Cyclic oligomers content in anionic poly (ϵ-caprolactam)

The influence of initiator and activator concentrations on the anionic polymerization of ϵ-caprolactam and, in particular, on the methanol – extractable fraction of the final polymer has been widely studied. Due to the increasing interest of this polymerization in the field of reaction injection molding (RIM) technology, a thorough investigation has been also carried out to find the best experimental conditions for this reaction in the mold. The effect of postpolymerization annealing on the overall amount of low-molecular mass substances, among which cyclic oligomers, has been evaluated. Thermal properties as well as crystallinity of the resultant materials have been examined. A comparison with literature data is given; the suggested correlation between the amount of the oligomeric fraction and the molecular arrangement of the polymer in the solid state is discussed.     

Nylon 6/polyisocyanurate interpenetrating polymer networks (IPNs)

Two component interpenetrating networks (IPNs) of the SIN type (simultaneous interpenetrating networks), composed of a polyisocyanurate network and a star-shaped nylon 6, were made. The overall polymerization rates and physical properties for reaction injection molding (RIM) have been studied by the quasi-adiabatic process. In order to model the actual rapid molding conditions, time versus temperature reaction profiles were measured, and the relative rates of polymerization subsequently determined from these data.     

On the behavior of organophosphorus lactam derivatives during anionic polymerization of ε-caprolactam

This article deals with the anionic polymerization of ε-caprolactam in the presence of N-substituted phosphorus-containing derivatives of ε-caprolactam: diethyl-(N-caprolactam)-phosphonite (PL₁); diethyl-(N-caprolactam)-phosphonate (PL₂), and 2,5-dichlorophenyl-bis-(N-caprolactam)-phosphinate (PL₃). It has been found out that PL₁ and PL₃ had an accelerating effect on the anionic polymerization of ε-caprolactam. The polymerization runs at high velocity and high degree of conversion. PL₂ does not accelerate the anionic polymerization of ε-caprolactam, but when the polymerization is activated by a strong activator of acyl lactam type, and the PL₂ concentration is commensurate with that of the activator, the process runs at a slightly lower rate and at a relatively high degree of conversion. The kinetics of the anionic polymerization in the presence of the three compounds was investigated. Equations describing the effect of the reagents on the polymerization rate were suggested. The activating energy of the polymerization was found out. The different actions of PL₁, PL₂, and PL₃ during the anionic polymerization of ε-caprolactam were explained by their structural differences.     

Anionic polymerization of ε-caprolactam and its copolymerization with ω-dodecanelactam in the presence of aromatic polyimides

The anionic polymerization of ε-caprolactam in the presence of aromatic polyimides as activators has been studied under adiabatic conditions. It has been shown that despite the crosslinked structure the produced graft copolymers of polycaproamide and polyimides contain the crystalline phase and are characterized by better water resistance and thermal stability, a higher content of the gel fraction, and improved mechanical properties as compared to copolymers prepared under the so-called isothermal conditions. It has been demonstrated that the catalytic system MgBr-ε-caprolactam-aromatic polyimide may be used for the anionic copolymerization of ε-caprolactam with ω-dodecanelactam, and experimental conditions providing a copolymer yield of 75% have been developed.     

Preparation of anionic polymerized polyamide 6 using internal mixer: The effect of styrene maleic anhydride as a macroactivator

The effect of styrene maleic anhydride (SMA) on the anionic polymerization of ?-caprolactam was investigated. Poly-caprolactam (PA6) was prepared at three levels of hexamethylene diisocyanate (HDI) as the microactivator and three levels of SMA in an internal mixer at 200 °C. Then, the polymerization characteristics obtained from the mixing torque curves were compared. With increasing HDI content, reaction time decreased and the reaction rate increased. Final torque, which is attributed to the molecular weight of the synthesized polymer, showed a peak in the average level of HDI. In the presence of SMA, final torque had the same trend, but reaction time increased and reaction rate decreased. Monomer conversion increased by raising both the HDI and SMA contents. In solvent separation by formic acid, samples were found to behave differently. Anionic polymerized polyamides with no SMA formed a uniform and transparent solution, while SMA-containing samples turned into a canescent solution having a colloidal suspension part. The remaining small amount of SMA after solvent separation proved the attribution of SMA in the reaction.FTIR spectra of samples indicated that SMA acts as a macroactivator in the anionic polymerization of ?-caprolactam. Also, samples containing SMA showed only one glass transition temperature which was higher than that of samples without SMA, suggesting the existence of a copolymer of SMA and PA6, which raises the Tg.     

