Cationic Ring-opening Polymerization Of Tetrahydrofuran Research Articles

Hemocompatible, biocompatible and antifouling Acylated dextran-g-polytetrahydrofuran graft copolymer with silver nanoparticles: Synthesis, characterization and properties

The novel amphiphilic acylated dextran-g-polytetrahydrofuran (AcyDex-g-PTHF) graft copolymers have been successfully synthesized via combination of living cationic ring-opening polymerization of tetrahydrofuran (THF) to prepare living PTHF chains with different molecular weights (Mn, PTHF) of 800–2800 g/mol with nucleophile substitution to mediate grafting numbers (GN) of 4–25 per 1000 Dex monosaccharide. The microphase separation in the graft copolymer exists for the incompatibility of hard dextran backbone and soft PTHF branches and the confined crystallization of backbone. This copolymer behaves excellent hemocompatibility with red blood cells, good biocompatibility with HeLa cells and strong resistance to bovine serum albumin adsorption. The microspheres (~1 μm) of graft copolymers loaded with drug ibuprofen exhibit pH sensitive controlled drug release behavior. Moreover, the AcyDex-g-PTHF/Ag nanocomposites show good antibacterial property against E. coli and S. aureus. This novel hemocompatible, biocompatible and antifouling AcyDex-g-PTHF graft copolymer will have potential application in biological and medical fields.

Nanocrystallization-locked Network of Poly(styrene-b-isobutylene-b-styrene)-g-Polytetrahydrofuran Block Graft Copolymer

Poly(styrene-b-isobutylene-b-styrene) triblock copolymer (SIBS), a kind of thermoplastic elastomer with biocompatibility and biostability containing fully saturated soft segments, could be synthesized via living cationic copolymerization. A novel poly[(styrene-co-methylstyrene)-b-isobutylene-b-(styrene-co-methylstyrene)]-g-polytetrahydrofuran (M-SIBS-g-PTHF) block graft copolymer was prepared to increase the polarity and service temperature of SIBS by grafting polar PTHF segments onto SIBS. A series of the above block graft copolymers with average grafting numbers from 2 to 6 and molecular weights of PTHF branches ranging from 200 g·mol−1 to 4200 g·mol−1 were successfully synthesized via living cationic ring-opening polymerization of tetrahydrofuran (THF) coinitiated by AgClO4. The introduction of PTHF branches led to an obvious microphase separation due to thermodynamic incompatibility among the three kinds of segments of polyisobutylene (PIB), polystyrene (PS) and PTHF. Moreover, the microphase separation promotes the rearrangement of PTHF branches to form the nanocrystallization-locked physically cross-linked network after storage at room temperature for 2 months, leading to insolubility of the copolymers even in good solvents. The melting temperature and enthalpy of PTHF nanocrystallization locked in hard domains of M-SIBS-g5-PTHF-1.1k block graft copolymer increased remarkably up to 153 °C and 117.0 J·g−1 by 23 °C and 11.6 J·g−1 respectively after storage for long time. Storage modulus (G′) is higher than loss modulus (G″) of M-SIBS-g-PTHF block graft copolymer at temperatures ranging from 100 °C to 180 °C, which is much higher than those of the SIBS triblock copolymer. To the best of our knowledge, this is the first example of high performance M-SIBS-g-PTHF block graft copolymers containing segments of PIB, PS and PTHF with nanocrystallization-locked architecture.

End-reactive poly(tetrahydrofuran) for functionalization and graft copolymer synthesis via a conjugate substitution reaction

