(5,10,15,20-Tetraphenylporphyrinato)manganese acetate as a novel initiator for the ring-opening polymerization of 1,2-epoxypropane

(5,10,15,20-Tetraphenylporphyrinat o)manganese acetate (2) was found to bring about the ring-opening polymerization of 1,2-epoxypropane (3) (R² = CH₃) under mild conditions to give the polymer with a bimodal molecular weight distribution consisting of a sharp main peak and a small shoulder on the higher molecular weight side. The polymerization was found to proceed even in the presence of a protic compound such as an alcohol or a carboxylic acid to give the polymer with a unimodal very narrow molecular weight distribution. The number of the polymer molecules is in good agreement with the sum of those of 2 and the protic compound, demonstrating the “immortal” nature of polymerization.     

Ring-opening-closing alternating copolymerization of 2-methyl-2-oxazoline with N-methyldiacrylamide

This paper describes a new ring-opening-closing alternating copolymerization (ROCAC) of 2-methyl-2-oxazoline (five-membered cyclic imino ether, 1 ) with N-methyldiacrylamide ( 2 ). The reaction of a 1 : 1 monomer feed ratio proceeded without any added catalyst to give an alternating copolymer 3 having two structural units formed by ring-opening and ring-closing (cyclization). The structure of copolymer 3 was determined by ¹H, ¹³C NMR, and IR spectroscopies. The extent of cyclization was at most 65%. The copolymerization was reasonably explained by a mechanism of propagation via zwitterion intermediates.     

Lanthanoid alkoxide as a novel initiator for the synthesis of polyester via polymerization of ketenes

The present study demonstrates the polymerization of ketenes by using lanthanoid isopropoxide as a novel initiator to produce a polyester of high molecular weight. This is the first example of an efficient room-temperature polymerization of ketenes. As a result of model reactions, it is indicated that the β-lactone type ketene cyclic dimer does not participate in the polyester formation from the ketene monomer with lanthanoid alkoxides, and that the alternating repetition of O-acylation of the La ketone-enolate and C-acylation of the La ester-enolate is the most likely mechanism.     

Kinetics and mechanism of the isomerization polymerization of 2-methyl-2-oxazoline by benzyl chloride and bromide initiators. Effect of halogen counteranions

Kinetic studies of the isomerization polymerization of 2-methyl-2-oxazoline ( 2 ) initiated with benzyl chloride ( 1a ) or bromide ( 1b ) were carried out by NMR spectroscopy. The polymerization initiated with 1a proceeded exclusively via a covalently bonded alkyl chloride species 5 , whereas the polymerization of the system initiated with 1b proceeded via a oxazolinium bromide 10 as the propagating end. The propagation rate constant k_p with 1a was about 1/40 of that found with 1b at 40°C in CD₃CN. The mechanistic difference is explained by the different nucleophilicities of the counteranions, Cl^— and Br^—. A model compound for the propagation with 1b as initiator was also examined changing the temperature and the solvent.     

Equilibrium polymerization with a multifunctional initiator

The equilibrium polymerization with a multifunctional initiator is re-treated theoretically. The expressions for the molecular weight distribution function, the number- and weight-average degrees of polymerization, the distribution of the degree of branching and the average degree of branching of the polymer formed are rigorously derived. All the formulae given are much simpler than those reported by Baur and Eisenberg. A theoretical method is established by which all the molecular parameters of the polymer can be calculated from polymerization conditions, such as the equilibrium constants, the functionality of the initiator and the initial concentrations of initiator and monomer.     

Anionic polymerization of 4-methyl-2-oxetanone

Potassium solutions, obtained by contacting the metal mirror with a THF solution of a crown ether were found to initiate the anionic polymerization of 4-methyl-2-oxetanone ( 1 ) (β-butyrolactone). The tacticity of the resulting polymer 2 was established by means of ¹³C NMR spectroscopy. The results indicate that living polymers of 1 were formed, and the polymerization proceeds without abstraction of hydrogen from the monomer and no termination and transfer reactions take place.     

