Effects Of Polymerization Temperature Research Articles

Synthesis of Poly(styrene)-g-Poly(oleic acid) Graft Copolymers via Reversible Addition/Fragmentation Transfer (RAFT) Polymerization Using a Poly Oleic Acid Macro-RAFT Agent

AbstractIn this study, a new polymeric oleic acid-derived macro addition/fragmentation transfer agent was utilized to produce a poly(styrene)-g-poly(oleic acid) graft copolymer. The double bond of oleic acid was initially saturated with bromine and the condensation polymerization between the carboxylic acid and the bromide resulted in polyoleic acid with pendant bromide groups. Xanthate groups were exchanged with the bromide groups to obtain the poly(oleic acid) macro RAFT agent (Pole-Xa). Poly(styrene)-g-poly(oleic acid) (PS-g-Pole) graft copolymers were synthesized via reversible addition fragmentation transfer (RAFT) polymerization of styrene and the reaction was evaluated in view of the polymerization kinetics. The effects of polymerization temperature and reaction time on graft copolymer yield, conversion and molecular weight were investigated. In the RAFT polymerization of styrene, the rate constant (k) was found to be 1.83 × 10–3 L/mol/dk and 7.27 × 10–4 L/mol/dk for the polymerization temperatures of 80 and 90 °C, respectively. The structural characteristics and thermal properties of the obtained products were characterized using FT-IR, 1H-NMR, GPC, TGA, DSC and SEM–EDX.

Synthesis and property of EPEG‐based polycarboxylate ether superplasticizers via RAFT polymerization

AbstractPolycarboxylate ether superplasticizers (PCEs) with comb‐shaped molecular structures have attracted considerable attention in the area of admixtures for construction engineering. However, there are some contradictions in studying the relationship between the molecular structure and property of PCE due to its random structure based on traditional free radical polymerization, which is confused for designing and developing novel PCEs. In this article, a series of reversible addition fragmentation chain transfer (RAFT) polymerization‐based polycarboxylate ether superplasticizers (RPCs) were prepared by the copolymerization of acrylic acid (AA) and ethylene‐glycol monovinyl polyethylene glycol (EPEG). The chemical structure and composition of RPCs were characterized and their adsorption behavior and dispersion properties were conducted. The results demonstrate that the molecular weights of RPCs do not vary significantly with prolonging reaction time, and the actual monomer ratio in RPCs displays a significant change to the feed one due to the monomer reactivity and conversion at higher reaction temperature, which is different from conventional free radical polymerization. The dispersion and adsorption properties of RPCs to cement were evaluated by slurry fluidity tests and total organic carbon (TOC) experiments. The effect of polymerization temperature and time on the dispersion ability has been systematically studied. The results indicate that the dispersion ability and adsorption capacity of RPCs are closely related to their molecular structures. The dispersion ability of RPCs were enhanced with increasing carboxyl group density in a certain range of monomer molar ratios (≤6:1). This study will provide a new platform for designing and developing high‐performance and rational cost‐effective superplasticizers with well‐defined structure and controlled molecular weight.

Influence of temperature on ethylene octene-1 copolymerization catalyzed by supported metallocene catalyst

A supported (nBuCp)2ZrCl2 metallocene catalyst was prepared and used in the slurry copolymerization of ethylene/octene-1 with triethylaluminium (TEAL) as co-catalyst. The effects of polymerization temperature on the properties of both the catalyst and resulted copolymers were investigated. The results show that the yield of supported metallocene catalyst reaches 4.3 kgPE/gcat and the bulk density of PE is higher than 0.4 g/cm3, the fines content of the polymer is less than 12.0 wt%, and the molecular weight distribution (MWD) of products ranges from 2.9 to 4.0 within the polymerization temperature range of 73~88 °C. These results are beneficial for large-scale industrialization of supported metallocene catalysts, and also provide a reference for academic research.