Homoionic inorganic montmorillonites as fillers for polyamide 6 nanocomposites

The homoionic montmorillonites Ca-MMT, Mg-MMT, Ba-MMT and Ca-MMT intercalated with ε-caprolactam - Ca-MMT·CL were prepared from commercial Na-MMT and characterized by WAXS and TGA. They were used as fillers for nanocomposites of polyamide 6 synthesized either by anionic polymerization of ε-caprolactam (monomer casting) or by melt blending. WAXS analysis showed that the intercalation of MMT by the polyamide was complete for all nanocomposites, with only a very small fraction of exfoliated platelets being detected by TEM. The decrease in the number of layers in the MMT tactoids suggests that tactoid splitting was lower for the blended nanocomposites than for the polymerized ones. Both the rate of polymerization and the polyamide yield in the nanocomposites were comparable to those of an unfilled system. The MMT fillers, the density of which was more than twice that of the ε-caprolactam in which they were suspended, sedimented during the first stage of polymerization. TGA was used to determine the degree of sedimentation at various levels of the resulting mold. In line with the coordination of polyamide chains to the surface cations of MMT particles, the sedimentation level increased in the following sequence: Mg-MMT < Ba-MMT < Ca-MMT·CL << Na-MMT. Ca-MMT was found to be the only non-sedimenting filler suitable for use in the synthesis of polyamide nanocomposites by either monomer casting or the use of reactive injection molding (RIM) technologies.     

Polymerization of lactams. 98: Influence of water on the non-activated polymerization of ε-caprolactam

The sensitivity of so-called non-activated polymerization of ε-caprolactam to the presence of water in the polymerization mixture has been studied. Polymerizations were initiated with 1 mol% sodium salt of ε-caprolactam, magnesium di(ε-caprolactamate) and/or ε-caprolactam magnesium bromide and were carried out at water concentration 0-1 mol% and in the temperature range of 190-230 °C. The influence of water content in the polymerization mixture on the polymerization rate and polymerization degree was evaluated. The studied initiators exhibited different sensitivity to the water added in the polymerization mixture and the role of water in the course of anionic polymerization of ε-caprolactam is discussed. Magnesium initiators are exceptional, they are capable to eliminate retardation effect of water on studied polymerization.     

Anionic polymerization of ɛ-caprolactam in the presence of piperidine N-carboxamides

Piperidine N-carboxamides were shown to activate the anionic polymerization of ?-caprolactam. The activator structure affects properties of the resulting polycaproamide.     

Initiation mechanisms of an anionic ring‐opening polymerization of lactam‐12

A novel liquid system has been developed to initiate the anionic polymerization of lactam‐12. This system, containing both an activator and a catalyst, has the primary advantage over previous systems of permitting infinite storage of the reactant, and it avoids premixing of batches. The anionic species of the system were identified with matrix‐assisted laser desorption/ionization time‐of‐flight measurements, and Fourier transform infrared was used to measure the change in their concentrations during the polymerization. A guanidine anion was formed, and the system initiated the polymerization by this guanidine and by the catalyst. The kinetics of the anionic polymerization of lactam‐12 into polyamide‐12 were followed with differential scanning calorimetry measurements. The determined reaction rates indicated that this liquid system was particularly well suited for initiating in situ polymerization during liquid molding. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3406–3415, 2002     

Ions and ion pairs in anionic activated polymerization of ϵ-caprolactam

The effect of concentration of the catalytic system on the initial rate of the anionic activated polymerization of ?-caprolactam (AAPC) has been studied. It is shown that the data can be rationalized only by considering (along with side reactions such as Claisen condensation) the fact that chain growth involves both free anions and ion pairs. The possibility of formation of various associates is discussed. Quantum-chemical calculations suggest that, in the alkali metal lactamate molecule, negative charge is delocalized among the O and N heteroatoms. A possible structure for the ion pair of catalyst is suggested. The states of the Li, Na and K lactamate molecules under the conditions for AAPC are determined from conductivity measurements. Kinetic studies of AAPC with various counter ions are also described. For the Li salt, the kinetic data conflict with the results of conductometric measurements. Suppression of the dissociation of sodium caprolactamate by addition of a neutral electrolyte, sodium tetraphenylborate, results in a drastic decrease in the initial rate of polymerization, suggesting that AAPC proceeds through both free anions and ion pairs. The possibility of polymerization through the ion-coordinative mechanism is considered.     

