Cationic grafting from carbon black. VII. Grafting of polyacetals by cationic ring-opening polymerization of trioxane and 1,3-dioxolane initiated by CO+ClO4− groups on carbon black

The cationic ring-opening polymerization of trioxane and 1,3-dioxolane was found to be initiated by CO⁺CIO₄^? groups on a carbon black surface, which were introduced by the reaction of COCI groups with AgCIO₄. The activation energy of the ring-opening polymerization of trioxane was estimated to be 15.5 kcal/mol. In the polymerization system, poly(oxymethylene) and poly(1,3-dioxolane) formed were effectively grafted onto carbon black depending upon the propagation of these polymers from the carbon black surface; for instance, the grafting ratio of poly(oxymethylene) onto carbon black increased with an increase in conversion and went up to about 180%. Although the grafted chain of poly(oxymethylene) was subject to stepwise thermal depolymerization from the chain ends, the thermal stability of poly(oxymethylene)-grafted carbon black was improved by acetylation of hemiformal end groups. The molecular weight of ungrafted poly(oxymethylene) formed in the polymerization was determined to be 1.8–2.0 × 10⁴. Furthermore, the copolymerization of trioxane with 1,3-dioxolane, styrene, and other comonomers initiated by CO⁺CIO₄^? groups and the thermal stability of these acetal copolymer-grafted carbon black were investigated.     

A Green One-pot Synthesis of PDMS Bis-Macromonomers Using an Ecologic Catalyst (Maghnite-H+)

PDMS bis-macromonomers bearing methyl methacrylate end groups is a material mainly used for making extended-wear contact lenses. Silicon-based materials give a good oxygen passage and methyl methacrylate has biocompatibility and mechanical properties of the elastomer. The present study shows the synthesis of this material. The polymerization of hexamethylcyclotrisiloxane (D₃) catalyzed by Maghnite-H⁺ (Mag-H⁺), a montmorillonite sheet silicate clay exchanged with protons, an efficient catalyst for cationic polymerization of manyheterocyclic and vinylicmonomers. The structural compositions of “Maghnite” have already been determined. The effects of the amount of Mag-H⁺, temperature and the reaction time were studied. Moreover, we used a simple method, one step in solution to prepare Poly dimethyl siloxane (PDMS) and PDMS bis-macromonomers. The structure of the resulting products is characterized and established by ¹H and ¹³C-NMR, where the methacrylate end groups are clearly visible. The presence of unsaturated end group was also determined by UV and FTIR analysis. The influence of the amount of methacrylic anhydride on monomer conversion was studied. The polymerization yield and the molecular weight of PDMS macromonomers depend on the amount of methacrylic anhydride used.     

Kinetics and mechanism of the anionic polymerization of cyclohexadienes initiated by naphthalene radical anions and dianions

The anionic polymerization of 1.3-cyclohexadiene (1.3-CHD) was investigated in temperatures that ranged from 25 to ?77°C. Initiation by lithium naphthalene (N^?·,Li⁺) in tetrahydrofuran at ?20°C yields polymers with fairly narrow molecular weight distribution. The M?_w of these polymers so prepared is ca. 20,000. Polymerization of 1.3-CHD conducted at room temperature is accompanied by the dehydrogenation and disproportionation of the monomer, especially when N^?·,K⁺ acts as initiator. Oligomers are formed when hexamethylphosphoramide is used as a solvent. The mechanism of the initiation of the polymerization of 1.3-CHD by N^?·,Li⁺ was elucidated and the rate constants at ?20°C in tetrahydrofuran of the elementary reactions were determined. It was established that the dianions formed by disproportionation of N^?·,Li⁺ act as effective initiators for 1.3-CHD. The adducts formed constitute the cyclohexanyl and naphthyl carbanionic groups. The former carbanions (λ_max ～ 275 nm) propagate the polymerization. The initially formed dimeric adducts are stabilized by the separation of the carbanionic end groups by the additional monomer units. Chain transfer to the monomer limits the growth of the polymers. The isomerization of the cyclohexadienyl anions, formed as result of chain transfer, may be followed by the elimination of lithium hydride. The latter reaction represents a termination step. Addition of 1.4-CHD to the reaction mixture enhances the chain transfer and the termination.     

