Synthesis of Cyclic Polyesters of Poly(Oxybutylene Oxymaleoyl)

In the present work cyclic oligomers of poly(oxybutylene oxymaleoyl) were prepared successfully and cleanly from the polycondensation of the tetrahydrofuran with maleïc anhydride using the Maghnite-H⁺ (Mag-H) as catalyst. Maghnite is a montmorillonite sheet silicate clay exchanged with protons to produce Maghnite-H⁺ (M. Belbachir, U.S. Patent 066969.0101–2001). The effects of reaction temperature, amount of Maghnite-H⁺ and reaction time on the yield and the molecular weight are investigated. The results indicate that the polymerization yield increases with increasing the proportion of catalyst.     

Synthesis of Biodegradable Diblock Copolymers of Glycolide and Poly(oxyethylene) Using a Montmorillonite Clay as Catalyst

Biodegradable diblock copolymers were prepared from glycolide and poly(oxyethylene) of M_n=600 (POE 600), 1500 (POE 1500) and 2000 (POE 2000). The copolymerization of glycolide and POE was induced in heterogeneous phase by “Maghnite-H⁺” under suitable conditions. Maghnite-H⁺ is a montmorillonite sheet silicate clay exchanged with protons. Various techniques, including ¹H NMR, ¹³C NMR, IR, DSC and Ubbelohde viscometer were used to elucidate structural characteristics and thermal properties of the resulting copolymers. The effect of the [glycolide]/[POE] molar ratio on the rate of copolymerization and on intrinsic viscosity of the resulting copolymers was studied. Data showed that the rate of copolymerization and intrinsic viscosity of copolymers increase with increasing [glycolide]/[POE] molar ratio.     

Maghnite-H, an ecocatalyst for cationic polymerization of N-vinyl-2-pyrrolidone

The polymerization of N-vinyl-2-pyrrolidone catalyzed by the Maghnite-H⁺ (Mag-H) was investigated. Mag-H is a montmorillonite sheet silicate clay, exchanged with protons. It was found that the cationic polymerization of N-vinyl-2-pyrrolidone (NVP) is initiated by Mag-H at 30 °C in bulk and in solution. The effect of the amount of Mag-H, the temperature and the solvent was studied. The polymerization rate increased with increase in the temperature and the proportion of catalyst, and it was larger in nitrobenzene than that in toluene. These results indicated the cationic nature of the polymerization. It may be suggested that the polymerization is initiated by proton addition to monomer from Mag-H.     

Kinetics of the Anionic Ring Opening Polymerization of Cyclosiloxanes Initiated with a Superbase

Kinetics of the anionic ring opening polymerization of octamethylcyclotetrasiloxane, D₄, and hexamethylcyclotrisiloxane, D₃, in toluene solution initiated by hexapyrrolidinediphosphazenium hydroxide, P₂Pyr₆ ⁺OH^– were studied. Reactions are first order both in monomer and in initiator. The specific rate of the D₃ polymerization is higher than that of D₄ by about 2–3 orders of magnitudes. Activation energies are 18.1 kcal mol^–1 for D₄ and 11 kcal mol^–1 for D₃. The back-biting reaction leading to decamethylcyclopentasiloxane, D₅, was followed in the polymerization of D₄. This reaction is retarded by the presence of monomer. The kinetics is interpreted in terms of a mechanism in which the active propagation center appears mostly as a monomer separated ion pair, which is also the intermediate in the propagation step.     

Maghnite‐H+ as a cationic catalyst in the synthesis of poly(1,3‐dioxolane) and α,ω‐methacryloyloxy‐poly(1,3‐dioxolane)

The polymerization of 1,3‐dioxolane catalyzed by Maghnite‐H^+; (Mag‐H⁺), a montmorillonite sheet silicate clay exchanged with protons, was investigated. The cationic ring‐opening polymerization of 1,3‐dioxolane was initiated by Mag‐H⁺ at different temperatures (20, 30, 50, and 70°C) in bulk and in a solvent (dichloromethane). The effects of the amount of Mag‐H⁺ and the temperature were studied. The polymerization rate and the average molecular weights increased with an increase in the temperature and the proportion of the catalyst. These results indicated the cationic nature of the polymerization and suggested that the polymerization was initiated by proton addition to the monomer from Mag‐H⁺. Moreover, we used a simple method, in one step in bulk and in solution at room temperature (20°C), to prepare a telechelic bismacromonomer: α,ω‐bisunsaturated poly(1,3‐dioxolane). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 78–82, 2006     

