First Stage Of Polymerization Research Articles

Preparation and Characterization of Soft-Hard Block Copolymer of 3,4-IP-b-s-1,2-PBD Using a Robust Iron-Based Catalyst System.

A series of well-defined diblock copolymers, namely, 3,4-polyisoprene-block-syndiotactic-1,2-polybutadiene (3,4-PI-b-s-1,2-PBD), with a soft-hard block sequence were synthesized via an in situ sequential polymerization process using a robust iron-based catalytic system Fe(acac)3/(isocyanoimino) triptenylphosphorane (IITP)/AliBu3. This catalyst exhibits vigorous activity and temperature tolerance, achieving a polymerization activity of 5.41 × 106 g mol(Fe)-1 h-1 at 70 °C with a [IP]/[Fe] ratio of 15,000. Moreover, the quasi-living polymerization characteristics of the catalyst were verified through kinetic experiments. The first-stage polymerization of isoprene (IP) is performed at 30 °C to give a soft 3,4-PI block, and then a quantitative amount of 1,3-butadiene was added in situ to the quasi-living polymerization system to produce a second hard s-1,2-PBD. The s-1,2-PBD segments in block copolymers display a rodlike morphology contrasting with the spherulitic morphology characteristic of s-1,2-PBD homopolymers. The precise tunability of the length of the soft and hard chain segments of these novel elastic materials with the feed ratio of IP and BD, endowing them with outstanding mechanical properties and excellent dynamic mechanical properties, which are expected to be promising high-performance rubber materials.

Metal-Containing Monomers Based on Copper and Zinc Salts of Unsaturated Acids and Pendent 4-phenyl-2,2′:6′,2′′-terpyridine Ligands: Synthesis, Characterization and Thermal Properties

Metal-containing monomers based on maleates of copper and zinc, cinnamate of copper and acrylate of zinc with 4-phenyl-2,2′:6′,2′′-terpyridine ligand were prepared for the first time and characterized using a number of analytical techniques including infrared spectroscopy, elemental analysis and thermal gravimetric analysis. According to the results of the thermal analysis, the coordination mixed-ligand complexes based on zinc salts are more stable than copper one both in the case of monocarboxylic acids and dicarboxylic acids. The first stage of polymerization according to results of mass spectra of gaseous products is initiated in accordance with the Borodin–Hunsdiecker mechanism: the initial decarboxylation leads to the formation of carboxy biradicals, which, in turn, cause the polymerization and the formation of polymers. In this paper we also describe facile two-step Kröhnke-type synthesis of 4′-phenyl-2,2′:6′,2′′-terpyridine from 2-acetylpyridine and its NMR spectrum.

Impact of Polymerization Protocol on Structure-Property Relationships of Entirely Lipid-Derived Poly(ester urethane)s

The impact of polymerization protocol on phase structure and properties of entirely lipid-derived thermoplastic poly(ester urethane)s (TPEU)s was investigated. The TPEUs were synthesized from 1,7-heptamethylene diisocyanate, polyester diols and 1,9-nonanediol (ND) as chain extender. A two-stage polymerization method was used to prepare two TPEUs; one in which ND was added in the first stage of polymerization as part of the prepolymer and another in the second stage after the prepolymer was formed. Two very different morphologies exhibiting different degrees of phase separation were obtained, driven by the sequence of addition of the chain extender. The incorporation of the chain extender in the prepolymer resulted in a TPEU with a narrow hard segment distribution, enhanced urethane-urethane hydrogen bonding and higher molecular weight. The hydrogen bond density, degree of crystallinity, glass transition temperature and mechanical properties of the TPEUs were directly related to the degree of phase separation and hence polymerization protocol.