Polymerization kinetics and control of the components of a mesophase pitch

It is important to increase the content of pyridine soluble in mesophase pitch to improve its spinnability. A naphthalene isotropic pitch was used as the raw material to prepare mesophase pitch by polymerization. The components of the polymerized products were analyzed by solvent extraction with benzene and pyridine, and classified as benzene soluble (BS), pyridine insoluble (PI) and benzene insoluble but pyridine soluble (BI-PS). The effects of polymerization temperature, time and the components of the raw material on the distribution of the components and optical texture of the mesophase pitch were investigated. The reaction kinetic constants were calculated assuming a consecutive reaction from BS to BI-PS, then to PI. Results show that a mesophase pitch with a relatively uniform distribution of components is obtained after reaction at 430 °C for 20 h from an isotropic pitch pre-polymerized at 400 °C for 10 h. The mesophase pitch synthesis reaction has a significant auto-acceleration effect in that the reaction rate constant of a heavy component is larger than a light one. The reaction rate becomes faster and faster as the molecular weight of the pitch increases in the latter stage of the synthesis reaction. Therefore, the initial component of raw pitch, reaction temperature and time have a decisive influence on the distribution of components in the mesophase pitch.

A Sol–gel Method for Preparing Poly (N-Isopropyl Acrylamide) Hybrid Column and Its Application in Small Molecular Analysis Using Capillary Liquid Chromatography

A poly (N-isopropyl acrylamide) (polyNIPA)-based hybrid column for capillary liquid chromatography (cLC) was prepared with N-isopropyl acrylamide (NIPA) and alkoxysilanes through a sol–gel “one-pot” method. In this process, the hydrolyzed tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) were the precursors for the synthesis of a silica-based monolith and subsequently reacted with organic monomer (NIPA) via free radical polymerization within the confines of a capillary. The effects of polymerization temperature, the volume of TMOS, VTMS, and acetic acid (HAc) as well as the amount of progens [polyethylene glycol 10,000 (PEG10000) and urea] on the morphology and permeability were investigated in detail. Uniform pore structure and good mechanical stability were obtained for columns prepared under optimized conditions. Separation of various neutral, acidic and basic analytes was achieved by cLC in reversed-phase liquid chromatography (RP-LC) mode. Moreover, the resulting hybrid column was also applied for the analysis of small organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), perfluorinated compounds (PFCs) and chlorophenols (CPs). The successful application demonstrated its potential in the separation of small molecules.

Highly conducting 1-D polypyrrole prepared in the presence of safranin

The schematic preparation of globular and 1-D polypyrrole and the effect of polymerization temperature on the conductivity.

Oscillating Swelling–Shrinking Dynamics and Diffusive Properties of Weakly Cationic Poly(Aminoalkyl Methacrylate)‐Based Cryogels: Quantifying the Influence of Polymer Network Parameters

AbstractThermodynamic properties of swelling equilibria and variability of dynamic response of pH‐sensitive polybases are examined. Poly(aminoalkyl methacrylate)‐based cryogels and hydrogels are prepared in a facile way by crosslinking polymerization of amine functional monomer N,N‐dimethylaminoethyl methacrylate (DMAEMA) in the presence of diethyleneglycol dimethacrylate as crosslinker at temperatures below and above freezing point of polymerization solvent, water, via cryogelation and conventional crosslinking polymerization. The effect of polymerization temperature on swelling characteristics of the prepared polybasic gels is investigated as a function of the gel‐preparation concentration. The overshooting effect is observed during pH‐dependent swelling of poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) hydrogels in acidic medium. Protonation/deprotonation of tertiary amine groups in network‐forming polymer demonstrates critical swelling behavior as pH of the swelling medium increases. Oscillating swelling–shrinking studies are performed and effective diffusion coefficient of water within PDMAEMA cryogel and hydrogel matrices is estimated using the dynamic swelling profiles. The mechanism of cyclic swelling–shrinking process of PDMAEMA cryogels and hydrogels are analyzed to control their pulsatile output patterns in metabolic oscillations. Considering the swelling process occurs through Fickian diffusion mechanism in acidic solutions, polybasic cryogels and hydrogels prepared in this study are thus proposed as good candidates for delivery applications.