Aqueous polymerization of protonated 4-vinylpyridine in montmorillonite

The polymerization of protonated 4-vinylpyridine (4-VPH⁺X⁻) in the interlayer zone of montmorillonite was studied. Polymerization is critically affected by the degree of surface coverage with a threshold value twice the cation exchange capacity of the mineral. Montmorillonite surfaces show selectivity for protonated 4-vinylpyridine favoring the formation of the quaternized form of the polyvinylpyridine polyelectrolyte. In situ polymerization of 4-VPH⁺X⁻ in the presence of 10 wt.% or lower sodium montmorillonite in aqueous solution yields exfoliated montmorillonite–polyelectrolyte heterostructures. The rate of polymerization in the presence of delaminated montmorillonite is much faster than in the absence. Mechanisms for intergallery and exogallery polymerization of 4-VPH⁺X⁻ are described.     

Aspects of coordination polymerization in heterogeneous and homogeneous catalysis. A computational survey

Theoretical studies on ethylene polymerization by single site homogeneous catalysts, as well as by Ziegler–Natta heterogeneous catalysts, have been reviewed. Studies on cation–anion interactions in ion-pair systems of the type [LLMR]⁺[A]^– [L, L=Cp, NCR₂, NPR₃; M=Ti, Zr; A=MeB(C₆F₅)₃^–, MAOMe^–, B(C₆F₅)₄^–] provided indications as to which ancillary ligands on the cation acted as good electron donors, and also revealed the importance of having a weakly coordinating anion to enable the ion-pair to separate more easily in solution. Subsequent calculations of barriers to ethylene insertion into the metal-methyl bond in ion-pair systems of the type LLMeM--B(C₆F₅)₃[M=Ti, Zr] revealed that the ease of separation of the anion from the cation in solution was an important criterion in determining the activity of the catalysts. The barrier to insertion was found to be the rate determining step during the first insertion of ethylene into the metal–methyl bond, but second insertion studies conducted for two different ion-pair systems showed that the barrier to uptake of the monomer became the rate determining step during the second insertion of the ethylene monomer. Theoretical studies conducted on TiCl₄/MgCl₂ heterogeneous Ziegler–Natta catalysts provided insights into the nature of the binding of the titanium catalysts (with the Ti in different oxidation states) on to the MgCl₂ support. The results indicated that the support worked best when a few Ti atoms replaced Mg atoms in the crystal lattice of the support. Ethylene polymerization studies, along with investigations on chain termination, led to the conclusion that the TiCl₃-based edge site on MgCl₂ would be the most promising model for the actual catalytic species. Studies on addition of tetrahydrofuran (THF) to the active sites showed that the presence of the base would lead to higher molecular weights of the polymers, as it acted to increase the barrier to termination (by chain transfer to monomer) more than the barrier to insertion.     

Measurements on the temperature dependence of the cationic polymerization of styrene in CH2Cl2 with CF3SO3H as catalyst

Summary The cationic polymerization of styrene in CH₂Cl₂ with CF₃SO₃H as catalyst and at low monomer concentrations shows, at –15°C, –45°C and –60°C, the same formal dependence on monomer concentration. The dependence on the catalyst concentration is approximately but not exactly of a third order.The unimodal molecular weight distributions at [M]_o<0.2 mol·1^–1 become broader with decreasing polymerization temperature and increasing monomer concentration and change to bimodal or trimodal distributions at [m]_o>0.2 mol·1^–1. The addition of (Bu)₄N⁺CF₃SO₃ ^– to the polymerization system shows that the two higher molecular peaks are produced by free ions. The activation energy of the total reaction is found to be 3.5 kcal·mol^–1.I thank Prof. G. V. Schulz for interesting discussions and the possibility to work in his group, G. Greschner for a computer program and the Alexander von Humboldt Stiftung for their financial help.     