Anionic ring-opening polymerization of cyclodisilazanes, 2. Influence of additives on the kinetics of polymerization

The kinetics of the anionic ring-opening polymerization of the DD_NMe cyclodisilazane, initiated by benzyllithium, has been investigated in different experimental conditions. In non-polar solvents, the active centers are aggregated ion pairs which are in equilibrium with a small amount of monomeric species. In the presence of additives such as THF, dioxane or tetramethyl-ethylenediamine, there is only one type of active center. The aggregates are dissociated into light ion pairs externally solvated by the additive. The paper demonstrates also that the kinetics of the polymerization (i.e., rate constant of propagation k_p) is a function of both the nature and the amount of additives.     

Cationic polymerization of 2-methyl-1.3-dioxepane

2-Methyl-1.3-dioxepane was polymerized in 1.2-dichloroethane with triethyl oxonium tetrafluoroborate and boron trifluoride as initiators. This polymerization involves a monomer-polymer equilibrium and the polymer consists of regularly alternating tetrahydrofuran and acetaldehyde units. The thermodynamic parameters for the polymerization were determined from the temperature dependence of the equilibrium monomer concentration as follows: ΔH_SS = ?2.1 ± 0.3 kcal/mole and ΔS⁰_SS = ?8.9 ± 1.3 cal/mole deg. The ceiling temperature for the 1 mole/1. solution is ?37°C. The attempted polymerization of 2.2-dimethyl-1.3-dioxepane gave only a crystalline cyclic dimer.     

Radical ring-opening polymerization behavior of ethyl 1-substituted 2-vinylcyclopropanecarboxylate

Ethyl 1-substituted 2-vinylcyclopropanecarboxylate derivatives (VCPs) were prepared from butadiene and the corresponding substituted diazoacetate in the presence of rhodium diacetate as a catalyst. The polymerization behavior of the obtained monomers was investigated revealing that VCPs undergo radical ring-opening polymerization to form poly(1-alkyl-1-ethoxycarbonyl-3-pentenylene)s and that there is a marked influence of the 1-substituent of VCPs on the polymerization rate. The reaction of VCPs with thiophenol was also carried out as a model reaction of their polymerization.     

Free radical polymerization of a sugar residue-carrying styryl monomer with a lipophilic alkoxyamine initiator: synthesis of a well-defined novel glycolipid

Controlled free radical polymerization of N-p-vinylbenzyl-2,3,5,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D -galactopyranosyl)-D -gluconamide (Ac-VLA) was achieved by the nitroxide-mediated free radical polymerization with a lipophilic alkoxyamine “initiator” with a dioctadecyl group in 1,2-dichloroethane at 90°C. The polymerization proceeds in a “living” fashion, providing Ac-VLA polymers with low polydispersity. The hydrolysis of the polymers results in well-defined glycopolymer-carrying amphiphiles, viz., artificial “glycolipids”.     

Investigations on the ring-opening polymerization of cyclic ketenacetals

The synthesis of five-membered cyclic ketenacetals was investigated. It was shown that 2-methylene-1,3-dioxolanes have various properties of polymerization in dependence on the substituents in 4- and 5-position. While 4-methylene-3,5-dioxatricyclo[5.2.1.0^2,6]decane ( 1 ) polymerizes without ring opening to high-molecular-weight polyacetals, which are insoluble in common solvents, 4-methylene-8,9:10,11-dibenzo-3,5-dioxatricyclo[5.2.2.0^2,6]undeca-8,10-diene ( 2 ) yields oligomers (number-average molecular weight M?_n (vapour pressure osmometry) = 900–1500) with ring-opened and non-ring-opend units.     

A novel side-chain liquid crystal polymer of 5-substituted cis-cyclooctene via ring-opening metathesis polymerization

In this communication, we report the synthesis and ring-opening metathesis polymerisation (ROMP) of a 5-substituted cyclooctene-derivative, (±)-cis-[11-(4′-cyanobiphenyl-4-yloxy)undecyl]cyclooct-4-enecarboxylate. A highly active molybdenum-carbene was used as initiator. The prepared polymer is liquid crystalline and shows a nematic phase between ?5 and 53°C.     

