were observed owing to the effect of water.     

Synthesis and polymerization of γ-alkoxy-β-hydroxypropyl acrylates

Several γ-alkoxy-β-hydroxypropyl acrylates were synthesized and polymerized. Both poly(MHPA) (IV_d) and poly(MHPMA) (IV_a) hydrogels possess high values of equilibrium water content, about seven and three times, respectively, that of the poly(β-hydroxyethyl methacrylate) hydrogel. These rather high values are attributed tentatively to the presence of a hydrophilic γ-methoxy-β-hydroxypropyl side group on the acrylic backbone.     

The polymerization of oxiranes with the α-chlorobenzyl methyl sulfide–antimony pentachloride initiator system

α-Thiomethoxyphenylmethylium hexachloroantimonate was prepared from α-chlorobenzyl methyl sulfide and antimony pentachloride and studied by visible spectroscopy. The salt is unstable at room temperature and used as in situ initiator for the polymerization of oxiranes in dichloromethane. Propylene oxide (PO) and cyclohexene oxide (CHO) were used as oxiranes. The microstructure of PO polymer is amorphous by ¹³C-NMR. The initiator was more effective for the polymerization of CHO than for that of PO.     

Al(Cap)3 as initiator in the anionic polymerization of ε-caprolactam at high temperature

Mechanism for polymerization of ε-caprolactam in the presence of both sodium and aluminum caprolactamate was investigated at 171°C. The role of Al(Cap)₃ as an initiator was revealed. The apparent rate constant of propagation reaction decreased with the increase in the concentration of Al(Cap)₃, as the two different metal salts interact even at 171°C. The activation energy of the overall polymerization reaction with this catalyst system was estimated to be 41.18 kcal/mole.     

Cocatalysis by epoxides in the polymerization of tetrahydrofuran with trityl hexachloroantimonate initiator

The polymerization of tetrahydrofuran (THF) with (C₆H₅)₃C⁺SbCl₆^- initiator is markedly accelerated by small concentrations of propylene oxide or other epoxides. Molar concentrations of propylene oxide 4 to 10 times those of the carbonium-ion salt showed increasing conversion to polymer. The equilibrium conversion level at different temperatures with epoxides is the same as in their absence; the approach to equilibrium is first-order in THF. NMR experiments in the presence of propylene oxide indicate the formation of a trityl ether intermediate. The cocatalysis effect is interpreted on the basis of an acceleration in the initiation process in the system.     

Lipase-catalyzed ring-opening polymerization of α-methyl-δ-valerolactone and α-methyl-ε-caprolactone

Lipase-catalyzed ring-opening polymerization of α-methyl-substituted medium-size lactones, α-methyl-δ-valerolactone and α-methyl-ε-caprolactone, were carried in bulk. Immobilized lipase derived from Candida antarctica is active in the polymerization of both monomers. The polymerization proceeds under mild reaction conditions to give the corresponding aliphatic polyester having a hydroxy group at one end and a carboxylic acid group at the other.     

Bulk polymerization of α-chloroacrylonitrile

Poly-α-chloroacrylonitrile, which may be regarded as a hybrid of poly(vinyl chloride) and polyacrylonitrile, is, like these polymers, insoluble in its own monomer. Its bulk polymerization is thus heterogeneous, showing abnormal kinetic features by comparison with homogeneous polymerizations. The polymerization exhibits autocatalytic properties. The initiator exponents at 0 and 5% polymerization are 0.45 and 0.44, respectively, and the overall energy of activation is 23.0 ± 2 Kcal./mole. There is no significant change in molecular weight with catalyst concentration in the range 0.057–0.90% nor with conversion up to 12%, but the reaction is accelerated by addition of polymer. Bulk polymerization results in colored products, the color deepening with conversion. These results have been compared with those of Bamford and Jenkins for acrylonitrile and Bengough and Norrish for vinyl chloride and are found to be in closer accord with the latter. They can be accounted for satisfactorily by Bengough and Norrish's suggestion that transfer occurs between growing polymer radicals and dead polymer molecules, the radicals thus formed on the surface of the polymer being removed by transfer to monomer.