Polystyrene-nylon 6 graft copolymers

The synthesis of well-defined polystyrene-g-Nylon 6 copolymers is described. The materials were prepared for study of their rheological behaviour and to compare it with the recent findings for 2-phase block copolymer systems.The anionic polymerization of ?-caprolactam in the presence of polystyrene-ethyl acrylate copolymer was chosen as the preparative route. The reasons for the choice were (1) the fact that ester groups are known to be good initiators for the lactam polymerization and (2) that it has been previously established that uniform copolymers can be obtained from styrene and acrylate esters. The present paper describes initial results on preparation and characterization of graft copolymers.It was found that cross-linked materials resulted when the polystyrene copolymer contained more than 1 per cent by weight of ethyl acrylate. At lower ester concentrations, soluble and thermoplastic materials were obtained. The cross-linking reaction was tentatively identified as arising from the presence of the tertiary hydrogen alpha to the ester group. In agreement with this postulate, methacrylate copolymers produced soluble, thermoplastic grafts at concentrations as high as 5 weight per cent.The mechanical properties and the modulus-temperature behaviour of the 2-phase graft copolymer systems are also presented.     

Polymerization of lactams: 97. Anionic polymerization of ε-caprolactam activated by esters

The anionic polymerization of ε-caprolactam initiated with 0.5 mol % ethyl magnesium bromide in the presence of cycloaliphatic esters (lactones), such as γ-butyrolactone, δ-valerolactone and ε-caprolactone, has been studied in the temperature range 150-190 °C and concentration up to 5 mol %. To explain reaction mechanism, the polymerizations carried out in the presence n-butyl acetate and dimethyl terephthalate were also evaluated. The apparent rate constants and apparent activation energies were determined for the initial stage of polymerization. The non-integer orders of the polyreaction with respect to the concentration of lactone introduced indicated complex polymerization mechanism.     

Anionic High Impact Polystyrene: A New Process for Low Residual and Low Cost HIPS

BASF has developed a new process for the manufacturing of High Impact Polystyrene (HIPS) via an anionic route: the so-called A-HIPS process. The driving forces were the development of a product with a low content of residuals and improved cost performance compared to the radical state of the art HIPS. The production of A-HIPS includes the synthesis of the rubber, a styrene-butadiene block copolymer. To overcome the main challenges of anionic polymerization such as reactivity control, solvent purity and initiator costs, BASF has developed its own proprietary technology, the Retarded Anionic Polymerization (R.A.P.) which allows styrene polymerization to 100% conversion under similar reaction conditions as the radical polymerization. A new low cost anionic initiator system (BuLi-free), based on sodium hydride and triethylaluminum, has been developed for perfect reactivity control over a broad temperature and concentration range even up to bulk conditions.     

Kinetic studies of photopolymerization using real time FT-IR spectroscopy

The real time FT-IR (RT/FT-IR) technique has been recognized as a very vital tool to quantitatively study the curing parameters such as the effects of initiator (or catalyst) type and concentration, accelerator, stabilizer, irradiation wavelength, temperature, and curing environments. Herein, our results in studies of photoinduced polymerizations for adhesive and coating applications are reported. The photoinduced polymerizations studied included anionic and hydrosilation (a polyaddition polymerization) reactions. In photoinduced anionic polymerization our studies for ethyl cyanoacrylate polymerization are described. The effect of the concentration of photoinitiator and inhibitor on the ethyl cyanoacrylate polymerization kinetic rate will be discussed. In photoinduced catalytic hydrosilation reaction studies, the effects of the catalyst concentration and staging irradiation are disclosed. The hydrosilation reaction was monitored using a Si? H silicone hydride stretching band located at 2169 cm^?1. The cyanoacrylate polymerization was monitored using the C?C stretching band occurring at 1617 cm^?1. The hydrosilation conversion was completed with an appropriate formulation. For monofunctional cyanoacrylate monomer, the photoinduced conversion to straight chain polymer was approximately 85% for a 60 s period. The intrinsic rates of the reactions were calculated for kinetic comparisons. For very fast cyanoacrylate polymerization studies, new FT-IR kinetic software was used to collect 204 spectra/min. Some detailed experimental techniques and polymerization reaction mechanisms are also discussed. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of polysiloxane–polyamide block and graft copolymers

The synthesis of copolymers constituted of a central polydimethylsiloxane (PDMS) block flanked by two polyamide (PA) sequences is described. α, ω-diacyllactam PDMS, when used as macroinitiator of lactam polymerization, gives rise to the expected triblock copolymer. Likewise, PDMS-g-PA graft copolymers are obtained from acyllactam containing polysiloxanes. NaAlH₂(OCH₂CH₂OMe)₂ turns out to be the best suited activating agent for the polymerization of ?-caprolactam, in the experimental conditions required for the synthesis of polysiloxane–polyamide copolymers. The nucleophilic species formed by reaction of NaAlH₂(OCH₂CH₂OMe)₂ with ?-caprolactam—2-[bis(methoxyethoxy) aluminumoxy]-1-azacycloheptane sodium—is indeed nucleophilic enough to bring about the growth of PA chains and mild enough to stay inert towards PDMS. © 1993 John Wiley & Sons, Inc.     

