Criticism of hypotheses by Gandini and Cheradame regarding the initiation of carbocationic polymerization

In the framework of their review of carbocationic initiation of olefin polymerization Gandini and Cheradame have hypothesized that carbocationic blocking and grafting of alkenes in the presence of Friedel-Crafts acids may also proceed by an “onto” mechanism and not by a “from” process suggested by Kennedy et al. A wide battery of facts and recently generated information substantiate the blocking and grafting from mechanisms and refute Gandini and Cheradame's onto hypothesis.     

The novel [(dME)2(HIM)P]2Ti(IV) complex: synthesize, characterization, and its utility in ROP of d,l-lactide

The novel {2,4-bis(1,1-dimethylethyl)-6-{[(2-hydroxyethyl)imino]methyl}phenoxy}₂ titanium(IV) complex {[(dME)₂(HIM)P]₂Ti(IV)} had been synthesized and characterized by EA, XRF, IR, and NMR methods. The [(dME)₂(HIM)P]₂Ti(IV) complex was reactive and promoted ring-opening polymerization (ROP) of d,l-lactide in the presence of benzyl alcohol (BnOH). And the results showed that ROP of d,l-lactide were produced upon addition of an excess (1–8?equiv.) of external BnOH. The complex showed a living and controlled fashion (M _w/M _n?=?1.15–1.32) for ROP of d,l-lactide and could produce the poly(d,l-lactide) with average molecular weight (M _n) up to 8.87?×?10⁴?g?mol^?1. The mechanism study by ¹H NMR spectrum of poly(d,l-lactide) with terminal benzyl ester group and [(dME)₂(HIM)P]₂Ti(IV) complex revealed that the polymerization proceeded through the traditional activated monomer mechanism and the acyl-oxygen bond cleavage mode of monomer. And the ¹³C NMR spectra and TG/DSC analysis showed that poly(d,l-lactide) was essential atactic and thermal stable polymer.     

The Dipole Mediated Surface Chemistry of p-Benzoquinonemonoimine Zwitterions

This article reviews the surface adsorption of p-benzoquinonemonoimine zwitterions from the class of N-alkyldiaminoresorcinones (or 4,6-bis-dialkylaminobenzene-1,3-diones, i.e. C₆H₂(···NHR)₂(···O)₂), where R = H, R = C₂H₅, n-C₄H₉), on a variety of conducting surfaces. These small molecules with a large electrical dipole exhibit molecular orientation and packing on surfaces depending on the deposition methodology (from solution or from the vapor) as well as the substrate. What is very clear from the investigations of this class of molecules is that inter-molecular interaction is not simply driven by dipolar interactions alone, but frontier orbital symmetry as well. This is illustrated by the reversible adsorption of di-iodobenzene on molecular films of (6Z)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate C₆H₂(···NHR)₂(···O)₂ where R = n-C₄H₉, where it is clear that absorption is isomer specific.     

Polyisobutylene-containing block polymers by sequential monomer addition

Novel poly(acenaphtylene-b-isobutylene-b-acenaphtylene) (PAc-PIB-PAc) triblock copolymers exhibiting thermoplastic elastomer (TPE) properties have been prepared. The synthesis involved the addition of acenaphtylene (Ac) to living polyisobutylene dications (PIB) obtained by living isobutylene (IB) polymerization induced by the dicumyl methyl ether (DiCumOMe)/TiCl₄ initiating system at-80°C. The triblocks contain very short polyacenaphtylene (PAc) blocks (M_n9,000) and consequently yield very soft, low modulus TPEs. Efforts to develop conditions for the living carbocationic polymerization (LCPzn) of Ac have failed.For Part VIII of this subseries see J. P. Kennedy, S. Midha, B. Keszler: Macromolecules (in press)     