α-(Chloromethyl)acryloyl cation, prepared from the corresponding acyl chloride and silver triflate, was used as an initiator for the living, cationic ring-opening polymerization of tetrahydrofuran. The α-end of the resulting poly(tetrahydrofuran) has an α-(chloromethyl)acrylate skeleton, which is an excellent substrate for nucleophilic conjugate substitution. In fact, treatment with a phenol resulted in a functionalized α-end. Moreover, 2-aminoethylanol and 2-mercaptoethanol afforded doubly functionalized polymers with two hydroxy groups at the α-ends via conjugate substitution and subsequent addition reactions. Since α-(chloromethyl)acrylate can be attacked by two equivalents of a nucleophile, it can function as a monomer in polycondensations with dithiols. Therefore, the α-(chloromethyl)acrylate chain end was subjected to polycondensation with 1,10-decandithiol in the presence of Bu3P, resulting in a graft copolymer. The above results suggest that the α-(chloromethyl)acryloyl cation is a functional initiator for incorporating a chain end reactive to a variety of nucleophiles for single and double end-functionalizations and the preparation of graft copolymers. Conjugate subst. allows single/double end-functionalization and graft copolymer synthesis.

Synthesis and characterization of a novel fluorinated polyether glycol with fluorinated side chains via “living/controlled” cationic polymerization

Abstract A novel fluorinated polyether glycol with fluorinated side chains is synthesized via “living/controlled” cationic ring-opening polymerization of tetrahydrofuran and fluorine-containing epoxy compounds (FO). The effects of polymerization conditions on monomer conversion, number-average molecular weight ( M n ), molecular weight distribution ( M w / M n ) are measured. Our investigations have shown that the use of a mixed solvent (dichloromethane/1,4-dioxane) can prevent intra- and intermolecular transfer reactions, due to more nucleophilic oxygen atom in 1,4-dioxane. Using BF 3 ·CH 3 OH/CH 2 OHCH 2 OH as initiation system, polymers with predictable number-average molecular weight, narrow molecular weight distribution (1.03 M w / M n

Real-time monitoring of living cationic ring-opening polymerization of THF and direct prediction of equilibrium molecular weight of polyTHF

A convenient real-time monitoring of monomer concentration during living cationic ring-opening polymerizations of tetrahydrofuran (THF) initiated with methyl triflate (MeOTf) has been developed for kinetic investigation and determination of equilibrium monomer concentration ([M]e) via in situ FTIR spectroscopy in combination with a diamond tipped attenuated total reflectance (ATR) immersion probe. The polymerization rate was first order with respect to monomer concentration and initiator concentration from the linear slope of ln([M]0-[M]e)/([M]-[M]e) versus polymerization time at different temperatures in various solvents. [M]e decreased linearly with initial monomer concentration while increased exponentially with increasing polymerization temperature. The equilibrium also strongly depends on solvent polarity and its interaction with monomer. The equilibrium polymerization time (t e) decreased with increasing solvent polarity and decreased linearly with increasing [M]0 in three solvents with different slopes to the same point of bulk polymerization in the absence of solvent. Equation of M n,e = 72.1/(0.14-0.04[M]e) has been established to provide a simple and effective approach for the prediction for the number-average molecular weight of polyTHFs at equilibrium state (M n,e) in the equilibrium living cationic ring-opening polymerization of THF at 0 °C.

Effect of chain length distribution on thermal characteristics of model polytetrahydrofuran (PTHF) networks

A series of model polytetrahydrofuran (PTHF) networks were synthesized via end-linking reactions of α, ω-allyl PTHF oligomers with a stoichiometric tetrafunctional crosslinker. The telechelic PTHF oligomers were synthesized by living cationic ring-opening polymerization of tetrahydrofuran followed by a termination reaction with allyl alcohol. Networks thus prepared have well-controlled architecture in terms of the inter-crosslink chain length (Mc) and chain length distribution: resulting in unimodal, bimodal and clustered structures. Unimodal network was prepared by using polymer chains of same molecular weight, bimodal networks were synthesized by using two groups of polymer chains with different average molecular weights, and the clusters are prepared by incorporating clusters of networks with small molecular weight chains in a network matrix made of longer chains. Thermal characteristics of these model networks were investigated as a function of crosslink density, as well as inhomogeneities of crosslink distribution using DSC. We demonstrate that glass transition temperature (Tg) and crystallization behavior (melting temperature and crystallinity) of the networks are both strongly influenced by crosslink density (Mc). By comparing the unimodal, bimodal and clustered networks with similar average Mc, the effects of inhomogeneities in the crosslink distribution on the thermal properties were also investigated. Results show that inhomogeneities have trivial influence on Tg, but strongly affects the crystallization behavior. Moreover, the effects of the content ratio and length ratio between long and short chains, and the effects of cluster size and size distribution on the thermal characteristics were also studied.