A novel observation in anionic ring-opening polymerization behavior of cyclic carbonates having aromatic substituents

The anionic ring-opening polymerization of six-membered cyclic carbonates having aromatic substituents, 5-methyl-5-phenyl-1,3-dioxan-2-one ( 1 ) and 5,5-diphenyl-1,3-dioxan-2-one ( 2 ), was carried out. The anionic homopolymerization of 1 readily proceeds to afford the corresponding polycarbonate, while 2 showed only a slight homopolymerizability. This is due to a rapid back biting reaction of the propagating polymer end to form 2 . The conformational restriction of the adduct of 2 with an alkoxide, originating from the electrostatic repulsion between the alkoxide anion and the π electrons of the aromatic rings, might cause the rapid back biting reaction. The anionic copolymerization of 2 with 5,5-dimethyl-1,3-dioxan-2-one ( 3 ) proceeds to afford the copolymer. The anionic ring-opening polymerization of 1 was confirmed to be an equilibrium polymerization. Monomer 1 was regenerated up to the equilibrium monomer concentration by depolymerization of poly( 1 ). A volume expansion (10.8%) was observed during the polymerization of 1 .     

Synthesis and ring-opening polymerization of 2-acetoxymethyl-2-alkyltrimethylene carbonates and of 2-methoxycarbonyl-2-methyltrimethylene carbonate; a comparison with the polymerization of 2,2-dimethyltrimethylene carbonate

The polymerization of 2-acetoxymethyl-2-alkyltrimethylene carbonates (alkyl = methyl: AMTC, alkyl = ethyl: AETC) and of 2-methoxycarbonyl-2-methyltrimethylene carbonate (MMTC) in toluene with sec-butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(-AETC) afford crystalline materials upon precipitation from solution while poly-(AMTC) is amorphous; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2-dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be k_app^DTC = 4 ċ 10⁻³ s⁻¹, k_app^AETC = 4,28 ċ 10⁻² s⁻¹, and k_app^MMTC = 2,57 ċ 10⁻² s⁻¹. Studies of ring-chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson-Stockmayer the characteristic ratios of the polymers are C_∞^PDTC = 7,1, C_∞^PMMTC = 8,6, C_∞^PAETC = 9,9, and C_∞^PAMTC = 13,4.     

Copolymerization via zwitterion, 5. β-butyrolactone and 2-methyl-2-oxazoline

The zwitterionic copolymerization of 2-methyl-2-oxazoline (MOX) as nucleophilic monomer with β-butyrolactone (BUL) as electrophilic monomer was investigated in bulk and in solution (CH₃CN) at 45°C. The copolymer composition was around 1,5/1,0 (BUL/MOX) as was established by ¹H NMR. ¹H and ¹³C NMR spectroscopy were used to identify the copolymers. The IR spectroscopy supported the NMR results. On the other hand, the copolymers behave as polyelectrolytes, according to viscosity determinations. A copolymerization mechanism through a zwitterion species is suggested.     

Cationic ring-opening polymerization behavior of 2-ethenyl-4-methylene-1,3-dioxolane

The cationic ring-opening polymerization of 2-ethenyl-4-methylene-1,3-dioxolane ( 3 ) was carried out. The unsaturated cyclic acetal 3 was prepared by dehydrochlorination of 4-chloromethyl-2-ethenyl-1,3-dioxolane, which was readily obtained from acrolein and epichlorohydrin, with sodium methoxide at ambient temperature. The cationic polymerization of 3 with BF₃OEt₂ or CF₃SO₃H at ?78°C afforded cross-linked polymers, whereas the polymerization by CH₃SO₃H gave a soluble poly(keto-ether) which consisted of a unit containing a carbon-carbon double bond in the side chain (unit 4 ) and a unit containing a vinyl ether group in the main chain (unit 5 ). The reaction of 3 with ethanethiol in the presence of a protic acid was also carried out as a model reaction of the polymerization. The reaction was initiated by addition of a proton to the 4-methylene group of 3 , followed by quantitative ring-opening isomerization to afford acyclic ketones containing the ethylthio group. On the basis of the model reaction, some speculation on the polymerization mechanism is disclosed.     

Anionic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate

The anionic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate in solution with sec-butyllithium as initiator was found to result under suitable conditions in a bimodal molecular weight distribution, vic. cyclic oligomers and a high-molecular-weight polymer. The concentration of cyclic oligomers approaches that of a ring chain equilibrium. In the kinetically controlled regime high polymer yields were obtained. Optimum reaction conditions for a polymer yield of 85 – 95% are a temperature of ?10°C, an initial monomer concentration of 10 weight-% and toluene as solvent. In THF the ring chain equilibrium is achieved readily. The ceiling temperature was determined to be ≈ 30°C. The homopolymer was characterized by spectroscopic, thermoanalytical and viscosity measurements. A high degree of crystallinity was observed.