Synthesis and Characterization of Terpolymers of poly(L-lactide-glycolide-ε-caprolactone)

Random terpolymers of poly(L-lactide-glycolide-ε-caprolactone) (PLLGC) was prepared by ring-opening polymerization of L-lactide, glycolide and ε-caprolactone monomers initiated with stannous octanoate. Fourier transform infrared spectra, nuclear magnetic resonance and gel permeation chromatography were employed to characterize the obtained PLLGC terpolymers. The effects of polymerization temperature, reaction time, the amount of initiator and the polymerization pressure on the weight average molecular mass and polydispersity index of the PLLGC were investigated. In addition, the water contact angle of the PLLGC was also tested. The characterization of chemical structure showed that the PLLGC was successfully synthesized. For instance, a PLLGC terpolymer with a weight average molecular mass of about 12.435 × 104 Da and a polydispersity index of 1.28 was obtained when the polymerization was conducted with a molar ratio of monomer to initiator ([M]/[I]) of 2000, polymerization temperature of 140 °C, polymerization pressure of 5.0 Pa and reaction time of 24 h. The random incorporation of ε-CL monomer units decreased the wettability of the PLGA copolymers.

Effect of MAO-modified nanoporous silica supports with single-site titanocene catalyst on ethylene polymerization

Three types of nanoporous silica support were modified by methylaluminoxane MAO and characterized by using BET, SEM, XRD and TGA. Dimethylsilyl (N-tert-butylamido)(tetramethylcyclopentadienyl) titanium dichlride was synthesized and immobilized on modified support. The prepared complex was then used as a reactive catalyst for ethylene polymerization. The effect of immobilization conditions on catalyst performance was studied. The results revealed elevated temperature grafting, decrease in precatalyst loading. Also, increasing of immobilization reaction time showed an increase in activity to 130 Kg poly/mol Ti.h.bar. The effects of polymerization temperature and [Al]/[Ti] ratio on the catalyst behavior, namely activity and bulk density, were investigated. According to the results, the activity of single-site catalyst depends on condition of immobilization and structure of nanoporous silica support.

The effect of polymerization temperature and reaction time on microwave absorption properties of Co-doped ZnNi ferrite/polyaniline composites.

This study presents the systematic potential effects of reaction parameters on the synthesis of Co-doped ZnNi ferrite/polyaniline composites prepared via novel interfacial polymerization. Through intensive experiments and analysis, optimum reaction conditions including the polymerization temperature and reaction time are proposed so that the performance of the material is significantly improved. The structure, functional groups and morphologies of composites are investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). In addition, the electromagnetic properties and microwave absorption properties of Co-doped ZnNi ferrite/polyaniline composites are examined by a vibrating sample magnetometer (VSM), Quantum Design (MPMS-VSM and MPMS-XL), the superconducting quantum interference device (SQUID) magnetometer and vector network analysis. Based on these analyses, it is found that by tuning the reaction conditions, i.e., polymerization temperature and reaction time, microwave absorption capabilities in terms of the maximum reflection loss (RL) value and absorber thickness can be readily optimized. The results show that the composite with an optimized polymerization condition of 20 °C for 12 h displays remarkable microwave absorption properties with maximum reflectivity of −54.3 dB, and the effective bandwidth (RL < −10 dB) is about 6.02 GHz at a thickness of 6.8 mm. Furthermore, the discussion shows that the promising microwave absorption may be due to the uniform urchin-like structure of the composites.

중합 온도가 임시 보철용 수지의 기계적 성질에 미치는 영향

본 연구의 목적은 2가지 임시 수지 (Bis-acryl resin composite 및 polymethyl methacrylate (PMMA))의 굴곡 강도 및 미세 경도에 대한 경화 순서 및 중합 온도의 영향을 조사하는 것에 있다. 중합은 대기 중 25℃ (대조) 및 온수 (40, 50, 60, 70 그리고 80℃)에서 다양한 조건하에 수행되었다. 굴곡 강도 시험은 ISO-4049에 따라 수행되었다. 또한, 누프 경도를 측정 하였다. Bis-acryl resin의 경우, 50℃까지의 온도는 굴곡 강도와 bis-acryl resin composite의 경도를 증가시키지 않았지만 (p 0.05), 온도가 높을수록 강도가 증가 하였다. PMMA 수지의 경우 굴곡 강도는 최대 70℃의 온도에서 증가하고 약간 감소합니다. Bis-acryl resin은 PMMA 수지보다 기계적 특성이 더 컸다. 열의 영향은 Bis-acryl resin에서 PMMA 수지보다 더 두드러졌다(p 0.05).