Enzyme-catalyzed ring-opening polymerization of cyclic esters in the presence of poly(ethylene glycol)

Low-molecular-weight polyesters were obtained by the ring-opening homopolymerization and copolymerization reaction of ϵ-caprolactone, rac- or L -lactide, and glycolide in the presence of poly(ethylene glycol) with an enzyme catalyst, a lipase from Candida antarctica, Pseudomonas cepacia, or Pseudomonas fluorescens. The influence of several parameters, including time, temperature, and enzyme and monomer concentration, on the polymerization rate was studied. The resulting polymers were characterized by ¹H-NMR or ¹³C-NMR, Fourier transform infrared spectroscopy, matrix-assisted laser desorption/ionization–time of flight mass spectroscopy, and gel permeation chromatography. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and Characterization of New Organometallic Hybrid Material LCP-1 Based on MOF (Metal–Organic Framework) and Maghnite-H<Superscript>+</Superscript>, a Protons Exchanged Montmorillonite Clay,as Catalytic Support

In this work, a new 3D crystalline metal–organic framework formulated as [Zn₂(BTC)₄, (BTC: 1,2,4,5-Benzenetetracarboxylate)] and called LCP-1 (LCP: Laboratoire de Chimie des Polymères), with unsaturated coordinated Zn(II) sites as metal ion and pyromellitic acid (H₄BTC: 1,2,4,5-Benzenetetracarboxylic acid) as organic ligand, has been successfully synthesized under solvothermal conditions. In-Situ polymerization of this material was also carried out using an amount of clay called Maghnite-H⁺, an acid-exchanged montmorillonite, as an eco-catalyst with the aim to respect the principles of green chemistry, to give a new hybrid composite material LCP-1/Mag-H⁺ with a better yield, a significantly reduced time and temperature reaction than those of LCP-1. LCP-1 and LCP-1/Mag-H⁺ have been structurally characterized and established by fourier transform infrared spectroscopy (FT-IR). The morphology of these compounds was studied by the X-ray diffraction (XRD) and revealed a highly crystalline and ordered structure for both LCP-1 and LCP-1/Mag-H⁺. FT-IR and XRD spectra showed also that the stability and structural integrity of LCP-1 and LCP-1/Mag-H⁺ was maintained even after being evacuated from the DMF solvent molecules. The thermal stability identified by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that Maghnite-H⁺, as inorganic support, has also improved the thermal stability of LCP-1 compound.     

Ring‐opening polymerization of D,L‐lactide by rare earth 2,6‐dimethylaryloxide

Ring‐opening polymerization of D,L ‐lactide (LA) has been successfully carried out by using rare earth 2,6‐dimethylaryloxide (Ln(ODMP)₃) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)₃ exhibits higher activity to prepare poly(D,L ‐lactide) (PLA) with a viscosity molecular weight of 4.5 × 10⁴ g mol^?1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)₃ has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)₃ is 69.6 kJ mol^?1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ‘coordination–insertion’ mechanism with selective cleavage of the acyl–oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry     

Activation of the hydrolytic polymerization of ε-caprolactam by ester functions: Straightforward route to aliphatic polyesteramides

The hydrolytic polymerization of ε-caprolactam (CLa) was carried out in bulk (in absence of solvent) at 250 °C in the presence of carboxylic esters and aqueous H₃PO₂. It turned out that by conducting the ring opening polymerization (ROP) of CLa in the presence of PEO–C(O)–O–C₅H₁₁, a selected model ester (PEO = poly(ethylene oxide)), a remarkable activating effect of the ester function on the hydrolytic polymerization of the lactam was observed yielding PEO–b–PCLa diblock copolymers. The comparison of the CLa monomer conversions obtained with or without the model ester activated by H₃PO₂, as determined by ¹H NMR spectroscopy, has enabled to propose a multi-step mechanism in which three major reactions occurred: (i) ester and lactam hydrolysis, (ii) aminolysis of the carboxylic ester by the resulting primary amine of the hydrolyzed/opened lactam ring and (iii) condensation reactions between carboxylic acids and both amine/hydroxyl functions. The overall result of this multi-step mechanism can be assimilated as an “insertion” of the opened lactam into the ester function. By conducting the hydrolytic polymerization of CLa in the presence of an aliphatic polyester chain, such as poly(ε-caprolactone) (PCLo), polyesteramides were recovered with high yields and random distributions of the CLa and CLo repetitive units as determined by ¹³C NMR.     

