Anionic Polymerization Process Research Articles

Evaluation of the titanium, aluminum and silicon oxides effect on the copolyamides synthesis and their properties

The effect of inorganic additives on the ε-caprolactam with ω-dodecalactam anionic (co)polymerization process and on the properties of synthesized samples is investigated. Aluminum oxide, titanium dioxide and silicon dioxide were used as inorganic additives. It is shown that the introduction of additives at a 1 mol.% concentration at the stage of copolycaproamide synthesis contributes to a decrease in the ε-caprolactam with ω-dodecalactam anionic (co)polymerization rate. The influence of the selected additives on the physico-mechanical, thermal and operational properties complex has also been studied. It was found that the use of inorganic additives at a 1 mol.% concentration at the synthesis stage contributes to an increase in destruction temperatures compared to unmodified samples. It was found that the introduction of aluminum oxide, titanium dioxide and silicon dioxide leads to an increase in physical and mechanical parameters and Shore hardness, a decrease in water absorption and oil and gasoline resistance.

Investigating The Kinetics of Anionic Polymerization of Butadiene in Presence of 1,2‐diethoxypropane Using Online Near‐Infrared Spectroscopy

AbstractOnline near‐infrared spectroscopy technique is employed to investigate the kinetics of the anionic polymerization of butadiene with n‐butyllithium initiator in the presence of the microstructure modifier 1,2‐diethoxypropane (DEP) in cyclohexane solvent. A phenomenological kinetic model is developed to describe the anionic polymerization process in the presence of DEP, and its influence on the microstructure of polybutadiene under different conditions is determined.

Thermoplastic Composite Materials Approach for More Circular Components: From Monomer to In Situ Polymerization, a Review

To move toward eco-sustainable and circular composites, one of the most effective solutions is to create thermoplastic composites. The strong commitment of world organizations in the field of safeguarding the planet has directed the research of these materials toward production processes with a lower environmental impact and a strong propensity to recycle the polymeric part. Under its chemical properties, Nylon 6 is the polymer that best satisfies this specific trade-off. The most common production processes that use a thermosetting matrix are described. Subsequently, the work aimed at investigating the use of thermoplastics in the same processes to obtain comparable performances with the materials that are currently used. Particular attention was given to the in situ anionic polymerization process of Nylon 6, starting from the ε-caprolactam monomer. The dependencies of the process parameters, such as temperature, time, pressure, humidity, and concentration of initiators and activators, were therefore investigated with reference to the vacuum infusion technique, currently optimized only to produce thermosetting matrix composites, but promising for the realization of thermoplastic matrix composite; this is the reason why we chose to focus our attention on the vacuum infusion. Finally, three production processes of the polymeric matrix and glass fiber composites were compared in terms of carbon footprint and cumulative energy demand (CED) through life-cycle assessment (LCA).

Synthesis and Characterization of Biodegradable Poly(butyl cyanoacrylate) for Drug Delivery Applications

Poly(butyl cyanoacrylate) (PBCA) is a biodegradable and biocompatible homopolymer which is used as a carrier matrix for drug delivery systems in the pharmaceutical industry. Typically, polymerization is carried out under aqueous conditions and results in molecular weights are mostly lower than 3000 g/mol due to the instability of the high molecular weight PBCA. However, the stability of polymer excipients is a major prerequisite for drug product development in the pharmaceutical industry. In this work, a reliable polymer synthesis strategy for PBCA was designed to control the molecular weight in a nonaqueous polymerization environment. The anionic polymerization process and the impact of key synthesis parameters were investigated. The results confirmed that the previously postulated depolymerization–repolymerization process (DPRP) in the literature can be used to tailor the molecular weight of PBCA. The amount of sodium methoxide present during the polymerization proved to be the key parameter to control the DPRP and the molecular weight as desired. In addition, it was discovered that end-capping the PBCA chain suppressed the DPRP and prevented monomer release by depriving the PBCA of its living character. Thus, neat PBCA polymer with varying molecular weights determined by Advanced Polymer Chromatography™ as well as end-capped PBCA were synthesized, and the improvement of the chemical and shelf-life stability were confirmed using NMR.