In situ polymerization synthesis of Z-scheme tungsten trioxide/polyimide photocatalyst with enhanced visible-light photocatalytic activity

Abstract A novel direct Z-scheme P-containing tungsten trioxide/polyimide (PWO/PI) photocatalyst was synthesized by an in-situ solid-state polymerization strategy to enhance the visible-light photocatalytic oxidation capacity of PI. The effects of polymerization temperature and PWO content on the physicochemical properties of PWO/PI composites and photocatalytic degradation efficiency of imidacloprid were investigated. The photocatalysts were characterized by X-ray powder diffraction, Fourier transformed infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–vis diffused reflection spectra and N 2 adsorption-desorption isothermals. The results showed that the photocatalysts with visible-light photocatalytic activity can already be prepared at 300 °C. The PWO/PI composites exhibited a lamellar structure and PWO was wrapped by PI. After PWO was introduced, there was a significant interaction between PWO and PI, and the visible light response of photocatalysts was also improved. The visible-light photocatalytic degradation efficiency of imidacloprid on 3% PWO/PI-300 composite was about 3.2 times of commercial P25, and the corresponding pseudo-first-order rate constant was about 2.9 times of pristine PI. The Z-scheme photocatalytic system of PWO/PI composites was confirmed by the electron spin resonance technology, terephthalic acid photoluminescence probing technique, reactive species trapping experiments, X-ray photoelectron spectroscopy and photoluminescence of PWO/PI composites and pristine photocatalysts.

Effect of polymerization temperature on the properties of autopolymerizing resin

Statement of problemThe polymerization conditions of an autopolymerizing resin affect its physical properties, and at chairside, 3 different methods are commonly used: cooling in cold water, warming in warm water, and heating in hot water. However, the effects of polymerization temperature on the physicomechanical properties of autopolymerizing resin are unclear. PurposeThe purpose of this in vitro study was to determine the effect of polymerization temperature on the physicomechanical properties of autopolymerizing resin, including shrinkage, water absorption, surface roughness, amount of residual monomer, and flexural strength. Material and methodsThe experiment was designed to simulate a direct technique commonly used for the fabrication of interim crowns. Autopolymerizing resin specimens were made according to the powder-to-liquid ratio recommended by the manufacturer and soaked in water at 13°C, 37°C, or 60°C for 2 minutes to mold the resin until polymerization was completed 4 minutes after mixing. Shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength were measured immediately after polymerization and after 1, 3, and 7 days in distilled water at 37°C. Differences among these properties among the 3 different temperatures groups were statistically analyzed by using 1-way ANOVA and the Tukey honest significant difference test (α=.05). ResultsShrinkage tests showed that the 13°C group had significantly lower shrinkage (P=.004 for 37°C and P<.001 for 60°C) than the other groups immediately after specimen preparation. The 13°C group had significantly higher surface roughness after 0 (P<.001 for 37°C and P<.001 for 60°C), 1 (P=.025 for 37°C and P=.012 for 60°C), 3 (P<.001 for 37°C and P<.001 for 60°C), and 7 days (P<.001 for 37°C and P<.001 for 60°C) than those in the other groups and significantly higher water absorption rates (P=.033 for 37°C and P<.001 for 60°C) than the other groups during the 7 days after fabrication. However, the 13°C group showed significantly higher weight percentage of residual monomers than the 60°C group at 0 (P<.001) and 1 day (P<.001). Finally, 3-point bend tests showed that the 13°C group had significantly lower flexural strength at 0 (P<.001), 1 (P<.001), 3 (P<.001), and 7 days (P<.001) than the other groups. ConclusionsThe temperature environment during dental chairside polymerization of the autopolymerizing resin affected the physicomechanical properties of shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength.