Preparation and characterization of core–shell polymer particles with protonizable shells prepared by oxyanionic polymerization

A series of polystyrene (PS)/poly(vinyl acetate) (PVAc) crosslinked particles (240, 210, or 90 nm) with different concentrations of PS (75, 50, or 25 wt %) were prepared by soap‐free emulsion polymerization. Based on the crosslinked polymer particles, three series of monodisperse core–shell particles with pH‐sensitive poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) shells were synthesized by oxyanionic polymerization. During the oxyanionic polymerization, the acetate groups of PVAc were hydrolyzed, and the hydroxyl groups that formed on the surfaces of the particles, acting as initiators, were transferred to ? O^?K⁺ by DMSO^?K⁺ (where DMSO is dimethyl sulfoxide) at the same time; then, ? O^?K⁺ initiated the polymerization of 2‐(dimethylamino)ethyl methacrylate. ¹H NMR and Fourier transform infrared studies confirmed the existence of PDMAEMA shells, and the contents of PDMAEMA were measured by elemental analysis. Because the PDMAEMA chain could be protonated at a low pH, these core–shell particles could adsorb negatively charged modified magnetite particles, and at higher pHs, the magnetite particles could be released again; this process was reversible. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6081–6088, 2004     

Magnesium chloride supported catalysts for olefin polymerization. XIX. Titanium oxidation states,catalyst deactivation,and active site structure

A precise method for the determinations of Ti⁺², Ti⁺³ and Ti⁺⁴ was developed. The CW-procatalyst before activation contains mostly Ti⁺⁴ ions with 6% Ti⁺³ and 4% Ti⁺² ions. Activation with AlEt₃ alone at room temperature reduced all the titaniums to lower valence states consisting of 71% Ti⁺³ and 29% Ti⁺². Reduction is incomplete when methyl-p-toluate was present as external Lewis base during activation: at 25°C the distribution of Ti⁺⁴ : Ti⁺³ : Ti⁺² is 36% : 25% : 38%; the distribution at 50°C is 37% : 22% : 40%. Aging of the activated catalyst caused little or no changes in the distribution of [Ti⁺ⁿ]; whereas the catalytic activity decays rapidly with aging. The aged catalysts have polymerization activity comparable to the decreased activity of the catalyst during a polymerization. The [Ti⁺ⁿ] was determined for the CW-catalyst during the course of a decene polymerization; they were found to be Ti⁺⁴ : Ti⁺³ : Ti⁺² = 30% : 27% : 43%, which did not change with polymerization time. These results suggest that the reducibility of Ti⁺⁴ species by AlEt₃ or 3AlEt₃/MPT to different valence states is predicated by their structures. These species do not undergo further changes in their oxidation states during either aging or polymerization. Their decays probably involve nonreductive metathesis reactions like those known for zirconium alkyls. Possible structures for the stereospecific and nonspecific sites are proposed.     

Metal-containing polyurethanes from tetradentate Schiff bases: synthesis,characterization, and biocidal activities

N,N′-bis(salicylidene)thiosemicarbazide Schiff base has been synthesized by the reaction of thiosemicarbazide with salicylaldehyde and then reacted with formaldehyde to generate phenolic groups, resulting in the formation of Schiff-base monomeric ligand. It was further incorporated with transition metals, Mn⁺², Co⁺², Ni⁺², Cu⁺², and Zn⁺², to form Schiff-base metal complex, which was then polymerized with toluene 2,4-diisocyanate to form metal-chelated polyurethanes. Monomeric ligand, its metal complexes, and its metal polychelates were characterized and compared by elemental analysis, FT-IR, ¹H NMR, thermal, and biocidal activities to evaluate the enhancement in physical and chemical properties on coordination with metal and on polymerization. SEM images of ligand and polymer metal complexes showed changes in surface morphology, while electronic spectra of polymer metal complexes were used to predict the geometry. Antimicrobial activities were determined by using agar-diffusion method with Staphylococcus aureus, Escherichia coli, Bacillus subtilis (bacteria), Aspergillus niger, Candida albicans, and Aspergillus flavus (yeast). The polymeric ligand had varied antibacterial and antifungal activities, enhanced after chelation and polymerization. Comparative results show that coordination of metal to the ligand enhances its physical and chemical properties which were meliorated on polymerization.     