From cationic ring-opening polymerization to atom transfer radical polymerization

Roots of controlled radical polymerization, including atom transfer radical polymerization (ATRP), originate in living ionic polymerizations accompanied by reversible deactivation, such as cationic ring-opening polymerization of tetrahydrofuran and other heterocyclics. Recent developments in ATRP, including mechanistic understanding, synthesis of polymers with precisely controlled architecture and some applications of polymers prepared by ATRP are presented.

Ring opening polymerization of tetrahydrofuran catalysed by maghnite-H+

The cationic ring-opening polymerization of tetrahydrofuran using maghnite-H+ is reported. Maghnite-H+, is a non-toxic solid catalyst issued from proton exchanged montmorillonite clay. Polytetrahydrofuran, also called “poly(butandiol) ether”, with acetate and hydroxyl end groups was successfully synthesized. Effects of reaction temperature, weight ratio of initiator/monomer and reaction time on the conversion of monomer and on the molecular weight are investigated. A cationic mechanism of the reaction was proposed. This chemistry can be considered as a suitable route for preparing poly(THF) as a soft segment for thermoplastic elastomers.

Poly(p -phenylene methylene)-based block copolymers by mechanistic transformation

The synthesis of poly(p-phenylene methylene) (PPM)-based block copolymers such as poly(p-phenylene methylene)-b-poly(ε-caprolactone) and poly(p-phenylene methylene)-b-polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid-catalyzed polymerization of tribenzylborate at 16 °C. Then, this polymer was used as macroinitiators in either ring-opening polymerization of ε-caprolactone or cationic ring-opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and 1H NMR investigations. The composition of block copolymers as determined by 1H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Cationic ring-opening polymerization of tetrahydrofuran with Keggin-type heteropolycompounds as solid acid catalysts

Three Keggin-type heteropolyanions, namely H3PMo12O40·13H2O, (NH4)3PMo12O40·4H2O and H3PW12O40·13H2O were prepared and tested in the ring-opening polymerization reaction of tetrahydrofuran. The effects of the counter-cation (H+, NH4 +) and the peripheral atoms (Mo, W) on the polymerization were investigated. It has been found that when the protons of H3PMo12O40·13H2O were replaced by the ammonium cations the polymerization rate decreased dramatically. Whereas, when the peripheral atoms (Mo) were replaced by their homologous (W), the polymerization rate increased twofold. As for the viscosity average molecular weight (M v) of polymer products, it was found that the high molecular weight (7930) was obtained by using H3PW12O40·13H2O. The molecular weight (M v) obtained by H3PMo12O40·13H2O and (NH4)3PMo12O40·4H2O was 6470 and 6810, respectively.

The Cationic Ring-Opening Polymerization of Tetrahydrofuran with 12-Tungstophosphoric Acid

The cationic ring-opening polymerization reaction of tetrahydrofuran at 20 °C was catalyzed by H3PW12O40·13H2O as solid acid catalyst. The effect of the proportions of acetic anhydride and catalyst, reaction time and support on the polymerization reaction was investigated. It has been found that the yield and the viscosity of the polymer depend on the proportion of acetic anhydride, the presence of the latter in the reactant mixture being required for the ring-opening. The catalytic activity of the alumina-supported heteropolyacid results showed that Brønsted acid sites are more effective than Lewis ones for the cationic ring-opening polymerization.

Glycosylation initiated cationic ring-opening polymerization of tetrahydrofuran to prepare neo-glycopolymers

An unprecedented and highly efficient glycosylation initiated cationic ring-opening polymerization (CROP) of tetrahydrofuran is disclosed employing glycosyl ortho-hexynylbenzoates as donors and gold(I) as a catalyst, that provides an easy access to novel glycopolymers which could self-assemble into nanostructures.