Ionic polymerization in aqueous emulsion

A kinetic study of the anionic polymerization of octamethylcyclotetrasiloxane (D₄) in aqueous emulsion has been carried out in the presence of ionic additives. The rate of polymerization of several cyclosiloxanes has been compared, leading to additional evidence for an interfacial mechanism of polymerization. The emulsion process has been applied to the cationic polymerization of D₄ and of tetramethylcyclotetrasiloxane (D^H₄) initiated by dodecylbenzenesulfonic acid. Very efficient for the synthesis of linear polymethylhydrogenosiloxanes (PMHS), these conditions did not seem suitable for the polymerization of D₄. The extension of the process to other heterocyclic monomers is discussed through the anionic polymerization of phenylglycidylether.     

Effect of single-walled carbon nanotubes with imide cycles on the synthesis and properties of polycaproamide

The anionic polymerization of ε-caprolactam in the presence of single-walled carbon nanotubes with grafted acyllactam groups or polyimide macromolecules is performed. It is shown that the polymerization of ε-caprolactam slows down with an increase in the filler concentration. The introduction of 0.01 wt % nanotubes with polyimide fragments into polycaproamide leads to a 25% increase in the compressive modulus. In this case, the Izod impact strength is 10 kJ/m², that is, 150% higher than that for an unfilled polycaproamide or polycaproamide containing other types of nanotubes.     

Anionically prepared poly(ε-caprolactam-co-ε-caprolactone) and poly(ε-caprolactam-co-δ-valerolactone) copolymers: Thermal and mechanical properties

Thermal and representative physico-mechanical properties of newly prepared poly[(ε-caprolactam)-co-(ε-caprolactone)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] copolymers were studied. The copolymers were synthesized by anionic polymerization of ε-caprolactam activated by isocyanate end-capped oligomeric aliphatic polyesters designated as the macroactivators (MAs). Type, concentration and molecular weight of the MAs were varied, which resulted in copolymers with different structure and properties. The impact of the new MAs used in this study on the glass transition temperature and the melting temperature of poly-ε-caprolactam was investigated by DSC. DMTA was used to analyze the effect of copolymerization on the storage modulus (E^′) and tan δ of poly-ε-caprolactam. Conventional and high-resolution TGA data revealed that all the synthesized polyesteramides possess good thermal stability. Mechanical properties were studied by notched impact and tensile testing. According to the experimental data the impact toughness increase with the MA content, being six time higher compared to the poly(ε-caprolactam) in the best situation. Water absorption was also considered in relation to the composition of the copolymers.     

Comparative study of classical surfactants and polymerizable surfactants (surfmers) in the reversible addition–fragmentation chain transfer mediated miniemulsion polymerization of styrene and methyl methacrylate

Cationic and anionic amphiphilic monomers (surfmers) were synthesized and used to stabilize particles in miniemulsion polymerization. A comparative study of classical cationic and anionic surfactants and the two surfmers was conducted with respect to the reaction rates and molecular weight distributions of the formed polymers. The reversible addition–fragmentation chain transfer process was used in the miniemulsion polymerization reactions to control the molecular weight distribution. The reaction rates of the surfmer‐stabilized miniemulsion polymerization of styrene and methyl methacrylate were similar (in most cases) to those of the classical‐surfactant‐stabilized miniemulsion polymerizations. The final particle sizes were also similar for polystyrene latexes stabilized by the surfmers and classical surfactants. However, poly(methyl methacrylate) latexes stabilized by the surfmers had larger particle sizes than latexes stabilized by classical surfactants. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 427–442, 2006     

阴（负）离子聚合二十年

近20多年负离子聚合在新引发剂体系、新单体开发以及聚合理论方面均取得了进展,出现了配伍负离子聚合LAP、阻滞负离子聚合RAP等概念。实现了对聚合物结构、聚合动力学的进一步控制。在工业方面,负离子聚合生产规模和产品应用范围扩大,同时也开发出多种新产品,如集成橡胶、负离子合成的高抗冲聚苯乙烯等国内的负离子产品开发十分迅速在加氢型负离子聚合产品方面还取得了突破性发展