Preparations and reactions of alkyl ethers of some aldohexoses

Aldohexose, such asd-glucose,d-galactose ord-mannose, reacted with acetone to give the following O-isopropylidene derivatives: 1,2;5,6-di-O-isopropylidene-d-glucofuranose (IA), 1,2;3,4-di-O-isopropylidene-d-galactopyranose (IB) or 2,3;5,6-di-O-isopropylidene-D-mannofuranose (IC). The O-isopropylidene derivative (IA～IC) reacted with alkyl/alkenyl halogenide to yield aldohexose ether compounds containing di-O-isopropylidene group, 3-O-alkyl-1,2;5,6-di-O-isopropylidene-d-glucofuranose (II), 6-O-alkyl-1,2;3,4-di-O-isopropylidene-d-galactopyranose (III) or 1-O-alkyl-2,3;5,6-di-O-isopropylidene-d-mannofuranoside (IV), in good yields. The Williamson ether synthesis was carried out using phase-transfer catalysis (PTC). The derived aldohexose alkyl ether containing di-O-isopropylidene group was hydrolyzed to give 3-O-alkyl-1,2-O-isopropylidene-d-glucofuranose (V) as a partial hydrolysis product; the complete hydrolysis of I～IV gave, as expected, 3-O-alkyl-glucopyranose (VI), 6-O-alkyl-galactopyranose (VII) or 1-O-alkyl-mannofuranoside (VIII). Further alkylation of (V) with Mel under PTC and subsequent acid hydrolysis gave 3-O-alkyl-5,6-di-O-methyl-d-glucofuranose (X). Methanolysis of III with catalytic amounts of H₂SO₄ gave 1-O-methyl-6-O-alkyl-d-galactofuranoside (XI). The elucidation of the galactofuranoside skeleton of (XI) was determined by means of its¹³C nuclear magnetic resonance spectra. The O-alkyl aldohexoses, e.g., X and XI, were evaluated and found to be emulsifiers.     

Living carbocationic polymerization

Summary Living carbocationic polymerization (LCPzn) of isobutylene (IB) has been achieved by the 2-chloro-2, 4, 4-trimethylpentate (TMPCl)/TiCl₄ initiating systems in the presence of KCl in conjunction with the 18-crown-6 ether in CH₂Cl₂/hexanes solvent mixture at –80°C. The rate of initiation is relatively slow and the molecular weight distribution (MWD) of the polyisobutylene (PIB) becomes narrower (M_w/M_n decreases from 1.8 to 1.2) in the course of incremental monomer addition (IMA). In the presence of the crown ether, and depending on its concentration, the charges become highly viscous rendering stirring difficult and preventing the synthesis of M_n's in excess of 15, 000 g/mole.     

A new iodine-free initiating system for the living polymerization of isobutyl vinyl ether

Summary A new iodine-free initiating system, MeCH(Oi-Bu)Cl/n-Bu₄NTiCl₅, was found to induce the living carbocationic polymerization (LCPzn) of isobutyl vinyl ether (IBuVE) at-20 °C in CH₂Cl₂. Using this system, poly(isobutyl vinyl ether) (PIBuVE) with the theoretical molecular weights (up toca. 45,000) calculated from the initiator/monomer input and narrow molecular weight distribution (M_w/M_n < 1.1) can be readily obtained. The polymerization is first order in the monomer. The coinitiating function ofn-Bu₄NTiCl₅ may be due to a salt effect or to its Lewis acid character. An attempt for the synthesis of the polyisobutylene (PIB)-PIBuVE block copolymer has failed most likely becausen-Bu₄NTiCl₅ is unable to activate the C(CH₃)₂-Cl bond of the PIB termini.     

Ethylene polymerization on polymer supported Ziegler-Natta catalyst

Poly(styrene-co-methyl methacrylate) has been used as a support for titanium based Ziegler?CNatta catalyst. We have prepared three polymer supported catalysts by varying the weight ratio of TiCl₄ and polymer to perform the ethylene polymerization. Triethylaluminium (TEA) is used as cocatalyst. Catalysts have been characterized by XPS, FT-IR, UV-visible spectroscopy, XRD, pH meter, TGA and SEM-EDX. The catalysts are found to be stable upto 100?°C. Density functional theory (DFT) has been used to elucidate the structure of TiCl₄ and the polymer supported complex. All these spectroscopic analysis and density functional study confirm the incorporation of titanium into the polymer matrix. The catalytic activity is found to be in the range of 0.6?C1.01?kg of polyethylene (PE)/g Ti/h and the catalytic activity depends on the optimum level of Ti content. The molecular weight ( $ \overline {{M_w}} $ ) of PE is in the range of 237,300?C275,600?g/mol. Present study also reports the stability and storability of the catalysts.