Polytetrahydrofuran/Clay Nanocomposites by In Situ Polymerization and “Click” Chemistry Processes

Polytetrahydrofuran (PTHF)/clay nanocomposites were prepared by two routes: in situ cationic ring opening polymerization (CROP) and a method involving click chemistry. In the first method, PTHF chains were grown from the surface of the organo-modified montmorillonite clay by CROP of tetrahydrofuran (THF) through the hydroxyl functions of the clay by using trifluoromethanesulfonic anhydride, in the presence of 2,6- di-tert-butylpyridine as proton trap and dichloromethane as solvent. The polymerizations were affected by the clay content ratios. The living characteristics of the polymerization were demonstrated by the semilogarithmic first order kinetic plot. In the second method, CROP of THF has been performed independently to produce alkyne- functionalized PTHF and the obtained polymers were subsequently anchored to azide-modified clay layers by a click reaction. The exfoliated polymer/clay nanocomposites obtained by both methods were characterized and compared by X-ray diffraction spectroscopy, thermogravimetric analysis, and transmission electron microscopy. Compared to the virgin polymer, the nanocomposites exhibited improved thermal stabilities regardless of the preparation method. However, the nanocomposites prepared by the click chemistry approach appeared to be thermally more stable than those prepared by in situ polymerization. Moreover, the click chemistry method also provided better exfoliation.

Block and Star-Block Copolymers by Mechanism Transformation. 3. S-(PTHF-PSt)4and S-(PTHF-PSt-PMMA)4from Living CROP to ATRP

Star-shaped poly(tetrahydrofuran) tetrols were prepared by living cationic ring-opening polymerization of tetrahydrofuran and esterified with bromoacetyl and bromoisobutyryl chloride. The intermediate produced was used as macroinitiator to initiate the atom transfer radical polymerization (ATRP) of styrene and subsequently atom transfer radical polymerization of methyl methacrylate at 80−110 °C with CuBr/2,2‘-bipyridine as catalyst. Kinetic studies and GPC analyses provided the evidences of “living” polymerization: constant concentration of active species, narrow molecular weight distribution, and well control of molecular weight. The NMR spectra and GPC analyses demonstrated the formations of four-armed star polymer and copolymers: S-(PTHF)4, S-(PTHF-PSt)4, and S-(PTHF-PSt-PMMA)4. For S-(PTHF-PSt)4, this conclusion was further confirmed by GPC analysis of the PSt obtained from hydrolysis of the copolymer.

Preparation of polytetrahydrofuran monomethacrylate macromonomers by cationic ring-opening polymerization of tetrahydrofuran

Polytetrahydrofuran monomethacrylate (MA-PTHF) macromonomer was prepared by cationic ring-opening polymerization(CROP) of tetrahydrofuran (THF) using boron trifloride etherate (BF3 · OEt2) as initiator and epichlorohydrin (ECH) as promoter. Two kinds of transfer agents were used: methacrylic acid (represented as TA1), and a mixture of methacrylic acid and sodium methacrylate (represented as TA2). The effects of polymerization conditions on molecular weight and molecular weight distribution of macromonomers were studied in this article, when the composition of reactants was kept constant. Under the same conditions, the molecular weight of macromonomer using TA2 is lower than that using TA1, which indicates that TA2 is more active than TA1. The molecular weight of MA-PTHF macromonomer varies with the polymerization time before transfer agents were added (T1), but molecular weight distribution remains constant. When T1 is limited in 30 min, the apparent number-average molecular weight of MA-PTHF increases significantly with the increase of T1, and ranges from 5000 to 18,000. Hence, the molecular weight of MA-PTHF macromonomer can be controlled by varying T1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 810–815, 2000

Influence of the alkyl group of triflate esters on their initiation ability for the cationic ring-opening polymerization of tetrahydrofuran

Esters of trifluoromethane sulfonic acid have been synthesized by reaction of different alcohols with triflic anhydride and used in situ as initiators for the polymerization of tetrahydrofuran. Kinetic studies of the polymerization showed that allyl triflate has the highest reactivity and that an increase of the alkyl chain length of the initiator leads to a significant decrease of the initiation rate. “Non-linear” triflate ester such as isobutyl triflate leads to incomplete initiation. It was impossible to synthesize quantitatively the triflate from tert-butyl alcohol due to spontaneous elimination leading to isobutylene.