C5 and C6 Polymerizations by Anion Migrated Ring-Opening of 1-Cyclopropylvinylbenzene and 1-Cyclobutylvinylbenzene

As an emerging method, anion migrated ring-opening polymerization (AMROP) can effectively regulate the carbon skeletons of polymer backbones with specific vinyl monomers. As reported here, polymers with C5 and C6 skeletons were synthesized by AMROP of 1-cyclopropylvinylbenzene (CPVB) and 1-cyclobutylvinylbenzene (CBVB). Moreover, C4 polymerization of 1-phenyl-1,3-butadiene (1-PB) was also conducted (in a general anionic polymerization process) for comparison with C5 and C6 polymerizations. Among the three base polymers prepared with the C4, C5, and C6 polymerizations, PCBVB exhibited the most flexible carbon skeleton structure and the lowest glass transition temperature (Tg = −18.8 °C). Then, the resultant base polymers with different carbon skeletons were hydrogenated and cyclized. The hydrogenation of P(1-PB), PCPVB, and PCBVB resulted in the formation of products with unique alternating styrene/ethylene (alt-SE), periodic styrene/ethylene/methylene (pd-SEM), and periodic styrene/ethylene/ethylene (pd-SEE) structures. Moreover, pd-SEM and pd-SEE can be considered as sequence-defined template polymers, and these structures cannot be synthesized through general copolymerization of styrene and ethylene. Owing to the specific carbon skeletons exhibited in alt-SE, pd-SEM, and pd-SEE, their Tg values showed significant differences (24.6, 10.9, and −6.0 °C, respectively). Additionally, the specific carbon skeletons of the base polymers resulted in the formation of cyclized polymers with different annular substituents. Moreover, diverse annular substitutes endowed the cyclized polymers with prominent thermal resistance and luminescence properties. Through the above investigations, it is clearly demonstrated that small changes in carbon skeleton structure can remarkably affect the polymer properties. Moreover, AMROP provides a new strategy to design novel polymers with C5 and C6 skeleton structures.

A simple and general approach for the synthesis of biodegradable triblock copolymers by organocatalytic ROP from poly(lactide) macroinitiators

To overcome the present limitations in the synthesis of biodegradable triblock copolymers with PLA as central building block, three different reactional mechanisms (coordination-insertion, anionic and cationic) have been involved, while employing the transition from organometallic to organic catalysis. Even though activated chain-end mechanism with stannous octanoate is well known for the successful ROP catalytic reactivity, the synthesis of PLA based triblock copolymers according to this route revealed not negligible transesterification reactions. In the same way, the activated chain-end mechanism through nucleophilic activation (TBD) presented either no reactivity or weak control over the anionic polymerization process. Herein, we therefore propose an activated monomer mechanism as general and simple route for obtaining controlled PTMC-b-PDLLA-b-PTMC and PCL-b-PDLLA-b-PCL triblock copolymers by using cationic organocatalysis (MSA). 1H, 13C NMR and DOSY-NMR spectra confirmed the well-controlled polymer architecture of the B-A-B triblock copolymer.

Anionic Polymerization of Butadiene Using Lithium/Potassium Multi-metallic Systems: Influence on Polymerization Control and Polybutadiene Microstructure

Thermal, mechanical, and viscoelastic properties of polybutadiene-based rubber materials are highly dependent on polybutadiene microstructure. The use of polar modifier in association with alkyllithium is a well-known method to obtain polybutadiene with a high vinyl content. Another approach is to use bimetallic initiating species such as alkyllithium combined to heavier alkali metal alkoxide (RONa, ROK…). The polymerization control is nevertheless not achieved and several parameters were found to influence it. Using bimetallic initiating systems based on alkyllithium and a potassium alkoxide, alkyllithium structure, initiator preformation time, and initiator composition were identified as parameters influencing the anionic polymerization process of butadiene and/or polybutadiene microstructure. In addition, the use of trimetallic systems based on alkyllithium, potassium alkoxide, and alkylaluminum was investigated in order to prevent side reactions regardless of the [K]/[Li] ratio and of the initiator preformation time.