Synthesis and Properties in Solution of Gaussian Homo Asymmetric Polysiloxanes with a Bulky Side Group

Ring opening polymerization (ROP) of 1,3,5-tri-n-hexyl,1,3,5-trimethylcyclotrisiloxane (D ₃ ^Hexa ) and 1,3,5-tri-n-heptyl,1,3,5-trimethylcyclotrisiloxane (D ₃ ^Hepta ) was promoted by acid-treated synthetic silica–alumina to obtain Gaussian homo asymmetric polysiloxanes. M_w was above 70?kg/mol, meaning that homo asymmetric bulky side-group polysiloxane chains with high molecular weight were obtained. The material was treated in an acidic medium to improve the contents of acid sites and successfully tested as an inorganic acidic catalyst for ROP of D ₃ ^Hexa and D ₃ ^Hepta cyclosiloxanes. The samples of poly(methylhexylsiloxane) (PMHS) and poly(methylheptylsiloxane) (PMHepS) obtained were structurally characterized mainly by ²⁹Si NMR. All the experimental values including the refractive index increment (dn/dc), the second virial coefficient (A₂), the square root of the mean square radius of gyration ( $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ ), the average molecular weight (M_w), the average molecular numeral (M_n), and the weight polydispersity (M_w/M_n) were obtained using a gel permeation chromatography/light scattering (GPC/LS) coupled system. The A₂ experimental value for the two polymers (between 4 and 6.5?×?10^?4?mol/mL?g²) indicated that toluene was a good solvent. In addition, PMHS and PMHepS $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ were greater than 30?nm, indicating that larger chains of high molecular weight were obtained.     

An Interesting Complex: [Cd(l -trp) (d-trp)] n

A novel coordination polymer [Cd(l-trp) (d-trp)] _n (where l-trp and d-trp are l-tryptophan and d-tryptophan or (S)-2-amino-3-(3-indolyl)propionic acid and (R)-2-amino-3-(3-indolyl)propionic acid) was prepared by a solvent-thermal method and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The compound(monoclinic space group P2(1)/c with a = 19.759(2) Å, b = 5.2496(10) Å, c = 9.7594(16) Å, β = 97.2760(10)°, Z = 2) shows a two-dimensional plane structure. The crystallized coordination polymer has a centrosymmetric space group. Each Cd²⁺ ion coordinates with a pair of racemes, and the complex is a mesomer. Although l-trp was used, both l-trp and d-trp appear in the complex.     

Synthesis of ε-caprolactone-b-l-lactide block copolymers by mean sequential polymerization,using diphenylzinc as initiator

Block copolymers of ε-caprolactone (CL) and l-lactide (l-LA) were synthesized by sequential polymerization using diphenylzinc as initiator. The composition of the copolymers was adjusted changing the comonomers in ratio. Copolymers were characterized by ¹H-NMR, ¹³C-NMR, DSC, and GPC. Results indicate that poly(ε-caprolactone)-b-poly(l-lactide) (PCL-b-PLA) block copolymers had a narrow molecular weight distribution and well-controlled sequences without random placement.     

Livig carbocationic polymerization

Summary Diblock copolymers of isobytylene (IB) — methyl vinyl ether (MeVE) have been prepared by sequential monomer addition by employing 2-chloro-2, 4, 4-trimethylpentane (TMPCl)/TiCl₄ initiating system in the presence of nBu₄NCl or dimethyl-acetamide (DMA) in CH₂Cl₂/hexanes at –80°C. In line with our earlier observations (1), living carbocationic polymerizations (LCPZn) were obtained in the presence of nBu₄NCl (i.e., the molecular weight of the poly(vinyl methyl ether) segment increased upon TiCl₄ addition), however, extensive chain transfer occurred in the presence of DMA. According to column chromatography analysis, the product prepared in the presence of nBu₄NCl is essentially pure PIB-b-PMeVE diblock (96w%) contaminated with a very small amount (4w%) of PIB. In contrast, the product obtained with DMA contains only 21w% PIB-b-PMeVe together with 72w% PIB and 5w% PMeVe homopolymers. This large difference in blocking efficiencies suggests that the structures of the growing species are different in the presence of the common anion salt,nBu₄NCl, and the electron donor, DMA.For paper LIII in this series see Polym. Bull., vol. 29/1     

Synthesis and Properties of X-Type Alkyl Sulfonate Gemini Surfactants Derived from Cyanuric Chloride

