J. Stehlíček

Anionic polymerization of ϵ-caprolactam-lix effect of the ratio of reacting components, of the medium and of the ring size on the initial stage of the anionic polymerization of lactams

Abstract Effects of the concentrations and ratio of reacting components and of temperature on the kinetics of reaction of N-propionyllactam (I) with potassium salt of lactam (KL) were studied for derivatives of ϵ-caprolactam, 8-octanelactam and 12-dodecanelactam. For ϵ-caprolactam, the initial rates of propagation, acylation of open-chain amide groups and condensation of growth centres were estimated. At the ratio of the starting components [I]0/[KL]0 = 0.5-3, the participation of the polymerization reaction is constant, amounting to ca 45% of the overall consumption of 1. The condensation reaction is 14–36% of the total consumption of I; its initial rate passes through a maximum at [I]0/[KL]0 = 2. With increasing permittivity of the medium, the total rate of consumption of I increases; in two media with the same bulk permittivity, however, the rates may differ by as much as one order of magnitude.

Block copolymers of ϵ-caprolactam and oxirane prepared by the activated anionic polymerization of ϵ-caprolactam

Abstract Block copolymers polycaprolactam-polyoxyethylene-polycaprolactam were prepared by anionic polymerization of caprolactam activated with α,ω-dicarbonylcaprolactam-polyoxyethylenes and characterized by the content of the polyether component, crystallinity of the polyamide component and sorption of water.

Block copolymers polycaprolactam-polystyrene-polycaprolactam prepared by the anionic polymerization of caprolactam

Abstract ABA block copolymers, where A and B represent polyamide and polystyrene segments respectively, were prepared by the anionic polymerization of caprolactam activated with polystyrene-bis-acyllactams. Under mild polymerization conditions (in a solvent at 120°), very pure copolymers were obtained containing only traces of polystyrene homopolymer and ≤ 2.5% of polycaprolactam. The length of the blocks A can be controlled by the polymerization time and by the amount and type of the solvent.

Block copolymers poly(8-octanelactam)-polystyrene-poly(8-octanelactam) and poly(12-dodecanelactam)-polystyrene-poly-(12-dodecanelactam) prepared by the anionic polymerization of lactams

Abstract Copolymers consisting of triblocks poly(8-octanelactam)-polystyrene-poly(8-octanelactam) and poly(12-dodecanelactam)-polystyrene-poly(12-dodecanelactam) were prepared by solution anionic polymerization of lactams with the appropriate polystyrene-bis-acyllactams at 120°. Both crosslinked and soluble products were formed with 8-octanelactam in toluene, while polymerization in dimethylacetamide gave rise to soluble copolymers. Thus, the solvent affects side condensation reactions leading to crosslinking.

Anionic polymerization of caprolactam—LII. Effect of reaction conditions on the content of acidic and basic groups in the polymer

Abstract The concentration of acidic groups in water-extracted polymers at rather short reaction times and temperatures of about 200° is predominantly determined by the initial concentration of activator; at higher temperatures and long reaction times, the concentration of acidic groups depends in the first place on the initial concentration of sodium caprolactam as initiator. The acidic groups are not composed of carboxylic groups only; some of the groups are due to the hydrolysis of labile structures during extraction of the polymer with boiling water. While the concentration of acidic groups in the polymer approximately attains the initial concentration of sodium caprolactam, the concentration of basic groups in the polymer may exceed this value several times. The rate of formation of basic groups is proportional to the instantaneous concentration of the strong base.

Non-activated and activated anionic polymerization of adipimide

Abstract The ring opening polymerization of adipimide was studied in the presence of sodium adipimide as catalyst and triacetamide as activator. Over the temperature range 120–220°, the polymer was insoluble in the monomer; therefore the polymerization ceased almost completely as soon as the reaction mixture solidified although the catalyst was still active. Attempts to copolymerize adipimide with 5- and 6-membered cyclic imides yielded polyadipimide only.

The preparation of copolymers with polydimethylsiloxane and polycaprolactam blocks by the anionic polymerization of caprolactam

Block copolymers of polydimethylsiloxane (PDMS) with polycaprolactam were obtained by the anionic polymerization of e-caprolactam using bifunctional PDMS activators prepared by the partial aminolysis of N,N′-isophthaloyl-bis(e-caprolactam) with α,ω-di(3-aminopropyl)-PDMS. Copolymers containing 10–43 wt% PDMS blocks were prepared by solvent-free polymerization (150°) or in boiling toluene and were characterized by extraction, PDMS content, viscosity of dilute solutions, light scattering and sorption of water vapour at relative humidities 65 and 93%.

Anionic polymerization of ϵ-caprolactam—LX. Ionization and solvation changes in the initial stage of the anionic polymerization of lactams in tetrahydrofuran☆

Abstract Interactions between potassium salts of lactams and N-acyllactam propagation centres in the initial stage of the anionic polymerization of lactams were studied by measuring changes in the electric conductivity and in the i.r. spectrum in the range of carbonyl vibration bands of these compounds and of the corresponding derivatives of open-chain alkylamides in tetrahydrofuran. The gradual rise in conductivity and u.v. absorption around 300 nm observed with these systems can be attributed to the formation of 3-oxoimide and 3-oxoamide structures by the condensation of imides.

Anionic polymerization of ϵ-caprolactam—LXI. transacylation of imides and salts derived from various lactams and N-alkyl amides

Abstract The exchange of acyl groups between N -acyllactams or N , N -diacylalkylamines and potassium salts of lactams or N -alkylamides was followed in THF at the initial molar ratio approx. 1:1 in systems either where propagation and other acylation reactions occur or where propagation is excluded and C-acylations are suppressed. The rate of exchange strongly depends on the acidity of the lactam (amide) from which the potassium salt is derived and on the structure of the acyl group.

Polymerization of lactams—XVI: Cyclic oligomers in copolymers of 6-caprolactam with 8-octanelactam and their determination by mass spectroscopy

Abstract The methanolic extract of a copolymer of 6-caprolactam with 8-octanelactam was analyzed; cyclic oligomers were identified by mass spectroscopy. The cyclic homodimers and codimer were separated by thin-layer chromatography. The quantitative analysis of methanolic extract involved direct evaporation into the ion source of mass spectrometer.