Synthesis of ArOTiCl 3 complexes and their application for ethylene polymerization and copolymerization

In this article, novel olefin polymerization catalyst with lower cost and simple synthetic process were developed, ArOTiCl3 complexes [(2-OMeC6H4O)TiCl3(C1), (2,4-Me2C6H3O)TiCl3(C2), TiCl3(1,4-OC6H4O)TiCl3 (C3), TiCl3(1,4-OC6H2O-Me2-2,5) TiCl3(C4)] and corresponding (ArO)2TiCl2 complexes [TiCl2(OC6H4-OMe-2)2(C5) and TiCl2(OC6H3-Me2-2,6)2(C6)] have been synthesized by the reaction of TiCl4 with phenol, all these complexes were well characterized with 1H NMR,13C NMR, MASS and EA. When combined with methylaluminoxane (MAO), the ArOTiCl3 / MAO system shows high activity for ethylene copolymerization with 1-octene and copolymer was obtained with broaden molecular weight distribution (MWD). The 13C NMR result of polymer indicates that the 1-octene incorporation in polymer reached up to 8.29 mol%. The effects of polymerization temperature, concentration of polymerization monomer and polymerization time on the catalytic activity have been investigated.

Synthesis of High Performance Polycarboxylate Superplasticizer through Redox Initiation System and its Application in Concrete

A high performance polycarboxylate superplasticizer (PCE) was successfully synthesized by a polymerization reaction among acrylic acid (AA), maleic anhydride (MA) and isopentenyl polyethylene glycol (IPEG) through redox initiation system. The composition and amounts of initiation system, and the ratio of monomers were investigated respectively. The proportion of IPGE: MA: AA: sodium methallyl sulfonate (SMAS): ammonium persulfate (APS): ascorbic acid (ASA) was determined as 1: 3: 1.5: 0.3: 0.015: 0.012. Moreover, the effect of polymerization temperature on PCE’s cement paste fluidity was studied. The results showed that the cement pastes mixed with PCE synthesized at 10°C, 20°C and 30°C respectively exhibited better fluidity performances than that mixed with common PCE. The Fourier Transform Infrared Spectroscopy (FTIR) measurements were used for the structural characterization. The results confirmed the occurrence of polymerization reaction and the ideal structure. Furthermore, the application performances of PCE synthesized through redox initiation system in mortar and concrete were tested. The results showed that the water reducing rate of PCE in mortar and the slump performances of PCE in concrete were better than those of the common commercial PCEs. This synthesis method presents the great research value and application prospect for the PCE preparation in concrete engineering.

Practical and theoretical study on the α-substituent effect on α-diimine Nickel(II) and Cobalt(II)-based catalysts for polymerization of ethylene

The Late transition metal catalysts based on Ni(II) and Co(II) were synthesized and their structure and activity in polymerization of ethylene were compared. Methylaluminoxane (MAO) was used as a co-catalyst. To discover the optimum polymerization conditions, the effect of polymerization temperature, monomer pressure, [Al]: [Ni] molar ratio and time of polymerization were studied. Activity of the catalysts was promoted by increasing of the monomer pressure. The viscosity average molecular weights M v of the synthesized polymers using 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide were increased with increasing of the monomer pressure from 1 up to 6 bar which studied. Explicitly, the ortho-substituent has a significant effect on the catalyst behavior. Melting point and crystallinity of the obtained polyethylene using 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide catalyst were increased with enhancing monomer pressure. The optimum and stable structures were computed and some factors related to the activity were studied. Catalyst 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide had the highest activity with the highest quantities of dipole moment (18.29 Debye), charge of Mullikan on metal atom (1.48) and Sum of electronic and thermal Energies (–7906.52 e.u.).

Ultrasound-assisted emulsion polymerization of poly(methyl methacrylate-co-butyl acrylate): Effect of initiator content and temperature

In this study, we propose an efficient method for preparation of large scale, monodisperse poly(methyl methacrylate-co-butyl acrylate) latexes by application of the low power ultrasound irradiation. The effect of polymerization temperature and initiator concentration on the polymerization nature, particle size, and particle size distribution were investigated. Results indicated that the ultrasound pulses in the first minutes of polymerization increase instant free radical to monomer ratio as well mixing efficiency which led to higher monomer conversion, improved polymerization rate (especially at first 15 min of the reaction), and remarkable decrease in molecular weight distribution. Transmittance electron microscopy (TEM) and dynamic light scattering (DLS) revealed that the particle size and particle size distribution were significantly affected, particle size decreased, and more uniform particles were obtained. Dynamic mechanical thermal analysis also showed that the initiator concentration affected glass transition temperature (Tg) of the final copolymers and in the case of ultrasound-assisted emulsion polymerization Tg was in a very good agreement with theoretical predictions for copolymerization. POLYM. ENG. SCI., 2015. © 2015 Society of Plastics Engineers