A series of X-type alkyl sulfonate Gemini surfactants (XC_n, n?=?6, 8, 10) was synthesized by a simple method. The chemical structures of the prepared compounds were confirmed by ¹H NMR, ¹³C NMR, ESI?CMS and Elementary analysis. The surface activity and thermodynamic properties of micellization of the X-type alkyl sulfonate Gemini surfactants were compared with sodium dodecylsulfate by means of surface tension. The properties of XC_n are superior to those of SDS such as the ??_CMC and CMC of XC₁₀ are 26.3?mN/m and 0.2?mmol/L respectively. The adsorption isotherms for XC_n were established by fitting the pre-CMC surface tension data with a quadratic function. The thermodynamic parameters of micellization ( $ \Updelta G_{m}^{ \circ } $ , $ \Updelta H_{m}^{ \circ } $ , $ \Updelta S_{m}^{ \circ } $ ) derived from electrical conductivity indicate that the micellization of XC_n is entropy-driven.     

The Catalytic Conversion of d-Glucose to 5-Hydroxymethylfurfural in DMSO Using Metal Salts

A wide range of metal halides and triflates were examined for the conversion of d-glucose to HMF in DMSO. Chromium and aluminium salts were identified as the most promising catalysts. The effect of process variables like initial d-glucose concentration (0.1?C1.5?M), reaction time (5?C360?min) and reaction temperature (100?C140?°C) on the yield of HMF were examined at a fixed Al(OTf)₃ concentration (50?mM). Highest yields of HMF (60?mol%) were obtained using 1?M d-glucose (16?wt%), Al(OTf)₃ (5?mol%) at a temperature of 140?°C. A reaction pathway involving initial isomerisation of d-glucose to d-fructose followed by a number of dehydration steps is proposed. Kinetic analysis reveals that the reaction is second order in d-glucose with an activation energy of 138?kJ?mol^?1.     

Surface characterization of cellulose acetate propionate by inverse gas chromatography

The purpose of this paper is to study the surface energetics of the polymer excipient cellulose acetate propionate (CAP) in the solid form. The net retention volumes, V _N, for n-alkanes and polar solutes have been measured in the temperature range 353.15–403.15 K by inverse gas chromatography. The dispersive surface free energy, $ \gamma_{\text{S}}^{\text{d}} $ , and Lewis acid–base parameters $ K_{\text{a}} $ and $ K_{\text{b}} $ , have been determined using V _N values. The $ \gamma_{\text{S}}^{\text{d}} $ values are decreased linearly with increase of temperature. The $ \gamma_{\text{S}}^{\text{d}} $ value at 353.15 K is 24.50 ± 1.54 mJ/m², and the temperature gradient was found to be ?0.287 mJ/m²/K¹. The $ K_{\text{a}} $ and $ K_{\text{b}} $ values are 0.410 ± 0.021 and 1.708 ± 0.388, respectively, which suggest that the CAP solid surface contain relatively more basic sites. The K _a and K _b values of CAP are compared with the similar values obtained on the cellulose acetate butyrate solid surface.     

Immobilized iron Schiff base histidine complexes on Al-MCM-41 and zeolite Y as catalyst for oxidation of cycloalkanes

Iron complexes of N-salicylidene-l-histidine with or without bipyridine ligand immobilized on Al-MCM-41 and zeolite Y designated as Fe(sal-l-his)(bipy)complex/Al-MCM-41 or Fe(sal-l-his)complex/Al-MCM-41 and Fe(sal-l-his)(bpy)complex/Y or Fe(sal-l-his)complex/Y respectively, were prepared and characterized by X-ray powder diffraction (XRD), FT-IR, N₂ adsorption/desorption and chemical analysis techniques. Fe(sal-l-his)/Al-MCM-41 and Fe(sal-l-his)(bipy)complex/Al-MCM-41 were found to successfully catalyze the oxidation of cyclohexane, methyl cyclohexane, cyclooctane and adamantane with H₂O₂. The oxidation results and promising catalytic behavior of Fe(sal-l-his)(bipy)complex/Al-MCM-41 for oxidation of cyclooctane with 90 % conversion and excellent selectivity toward the formation of cyclooctanone will be discussed in this presentation.     