Synthesis and characterization of novel fluoropolymers containing sulfonyl and perfluorocyclobutyl units

A novel sulfonyl-containing monomer, 4,4′-sulfonyl-bis(trifluorovinyloxy)biphenyl, and the resulting fluoropolymers with good thermal stability have been prepared. The monomer was synthesized by two steps using 4,4′-sulfonyldiphenol as starting material and characterized by FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR and element analysis in detail. Fluoropolymers containing sulfonyl and perfluorocyclobutyl units were prepared by different polymerization methods. A series of fluoropolymers with higher molecular weights were obtained by solution polymerization in diphenyl ether. The molecular weight is dependent on the polymerization time, polymerization temperature and the concentration of the monomer. The resulting polymers show excellent solubility in conventional solvents and good thermal stability with a high decomposition temperature about 500 °C measured by TGA.     

One‐step synthesis of bis‐macromonomers of poly(1,3‐dioxolane) catalyzed by Maghnite‐H+

Telechelic poly(1,3‐dioxolane) (PDXL) bis‐macromonomers bearing methyl methacrylate end groups were prepared by cationic ring‐opening polymerization of 1,3‐dioxolane (DXL), in the presence of methacrylic anhydride, catalyzed by Maghnite‐H⁺ (Mag‐H⁺), in bulk and in solution. Maghnite is a montmorillonite sheet silicate clay, which exchanged with protons to produce Mag‐H⁺. The influence of the amount of Mag‐H⁺, monomer (DXL), and methacrylic anhydride on monomer conversion was studied. The polymerization yield and the molecular weight of α,ω‐bis‐unsaturated PDXLs prepared depend on the amount of Mag‐H⁺ used and the reaction time. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Effects of reaction conditions on laccase‐catalyzed α‐naphthol polymerization

Enzymatic oxidative polymerization of α‐naphthol was carried out batch‐wise with the laccase enzyme, produced by Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone (solvent) and sodium acetate buffer for pH control. The effects of the organic solvent (acetone) composition, monomer (α‐naphthol) and enzyme concentrations, buffer pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen. The optimum acetone composition, pH, monomer, dissolved oxygen and enzyme concentrations were determined as 50% (v/v), 5, 3409 gm⁻³, 20.3 gm⁻³ and 0.173 U cm⁻³, respectively; these values provided the most desirable conditions for initial reaction rate. Temperature rise supported the rate increase up to 37 °C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration. The product polymer, poly(α‐naphthol), with an average molecular weight of 4920 Da was soluble in common organic solvents. © 2000 Society of Chemical Industry     

Polymerization of Vinyl Acetate Initiated by a Copper Alginate Coordination Polymer Film/Na2SO3/H2O System

A hydrophobic film of copper alginate coordination polymer was prepared by soaking a sodium alginate film in a 13% CuCl₂ aqueous solution at room temperature for more than 24 h. The composition, structure, and property of copper alginate as a coordination catalyst were studied by ESR, IR, XPS, and electric conductivity methods. It was shown that a low-spin copper complex was formed as a result of the acceptance by dsp² hybrid orbitals of nonpaired electrons transferred from oxygen atoms of two carbonyl hydroxyl groups and negatively charged oxygen atoms of two deprotonated carbonyl hydroxyl groups of two alginate chains. The coordination number of the central Cu²⁺ ions in copper alginate is 4. It can be concluded that the vacant site on the active catalysis resulted from the distorted tetragonal configuration that was caused by a crimped chain of the alginate molecule. HSO ₃ ^– produced primary free-radical hydrogen by a coordination catalysis mechanism and vinyl acetate (VAc) polymerization by a free-radical mechanism that is different from polymerization initiated by a CuCl₂–Na₂SO₃–H₂O oxidation–reduction system. The induction period for VAc polymerization is 90 s and the yield is 82%. The M _w, M _n, and M _w/M _n of poly(vinyl acetate) (PVAc) were found to be 1.23×10⁶, 2.27×10⁵, and 4.51, respectively.     