Kinetics of the Structural Relaxation in Borosilicate Melts

The kinetics of structural relaxation in oxide systems containing complexing elements—boron and silicon— was studied by the potentiometric method. The effect of the nature and composition of the oxide electrolyte and the quenching temperature on the kinetic parameters of the anionic polymerization process was uncovered. Modeling of the relaxation processes in liquid borosilicates was conducted. Two kinetic schemes of structural relaxation, taking account of the slowness of the depolymerization of silicon oxide complexes and change of the coordination of boron, are examined. The influence of different physical and chemical factors on the rate of the relaxation processes and the equilibration time are analyzed.

New Vistas on the Anionic Polymerization of Styrene in Non-Polar Solvents by Means of Density Functional Theory.

The elementary processes of anionic styrene polymerization in the gas phase and in cyclohexane were studied using M062X (a recently developed density functional theory (DFT) method) combined with the 6-31+G(d) basis sets, in order to clarify the complicated phenomena caused by the association of the active chain-ends and elucidate the details of the polymerization mechanism. Three types of HSt2Li (a model structure of polystyryllithium chain-ends) were obtained; the well-known first structure in which Li is coordinated to the side chain, the second structure in which Li is coordinated to the phenyl ring, (both without the penultimate unit coordination), and the third structure in which Li is coordinated to both the chain-end unit and the penultimate styrene unit. Although the third HSt2Li is the most stable as expected, the free energy for the transition state of its reaction with styrene is higher than those for the other two transition states due to its steric hindrance. The free energy for the transition state of the reaction of the second HSt2Li with styrene is the lowest, suggesting that the route through it is the predominant reaction path. The penultimate unit effect, slower addition of styrene to HSt2Li than to HStLi, is attributed to coordination of the penultimate styrene units of the polystyryllithium dimer (one of the starting materials) to its Li atoms. The calculated enthalpy for the reaction barrier of the second HSt2Li with styrene in cyclohexane was found to agree with the observed apparent activation energy in benzene.

Ionic polymerization in an electric field and consequences of the spatial redistribution of growing macroions and counterions

Reaction mixtures in which polymerization processes proceed are investigated both in an electric field and under classical conditions. The observed kinetic effects are explained using a model concept of the primary contribution to the revealed field effects from the dissociation of ion pairs due to the spatial redistribution of ions. This model may be applied to both cationic and anionic polymerization processes.

Feasibility Study on Continuous Flow Controlled/Living Anionic Polymerization Processes

A practical microchemical reaction system for keeping process flow at defined conditions, which is one of the key issues of industrial production, was developed. Controlled/living anionic polymerization was chosen as a test reaction because the molecular weight and molecular weight distribution of polymer products are quite sensitive to the relative flow rate of an initiator solution and that of a monomer solution. The polymerization of styrene in THF/hexane was carried out using a flow microreactor system consisting of two T-shaped micromixers and two microtube reactors using Smoothflow pumps at 0 °C. Poly(styrene) with higher molecular weight such as Mn > 10000 could be synthesized using s-BuLi (Mn = 14 000, Mw/Mn = 1.11). n-BuLi could also be used as an initiator. The continuous operation was performed for 3 h without any problems to obtain ca. 1 kg of the polymer, indicating the feasibility of continuous flow processes for controlled/living anionic polymerization on a relatively large scale.

Microencapsulation of 1-methylimidazole using solid epoxy resin: study on microcapsule residence time and properties of the system

In this study for the first time 1-methylimidazole was microencapsulated successfully by solid epoxy resin using solvent evaporation method. Fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric and differential scanning calorimetry were used for characterization of microcapsule and epoxy resin/microcapsule systems. The results revealed that although the solid epoxy shell was in contact with imidazole curing agent for a long time, it still remained as a thermoplastic. The chain length of the solid epoxy resin was grown in anionic polymerization process which led to an increase in the melting temperature from 64 to 78 °C. On the other hand, all epoxy functional groups of the shell did not participate in the curing reaction of resin with core curing agent of the microcapsule. The results showed that by increasing the residence time of the microcapsules, the number of epoxy groups of liquid epoxy decreased slightly but the rate of complex viscosity increase or the rate of curing reaction was increased and the cured epoxy system exhibited a single-phase morphology. On the other hand, in the presence of microcapsules the curing reaction of epoxy resin was successfully carried out and the curing temperature and the onset of viscosity increase or gel time at 120 °C were not more or less affected by sufficiently long contact time of epoxy and microcapsule.