New host–guest supramolecular coordination polymers based on [(Me3Sn)3Fe(CN)6]n with alkali metal iodides and their applications as electrode materials in batteries

The metal iodides reduce partially the host coordination polymer of the type $ ^{ 3}_{\infty } \left[ {\left( {{\text{Me}}_{ 3} {\text{Sn}}} \right)_{ 3} {\text{Fe}}\left( {\text{CN}} \right)_{ 6} } \right] $ , I, to give new host–guest supramolecular coordination polymers (SCP). The physical and chemical characteristics of the new products were studied by elemental analyses, X-ray powder diffraction, IR, UV/Vis, and solid state NMR spectra. The host–guest SCP are [M_x(Me₃Sn)₃Fe_(1–x)^IIIFe _x ^II (CN)₆]_n M = Li⁺·2H₂O, 1; Li⁺, 2; Na⁺, 3; K⁺, 4; Cu⁺, 5, [Li(Me₃Sn)₃Fe^II(CN)₆]_n, 6 and [(LiDEE)_0.9(Me₃Sn)₃Fe _o.1 ^III Fe _o.9 ^II (CN)₆]_n, 7. The stoichiometry and nature of the guest depend on the type of the metal iodide and the reaction conditions. The polymeric nature of these SCP is due to the presence of trigonal bipyramidal configured structure which bridges between the single d-transition metal ions. The host–guest SCP containing the Li ions have been tested as electrodes to construct four different lithium-ion batteries.     

Heterocycles oligomerization in acidic zeolites: a UV-visible and IR study

FTIR spectroscopy shows that the first step of the interaction of pyrrole, furan and thiophene with H- $\beta $ and H-ZSM-5 zeolites is the formation of hydrogen bonded (precursor) species involving the Brønsted acid sites of the zeolite and the $\pi $ -electron system of the heterocyclic molecule. The precursors are then protonated to give monomeric BH⁺ (where B = C₄H₄NH, C₄H₄O or C₄H₄S) species which, in the presence of excess B, can further react to form entrapped coloured B_nH⁺ oligomeric species. Characterization by means of in situ UV-Vis reflectance spectroscopy shows that the oligomeric products contain up to six conjugated double bonds and that they have carbocationic nature. However, the precise structure of the responsible species (particularly those absorbing in the visible) cannot be completely elucidated. The carbocationic character of the oligomers is also documented by the changes induced in the electronic spectra by adsorption of NH₃, i.e., of a base capable of extracting H⁺ ions from B_nH⁺ to give NH ₄ ⁺ and B_n. The role of intermolecular hydrogen transfer in the intrazeolitic oligomerization process is also evidenced and discussed.     

Preparation of emulsifier-free acrylate cross-linkable copolymer emulsion and application in coatings for controlling indoor humidity

Indoor humidity has an important influence on our lives. Too high relative humidity (RH > 60 %) can cause the metal surface corrosion, electrical insulation fall, material deformation and so on. On the contrary, when the moisture content is too low (RH < 40 %), it causes skin chapping, decrease in respiratory system resistance, static electricity, etc. The humidity controlling coating is a kind of composite that controls the humidity of materials. In this study, the emulsifier-free acrylate copolymer emulsion (EF-AAC) containing ketocarbonyl and carboxyl groups was synthesized and the humidity controlling coating (EF-AAC-C) was prepared by EF-AAC, adipic dihydrazide (ADH) and porous fillers. The different proportions and the contents of KPS, NaHCO₃, and the effects of polymerization time and reaction temperature on the stability of emulsion were investigated. The different ratios of fillers/emulsion and ADH/diacetone acrylamide for water resistance of coatings were also studied. Moreover, the structure of emulsifier-free acrylate copolymer was characterized by FTIR and TGA techniques. The particle morphologies were measured by transmission electron microscopy and dynamic light scattering. It showed that the distribution of emulsion particle size was narrow and uniform. The properties of humidity controlling coatings were studied with particular attention to the effects of the humidity controlling. Meanwhile, the water absorption of humidity controlling coatings was up to 260 %. The humidity controlling coatings revealed excellent properties of humidity sensitivity and humidity retention because of the composite porous structure due to fillers with emulsifier-free acrylate copolymer. The mechanism of breathing water molecules in obtained coatings was suggested and the composite could be widely used as indoor coatings for controlling humidity.