Poly(DCAQI): Synthesis and characterization of a new redox‐active polymer

Redox‐active anthraquinone based polymers are synthesized by the introduction of a polymerizable vinyl and ethynyl group, respectively, resulting in redox‐active monomers, which electrochemical behaviors are tailored by the modification of the keto groups to N‐cyanoimine moieties. These monomers can be polymerized by free radical polymerization and Rh‐catalyzed polymerization methods, respectively. The resulting polymers are obtained in molar masses (M_n) of 4,400 to 16,800 g mol^?1 as well as high yields of up to 97%. The monomers and polymers are furthermore electrochemically characterized by cyclic voltammetry. The monomers exhibit two one‐electron redox reactions at about ?0.6 and ?1.0 V versus Fc⁺/Fc. The N‐cyanoimine units are, however, partially hydrolyzed during the polymerization step or during the electrochemical measurements and degenerate to carbonyl groups, resulting in a new reduction signal at ?1.26 V versus Fc⁺/Fc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1998–2003     

Pressure-induced polymerization of butyndioic acid and its Li+ salt

2-Butyndioic acid and its Li-salt polymerize under high pressure to form potential cathode material for Li-battery.     

Counterion and solvent effects on the anionic polymerization of β-butyrolactone initiated with acetic acid salts

The comparative studies on the anionic polymerization of β-butyrolactone (BL) initiated with various salts of acetic acid have revealed strong sensitivity of the reaction rate on solvent polarity (benzene, THF, DMSO) and size of counterion. It was found that the polymerization rate in THF depends on the size of counterion and the type of macrocyclic ligand; it decreases in the following order: K⁺/Kryptofix® 222 ≈TBA⁺ > K⁺/18C6 > Na⁺/18C6 > Na⁺/15C5 > K⁺. It was also shown that the anionic polymerization of BL initiated with carboxylic acid salts depends strongly on the solvent polarity. In the polymerization initiated by acetate anions with a large counterion, the high-polar solvent as DMSO affects unfavorably the reaction rate, however, when a small counterion is applied, the opposite tendency is observed.     

Preparation of anti-CD4 monoclonal antibody-conjugated magnetic poly(glycidyl methacrylate) particles and their application on CD4+ lymphocyte separation

Novel immunomagnetic particles have been prepared for separation of CD4⁺ lymphocytes. The magnetic nanoparticles with a diameter of approximately 5-6 nm were first synthesized by co-precipitation from ferrous and ferric iron solutions and subsequently encapsulated with poly(glycidyl methacrylate) (PGMA) by precipitation polymerization. Monoclonal antibody specific to CD4 molecules expressed on CD4⁺ lymphocytes was conjugated to the surface of magnetic PGMA particles through covalent bonding between epoxide functional groups on the particle surface and primary amine groups of the antibodies. The generated immunomagnetic particles have successfully separated CD4⁺ lymphocytes from whole blood with over 95% purity. The results indicated that these particles can be employed for cell separation and provide a strong potential to be applied in various biomedical applications including diagnosis, and monitoring of human diseases.     

Electrochemical Generation of the 9,10-Antraquinone Radical Anions and Its Use in the Polystyrene Synthesis

The nature of active centers and anionic mechanism of the styrene polymerization during the 9,10-antraquinone electroreduction in the monomer-dimethylacetamide-alkali metal (or ammonium) perchlorate system is studied by voltammetry, ESR, IR- and UV-spectroscopy. It is shown that the potential of electrolysis depends on the supporting electrolyte composition; the association of the supporting electrolyte cation with the organic anion, in turn, affects the mechanism of the polymerization initiation and the macromolecule growth kinetics. The potential of generation of 9,10-antraquinone and the styrene conversion in catholyte increase with increasing radius of the supporting cation in the series Li⁺ <; Na⁺ <; K⁺ <; Rb⁺ <; Cs⁺ <; (C₂H₅)₄N⁺ <; (C₄H₉)₄N⁺.     