Electrical properties of a cyclotriphosphazene matrix polymer: Cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy)phosphazene matrix polymer

Cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy)phosphazene compound is synthesized from the cyclic trimer of dichlorophosphazene by replacing two CI atoms with trifluoroethoxy and acryloyloxy-ethyleneoxy groups. This compound was polymerized by UV irradiation with the aid of a photosensitizer. The polymerization proceeds in the acrylate group by opening the double bond. Whereas the matrix polymer is an insulator at low temperatures, it is a semiconductor at high temperatures. Namely, the conductivity is 8.84×10^–9 S/cm at 19.2°C and 1.17×10^–6 S/cm at 75.0°C. Both dielectric constant and dielectric loss increase with increasing temperature and with decreasing frequency. The conductivity of the cyclotri(trifluoroethoxy, acryloyloxy-ethyleneoxy) phosphazene monomer is higher than that of the corresponding polymer and the dielectric constants are higher at lower frequencies. These results are consistent with the existence of a charge transfer complex.     

Maghnite‐H+, a solid catalyst for the cationic polymerization of α‐methylstyrene

The polymerization of α‐methylstyrene (AMS) catalyzed by Maghnite‐H⁺ (Mag‐H) was investigated. Mag‐H is a montmorillonite sheet silicate clay, exchanged with protons. It was found that the cationic polymerization of AMS is initiated by Mag‐H at ambient temperature in bulk and in solution. The effect of the amount of Mag‐H, the temperature, and the solvent was studied. The polymerization rate increased with increase in the temperature and the proportion of catalyst, and it was larger in nonpolar solvents. These results indicated the cationic nature of the polymerization. It may be suggested that the polymerization is initiated by proton addition to monomer from Mag‐H. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Spontaneous polymerization and chain microstructure evolution in high-temperature solution polymerization of n-butyl acrylate

This study concerns understanding of the underlying mechanistic pathways in high temperature solution polymerization of n-butyl acrylate (nBA) in the absence of added thermal initiators. The particular system of interest is the batch polymerization of nBA in xylene at temperatures between 140 and 180 °C with initial monomer content between 20 and 40 wt%. A mechanistic process model is developed to capture the dynamics of the polymerization system. Postulated reaction mechanisms include chain-initiation by monomer (self-initiation), chain-initiation by unknown impurities, chain-propagation by secondary and tertiary radicals, intra-molecular chain-transfer to polymer (back-biting), chain-fragmentation (β-scission), chain-transfer to monomer and solvent, and chain termination by disproportionation and combination. The extent of the reactions is quantified by estimating the reaction rate constants of the initiation and the secondary reactions, based on a set of process measurements. The set of measurements considered in the parameter estimation includes monomer conversion, number- and weight-average molecular weights, and average number of chain-branches per chain (CBC). Effect of temperature on chain microstructures was observed to be most evident when microstructures are expressed in terms of their quantities per chain. The evolution of other microstructural quantities such as average number of terminal double bonds per chain (TDBC) and average number of terminal solvent groups per chain (TSGC) was then also investigated. Microstructural quantities per polymer chain (TDBC, TSGC, CBC) are defined based on combinations of ¹³C, ¹H NMR and chromatographic measurements. This study presents (i) a mechanistic explanation for the competing nature of short-chain-branch and terminal double bond formation (i.e. as temperature increases, number of chain branches per chain decreases and number of terminal double bonds per chain increases), (ii) quantitative insights into dominant modes of chain-initiation and chain-termination reactions, and (iii) mechanistic explanations for the observed spontaneous polymerization. The study also reports estimated Arrhenius parameters for second-order self initiation, tertiary radical propagation, secondary radical backbiting and tertiary radical β-scission reaction rate constants. Validation of the mechanistic process model with the estimated Arrhenius parameters and comparison of estimated parameter values to recently reported estimates are also presented.     

Polymerization of lactides and lactones. IV. Ring-opening polymerization of ε-caprolactone by rare earth phenyl compounds

Ring-opening polymerization of ε-caprolactone (CL) has been initiated with rare earth phenyl compounds in both bulk and solution. These rare earth phenyl initiators can give polycaprolactone (PCL) with high yield and high molecular weight. The polymerization mechanism is through a coordination-deprotonation-insertion process, by which the monomer inserts on the Ln O bond of rare earth enolate. The efficiency of rare earth phenyl compounds for CL is high. The effects of reaction conditions, such as reaction time, reaction temperature, and monomer/initiator molar ratio, on the polymerization are discussed. The polymer was characterized by FTIR, ¹H-NMR. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1401–1408, 1999