Enhanced antitumoral activity of doxorubicin against lung cancer cells using biodegradable poly(butylcyanoacrylate) nanoparticles.

Doxorubicin (Dox) is widely used for the combined chemotherapy of solid tumors. However, the use of these drug associations in lung cancer has low antitumor efficacy. To improve its efficacious delivery and activity in lung adenocarcinoma cells, we developed a biodegradable and noncytotoxic nanoplatform based on biodegradable poly(butylcyanoacrylate) (PBCA). The reproducible formulation method was based on an anionic polymerization process of the PBCA monomer, with the antitumor drug being entrapped within the nanoparticle (NP) matrix during its formation. Improved drug-entrapment efficiencies and sustained (biphasic) drug-release properties were made possible by taking advantage of the synthesis conditions (drug, monomer, and surfactant-agent concentrations). Dox-loaded NPs significantly enhanced cellular uptake of the drug in the A549 and LL/2 lung cancer cell lines, leading to a significant improvement of the drug’s antitumoral activity. In vivo studies demonstrated that Dox-loaded NPs clearly reduced tumor volumes and increased mouse-survival rates compared to the free drug. These results demonstrated that PBCA NPs may be used to optimize the antitumor activity of Dox, thus exhibiting a potential application in chemotherapy against lung adenocarcinoma.

Thermally cross-linkable hole transporting polymer synthesized by living anionic polymerization for effective electron blocking and reduction of exciton quenching in multilayer polymer light emitting diodes

A new cross-linkable polymer (d-PBAB), which has triphenylamine as the hole transporting moiety and ethynyl group as the thermal cross-linker, was synthesized by a living anionic polymerization and deprotection process. The thermally cross-linked d-PBAB layer had a smooth surface and excellent solvent resistance. The PLED fabricated with cross-linked d-PBAB as hole transporting layer (HTL) showed approximately one and half times higher luminance and four times higher luminous efficiency than those obtained from PLED with PEDOT:PSS. This is ascribed to better abilities of cross-linked d-PBAB to block electrons and prevent exciton quenching than those of PEDOT:PSS at the emitting layer (EML) interface. These results strongly suggested that cross-linked d-PBAB can be a promising material to replace conventional PEDOT:PSS.

Ionic oligomerization of acrolein in water

The main purpose of this study was to generate aldehyde-functionalized macromolecules that are soluble in common solvents, to be used as new cross-linkers for polymer materials. To do so, the synthesis of oligo(acrolein)s in water, at room temperature, has been performed by anionic and cationic polymerization processes. Using indium metal as a Lewis acid, optimized polymerization conditions reached molar masses around 2000 g mol−1 and a final aldehyde content of typically 30–40 mol%, as measured by chemical titration and 1H NMR spectroscopy.

Isotactic-specific anionic polymerization of N-isopropylacrylamide with dilithium tetra-tert-butylzincate in the presence of a fluorinated alcohol or Lewis acid

The polymerization of N-isopropylacrylamide (NIPAAm) with dilithium tetra-tert-butylzincate (TBZL) has been investigated in toluene at low temperatures in the presence of alkyl and fluorinated alcohols. Of the alcohols examined, 1,1,1,3,3,3-hexafluoro-2-propanol induced isotactic specificity and accelerated the polymerization process, affording the corresponding poly(NIPAAm)s with meso (m) diad contents of 82% in relatively high yields. It is worthy of note that the introduction of a fluorinated alcohol, which is typically used as an inhibitor in conventional anionic polymerization processes, enabled control over the stereospecificity and rate of the anionic polymerization of NIPAAm when TBZL was used as an initiator. Yttrium trifluoromethanesulfonate also induced isotactic specificity in the NIPAAm polymerization process in methanol and gave poly(NIPAAm) with an m diad content of 88% in high yield.