Ring-opening polymerization of macrocyclic aryl ether ketone oligomers containing the 1,2-dibenzoylbenzene moiety

Facile ring-opening polymerization of cyclic aryl ether oligomers containing the 1,2-dibenzoylbenzene moiety to form high molecular weight linear polymers in the presence of a nucleophilic initiator is described. The polymerization can be initiated in the melt in the presence of a nucleophilic initiator such as potassium carbonate, cesium fluoride, and alkali phenoxides. Various alkali phenoxides were investigated as potential nucleophilic initiators. The polymerization reaction rate in the melt increases in the order of K⁺ > Na⁺ > Cs⁺, and in the order of ⁻OPhPhO⁻ > PhO⁻ > PhOPhO⁻ > PhPhO⁻. However, the polymerization in an aprotic dipolar solvent is faster in the presence of cesium phenoxide than in the presence of potassium phenoxide. Polymerization of the cyclic oligomers in solution demonstrates that the ring-opening polymerization proceeds via a chain-growth mechanism and involves a transetherification reaction between linear and cyclic aryl ether oligomers. The ring-chain equilibrium is much more favorable towards linear polymers. Since little or no ring strain exists in the cyclic system, the transetherification reactions are indiscriminate with regards to cyclic or linear chains and the interchain equilibration is also a facile process during polymerization. This intermolecular transetherification has been demonstrated by using low molecular weight aryl ethers to control the molecular weight of the polymer formed via ring-opening polymerization. © 1996 John Wiley & Sons, Inc.     

Fluorine-Rich Supramolecular Nano-Container Crosslinked Hydrogel for Lithium Extraction with Super-High Capacity and Extreme Selectivity

Extraction and recovery of lithium from reserves play a critical role in the sustainable development of energy due to the explosive growth of the lithium-battery market. However, the low efficiency of extraction and recovery seriously threatens the sustainability of lithium supply. In this contribution, we fabricate a novel mechanically robust fluorine-rich hydrogel, showing highly efficient Li⁺ extraction from Li-containing solutions. The hydrogel was facilely fabricated by simple one-pot polymerization of supramolecular nanosheets of fluorinated monomers, acrylic acid and a small amount of chemical crosslinkers. The hydrogel exhibits a remarkable lithium adsorption capacity (Q_m Li⁺=122.3 mg g⁻¹) and can be reused. Moreover, it can exclusively extract lithium ions from multiple co-existing metal ions. Notably, the separation of Li⁺/Na⁺ in actual wastewater is achieved with a surprising separation factor of 153.72. The detailed characterizations as well as calculation showed that the specific coordination of Li−F plays a central role for both of the striking recovery capability and selectivity for Li⁺. Furthermore, an artificial device was constructed, displaying high efficiency of extracting lithium in various complex actual lithium-containing wastewater. This work provides a new and promising avenue for the efficient extraction and recovery of lithium resource from complex lithium-containing solutions.     

Free Radical Production upon Photoinduced Electron Transfer Reactions in the Presence of Vinyl Monomers. Effect of Water Addition*

Free radical fragments produced in the photoinduced electron transfer from triethylamine (TEA) to excited pyrenebutyltrimethylammonium (*PyBu⁺) lead to 1-vi-nyl-2-pyrrolidinone (VP) and 2-hydroxyethyl methacry-late (HEMA) polymerization. Experiments carried out in water/acetonitrile solvent mixtures showed that the polymerization rate of VP increases upon increasing the water content, whereas the polymerization rate of HEMA follows the opposite trend. These results are interpreted in terms of the strong dependence on the solvent properties of the photochemical behavior of PyBu⁺ in the presence of the amine or monomers. Thus, the *PyBu⁺ quenching by VP is almost negligible in both solvents (water and acetonitrile). Whereas, the *PyBu⁺ quenching rate constant by HEMA in water is 4 times 10⁹M^?l s^?1 and decreases four orders of magnitude in acetonitrile. The quenching of *PyBu⁺ by TEA in aqueous solutions is controlled by hydrogen-bonding interactions between water molecules and the amine. Quantum yields of the pyrene radical anion (φ_Py) also strongly depend on the water content, decreasing from 0.28 to 0.015 upon going from acetonitrile to water.     

Synthesis of aromatic polyethers by Scholl reaction. VII. Oxidative polymerization of 2,2-bis[4-(1-naphthoxy)phenyl]propane and 2,2-bis [4-(1-naphthyl)phenyl]propane

The synthesis and the mechanism of oxidative polymerization of 2,2-bis[4-(1-naphthoxy)phenyl]propane ( 4 ) and 2,2-bis[4-(1-naphthyl)phenyl]propane ( 9 ) are presented. Both monomers polymerize by two different propagation steps. The first one represents a cation-radical dimerization of the naphthyl groups to dinaphthyl structure. H⁺[FeCl₄]^? generated from the first propagation step initiates a transalkylation reaction which provides structural units containing isopropylidenic groups inserted between phenyl and naphthyl, and between two naphthyl groups, respectively. Since the phenyl groups resulted from the second propagation reaction are unreactive in both the oxidative coupling and the transalkylation steps this polymerization reaction leads to polymers with low molecular weights containing phenyl chain ends.     