Synthesis and characterization of soft-hard stereoblock polybutadiene with Fe(2-EHA)3 /Al(i -Bu)3 /DEP catalyst system

Stereoblock polybutadiene (pbd) composed of amorphous equibinary cis-1,4/1,2 pbd (e-pbd, soft) and crystalline syndiotactic 1,2-pbd (s-1,2-pbd, hard) segments is synthesized through one-pot sequential polymerization with iron(iii)2-ethylhexanoate/triisobutylaluminum/diethyl phosphate [fe(2-eha)(3)/al(i-bu)(3)/dep] catalyst system. the first-stage polymerization of 1,3-butadiene (bd) is carried out at a low [al]/[fe] ratio to give amorphous e-pbd block, and sequentially, the in situ addition of excessive al(i-bu)(3) and bd to the living polymerization system give rise to a second crystalline s-1,2-pbd block. the length of each block is controllable by adjusting cocatalyst and monomer feed ratio. the syndiotactic pentad content is in the range of 63.8-76.6% and increases with the length of s-1,2-pbd block. the copolymer exhibits glass transition temperature (t-g) around -40 degrees c and melting point (t-m) around 168 degrees c originating from e-pbd and s-1,2-pbd blocks, respectively. the incompatibility between s-1,2-pbd and e-pbd blocks as well as the crystallization of s-1,2-pbd block induce the microphase separation in stereoblock pbd. (c) 2015 wiley periodicals, inc. j. polym. sci., part a: polym. chem. 2015, 53, 1182-1188

Industrial Production of Poly Vinyl Acetate Dispersions: Relationship Between Latex Properties and Polymerization Start-Up Temperature

An industrial polymerization process for the production of polyvinyl alcohol stabilized polyvinylacetate dispersions has been examined to investigate the influence of the start-up temperature on production process and latex characteristics. The product investigated is a high solids, high viscosity latex, obtained by a semi-batch emulsion polymerization process, initiated with persulfate. The main finding shows that small variations of the start-up temperature affect the reaction kinetics in the first stage of polymerization and have a direct influence on physicochemical and rheological properties of the finished products.

Polymer particles with a pomegranate-like internal structure via micro-dispersive polymerization in a geometrically confined reaction space I. Experimental study

The synthesis of micron-sized polymer particles with a core-shell pomegranate-like morphology is presented. The proposed polymerization technique takes advantage of a reaction-induced micro-phase separation within a suspended organic liquid droplet containing monomer, a chemical initiator, a steric stabilizer, and a poor solvent for the polymer. With an increase in monomer conversion, the monomer droplet suspended in a continuous aqueous medium is transformed first into a micro-capsule with a thick pericellular membrane, and eventually into a polymer particle packed with 300–500 nm polymer sub-particles. The experimentally observed evolution of particle morphology indicates that the reaction pathway is strongly influenced by micro-phase separation and transport phenomena. In the first stage of polymerization, a pseudo-homogeneous polymerization takes place at the droplet surface, followed by a starved macro-dispersive polymerization in the inner region where polymer precipitates out from the solvent phase as nano-sized sub-particles.

Synthesis of monodisperse hollow polymer microspheres with functional groups by distillation precipitation polymerization

Monodisperse hollow polymer microspheres having various functional groups on the shell-layer, such as carboxylic acid, pyridyl and amide, were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive, during which monodisperse poly(methacrylic acid) (PMAA) afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization. The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) as crosslinker and the functional comonomers, in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers, including carboxylic acid, amide and pyridyl, played an essential role for the formation of monodisperse core-shell functional microspheres. The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the morphology of the resultant PMAA core, functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups. FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.

Preparation and characterization of magnetic composite microspheres using a free radical polymerization system consisting of DPE

In this paper, a free radical polymerization system consisting of DPE was used to prepare magnetic composite microspheres. Fe3O4/P(AA–MMA–St) core-shell magnetic composite microspheres have been synthesized by copolymerization of acrylic acid, methyl methacrylate and styrene using DPE as radical control agent in the presence of Fe3O4 nanoparticles. The structure and properties of the magnetic composite microspheres were analyzed by FTIR, 1H NMR, SEC-MALLS, TEM, TGA, VSM and other instruments, and the formation mechanism of composite microspheres was supposed by those results. It was found that the Fe3O4/P(AA–MMA–St) microspheres were nano-size with relatively homogeneous particle size distribution, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 18.430emu/g, and high magnetic content with a value of 40%. 1H NMR and TEM analysis indicated that at the first stage of polymerization, a DPE-containing copolymer of acrylic acid, methyl methacrylate formed and was then absorbed on the surface of Fe3O4 nanoparticles. Contact angle analysis indicated that the DPE-containing copolymer improved hydrophobicity of Fe3O4 nanoparticles through chemical absorption. In the second step polymerization, certain amount of monomers of styrene and residue methacrylate were initiated by the DPE-containing copolymer on the Fe3O4 nanoparticles' surface and resulted in the formation of Fe3O4/P(AA–MMA–St) composite microspheres.