Polyamide 6/Polyurethane/Graphite Composites Prepared by Anionic Polymerization Process. I. Mechanical Properties

Polyamide 6/polyurethane/graphite composites have been prepared by anionic polymerization process. The effect of graphite concentration on mechanical properties of the composites was investigated. The test results show that with increment of graphite content, tensile strength of the composites increases firstly, and then decreases, while notch impact strength decreases. The change of mechanical properties of the composites is attributed to the dispersion of graphite, the interfacial properties between the matrix and graphite and the nucleation effect of graphite. In addition, the relationships between loss factor(Tan δ), storage module(E’) and temperature were investigated using Dynamic Mechanical Analysis(DMTA), and the morphological characteristic of the composites were studied using Scanning Electronic Microscope (SEM).

Polyamide 6/Polyurethane/Graphite Composites Prepared by Anionic Polymerization Process. II. Friction and Wear

Polyamide 6-polyurethane (PA6-PU) block copolymers filled with graphite particles were prepared by anionic polymerization process. The friction and wear experiments were conducted using a UMT-3 machine with the chromium steel ball sliding on surface of the composites at high sliding speeds of 500rpm, 1000rpm and 1500rpm and loads of 78.5N and 157N. With adding of graphite, coefficient of friction and wear rate values of the composites decreased firstly, and then increased. And the influence of the applied load and sliding speed on tribological properties of the composites was explored in this study. The results showed coefficient of friction and wear rate values increased with the increasing of load. Coefficient of friction decreased and wear rate values increased with increasing of sliding speed. Microstructure of wear surface of the tested composites was inspected by scanning electronic microscope(SEM) and wear mechanism of the composites was studied.

Two‐Dimensional Chromatographic Analysis of Polystyrene‐block‐poly(methyl methacrylate) Copolymers Synthesized by Selective Oxidation of Polystrene‐9‐borabicyclo[3.3.1]nonane

AbstractSummary: The preparation of polystyrene block methyl methacrylate copolymers (PS‐b‐PMMA) is described. The polystyrene segment was prepared by anionic polymerization and the methylmethacrylate segment was prepared via free radical autoxidation of a borane agent attached to the styrene chain.1 The chemistry involves a transformation of the anionic polymerization process to borane chemistry by firstly producing polystyrene with chain end unsaturated alkyl functional groups prepared using a n‐butyllithium initiator and termination with allylchlorodimethylsilane. Secondly, the unsaturated macroinitiator end was hydroborated by 9‐borabicyclo[3.3.1]nonane (9‐BBN) to produce a borane terminated PS. Thirdly, the borane group at the chain end was selectively oxidized and converted to polymeric radicals in the presence of methyl methacrylate which then initiated radical polymerization to produce block copolymers. The polymer obtained was characterized using several chromatographic techniques including LC‐CC (liquid chromatography under critical conditions) for the polystyrene segments and two‐dimensional chromatography with LC‐CC in the first dimension and SEC in the second. The results show that block formation was successful although significant homopolymerization of methyl methacrylate is also obtained.

Architecturally and Chemically Modified Poly(1,3‐cyclohexadiene)

AbstractStar‐shaped, star‐block‐linear, and hyperbranched poly(1,3‐cyclohexadiene) (PCHD) (co)polymers were synthesized through a convergent living anionic polymerization process or via addition of divinylbenzene. Chemical modification of star‐shaped PCHDs, including aromatization, hydrogenation, fluorination, and sulfonation, was carried out in order to manipulate the physical and thermal properties of these materials. The obtained (co)polymers were characterized by gel permeation chromatography, 1H NMR, DSC, and thermal gravimetric analysis in order to elucidate their molecular weights, molecular weight distributions, chemical nature, and physical and thermal properties. The synthetic approaches described herein offer routes to novel structure and functionality in PCHD‐based materials.magnified image