Analysis of the end groups of poly(methyl methacrylate)

Methyl methacrylate polymerization by potassium hydride results in macromolecules with the methyl starting group. A side-reaction occurs during the process leading to potassium methoxide. It serves as the second initiator of the polymerization and gives macromolecules with the methoxy starting group. All macromolecules possess the methine group at the chain end after protonation. Potassium alkalide K⁻, K⁺(15-crown-5)₂ produces various active centres in the initial step of the polymerization. It results in macromolecules with the methyl, ethyl, methoxy and vinyl ether starting groups. However, the majority of macromolecules are formed on the species with two active centres. The termination reaction takes place during the polymerization, therefore, not all chains have the methine end group after protonation.     

Polymerization of styrene by photoexcited safranine T without additives

Styrene can be photopolymerized with methanolic solutions of safranine T(STH⁺) in the absence of any additives. Under these conditions the monomer acts as an electron donor for the excited singlet state of STH⁺, and after electron transfer an initiating semireduced STH⁺ radical is produced. The experimentally determined monomer exponent of α = 2 indicates additional deactivation reactions of the primary radicals. The polymerization rate depends on the dye concentration also in those regions, in which all light is already absorbed. Presumably, this dependence is caused by a comproportionation reaction between STH⁺ and substituted leuco-safranine T formed in the course of polymerization. © 1993 John Wiley & Sons, Inc.     

Kinetics of styrene emulsion polymerization in the presence of montmorillonite

The effect of the pristine sodium montmorillonite (Na⁺-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na⁺-MMT compared to the counterpart without Na⁺-MMT. Micelle nucleation predominates in the polymerizations with [SDS] ≧ 13 mM. On the other hand, the contribution of the polymerization associated with the Na⁺-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the Na⁺-MMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na⁺-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na⁺-MMT.     

Structure of poly(propylene oxide) obtained in the presence of K, K(15-crown-5)2

Potassium isopropoxide and potassium tetraethylene glycoxide vinyl ether as well as small amounts of dipotassium tri- and tetraethylene glycoxides are formed in the initiation step of propylene oxide polymerization by K⁻, K⁺(15-crown-5)₂. Chain transfer reactions occur during the polymerization. Therefore, macromolecules with various starting groups, i.e. with the isopropyl, vinyl, allyl, and propenyl ones, are obtained in the process. The kind of end groups generally depends on the quenching agent used for termination. However, the macromolecules terminated in the chain transfer reactions possess exclusively the hydroxyl end group. The functionality of protonated polymers is equal to about 1.2 as a result of propagation occurring on dipotassium glycoxides.     

Advanced environmentally friendly anticorrosive materials prepared from water-based polyacrylate/Na-MMT clay nanocomposite latexes

A series of novel advanced environmentally friendly anticorrosive materials have been successfully prepared by effectively dispersing nanolayers of Na⁺-montmorillonite (Na⁺-MMT) clay into water-based polyacrylate latex (i.e., vinyl acrylic terpolymers). First of all, a polyacrylate latex was synthesized through co-polymerizing organic monomers of MMA, BMA and styrene (St) using conventional emulsion polymerization technique with SDS, 1-pentanol and KPS as surfactant, co-surfactant and initiator, respectively. Subsequently, the commercial purified hydrophilic Na⁺-MMT was effectively dispersing into the polyacrylate latex through the direct solution dispersion technique.The as-prepared neat polyacrylate and the series of water-based polyacrylate/Na⁺-MMT clay nanocomposite (Na⁺-PCN) materials were subsequently characterized by FTIR spectroscopy, XRD, TEM and GPC. The water-based Na⁺-PCN materials loaded with low content of Na⁺-MMT when in the form of coating on the cold rolled steel (CRS) coupons was found to be remarkably superior in anticorrosion efficiency over those of neat polyacrylate based on a series of electrochemical measurements of corrosion potential, polarization resistance, corrosion current, and impedance spectroscopy in saline. Effect of material composition on the molecular barrier, optical clarity and thermal stability were also studied by molecular permeability analysis, ultraviolet-visible transmission spectra, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Organo-PCN materials were also prepared as a control experiment for comparative studies.