Elucidation of high ring‐opening polymerizability of methylated 1,6‐anhydro glucose

Abstract1,6‐Anhydro glucose was extracted from a wood tar that is a by‐product of charcoal manufacture. After methylation of the 1,6‐anhydro glucose, the starting monomer, 1,6‐anhydro‐2,3,4‐tri‐O‐methyl‐β‐D‐glucopyranose (LGTME), was obtained. We found that LGTME had high ring‐opening polymerizability and polymerized under mild conditions. With BF3OEt2 catalyst under ordinary pressure and N2 atmosphere at 0 °C, LGTME gave high molecular weight of polymer with 1,6‐α stereoregularity in a high yield, even though benzylated 1,6‐anhydro glucose monomer (LGTBE) gave no polymers by the same polymerization conditions. The GPC profile showed two absorptions corresponding to = 272 × 103 and = 390 × 104 in the proportion of 4.5:1. Furthermore, under high vacuum condition at 0 °C, LGTME gave the corresponding polymer and the lower molecular weight increased to = 364 × 103. To reveal the high polymerizability of LGTME, two‐step polymerization was performed. After the first stage of polymerization under ordinary pressure for 6 h at 0 °C, the second LGTME monomer was added to the polymerization mixture and then the polymerization was continued. It was found that the lower molecular weight of the resulting polymer increased to = 394 × 103 and the yield was 78%. These results suggest that poly(LGTME) after the first‐stage polymerization has stable propagating end which has a restarting ability for the ring‐opening polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1013–1022, 2009

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.

Preparation of monodisperse fluorescent core–shell polymer microspheres with functional groups in the shell layer by two‐stage distillation–precipitation polymerization

AbstractMonodisperse crosslinked core–shell micrometer‐sized microspheres bearing a brightly blue fluorescent dye, carbazole, and containing various functional groups in the shell layers were prepared by a two‐stage distillation–precipitation polymerization in acetonitrile in the absence of any stabilizer. Commercial divinylbenzene (DVB), containing 80 vol.% of DVB, was polymerized by distillation–precipitation in acetonitrile without any stabilizer using 2,2′‐azobisisobutyronitrile (AIBN) as the initiator for the first stage of polymerization which resulted in monodisperse polyDVB microspheres used as the core. Several functional monomers, including 2‐hydroxyethyl methacrylate and acrylonitrile together with N‐vinylcarbazole blue fluorescent comonomer, were incorporated into the shell layers with AIBN as initiator during the second stage of polymerization. The resultant core–shell polymer microspheres were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, UV‐visible spectroscopy and fluorescence spectroscopy. Copyright © 2006 Society of Chemical Industry

Synthesis of fully conjugated aromatic polyazomethine from AB‐type monomer using soluble precursor method

AbstractA new AB‐type monomer, N,N‐bistrimethylsilylated p‐aminobenz‐aldehyde diethyl acetal was prepared via three steps from p‐bromoaniline as a starting material. The two‐stage polymerization involving a soluble precursor polymer process gave a poly(p‐phenylenevinylene)‐type polyazomethine, poly(1,4‐phenylene‐nitrilomethylidyne). The first stage of polymerization was carried out in tetrahydrofuran or hexamethylphosphoramide containing water at room temperature. In the second stage, the polymer was thermally converted into the final polyazomethine by heating over 300°C to form a free‐standing film. The film was reddish brown and insoluble in common organic solvents. The investigation of the first‐stage products by means of MALDI‐TOF mass spectroscopy proved the oligomers with 4‐11 repeating units per molecule. From the 1H‐NMR analysis of the model reaction, the polymerization mechanism was found to be a stepwise polycondensation of 4‐diethoxymethylaniline which was formed by removal of two silyl groups of the monomer.