Influences for preparation of PMMA-b-PtBA block copolymer mediated by DPE-containing macroinitiator

Poly(methyl methacrylate)-b-poly(tert-butyl acrylate) (PMMA-b-PtBA) block copolymers were prepared based on the new mechanism of 1,1-diphenylethylene (DPE) controlled radical polymerization in homogeneous systems. Firstly, monomer methyl methacrylate (MMA), initiator 2,2-azobisisoheptonitrile (ABVN) and a control agent DPE were solution polymerized to form DPE-containing PMMA precursor. Then the second monomer tert-butyl acrylate (tBA) was simply heated in the presence of DPE-containing PMMA precursor used as macroinitiator, and block copolymers were synthesized successfully. The effects of polymerization temperature and solvent on molecular weight and molecular weight distribution of polymers throughout the polymerization were investigated. DPE-containing poly(styrene) precursor could not induce block polymerization.

Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline-Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes.

The extent to which anionic spherical polyelectrolyte brushes (ASPB) as dopant improved the performance of polyaniline-polypyrrole (PANI-PPy) nanocomposite was investigated. Different characterization and analytical methods including Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed that ASPB serving as dopant could improve the comprehensive properties of PANI-PPy nanocomposite. It was different from dopants such as SiO2, poly(sodium-p-styrenesulfonate) (PSS), and canonic spherical polyelectrolyte brushes (CSPB) which only enhanced the performance of PANI-PPy nanocomposite on one or two sides. The electrical conductivity of (PANI-PPy)/ASPB nanocomposite at room temperature was 8.3 S/cm, which was higher than that of PANI-PPy (2.1 S/cm), (PANI-PPy)/PSS (6.8 S/cm), (PANI-PPy)/SiO2 (7.2 S/cm), and (PANI-PPy)/CSPB (2.2 S/cm). Meanwhile, (PANI-PPy)/ASPB nanocomposite possessed enhanced thermal stability and good solubility. In addition, the effects of polymerization temperature, the molecular weight of grafted polyelectrolyte brushes, and storage time on electrical conductivity were discussed.

Kinetic evidences for reversible transformations of active centers in ethylene polymerization by titanium–magnesium catalyst: Effect of the polymerization temperature

The kinetics of ethylene polymerization at varied polymerization temperature over two modifications of titanium–magnesium catalysts that differ in their compositions and the molecular weight of the resulting polymers were studied by polymerization quenching by radioactive carbon monoxide. An increase in polymerization temperature in the range of 40–80 °C was found to significantly increase the number of active centers (CP), which contributes to the polymerization rate more significantly than an increase in the propagation rate constant (kP) does. The rise in the number of active centers with increasing polymerization temperature is shown to result in effective activation energy (Eeff) determined from the temperature dependence of polymerization rate being significantly higher than the activation energy of propagation reaction (EP) determined from the temperature dependence of the kP value. It was shown too the changes of the number of active centers and polymerization rate at variation of temperature in the single experiment have the reversible nature. The data on the number of active centers and the propagation rate constants at ethylene polymerization in the presence of hydrogen as a chain transfer agent are obtained. Introduction of hydrogen reduces the number of active centers at elevated polymerization temperatures (60–80 °C) and has virtually no effect on the CP value at lower temperatures; it also reduces the kP value at 40–80 °C. The findings on the effect of polymerization temperature on the number of active centers were used to propose a kinetic scheme including the reaction of reversible transformation of the precursors of active centers (alkyl derivatives of titanium) into an inactive state due to adsorption of a co-catalyst (triethylaluminum). The transformation of these complexes into active centers depends on polymerization temperature, presence of hydrogen, concentrations of monomer and organoaluminum activator.