Kinetic Studies of Poly(tetrahydrofuran) Epitaxial Film Formed by Polymerization-Induced Epitaxy Using Atomic Force Microscopy

To understand the mechanism of polymer epitaxy during solution polymerization (polymerization-induced epitaxy, PIE), the kinetics of the epitaxial film growth was compared with that of polymerization in solution. The surface coverage and the domain size of epitaxial films as well as the molecular weight of the polymer formed in solution were examined as functions of the reaction time, the monomer concentration, and the initiator concentration. Atomic force microscopy was used to evaluate the coverage and the apparent island size distribution. Cationic ring-opening polymerization of tetrahydrofuran (THF) in dichloromethane at 0 °C on a graphite substrate in the reaction mixture induces an epitaxial film of poly(THF), consisting of 0.5 nm thick, flat, rectangular islands. The reaction time dependence indicates that the film has developed much faster than the polymer growth in solution. When the monomer concentration was varied, no polymer was formed in solution below 3 mol/L, corresponding to the equilibriu...

Cationic graft polymerization of polymers from carbon fiber initiated by acylium perchlorate groups introduced onto the surface

The cationic graft polymerization of several monomers initiated by acylium perchlorate groups introduced onto the carbon fiber surface was investigated to modify the surface. The introduction of acylium perchlorate groups was successfully achieved by the reaction of silver perchlorate with acyl chloride groups, which were introduced by the reaction of surface carboxyl groups with thionyl chloride. It was found that the cationic polymerization of styrene is initiated by acylium perchlorate groups on the carbon fiber. In the polymerization, polystyrene was grafted onto the carbon fiber surface through the propagation of polystyrene from the surface. Ungrafted polymer was also formed by the chain transfer reaction of growing polymer cation to the monomer. The acylium perchlorate groups have the ability to initiate cationic ring-opening polymerization of tetrahydrofuran (THF) and ε-caprolactone (CL), polyTHF and polyCL being grafted onto the carbon fiber surface, respectively. Polyacetals, such as poly(1,3-dioxolane) and polyoxymethylene, were able to graft onto the carbon fiber by cationic ring-opening polymerization of the corresponding monomers.

Cationic ring‐opening polymerization of tetrahydrofuran with boron, aluminum, and gallium tristriflate

AbstractBoron, aluminum, and gallium tristriflate are new effective catalysts for the polymerization of tetrahydrofuran (THF). High‐molecular‐weight polytetrahydrofuran (PTHF) was obtained in excellent yield in the bulk polymerization of THF at ambient temperature with all three catalysts. The PTHF samples were characterized and some of their thermodynamic and mechanical properties were investigated and discussed.

Cationic Grafting from Carbon Black. 4. Grafting of Poly(Oxytetramethylene) to Carbon Black by Ring-Opening Polymerization of Tetrahydrofuran Initiated by CO + ClO4- Groups on Carbon Black

Abstract It was found that the cationic ring-opening polymerization of tetrahydrofuran (THF) was initiated by carbon black containing CO+ClO4-groups, which had been introduced by the reaction of COCl groups with AgClO4, in the presence of promoters such as epichlorohydrin (ECH) and diketene. It was confirmed that formation of poly(oxytetramethylene), i.e., poly-THF, was propagated from CO+ClO4-groups on carbon black surfaces and effectively grafted onto it. The grafting ratio with ECH as promoter increased to 66.8% as conversion increased. The activation energy of the polymerization initiated by CO+ClO4- groups in the presence of ECH was determined to be 8.1 kcal/mol. Furthermore, poly-ECH, poly(styrene oxide), and poly(propylene oxide) can be grafted onto carbon black surfaces by the ring-opening polymerization of the corresponding alkylene oxides with CO+ClO4- groups on the carbon black as initiator. The polyether-grafted carbon black obtained from the above polymerization produced a stable colloidal dispersion in a good solvent for polyether.