Polylactones, 50. The Reactivity of Cyclic and Noncyclic Dibutyltin Bisalkoxides as Initiators in the Polymerization of Lactones

Dibutyltin bisethoxide and bis(2,2,2-trifluoroethoxide), the cyclic alkoxides derived from cis-1,4-butenediol, 1,4-butanediol, 1,8-octanediol and triethylene glycol as well as bis(4-nitrophenoxide), bis(4-meth-oxyphenoxide) and tetrabutylstannoxane bisacetae were used as initiators in the polymerization of e-caprolactone (e-CL) and β-BL). Most polymerizations were conducted at 60°C with 2 M solutions in chlorobenzene, and time-conversion curves were recorded. The less reactive initiators yielded sigmoidal time-conversion curves with autoacceleration during the first stage of polymerization. Dibutyltin bisethoxide and the cyclic 1,8-octane dioxide showed the highest reactivities. The less reactive initiators yielded degrees of polymerization (DPs) exceeding the monomer/initiator (M/I) ratios after short reaction times, but a longer reaction times, an equilibration between unreacted initiator and the poly(e-CL) chain took place. The slower polymerizing β-BL yielded DPs paralleling the M/I ratio even with less reactive initiators. The stannoxane and the dibutyltin bisphenoxides were considerably less reactive than the bisalkoxides were considerably less reactive than the bisalkoxides, and only traces of phenylester endgroups were detectable by 1 H NMR spectroscopy. MALDI-TOF mas spectrometry proved the formation of cyclic oligolactones with masses greather than 600 Da for reaction temperatures ≥60°C.

Application of ketenes to well-defined polyester synthesis. III. Living anionic polymerization of ethyl(4-methoxyphenyl)ketene?Development of polyester having masked phenol side chain

A novel ketene, ethyl(4-methoxyphenyl)ketene (EMPK), was synthesized by the dehydrochlorination of 2-(4-methoxyphenyl)butanoyl chloride. The anionic polymerizations of EMPK by butyllithium in tetrahydrofuran at −20 °C were carried out with a varying feed ratio to give the corresponding polyesters having predictable molecular weights and narrow molecular weight distributions, quantitatively. The selective formation of the polyester was confirmed by IR analysis, and the reductive degradation of the polymer was supported by lithium–aluminium hydride. The second feed of the monomer (after the first stage of polymerization) resulted in the formation of the polymer with the expectedly increased molecular weight and low polydispersity to strongly support the living mechanism of this polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1596–1600, 2001

Polystyrene-graft-poly(ethylene oxide) copolymers prepared by macromonomer technique in dispersion. 2. Mechanism of dispersion copolymerization

The reaction mechanism of dispersion copolymerization of methacryloyl-terminated poly(ethylene oxide) macromonomer and styrene in the polar media is discussed. The copolymerization products were analyzed by means of liquid chromatography. This analysis revealed presence of rather large amount of polystyrene in the final polymer product. It is assumed that the system undergoes phase separation in the course of copolymerization. The graft copolymer created in the first stage of polymerization acts as a detergent (amphiphile). The hydrophobic phase is hardly accessible for hydrophilic macromonomer but well dissolves styrene and benzoylperoxide initiator. Therefore, polystyrene homopolymer is intensively formed in this reaction locus. Its molar mass is rather low because of high initiator and low monomer concentration at the reaction loci. We suppose existence of at least two different polymerization loci; the continuous phase and the particle core. The existence of third polymerization locus, viz. particle surface layer cannot be excluded, either.

Effect of protein concentration on whey protein gels obtained by a two-stage heating process

The influence of protein concentration on the properties of gels obtained by a two-stage heating process was determined. In the first stage, whey protein dispersion (3–10%) was heated at pH 8.0, and in the second stage it was diluted to 3% protein, adjusted to pH 7.0 and heated again. Increased protein concentration in the first stage of polymerization resulted in the gels obtained in the second stage having a lower phase angle, increased storage modulus and increased hardness. Increased protein concentration also resulted in gels with an increased optical density, which suggests thathigher protein concentration leads to more and larger aggregates. Gels obtained from dispersions preheated at a higher protein concentration had higher permeability coefficient (B gel) values. The increase in B gel suggests that the higher protein concentration increased the size of the aggregates, which in a second stage of heating formed a gel matrix with a larger pore size.

Kinetics of Particle Formation at the Graft Polymerization of Methylacrylate onto Hydroxyethyl Cellulose

The kinetics of polymer particle formation and distribution of monomers between a solution and a dispersed phase at the graft polymerization of methylacrylate onto hydroxyethyl cellulose has been studied. The particle number increases at the first stage of polymerization, then it is constant. The concentration of adsorbed monomer decreases during the polymerization process. The monomer concentration in the dispersed phase is greater than in the solution. A mathematical model of particle formation and monomer adsorption in the polymerization process has been suggested. Some values of rate constant ratios have been calculated.

Ring-opening polymerization of the cyclobutane adduct of tetracyanoethylene and ethyl vinyl ether by the initiating system vinyl ether-acetic acid adduct/zinc iodide. Synthesis of a molecular weight-controlled alternating copolymer of the two olefins

Ring-opening polymerization of the cyclobutane adduct (1) of tetracyanoethylene (TCNE) and ethyl vinyl ether (EVE) was carried out with protonic acid/Lewis acid or EVE-acetic acid adduct (2)/ZnI2 as initiating systems in CH3NO2 at ambient temperature. Poly1s with narrow molecular weight distribution (MWD) were obtained with the systems acetic acid(AcOH)/ZnI2 or 2/ZnI2. In the polymerization with 2/ZnI2, the number-average molecular weight (M̄n) of the polymers decreases with increasing amount of 2/ZnI2, and increases in direct proportion to the monomer conversion. Furthermore, M̄n increases on addition of a fresh feed of monomer at the end of the first-stage polymerization. The MWD remains narrow throughout the reaction. On the basis of the reaction of 1 with an equimolar amount of 2 in the presence of ZnI2 and the diene 5 as a by-product formed by elimination of hydrogen cyanide from 1 in the polymerization, it was proposed that ZnI2 activates both the CH-OAc terminal groups of the growing polymer chain and monomer 1.

Ring-opening polymerization of the cyclobutane adduct of tetracyanoethylene and ethyl vinyl ether by the initiating system vinyl ether-acetic acid adduct/zinc iodide. Synthesis of a molecular weight-controlled alternating copolymer of the two olefins

Ring-opening polymerization of the cyclobutane adduct (1) of tetracyanoethylene (TCNE) and ethyl vinyl ether (EVE) was carried out with protonic acid/Lewis acid or EVE-acetic acid adduct (2)/ZnI2 as initiating systems in CH3NO2 at ambient temperature. Poly1s with narrow molecular weight distribution (MWD) were obtained with the systems acetic acid(AcOH)/ZnI2 or 2/ZnI2. In the polymerization with 2/ZnI2, the number-average molecular weight (M̄n) of the polymers decreases with increasing amount of 2/ZnI2, and increases in direct proportion to the monomer conversion. Furthermore, M̄n increases on addition of a fresh feed of monomer at the end of the first-stage polymerization. The MWD remains narrow throughout the reaction. On the basis of the reaction of 1 with an equimolar amount of 2 in the presence of ZnI2 and the diene 5 as a by-product formed by elimination of hydrogen cyanide from 1 in the polymerization, it was proposed that ZnI2 activates both the CH-OAc terminal groups of the growing polymer chain and monomer 1.

Transient Electric Birefringence Study of Intermediate Filament Formation from Vimentin and Glial Fibrillary Acidic Protein

Mg2+-induced polymerization of type III intermediate filament proteins vimentin and glial fibrillary acidic protein was studied by transient electric birefringence. In the absence of MgCl2 we found a net permanent dipole moment, approximately 45-nm-long dimers for vimentin, approximately 65-nm-long tetramers, hexamers, and possibly octamers for both proteins, and 100-nm aggregates for glial fibrillary acidic protein. Controlled oligomerization occurred after the addition of MgCl2. Although the solutions contained (small) aggregates of different sizes, more or less discrete steps in polymer formation were observed, and it was possible to discriminate between an increase in width and length. At the first stage of polymerization (in 0.3 mM MgCl2 for vimentin and 0.2 mM MgCl2 for glial fibrillary acidic protein), the permanent dipole moment disappeared without a change in length of the particles. At higher MgCl2 concentrations, structures of approximately 100 nm were formed, which strongly tended to laterally assemble into full-width intermediate filament structures consisting of about 32 monomers. This contrasts with previous models where first full-width (approximately 10-nm) aggregates are formed, which then increase in length. Subsequently, two discrete elongation steps of 35 nm are observed that increase the length to 135 and 170 nm, respectively. Possible structural models are suggested for the polymerization.